Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy...Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.展开更多
Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated...Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.展开更多
This work managed the extrusion strain path by designing various extrusion die cavities,successfully realizing the texture modification for the ZK60 magnesium alloy.The mechanisms involving the texture dependence on t...This work managed the extrusion strain path by designing various extrusion die cavities,successfully realizing the texture modification for the ZK60 magnesium alloy.The mechanisms involving the texture dependence on the extrusion die cavity as well as their effects on the mechanical properties were emphatically investigated.Results showed that dynamic recrystallization refined the grain size and improved the microstructure homogeneity in the three extrusion specimens,but did not produce too large microstructure differences.By comparison,significant texture differences developed owing to the various extrusion die cavities,which here were mainly reflected in the strong or weak texture components for the c-axes//TD and the c-axes//ND.Such texture differences started from the deformation texture instead of the recrystallization texture whose roles only consisted in dispersing the texture component and reducing the texture intensity.The results from the finite element analysis and the visco-plastic self-consistent model indicated that,in order to accommodate the different strain components induced by the extrusion die cavities,slip systems or tension twinning were activated differently,and this was the critical reason causing the above texture differences.One modified Hall-Petch relationship was adopted to analyze the conjoint effects of grain refinement and texture variation on the yield stress.Additionally,the quantitative results about deformation mechanism activation fractions demonstrated that the texture variations influenced the competition relationships between the twinning induced deformation and the slip dominant deformation,and the former generally produced the lower yield stress and the increasing stage of strain hardening rate,while the latter produced the higher yield stress and the continuous decline of strain hardening rate.展开更多
Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study...Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.展开更多
Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance ...Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance the mechanical properties and corrosion resistance of Mg-Li alloy.Key alloy factors(KAFs)influencing ultimate tensile strength(UTS),elongation(EL),and corrosion rate(CR)were identified through alloy factor construction and screening.Using KAFs and processing parameters as inputs,gradient boosting regression models for UTS,EL,and CR were established,achieving the coefficients of determination of test-set above 0.85.Then,SHapley Additive exPlanations(SHAP)analysis quantified the impact of KAFs,and an element evaluation method was established to identify Al,Si,Ca,and Zn as candidates for alloy design.Finally,three new alloys were designed via multi-objective optimization.In the hot-extruded state,they exhibited UTS of 253∼273 MPa,EL of 18.4%∼27.9%,CR of 0.55∼1.61 mg/(cm^(2)·day),and ρ of 1.49∼1.54 g/cm^(3).Compared to LAZ103,the new alloys show 34%∼44%higher UTS,35%∼79%lower CR,and comparable ρ.Microstructural analysis revealed increasedα-Mg,decreasedβ-Li,reduced coarse secondary phases,and fine Ca-/Si-rich precipitates which are conducive to grain refinement and dislocation density increasing,synergistically enhancing comprehensive property.展开更多
Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new...Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new pathway to improve properties, by preparation of nanometer lamellar discontinuous precipitates(DPs) arranged with the approximate same direction through a combination of deformationaging and cold rolling process. The strengthening effect is primarily attributed to nanometer-lamellar DPs strengthening and dislocation strengthening mechanism. The accumulation of dislocations at the interface between nanometer lamellar DPs and matrix during cold deformation process can results in the decrease of dislocation density inside the matrix grains, leading to the acceptably slight reduction of electrical conductivity during cold rolling. The alloy exhibits an electrical conductivity of 45.32%IACS(international annealed copper standard, IACS), a tensile strength of 882.67 MPa, and a yield strength of 811.33 MPa by this method. This study can provide a guidance for the composition and microstructure design of a Cu–Ni–Si alloy in the future, by controlling the morphology and distribution of DPs.展开更多
It is difficult to rapidly design the process parameters of copper alloys by using the traditional trial-and-error method and simultaneously improve the conflicting mechanical and electrical properties.The purpose of ...It is difficult to rapidly design the process parameters of copper alloys by using the traditional trial-and-error method and simultaneously improve the conflicting mechanical and electrical properties.The purpose of this work is to develop a new type of Cu-Ni-Co-Si alloy saving scarce and expensive Co element,in which the Co content is less than half of the lower limit in ASTM standard C70350 alloy,while the properties are as the same level as C70350 alloy.Here we adopted a strategy combining Bayesian optimization machine learning and experimental iteration and quickly designed the secondary deformation-aging parameters(cold rolling deformation 90%,aging temperature 450℃,and aging time 1.25 h)of the new copper alloy with only 32 experiments(27 basic sample data acquisition experiments and 5 iteration experiments),which broke through the barrier of low efficiency and high cost of trial-and-error design of deformation-aging parameters in precipitation strengthened copper alloy.The experimental hardness,tensile strength,and electrical conductivity of the new copper alloy are HV(285±4),(872±3)MPa,and(44.2±0.7)%IACS(international annealed copper standard),reaching the property level of the commercial lead frame C70350 alloy.This work provides a new idea for the rapid design of material process parameters and the simultaneous improvement of mechanical and electrical properties.展开更多
Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3-2400 s-1 with the compressive direction parallel to th...Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3-2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar （SHPB） were used to investigate the effect of strain rate on the compressive deforma-tion behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate （〈1.0 s^-1）, the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s^-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.展开更多
Metal additive manufacturing(AM)has been extensively studied in recent decades.Despite the significant progress achieved in manufacturing complex shapes and structures,challenges such as severe cracking when using exi...Metal additive manufacturing(AM)has been extensively studied in recent decades.Despite the significant progress achieved in manufacturing complex shapes and structures,challenges such as severe cracking when using existing alloys for laser powder bed fusion(L-PBF)AM have persisted.These challenges arise because commercial alloys are primarily designed for conventional casting or forging processes,overlooking the fast cooling rates,steep temperature gradients and multiple thermal cycles of L-PBF.To address this,there is an urgent need to develop novel alloys specifically tailored for L-PBF technologies.This review provides a comprehensive summary of the strategies employed in alloy design for L-PBF.It aims to guide future research on designing novel alloys dedicated to L-PBF instead of adapting existing alloys.The review begins by discussing the features of the L-PBF processes,focusing on rapid solidification and intrinsic heat treatment.Next,the printability of the four main existing alloys(Fe-,Ni-,Al-and Ti-based alloys)is critically assessed,with a comparison of their conventional weldability.It was found that the weldability criteria are not always applicable in estimating printability.Furthermore,the review presents recent advances in alloy development and associated strategies,categorizing them into crack mitigation-oriented,microstructure manipulation-oriented and machine learning-assisted approaches.Lastly,an outlook and suggestions are given to highlight the issues that need to be addressed in future work.展开更多
On the interface of the Cu-Al composite plate from horizontal continuous casting,the eutectic microstructure layer thickness ac-counts for more than 90%of the total interface thickness,and the deformation in rolling f...On the interface of the Cu-Al composite plate from horizontal continuous casting,the eutectic microstructure layer thickness ac-counts for more than 90%of the total interface thickness,and the deformation in rolling forming plays an important role in the quality of the composite plate.The eutectic microstructure material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated.The results show that when the deformation temperature is over 300℃,the softening effect of dynamic recrystallization ofα-Al is greater than the hardening effect,and uniform plastic deformation of eutectic microstructure is caused.The constitutive equation of flow stress in the eutectic microstructure layer was established by Arrhenius hy-perbolic-sine mathematics model,providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.展开更多
In the present investigation, a coupled crystal plasticity finite-element(CPFE) and cellular automaton(CA) model was developed to predict the microstructure of recrystallization in single-crystal(SX) Ni-based superall...In the present investigation, a coupled crystal plasticity finite-element(CPFE) and cellular automaton(CA) model was developed to predict the microstructure of recrystallization in single-crystal(SX) Ni-based superalloy.The quasi-static compressive tests of [001] orientated SX DD6 superalloy were conducted on Gleeble3500 tester to calibrate the CPFE model based on crystal slip kinematics.The simulated stress-strain curve agrees well with the experimental results. Quantitative deformation amount was introduced in the deformed samples of simulation and experiment, and these samples were subsequently subjected to the standard solution heat treatment(SSHT).Results of CA simulation show that the recrystallization(RX) nucleation tends to occur at the third stage of SSHT process due to the high critical temperature of RX nucleation for the samples deformed at room temperature. The inhomogeneous RX grains gradually coarsen and compete to reach more stable status by reducing the system energy.Simulated RX grain density decreases from 7.500 to1.875 mm,agreeing well with the value of 1.920 mmfrom electron backscattered diffraction(EBSD) detection of the experimental sample.展开更多
Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-...Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-speed rail contact wires,electronic component connectors,and other devices.Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys.Taking the typical solid solution-strengthened alloy Cu-4Zn-1Sn as the research object,we proposed using the element In to replace Zn and Sn to achieve low alloying in this work.Two new alloys,Cu-1.5Zn-1Sn-0.4In and Cu-1.5Zn-0.9Sn-0.6In,were designed and prepared.The total weight percentage content of alloying elements decreased by 43%and 41%,respectively,while the product of ultimate tensile strength(UTS)and electrical conductivity(EC)of the annealed state increased by 14%and 15%.After cold rolling with a 90%reduction,the UTS of the two new alloys reached 576 and 627MPa,respectively,the EC was 44.9%IACS and 42.0%IACS,and the product of UTS and EC(UTS×EC)was 97%and 99%higher than that of the annealed state alloy.The dislocations proliferated greatly in cold-rolled alloys,and the strengthening effects of dislocations reached 332 and 356 MPa,respectively,which is the main reason for the considerable improvement in mechanical properties.展开更多
To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.Thi...To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.This model incorporates incremental learning and transfer learning,thus improves the predictive accuracy and generalization performance.To account for the anisotropy of the directionally solidified alloy,a deformation direction parameter is added to the model,enabling prediction of the stress-strain relationship of the alloy under different deformation directions.The predictive capabilities of both models are evaluated using correlation coefficient(R),average relative error(δ),and value of relative error(RE).Compared to the traditional model,the machine learning constitutive model achieves higher prediction accuracy and better generalization performance.This offers a new approach for the establishment of flow constitutive models for other directionally solidified and single-crystal superalloys.展开更多
The impact of Fe content on the microstructures and mechanical properties of an ultra-high strength aluminum alloy,namely,Al−10.50Zn−2.35Mg−1.25Cu−0.12Cr−0.1Mn−0.1Zr−0.1Ti,was investigated.It is found that the increas...The impact of Fe content on the microstructures and mechanical properties of an ultra-high strength aluminum alloy,namely,Al−10.50Zn−2.35Mg−1.25Cu−0.12Cr−0.1Mn−0.1Zr−0.1Ti,was investigated.It is found that the increase of Fe content leads to a notable rise in the volume fraction of microscale secondary phases,including(Cu,Fe,Mn,Cr)Al_(7),σphase(composed of Al,Zn,Mg,and Cu elements),and Al_(3)(Zr,Ti).The formation of these secondary phases results in the depletion of certain phase-forming elements,thereby significantly reducing the quantity of strengthening phases.Fe imposes minimal impact on tensile strength,but it can significantly alter the elongation(δ).For instance,the average elongation of the alloy with 0.18 wt.%Fe(δ=4.5%)is less than half that of the alloy with Fe less than 0.1 wt.%(δ=9.9%−10.9%).The reduction in elongation is attributed to the combined effects of the formation of coarse secondary phases and the diminished quantity of strengthening phases around these coarse phases.展开更多
The evolution of the microstructure and mechanical properties of WE43 magnesium alloy during multipass hot rolling was investigated.Results revealed that multipass hot rolling promoted the formation of small second ph...The evolution of the microstructure and mechanical properties of WE43 magnesium alloy during multipass hot rolling was investigated.Results revealed that multipass hot rolling promoted the formation of small second phases,which was conducive to multiple dynamic recrystallization,consequently improving the microstructure homogeneity and refining the average grain size from 34.3μm in the initial material to 8.83μm.Meanwhile,the rolling deformation rotated abundant c-axis of the grains in the normal direction,resulting in a strong fiber texture.The yield strength in the rolling direction(RD)was improved from 164 MPa in the initial material to 324 MPa in the Pass 3 sheet due to fine-grained strengthening,second-phase strengthening,and texture modification.In addition,the distribution maps of the deformation mechanism indicated that the yield strength anisotropy between the RD and the transverse direction(TD)can be attributed to the effects of the texture component on the dominant mechanism.The dominant deformation mechanism during the tensile test was the prismatic slip caused by the strong basal texture of the RD,whereas it had a lesser proportion of prismatic slip under the influence of the weak basal texture of the TD.Compared to the basal slip,the higher critical resolved shear stress of the prismatic slip resulted in a higher increase in yield strength along the RD at approximately 51 MPa than that along the TD(RD:increase of 160 MPa;TD:increase of 109 MPa).展开更多
Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its...Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its additive manufacturing(AM)and no dedicated heat treatments have been developed for additively manufactured C465 to optimize its strength-ductility trade-off.In this work,the C465 was fabricated via laser powder bed fusion.The effect of hot isostatic pressing,solid solution,cryogenic treatment(−78.5℃),and aging on the composition homogenization,austenite-to-martensite transition,and Ni_(3)Ti precipitation were systemically investigated.The atom probe tomography analysis reveals that Mo atoms accumulate on Ni_(3)Ti precipitate surfaces and inhibits the Ni_(3)Ti growth,con-tributing to the enhanced strength of C465.The modified heat treatment for additively manufactured C465 reaches comparable tensile strength with the wrought counterpart,yielding an ultimate tensile strength of 1773 MPa,yield strength of 1686 MPa,and elongation of 6.5%.A yield strength calculation model was proposed and validated with measured strength under various heat treatments,providing valuable insight for heat treatment design towards diverse industrial applications.展开更多
Recent studies have shown that synergistic precipitation of continuous precipitates(CPs)and discontinuous precipitates(DPs)is a promising method to simultaneously improve the strength and electrical conductivity of Cu...Recent studies have shown that synergistic precipitation of continuous precipitates(CPs)and discontinuous precipitates(DPs)is a promising method to simultaneously improve the strength and electrical conductivity of Cu-Ni-Si alloy.However,the complex relationship between precipitates and two-stage aging process presents a significant challenge for the optimization of process parameters.In this study,machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs.Two-stage aging parameters of 400℃/75 min+400℃/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy,resulting in a tensile strength of 875 MPa and a conductivity of 41.43%IACS,respectively.Such an excellent comprehensive performance of the alloy is attributed to the combined precipitation of DPs and CPs(with a total volume fraction of 5.4%and a volume ratio of CPs to DPs of 6.7).This study could provide a new approach and insight for improving the comprehensive properties of the Cu-Ni-Si alloys.展开更多
Aluminum alloys with ultra-strength and high-toughness are fundamental structural materials applied in the aerospace industry.Due to the intrinsic restriction between strength and toughness,optimizing a desirable comb...Aluminum alloys with ultra-strength and high-toughness are fundamental structural materials applied in the aerospace industry.Due to the intrinsic restriction between strength and toughness,optimizing a desirable combination of these conflicting properties is always challenging in material development.In this study,171 sets of data were curated based on the characteristics of high-strength and high-toughness aluminum alloys in the literature.Then,a machine learning design system(MLDS)with a property-oriented design strategy was established to rapidly discover novel aluminum alloys with ductility and toughness indexes(with elongationδ=8%–10%and fracture toughness K_(IC)=33–35 MPa·m^(1/2))comparable to those of current state-of-the-art AA7136 aluminum alloys when the ultimate tensile strength(UTS)exceeded approximately 100 MPa,with values reaching 700–750 MPa.With the MLDS for experimental verification,three typical candidate alloys show satisfactory performance with UTS of 707–736 MPa,δof 7.8%–9.5%,and K_(IC)of 32.2–33.9 MPa·m^(1/2).The high contents of Mg and Zn alloying elements in the novel alloys form abundantη'phases,which produce a significant hardening effect,while the reasonable matching of Cr,Mn,Ti and Zr dispersoids refines the grain size.The decreased Cu content compared with that in the AA7136 alloy inhibits the formation of theσphase and S phase,so that the alloys show high toughness.展开更多
Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the in...Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube （φ50 mm × 5 mm）. HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250℃ melting and holding temperature, 1200-1250℃ mold heating temperature, 50-80 mm/min mean drawing speed, and 500-700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure （{hkl}〈621〉, {hkl}〈221〉） due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%-47.2% and 210-221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.展开更多
This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. L...This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.展开更多
基金financially supported by the National Key Research and Development Program of China (No. 2023YFB3812601)the National Natural Science Foundation of China (No. 51925401)the Young Elite Scientists Sponsorship Program by CAST, China (No. 2022QNRC001)。
文摘Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.
基金support from Interdisciplinary Research Project for Young Teachers of USTB Fundamental Research Funds for the Central Universities(Grant no.FRF-IDRY-23-030).
文摘Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.
基金supported by National Natural Science Foundation of China(Grant No.52205344,51925401)Postdoctoral Research Foundation of China(Grant No.2023M732398)+1 种基金National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(Grant No.WDZC2023-1)Key Research and Development Program of Shandong Province(Grant No.2023CXPT066).
文摘This work managed the extrusion strain path by designing various extrusion die cavities,successfully realizing the texture modification for the ZK60 magnesium alloy.The mechanisms involving the texture dependence on the extrusion die cavity as well as their effects on the mechanical properties were emphatically investigated.Results showed that dynamic recrystallization refined the grain size and improved the microstructure homogeneity in the three extrusion specimens,but did not produce too large microstructure differences.By comparison,significant texture differences developed owing to the various extrusion die cavities,which here were mainly reflected in the strong or weak texture components for the c-axes//TD and the c-axes//ND.Such texture differences started from the deformation texture instead of the recrystallization texture whose roles only consisted in dispersing the texture component and reducing the texture intensity.The results from the finite element analysis and the visco-plastic self-consistent model indicated that,in order to accommodate the different strain components induced by the extrusion die cavities,slip systems or tension twinning were activated differently,and this was the critical reason causing the above texture differences.One modified Hall-Petch relationship was adopted to analyze the conjoint effects of grain refinement and texture variation on the yield stress.Additionally,the quantitative results about deformation mechanism activation fractions demonstrated that the texture variations influenced the competition relationships between the twinning induced deformation and the slip dominant deformation,and the former generally produced the lower yield stress and the increasing stage of strain hardening rate,while the latter produced the higher yield stress and the continuous decline of strain hardening rate.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3706901)the National Natural Science Foundation of China(No.52090041)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC 001).
文摘Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.
基金supported by the Advanced Materials-National Science and Technology Major Project(No.2025ZD0619700)National Natural Science Foundation of China(No.52401002,92570301)+1 种基金China Postdoctoral Science Foundation funded project(No.2024M760200)Fundamental Research Funds for the Central Universities(No.FRF-BD-25-007).
文摘Designing low-density,high-strength Mg-Li alloys is a major challenge in achieving extreme lightweighting of high-end equipment.This study proposes an interpretable machine learning strategy to simultaneously enhance the mechanical properties and corrosion resistance of Mg-Li alloy.Key alloy factors(KAFs)influencing ultimate tensile strength(UTS),elongation(EL),and corrosion rate(CR)were identified through alloy factor construction and screening.Using KAFs and processing parameters as inputs,gradient boosting regression models for UTS,EL,and CR were established,achieving the coefficients of determination of test-set above 0.85.Then,SHapley Additive exPlanations(SHAP)analysis quantified the impact of KAFs,and an element evaluation method was established to identify Al,Si,Ca,and Zn as candidates for alloy design.Finally,three new alloys were designed via multi-objective optimization.In the hot-extruded state,they exhibited UTS of 253∼273 MPa,EL of 18.4%∼27.9%,CR of 0.55∼1.61 mg/(cm^(2)·day),and ρ of 1.49∼1.54 g/cm^(3).Compared to LAZ103,the new alloys show 34%∼44%higher UTS,35%∼79%lower CR,and comparable ρ.Microstructural analysis revealed increasedα-Mg,decreasedβ-Li,reduced coarse secondary phases,and fine Ca-/Si-rich precipitates which are conducive to grain refinement and dislocation density increasing,synergistically enhancing comprehensive property.
基金supported by the National Key Research and Development Program of China (No. 2023YFB3812601)the National Natural Science Founda tion of China (Nos. 51925401, 92066205, and 92266301)。
文摘Simultaneously achieving high strength and high electrical conductivity in Cu–Ni–Si alloys pose a significant challenge, which greatly constrains its applications in the electronics industry. This paper offers a new pathway to improve properties, by preparation of nanometer lamellar discontinuous precipitates(DPs) arranged with the approximate same direction through a combination of deformationaging and cold rolling process. The strengthening effect is primarily attributed to nanometer-lamellar DPs strengthening and dislocation strengthening mechanism. The accumulation of dislocations at the interface between nanometer lamellar DPs and matrix during cold deformation process can results in the decrease of dislocation density inside the matrix grains, leading to the acceptably slight reduction of electrical conductivity during cold rolling. The alloy exhibits an electrical conductivity of 45.32%IACS(international annealed copper standard, IACS), a tensile strength of 882.67 MPa, and a yield strength of 811.33 MPa by this method. This study can provide a guidance for the composition and microstructure design of a Cu–Ni–Si alloy in the future, by controlling the morphology and distribution of DPs.
基金supported by the National Key Research and Development Program of China(No.2021YFB 3803101)the National Natural Science Foundation of China(Nos.52090041,52022011,and 51974028)。
文摘It is difficult to rapidly design the process parameters of copper alloys by using the traditional trial-and-error method and simultaneously improve the conflicting mechanical and electrical properties.The purpose of this work is to develop a new type of Cu-Ni-Co-Si alloy saving scarce and expensive Co element,in which the Co content is less than half of the lower limit in ASTM standard C70350 alloy,while the properties are as the same level as C70350 alloy.Here we adopted a strategy combining Bayesian optimization machine learning and experimental iteration and quickly designed the secondary deformation-aging parameters(cold rolling deformation 90%,aging temperature 450℃,and aging time 1.25 h)of the new copper alloy with only 32 experiments(27 basic sample data acquisition experiments and 5 iteration experiments),which broke through the barrier of low efficiency and high cost of trial-and-error design of deformation-aging parameters in precipitation strengthened copper alloy.The experimental hardness,tensile strength,and electrical conductivity of the new copper alloy are HV(285±4),(872±3)MPa,and(44.2±0.7)%IACS(international annealed copper standard),reaching the property level of the commercial lead frame C70350 alloy.This work provides a new idea for the rapid design of material process parameters and the simultaneous improvement of mechanical and electrical properties.
基金financially supported by the National Natural Science Foundation(No.50904004)
文摘Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3-2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar （SHPB） were used to investigate the effect of strain rate on the compressive deforma-tion behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate （〈1.0 s^-1）, the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s^-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.
基金financially supported by the National Key Research and Development Program of China(2022YFB4600302)National Natural Science Foundation of China(52090041)+1 种基金National Natural Science Foundation of China(52104368)National Major Science and Technology Projects of China(J2019-VII-0010-0150)。
文摘Metal additive manufacturing(AM)has been extensively studied in recent decades.Despite the significant progress achieved in manufacturing complex shapes and structures,challenges such as severe cracking when using existing alloys for laser powder bed fusion(L-PBF)AM have persisted.These challenges arise because commercial alloys are primarily designed for conventional casting or forging processes,overlooking the fast cooling rates,steep temperature gradients and multiple thermal cycles of L-PBF.To address this,there is an urgent need to develop novel alloys specifically tailored for L-PBF technologies.This review provides a comprehensive summary of the strategies employed in alloy design for L-PBF.It aims to guide future research on designing novel alloys dedicated to L-PBF instead of adapting existing alloys.The review begins by discussing the features of the L-PBF processes,focusing on rapid solidification and intrinsic heat treatment.Next,the printability of the four main existing alloys(Fe-,Ni-,Al-and Ti-based alloys)is critically assessed,with a comparison of their conventional weldability.It was found that the weldability criteria are not always applicable in estimating printability.Furthermore,the review presents recent advances in alloy development and associated strategies,categorizing them into crack mitigation-oriented,microstructure manipulation-oriented and machine learning-assisted approaches.Lastly,an outlook and suggestions are given to highlight the issues that need to be addressed in future work.
基金This work was financially supported by the National Key Research and Development Program of China(No.2018YFA0707303)the National Natural Science Foundation for Distinguished Young Scholars of China(No.51925401).
文摘On the interface of the Cu-Al composite plate from horizontal continuous casting,the eutectic microstructure layer thickness ac-counts for more than 90%of the total interface thickness,and the deformation in rolling forming plays an important role in the quality of the composite plate.The eutectic microstructure material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated.The results show that when the deformation temperature is over 300℃,the softening effect of dynamic recrystallization ofα-Al is greater than the hardening effect,and uniform plastic deformation of eutectic microstructure is caused.The constitutive equation of flow stress in the eutectic microstructure layer was established by Arrhenius hy-perbolic-sine mathematics model,providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.
基金financially supported by the National Key R&D Program of China (No.2017YFB0701503)the National Basic Research Program of China(No.2011CB706801)
文摘In the present investigation, a coupled crystal plasticity finite-element(CPFE) and cellular automaton(CA) model was developed to predict the microstructure of recrystallization in single-crystal(SX) Ni-based superalloy.The quasi-static compressive tests of [001] orientated SX DD6 superalloy were conducted on Gleeble3500 tester to calibrate the CPFE model based on crystal slip kinematics.The simulated stress-strain curve agrees well with the experimental results. Quantitative deformation amount was introduced in the deformed samples of simulation and experiment, and these samples were subsequently subjected to the standard solution heat treatment(SSHT).Results of CA simulation show that the recrystallization(RX) nucleation tends to occur at the third stage of SSHT process due to the high critical temperature of RX nucleation for the samples deformed at room temperature. The inhomogeneous RX grains gradually coarsen and compete to reach more stable status by reducing the system energy.Simulated RX grain density decreases from 7.500 to1.875 mm,agreeing well with the value of 1.920 mmfrom electron backscattered diffraction(EBSD) detection of the experimental sample.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3803101)the National Natural Science Foundation of China(Nos.52022011,51974028,and 52090041)+1 种基金the Xiaomi Young Scholars ProgramChina National Postdoctoral Program for Innovative Talents(No.BX20230042)。
文摘Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-speed rail contact wires,electronic component connectors,and other devices.Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys.Taking the typical solid solution-strengthened alloy Cu-4Zn-1Sn as the research object,we proposed using the element In to replace Zn and Sn to achieve low alloying in this work.Two new alloys,Cu-1.5Zn-1Sn-0.4In and Cu-1.5Zn-0.9Sn-0.6In,were designed and prepared.The total weight percentage content of alloying elements decreased by 43%and 41%,respectively,while the product of ultimate tensile strength(UTS)and electrical conductivity(EC)of the annealed state increased by 14%and 15%.After cold rolling with a 90%reduction,the UTS of the two new alloys reached 576 and 627MPa,respectively,the EC was 44.9%IACS and 42.0%IACS,and the product of UTS and EC(UTS×EC)was 97%and 99%higher than that of the annealed state alloy.The dislocations proliferated greatly in cold-rolled alloys,and the strengthening effects of dislocations reached 332 and 356 MPa,respectively,which is the main reason for the considerable improvement in mechanical properties.
基金supported by the National Science and Technology Major Project(2017-VII-0008-0101).
文摘To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.This model incorporates incremental learning and transfer learning,thus improves the predictive accuracy and generalization performance.To account for the anisotropy of the directionally solidified alloy,a deformation direction parameter is added to the model,enabling prediction of the stress-strain relationship of the alloy under different deformation directions.The predictive capabilities of both models are evaluated using correlation coefficient(R),average relative error(δ),and value of relative error(RE).Compared to the traditional model,the machine learning constitutive model achieves higher prediction accuracy and better generalization performance.This offers a new approach for the establishment of flow constitutive models for other directionally solidified and single-crystal superalloys.
基金supported by the National Key Research and Development Program of China(No.2023YFB3710501)the National Natural Science Foundation of China(No.52401002)the Beijing Municipal Science and Technology Commission,China(No.Z191100001119125).
文摘The impact of Fe content on the microstructures and mechanical properties of an ultra-high strength aluminum alloy,namely,Al−10.50Zn−2.35Mg−1.25Cu−0.12Cr−0.1Mn−0.1Zr−0.1Ti,was investigated.It is found that the increase of Fe content leads to a notable rise in the volume fraction of microscale secondary phases,including(Cu,Fe,Mn,Cr)Al_(7),σphase(composed of Al,Zn,Mg,and Cu elements),and Al_(3)(Zr,Ti).The formation of these secondary phases results in the depletion of certain phase-forming elements,thereby significantly reducing the quantity of strengthening phases.Fe imposes minimal impact on tensile strength,but it can significantly alter the elongation(δ).For instance,the average elongation of the alloy with 0.18 wt.%Fe(δ=4.5%)is less than half that of the alloy with Fe less than 0.1 wt.%(δ=9.9%−10.9%).The reduction in elongation is attributed to the combined effects of the formation of coarse secondary phases and the diminished quantity of strengthening phases around these coarse phases.
基金financially supported by National Natural Science Foundation of China(Nos.52205344 and 51925401)the Postdoctoral Research Foundation of China(No.2023M732398)+1 种基金the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact,China(No.WDZC2023-1)the Key Research and Development Program of Shandong Province,China(No.2023CXPT066)。
文摘The evolution of the microstructure and mechanical properties of WE43 magnesium alloy during multipass hot rolling was investigated.Results revealed that multipass hot rolling promoted the formation of small second phases,which was conducive to multiple dynamic recrystallization,consequently improving the microstructure homogeneity and refining the average grain size from 34.3μm in the initial material to 8.83μm.Meanwhile,the rolling deformation rotated abundant c-axis of the grains in the normal direction,resulting in a strong fiber texture.The yield strength in the rolling direction(RD)was improved from 164 MPa in the initial material to 324 MPa in the Pass 3 sheet due to fine-grained strengthening,second-phase strengthening,and texture modification.In addition,the distribution maps of the deformation mechanism indicated that the yield strength anisotropy between the RD and the transverse direction(TD)can be attributed to the effects of the texture component on the dominant mechanism.The dominant deformation mechanism during the tensile test was the prismatic slip caused by the strong basal texture of the RD,whereas it had a lesser proportion of prismatic slip under the influence of the weak basal texture of the TD.Compared to the basal slip,the higher critical resolved shear stress of the prismatic slip resulted in a higher increase in yield strength along the RD at approximately 51 MPa than that along the TD(RD:increase of 160 MPa;TD:increase of 109 MPa).
基金supported by the National Key Research and Development Program of China(No.2022YFB4600302)the Fundamental Research Funds for the Central Universities,China(No.FRF-IDRY-23-011).
文摘Custom 465(C465)is a martensitic stainless steel known for its high strength,toughness,and corrosion resistance,widely used in aerospace,automotive,and medical industries.However,limited work has been conducted on its additive manufacturing(AM)and no dedicated heat treatments have been developed for additively manufactured C465 to optimize its strength-ductility trade-off.In this work,the C465 was fabricated via laser powder bed fusion.The effect of hot isostatic pressing,solid solution,cryogenic treatment(−78.5℃),and aging on the composition homogenization,austenite-to-martensite transition,and Ni_(3)Ti precipitation were systemically investigated.The atom probe tomography analysis reveals that Mo atoms accumulate on Ni_(3)Ti precipitate surfaces and inhibits the Ni_(3)Ti growth,con-tributing to the enhanced strength of C465.The modified heat treatment for additively manufactured C465 reaches comparable tensile strength with the wrought counterpart,yielding an ultimate tensile strength of 1773 MPa,yield strength of 1686 MPa,and elongation of 6.5%.A yield strength calculation model was proposed and validated with measured strength under various heat treatments,providing valuable insight for heat treatment design towards diverse industrial applications.
基金financially supported by the National Key Research and Development Program of China(No.2023YFB3812601)the National Natural Science Foundation of China(Nos.51925401,92066205 and 92266301)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001).
文摘Recent studies have shown that synergistic precipitation of continuous precipitates(CPs)and discontinuous precipitates(DPs)is a promising method to simultaneously improve the strength and electrical conductivity of Cu-Ni-Si alloy.However,the complex relationship between precipitates and two-stage aging process presents a significant challenge for the optimization of process parameters.In this study,machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs.Two-stage aging parameters of 400℃/75 min+400℃/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy,resulting in a tensile strength of 875 MPa and a conductivity of 41.43%IACS,respectively.Such an excellent comprehensive performance of the alloy is attributed to the combined precipitation of DPs and CPs(with a total volume fraction of 5.4%and a volume ratio of CPs to DPs of 6.7).This study could provide a new approach and insight for improving the comprehensive properties of the Cu-Ni-Si alloys.
基金supported by the National Natural Science Foundation of China(Nos.52090041,51921001,52022011)the Beijing Municipal Science and Technology Commission(Nos.Z191100007219002,Z191100001119125)the Key Scientific and Technological Project of Foshan City(No.1920001000409)
文摘Aluminum alloys with ultra-strength and high-toughness are fundamental structural materials applied in the aerospace industry.Due to the intrinsic restriction between strength and toughness,optimizing a desirable combination of these conflicting properties is always challenging in material development.In this study,171 sets of data were curated based on the characteristics of high-strength and high-toughness aluminum alloys in the literature.Then,a machine learning design system(MLDS)with a property-oriented design strategy was established to rapidly discover novel aluminum alloys with ductility and toughness indexes(with elongationδ=8%–10%and fracture toughness K_(IC)=33–35 MPa·m^(1/2))comparable to those of current state-of-the-art AA7136 aluminum alloys when the ultimate tensile strength(UTS)exceeded approximately 100 MPa,with values reaching 700–750 MPa.With the MLDS for experimental verification,three typical candidate alloys show satisfactory performance with UTS of 707–736 MPa,δof 7.8%–9.5%,and K_(IC)of 32.2–33.9 MPa·m^(1/2).The high contents of Mg and Zn alloying elements in the novel alloys form abundantη'phases,which produce a significant hardening effect,while the reasonable matching of Cr,Mn,Ti and Zr dispersoids refines the grain size.The decreased Cu content compared with that in the AA7136 alloy inhibits the formation of theσphase and S phase,so that the alloys show high toughness.
基金financial support of National Key Technology R&D Program of China (No.2011BAE23B00)
文摘Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube （φ50 mm × 5 mm）. HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250℃ melting and holding temperature, 1200-1250℃ mold heating temperature, 50-80 mm/min mean drawing speed, and 500-700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure （{hkl}〈621〉, {hkl}〈221〉） due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%-47.2% and 210-221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.
基金financially supported by the National Key Research and Development Program of China(2016YFB0301200)
文摘This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.
