A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12...A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al_(0.8)Si_(0.2)-Ti_(12)Zr_(2)](V_(0.8)Mo_(0.2)Nb_(1)Ti)features an enhancedβ-Ti via co-alloying of Zr,V,Mo,Nb and Si.The experimental results show that the cluster formula ofαandβphases in the novel alloy are respectivelyα-[Al-Ti_(11.5)Zr_(0.5)](Al_(1)Ti_(2))andβ-[Al_(0.8)Si_(0.2)-Ti_(13.2)Zr_(0.8)](V_(1)Mo_(0.4)Nb_(1.6)),both containing Zr elements.The fitted composition via the α andβphase cluster formulas has little difference with the actual alloy composition,suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design.After hot isostatic pressing(HIP),both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-βcolumnar grains,while the typical<100>texture disappears.Compared with Ti-6Al-4V,Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength(1,056 MPa)and higher ductility(14%)at room temperature and higher strength(580 MPa)at 550℃ after HIP,and can potentially serves as LMD materials.展开更多
A novel Ni-Cr-Si-B filler metal with the cluster formula of[Cr-Ni12]B2Cr+[B-Ni8Cr]BSi Cr based on the cluster-plus-glue-atom model was designed for vacuum brazing GH4169 alloy.The effect of brazing temperature and bra...A novel Ni-Cr-Si-B filler metal with the cluster formula of[Cr-Ni12]B2Cr+[B-Ni8Cr]BSi Cr based on the cluster-plus-glue-atom model was designed for vacuum brazing GH4169 alloy.The effect of brazing temperature and brazing time on microstructure and shear strength of GH4169 alloy joints was investigated.The brazed seam was mainly composed ofγ-Ni solid solution.(Nb,Ti)-rich phase and(Cr,Nb,Mo)-rich borides distributed in diffusion zones.The diffusion and aggregation of B,Cr,Nb,and Mo resulted in the variation of phase contrast and morphology of borides.Coarse precipitations in the joint brazed at1240℃consisted of borides,Laves phase andδphase.The shear strength of joints was principally dominated by the brittle precipitations in diffusion zone,and the homogenization of microstructure improved the room-temperature shear strength to 820 MPa with the high-temperature shear strength of 627 MPa for the joint brazed at 1240℃/20 min.The joint fractured in diffusion zone and brazed seam,and the existence of borides and Laves phase in diffusion zone provide the potential origin for crack growth.展开更多
Multi-principal element alloys(MPEAs)have shown extraordinary properties in different fields.However,the composition design of MPEAs is still challenging due to the complicated interactions among principal elements(PE...Multi-principal element alloys(MPEAs)have shown extraordinary properties in different fields.However,the composition design of MPEAs is still challenging due to the complicated interactions among principal elements(PEs),and even more challenging with precipitates formation.Precipitation can be either beneficial or detrimental in alloys,thus it is important to control precipitates formation on purpose during alloy design.In this work,cluster-plus-glue-atom model(CGM)composition design method which is usually used to describe short-range order in traditional alloys has been successfully extended to MPEAs for precipitation design.The key challenge of extending CGM to MPEAs is the determination of center atom since there are no solvent or solute in MPEAs.Research has found that the element type of center atom was related not only with chemical affinity,but also with atomic volume difference in MPEAs,which has inevitable effect on atomic arrangement.Based on experimental data of MPEAs with precipitates,it was found that elements with either stronger chemical affinity or larger volume difference with other PEs would occupy the center site of clusters.Therefore,a cluster index(P_(C)),which considers both chemical affinity and atomic volume factors,was proposed to assist the determination of center atom in MPEAs.Based on the approach,a solid-solution Zr-Ti-V-Nb-Al BCC alloy was obtained by inhibiting the precipitation,while precipitation-strengthened Al-Cr-FeNi-V FCC alloy and Al-Co-Cr-Fe-Ni BCC alloy were designed by promoting the precipitation.Corresponding experimental results demonstrated that the approach could provide a relatively simple and accurate predication of precipitation and the compositions of precipitations were in line with PEs in cluster in MPEAs.The research may open an effective way for composition design of MPEAs with desired phase structure.展开更多
High-entropy alloys(HEAs)are based on solid solutions which characterized by chemical short-range ordering(CSRO),but there is no accurate structural tool to address CSRO characteristic,which obstacles precise composit...High-entropy alloys(HEAs)are based on solid solutions which characterized by chemical short-range ordering(CSRO),but there is no accurate structural tool to address CSRO characteristic,which obstacles precise composition design for HEAs.In this study,based on the cluster-plus-glue-atoms model,the composition law of Al-TMs(TMs,transition metals)HEAs with BCC and FCC structures was revealed.In BCC structure,with five elements in equi-atomic ratio,the composition formula of Al-TMs HEAs can be expressed by a cluster formula[Al-M_(14)]Al_(3),and in non equi-atomic ratio can be expressed by[Al-M_(14)]Al,where M is the average atom of the TMs.But in FCC structure,both Al-TMs HEAs with five elements in equiatomic and non equi-atomic ratios can be expressed by a cluster formula[Al-M_(12)]Al.To confirm the effectiveness of cluster formula for Al-TMs,two alloys were designed,[Al-Ti_(4)V_(3)Nb_(4)Mo_(3)]Mo and[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al.Results show that the[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al alloy has both higher strength and higher plastic deformation at room temperature.Besides,[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al alloy shows slower soften effect at 800℃,contributed to its higher strength.By substituting Ta for some of Mo,the strength of[Al-Ti_(3)V_(3)Nb_(4)Mo_(3)Ta]Al at room temperature and high temperature drastically decreases,suggesting that Ta element deteriorates the properties of Al-TMs alloys.展开更多
Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the a...Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the aid of Mg matrix and Mg_(5) Gd precipitate phase.First,based on the structural homologue between Gd-containing Mg solid solution and Mg_(5) Gd precipitate phase and in combination with our previously established method for calculating the glue atoms,[Gd-Mg_(12)]Mg_(5) is obtained as the chemical unit of Gd-containing Mg solid solution.Then,seven compositions are designed using different combinations of this unit and that of pure Mg[Mg-Mg_(12)Mg3.After a systematic experimental investigation on the microstructure and mechanical property evolutions as a function of the unit proportions,it is revealed that the Mg-10.1 Gd-3.3 Y-0.9 Zr alloy,being issued from equi-proportion mixing of the two units,shows the strongest tendency of precipitation and reaches the highest strength of 374 MPa after aging.The composition and strength of this alloy are quite close to GW103 K which is well recognized for its general mechanical performance in Mg-Gd-Y-Zr system.展开更多
In this study,α+βTi-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing(LAM)were designed according to a Ti-6Al-4V cluster formula.This formula can be expresse...In this study,α+βTi-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing(LAM)were designed according to a Ti-6Al-4V cluster formula.This formula can be expressed as 12[Al-Ti12](AlTi2)+5[Al-Ti14]((Mo,V,Nb)2Ti),in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb,Ti-5.97Al-2.33V-2.93Mo,and Ti-5.97Al-2.33V-2.20Mo-0.71Nb(wt.%).The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined.The sizes of theβcolumnar grains andαlaths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy,whereas Mo-or Mo/Nb-added alloys contain finer grains.It indicates that Nb gives rise to coarsenedβcolumnar grains andαlaths,while Mo significantly refines them.Furthermore,the single addition of Nb improves the elongation,whereas the single addition of Mo enhances the strength of the alloys.The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys,leading to the best properties with an ultimate tensile strength of 1,070 MPa,a yield strength of 1,004 MPa,an elongation of 9%,and micro-hardness of 355 HV.The fracture modes of all the alloys are ductile-brittle mixed fracture.展开更多
Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. ...Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. After a calculation using the cluster-plus-glue-atom model, the stable Mg-Gd structural unit is derived, [Gd-Mg12 ]Mg6, where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg12 ] and this cluster is matched with six Mg glue atoms. Such a local unit is then mixed with [Mg-Mg12 ]Mg3, the stable unit for pure Mg. Assuming that the Gd-containing units are arranged in fcc- or bcc-like lattice points and the Mg units in their octahedral interstices, three proportions between the two units are obtained, 1：1, 2：3, and 1：3, which constitute three solute homogenization modes. The prevailing Mg-Gd-based alloys are consequently classified into three groups, respectively exemplified by GW103 K （Mg-10Gd-3Y-0.4Zr, wt%）, GW83 K （Mg-SGd-3Y-0.4Zr）, and GW63 K （Mg-6Gd- 3Y-0.4Zr）. Mg-Gd-Y-Zr alloys were designed following the model （where Y and Zr were also added in substitution for Gd） and prepared by permanent-mould casting. According to their mechanical properties, the 1：3 alloy （Mg-5.9Gd-1.6Y-0.4Zr） shows the best comprehensive properties （ultimate tensile strength 305 MPa, yield strength 186 MPa, elongation 9.0%） in solution plus ageing state.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
It has been recently pointed out that the compositions of industrial alloys are originated from cluster-plus-glueatom structure units in solid solutions. Specifically for Ni-based superalloys, after properly grouping ...It has been recently pointed out that the compositions of industrial alloys are originated from cluster-plus-glueatom structure units in solid solutions. Specifically for Ni-based superalloys, after properly grouping the alloying elements into Al, Ni-like（Ni^-）, γ＇-forming Cr-like（Cr^-γ＇） and γ-forming Cr-like（Cr^-γ＇）, the optimal formula for single-crystal superalloys is established [Al–Ni^-12]（AlCr^-γ0：5Cr^-γ1：5）. The Co substitutions for Ni at the shell sites are conducted on the basis of the first-generation single-crystal superalloy AM3, formulated as [Al-Ni2-xCox]（Al1Ti0.25Ta0.25Cr1W0.25Mo0.25）, with x = 1.5, 1.75, 2 and 2.5（the corresponding weight percents of Co are 9.43, 11.0, 12.57 and 15.71, respectively）. The900 ℃ long-term aging follows the Lifshitz–Slyozov–Wagner theory（LSW theory）, and the Co content does not have noticeable influence on the coarsening rate of c0. The microstructure and creep behavior of the four（001） single-crystal alloys are investigated. The creep rupture lifetime is reduced as Co increases. The alloy with the lowest Co（9.43 Co） shows the longest lifetime of about 350 h at 1050 ℃/120 MPa, and all the samples show N-type rafting after creep tests.展开更多
Ti-Al-V-Zr quaternary titanium alloys were designed followingα-{[Al-Ti12](AlTi2)}17-n+β-{[Al-Ti12Zr2](V3)}n,where n=1-7(the number ofβunits),on the basis of the dual-cluster formula of popular Ti-6Al-4V alloy.Such ...Ti-Al-V-Zr quaternary titanium alloys were designed followingα-{[Al-Ti12](AlTi2)}17-n+β-{[Al-Ti12Zr2](V3)}n,where n=1-7(the number ofβunits),on the basis of the dual-cluster formula of popular Ti-6Al-4V alloy.Such an alloying strategy aims at strengthening the alloy via Zr and V co-alloying in theβ-Ti unit,based on the originalβformula[Al-Ti14](V2Ti)of Ti-6Al-4V alloy.The microstructures of the as-cast alloys by copper-mold suction-casting change from pureα(n=1)toα+α’martensite(n=7).When n is 6,Ti-5.6Al-6.8V-8.1Zr alloy reaches the highest ultimate tensile strength of 1,293 MPa and yield strength of 1,097 MPa,at the expense of a low elongation of 2%,mainly due to the presence of a large amount of acicularα’martensite.Its specific strength far exceeds that of Ti-6Al-4V alloy by 35%.展开更多
Superalloys feature multi-elements and complex elemental ranges,which makes the proper composition selection difficult.In fact,more strict composition standards generally apply in practical productions.The objective o...Superalloys feature multi-elements and complex elemental ranges,which makes the proper composition selection difficult.In fact,more strict composition standards generally apply in practical productions.The objective of this paper is to understand and eventually to renew the composition standard via example of the most common grade Inconel 718.We have recently shown that t he alloy chemistry originates from a nearest-neighbor cluster[center-shell]plus a few next-neighbor glue atoms,or expressed in cluster for-mula[center-shell](glue atoms).By grouping the elements into Ni=(Ni,Co,Cu,Fe),Cr=(Cr,Mn,Si,Mo),and Nb=(Nb,Al,Ti),it is found that the reported alloys fall within a narrow composition zone Ni_(11.0-13.0)-Cr_(3.5-4.5)-Nb_(1) confined by cluster formulas of 16 and 18 atoms.This composition zone is also expressed in terms of 288-atom supercluster formulas,Ni_(198-208)-Cr_(63-72)-Nb_(16-18),which leads to coordi-nated elemental variations in wt.%:69.0≤Ni+Co+Cu+Fe≤72.7;19.8≤Cr+Mn+1.7 Si+0.6 Mo≤22.8;8.7≤Nb+3.2 Al+1.9 Ti≤9.8.Within this composition zone,Ni_(206)-Cr_(65.5)-Nb_(16.5) is further pinpointed and validated by our own experiments to possess the optimal match of strength and plasticity both at room and at 923 K.展开更多
The segregation of Sn and discontinuous precipitation at grain boundaries are detrimental to the strength,ductility,and machinability of the Cu−Ni−Sn alloy.A strategy to solve the above problems is multi-component com...The segregation of Sn and discontinuous precipitation at grain boundaries are detrimental to the strength,ductility,and machinability of the Cu−Ni−Sn alloy.A strategy to solve the above problems is multi-component composition design by introducing strong enthalpic interaction element.In this work,a series of Cu_(80)Ni_(15)Sn_(5−x)Ti_(x)(at.%)alloys were designed by cluster-plus-glue-atom model,and the effects of Ti content on the microstructure and properties of the alloys were systematically investigated using TEM and other analysis methods.The results demonstrate that Ti can effectively inhibit the segregation and discontinuous precipitation while promoting continuous precipitation to improve the high-temperature stability of the alloys.As the Ti content increases,the distribution of Ti changes from uniform distribution to predominant precipitation.The hardness and conductivity of the alloy exceed those of the C72900(Cu−15Ni−8Sn(wt.%))commercial alloy and the Cu_(80)Ni_(15)Sn_(5)(at.%)reference alloy when Ti is in the solution state.展开更多
A novel Ti-6.38Al-3.87V-2.43Mo alloy was designed with a cluster formula of 12[Al-Ti12](V0.75Mo0.25Ti2)+4[Al-Ti12](Al3)by replacing Ti with Mo/V on the basis of the Ti-Al congruent alloy.The effects of laser power and...A novel Ti-6.38Al-3.87V-2.43Mo alloy was designed with a cluster formula of 12[Al-Ti12](V0.75Mo0.25Ti2)+4[Al-Ti12](Al3)by replacing Ti with Mo/V on the basis of the Ti-Al congruent alloy.The effects of laser power and scanning speed on the molten pool size,surface roughness,relative density,microstructure,and micro-hardness of single-track and bulk Ti-6.38Al-3.87V-2.43Mo samples prepared via laser additive manufacturing(LAM)were investigated.The results show that processing parameters significantly affect the formability,microstructure,and micro-hardness of the alloy.With decreasing laser power from 1,900 W to 1,000 W,the relative density is decreased from 99.86%to 90.91%due to the increase of lack-of-fusion;however,with increasing scanning speed,the relative density does not change significantly,but exceeds 99%.In particular,Ti-6.38Al-3.87V-2.43Mo samples of single-track and bulk exhibit a good formability under an input laser power of 1,900 W and a scanning speed of 8 mm·s_(-1),and display the lowest surface roughness(Ra=13.33μm)and the highest relative density(99.86%).Besides,the microstructure of LAM Ti-6.38Al-3.87V-2.43Mo alloy coarsens with increasing laser power or decreasing scanning speed due to the greater input energy reducing the cooling rate.The coarsening of the microstructure decreases the microhardness of the alloy.展开更多
Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpre...Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpreting Ti-6A1-4V and other popular dual-phaseα+βTi alloy s with well-established chemical compositions.Our model identifiedαmolecule-like structural unit that covers onlyαnearest-neighbor cluster along withαfew next-neighbor glue atoms,which can be represented as"[cluster](glue atoms)x".The structural units of theαandβphases in Ti-6Al-4V,α-[Al-Ti_(12)](AlTi_(2)),andβ-[Al-Ti_(14)](V2Ti),were derived first and were in an unusual unit ratio of about 2.33:1.To obtain an alloy composition formula that satisfied this unit ratio,the two clusters were treated as hard spheres of different radii and packed according to the clusterplusglueatom model.Our calculations determined that the Ti-6A1-4V alloy unit is composed of 12α-[Al-Ti_(12)](AlTi_(2))and 5β-[Al-Ti_(14)](V2Ti)units(Ti-6.05A1-3.94V wt.%),with the fractional volume of theβphase being 32.5 vol.%,which is in agreement with experimental data.Finally,we describe how the chemical formulas of theαand p phases explain the high temperature near-a alloys(such as Ti-1100,[Al-(Ti_(0.97)Zr_(0.03))_(12)](Al_(0.67)Si_(0.12)Sn_(0.18)Mo_(0.03))_(1.01)Ti_(1.99))and high-strengthβ-Ti alloys(such as Ti-5553,[Al-Ti_(14)](Al_(0.24)Fe_(0.03)Cr_(0.20)-Mo_(0.18)V0.35)_(2.45)Ti_(0.55)),respectively.展开更多
Each conventional alloy has its own specific compositions but the compositional origin is largely unknown due to our insufficient understanding about chemical shortrange ordering in the alloy,in particular,in the soli...Each conventional alloy has its own specific compositions but the compositional origin is largely unknown due to our insufficient understanding about chemical shortrange ordering in the alloy,in particular,in the solid-solution state.In the present paper,the compositions of metallic alloys are discussed and formulated,by unveiling the basic moleculelike structural units in solid solutions.Friedel oscillation theory,which describes the partial charge screening behavior in solid solutions,and henceforth the origin of short-range ordering,is applied to pin down the ideal chemical compositions of conventional metallic alloys.We propose that,at a specific composition,atoms self-assemble into an ideally ordered structure consisting of atoms residing in the nearestneighbor shell(denoted as cluster)plus those in the next outer shell(denoted as glue atoms),which can be formulated as[cluster](glue atoms).This simplified version of short-rangeorder structure represents the smallest charge-neutral and mean-density zone(termed as“chemical units”)and can be regarded as the‘molecules’of solid solutions.Accordingly,the chemical units and the corresponding molecule-like formulas for face-centered-cubic(FCC),hexagonal close-packed(HCP),and body-centered cubic(BCC)structures are analyzed and equations are obtained to identify the chemical formulas for FCC solid solutions.For instance,well-knownα-brass Cu-30 Zn alloy is formulated as[Zn-Cu_(12)]Zn4.Examples of aluminum alloys,superalloys and stainless steels are also illustrated,demonstrating the versatility of the present model to interpret chemically complex alloys.展开更多
Bulk amorphous formation in Ti-Cu-based multicomponent alloys, free of Ni, Pd and Be elements, were studied using the cluster-plus-glue-atom model. The basic cluster formula was revealed as [Ti9Cu6]Cu3 to explain the ...Bulk amorphous formation in Ti-Cu-based multicomponent alloys, free of Ni, Pd and Be elements, were studied using the cluster-plus-glue-atom model. The basic cluster formula was revealed as [Ti9Cu6]Cu3 to explain the best binary glass forming composition Ti50Cu50=Ti9Cu9, where the CN14 rhombi-dodecahedron Ti9Cu6 was the principal cluster in the devitrification phase CuTi. This basic cluster formula was further alloyed with Zr and Sn and a critical glass forming ability was reached at （Ti7.2Zr1.8）（Cus.72Sn0.28） and （Ti7.2Zr1.8）（Cu8.45Sn0.55） up to 5 mm in diameter by suction casting, which was the largest in Ti-Cu- based and Ni-, Pd- and Be-free alloys.展开更多
It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. He...It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. Here it is revealed that the same order is just hidden in the atomic global packing modes of the crystalline phases relevant to bulk metallic glasses. Among the multiple nearest-neighbor dusters devel- oped from all the non-equivalent atomic sites in a given phase, there always exists a principal duster, centered by which the spherical periodicity, both topologically and chemically, is the most distinct. Then the principal dusters plus specific glue atoms just constitute the cluster-plus-glue-atom structural units shared by both metallic glasses and the corresponding crystalline phases. It is further pointed out that the spherical periodicity order represents the common structural homology of crystalline and amorphous states in the medium-range through scrutinizing all binary bulk-glass-relevant phases in Cu-（Zr, Hf）, Ni-（Nb, Ta）, Al-Ca, and Pd-Si systems.展开更多
基金supported by the Natural Science Foundation of Shenyang,China(Grant No.22315605).
文摘A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al_(0.8)Si_(0.2)-Ti_(12)Zr_(2)](V_(0.8)Mo_(0.2)Nb_(1)Ti)features an enhancedβ-Ti via co-alloying of Zr,V,Mo,Nb and Si.The experimental results show that the cluster formula ofαandβphases in the novel alloy are respectivelyα-[Al-Ti_(11.5)Zr_(0.5)](Al_(1)Ti_(2))andβ-[Al_(0.8)Si_(0.2)-Ti_(13.2)Zr_(0.8)](V_(1)Mo_(0.4)Nb_(1.6)),both containing Zr elements.The fitted composition via the α andβphase cluster formulas has little difference with the actual alloy composition,suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design.After hot isostatic pressing(HIP),both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-βcolumnar grains,while the typical<100>texture disappears.Compared with Ti-6Al-4V,Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength(1,056 MPa)and higher ductility(14%)at room temperature and higher strength(580 MPa)at 550℃ after HIP,and can potentially serves as LMD materials.
基金financially supported by the National Natural Science Foundation of China(51674060)the Fundamental Research Funds for the Central Universities(DUT18LAB01).
文摘A novel Ni-Cr-Si-B filler metal with the cluster formula of[Cr-Ni12]B2Cr+[B-Ni8Cr]BSi Cr based on the cluster-plus-glue-atom model was designed for vacuum brazing GH4169 alloy.The effect of brazing temperature and brazing time on microstructure and shear strength of GH4169 alloy joints was investigated.The brazed seam was mainly composed ofγ-Ni solid solution.(Nb,Ti)-rich phase and(Cr,Nb,Mo)-rich borides distributed in diffusion zones.The diffusion and aggregation of B,Cr,Nb,and Mo resulted in the variation of phase contrast and morphology of borides.Coarse precipitations in the joint brazed at1240℃consisted of borides,Laves phase andδphase.The shear strength of joints was principally dominated by the brittle precipitations in diffusion zone,and the homogenization of microstructure improved the room-temperature shear strength to 820 MPa with the high-temperature shear strength of 627 MPa for the joint brazed at 1240℃/20 min.The joint fractured in diffusion zone and brazed seam,and the existence of borides and Laves phase in diffusion zone provide the potential origin for crack growth.
基金financially supported by the China Postdoctoral Science Foundation(No.2019M660482)Use of the Advanced Photon Source is supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357。
文摘Multi-principal element alloys(MPEAs)have shown extraordinary properties in different fields.However,the composition design of MPEAs is still challenging due to the complicated interactions among principal elements(PEs),and even more challenging with precipitates formation.Precipitation can be either beneficial or detrimental in alloys,thus it is important to control precipitates formation on purpose during alloy design.In this work,cluster-plus-glue-atom model(CGM)composition design method which is usually used to describe short-range order in traditional alloys has been successfully extended to MPEAs for precipitation design.The key challenge of extending CGM to MPEAs is the determination of center atom since there are no solvent or solute in MPEAs.Research has found that the element type of center atom was related not only with chemical affinity,but also with atomic volume difference in MPEAs,which has inevitable effect on atomic arrangement.Based on experimental data of MPEAs with precipitates,it was found that elements with either stronger chemical affinity or larger volume difference with other PEs would occupy the center site of clusters.Therefore,a cluster index(P_(C)),which considers both chemical affinity and atomic volume factors,was proposed to assist the determination of center atom in MPEAs.Based on the approach,a solid-solution Zr-Ti-V-Nb-Al BCC alloy was obtained by inhibiting the precipitation,while precipitation-strengthened Al-Cr-FeNi-V FCC alloy and Al-Co-Cr-Fe-Ni BCC alloy were designed by promoting the precipitation.Corresponding experimental results demonstrated that the approach could provide a relatively simple and accurate predication of precipitation and the compositions of precipitations were in line with PEs in cluster in MPEAs.The research may open an effective way for composition design of MPEAs with desired phase structure.
基金supported by the National Key Research and Development Program of China(Grant Nos.2020YFB2008305,2020YFB2008303).
文摘High-entropy alloys(HEAs)are based on solid solutions which characterized by chemical short-range ordering(CSRO),but there is no accurate structural tool to address CSRO characteristic,which obstacles precise composition design for HEAs.In this study,based on the cluster-plus-glue-atoms model,the composition law of Al-TMs(TMs,transition metals)HEAs with BCC and FCC structures was revealed.In BCC structure,with five elements in equi-atomic ratio,the composition formula of Al-TMs HEAs can be expressed by a cluster formula[Al-M_(14)]Al_(3),and in non equi-atomic ratio can be expressed by[Al-M_(14)]Al,where M is the average atom of the TMs.But in FCC structure,both Al-TMs HEAs with five elements in equiatomic and non equi-atomic ratios can be expressed by a cluster formula[Al-M_(12)]Al.To confirm the effectiveness of cluster formula for Al-TMs,two alloys were designed,[Al-Ti_(4)V_(3)Nb_(4)Mo_(3)]Mo and[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al.Results show that the[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al alloy has both higher strength and higher plastic deformation at room temperature.Besides,[Al-Ti_(3)V_(3)Nb_(4)Mo_(4)]Al alloy shows slower soften effect at 800℃,contributed to its higher strength.By substituting Ta for some of Mo,the strength of[Al-Ti_(3)V_(3)Nb_(4)Mo_(3)Ta]Al at room temperature and high temperature drastically decreases,suggesting that Ta element deteriorates the properties of Al-TMs alloys.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0701201)the Natural Science Foundation of China(No.11674045)。
文摘Mg-Gd-Y-Zr alloys with high strength fall within narrow composition range.The present paper explains their composition rule by establishing the cluster-plus-glue-atom unit of Gd-containing Mg solid solution with the aid of Mg matrix and Mg_(5) Gd precipitate phase.First,based on the structural homologue between Gd-containing Mg solid solution and Mg_(5) Gd precipitate phase and in combination with our previously established method for calculating the glue atoms,[Gd-Mg_(12)]Mg_(5) is obtained as the chemical unit of Gd-containing Mg solid solution.Then,seven compositions are designed using different combinations of this unit and that of pure Mg[Mg-Mg_(12)Mg3.After a systematic experimental investigation on the microstructure and mechanical property evolutions as a function of the unit proportions,it is revealed that the Mg-10.1 Gd-3.3 Y-0.9 Zr alloy,being issued from equi-proportion mixing of the two units,shows the strongest tendency of precipitation and reaches the highest strength of 374 MPa after aging.The composition and strength of this alloy are quite close to GW103 K which is well recognized for its general mechanical performance in Mg-Gd-Y-Zr system.
基金the National Key Research and Development Program of China(No.2016YFB1100103)the Key Discipline and Major Project of Dalian Science and Technology Innovation Foundation(No.2020JJ25CY004)。
文摘In this study,α+βTi-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing(LAM)were designed according to a Ti-6Al-4V cluster formula.This formula can be expressed as 12[Al-Ti12](AlTi2)+5[Al-Ti14]((Mo,V,Nb)2Ti),in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb,Ti-5.97Al-2.33V-2.93Mo,and Ti-5.97Al-2.33V-2.20Mo-0.71Nb(wt.%).The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined.The sizes of theβcolumnar grains andαlaths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy,whereas Mo-or Mo/Nb-added alloys contain finer grains.It indicates that Nb gives rise to coarsenedβcolumnar grains andαlaths,while Mo significantly refines them.Furthermore,the single addition of Nb improves the elongation,whereas the single addition of Mo enhances the strength of the alloys.The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys,leading to the best properties with an ultimate tensile strength of 1,070 MPa,a yield strength of 1,004 MPa,an elongation of 9%,and micro-hardness of 355 HV.The fracture modes of all the alloys are ductile-brittle mixed fracture.
基金supported financially by the National Key Research and Development Program of China (No. 2016YFB0701201)the Natural Science Foundation of China (No. 11674045)
文摘Composition homogenization in solid solution is important for industrial alloys. In the present work, a solute homogenization model is proposed based on the chemical short-range-order tendency in Mg-Gd- based alloys. After a calculation using the cluster-plus-glue-atom model, the stable Mg-Gd structural unit is derived, [Gd-Mg12 ]Mg6, where one solute Gd is nearest-neighbored with twelve Mg atoms to form the characteristic hcp cluster [Gd-Mg12 ] and this cluster is matched with six Mg glue atoms. Such a local unit is then mixed with [Mg-Mg12 ]Mg3, the stable unit for pure Mg. Assuming that the Gd-containing units are arranged in fcc- or bcc-like lattice points and the Mg units in their octahedral interstices, three proportions between the two units are obtained, 1：1, 2：3, and 1：3, which constitute three solute homogenization modes. The prevailing Mg-Gd-based alloys are consequently classified into three groups, respectively exemplified by GW103 K （Mg-10Gd-3Y-0.4Zr, wt%）, GW83 K （Mg-SGd-3Y-0.4Zr）, and GW63 K （Mg-6Gd- 3Y-0.4Zr）. Mg-Gd-Y-Zr alloys were designed following the model （where Y and Zr were also added in substitution for Gd） and prepared by permanent-mould casting. According to their mechanical properties, the 1：3 alloy （Mg-5.9Gd-1.6Y-0.4Zr） shows the best comprehensive properties （ultimate tensile strength 305 MPa, yield strength 186 MPa, elongation 9.0%） in solution plus ageing state.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金financially supported by the National Key Research and Development Program of China (Grant No. 2016YFB0701401)the National Natural Science Foundation of China (No. 11674045)
文摘It has been recently pointed out that the compositions of industrial alloys are originated from cluster-plus-glueatom structure units in solid solutions. Specifically for Ni-based superalloys, after properly grouping the alloying elements into Al, Ni-like（Ni^-）, γ＇-forming Cr-like（Cr^-γ＇） and γ-forming Cr-like（Cr^-γ＇）, the optimal formula for single-crystal superalloys is established [Al–Ni^-12]（AlCr^-γ0：5Cr^-γ1：5）. The Co substitutions for Ni at the shell sites are conducted on the basis of the first-generation single-crystal superalloy AM3, formulated as [Al-Ni2-xCox]（Al1Ti0.25Ta0.25Cr1W0.25Mo0.25）, with x = 1.5, 1.75, 2 and 2.5（the corresponding weight percents of Co are 9.43, 11.0, 12.57 and 15.71, respectively）. The900 ℃ long-term aging follows the Lifshitz–Slyozov–Wagner theory（LSW theory）, and the Co content does not have noticeable influence on the coarsening rate of c0. The microstructure and creep behavior of the four（001） single-crystal alloys are investigated. The creep rupture lifetime is reduced as Co increases. The alloy with the lowest Co（9.43 Co） shows the longest lifetime of about 350 h at 1050 ℃/120 MPa, and all the samples show N-type rafting after creep tests.
基金financially supported by the Key Discipline and Major Project of Dalian Science and Technology Innovation Foundation(Grant No.2020JJ25CY004)the National Basic Research Program of China(Grant No.2020JCJQZD165)。
文摘Ti-Al-V-Zr quaternary titanium alloys were designed followingα-{[Al-Ti12](AlTi2)}17-n+β-{[Al-Ti12Zr2](V3)}n,where n=1-7(the number ofβunits),on the basis of the dual-cluster formula of popular Ti-6Al-4V alloy.Such an alloying strategy aims at strengthening the alloy via Zr and V co-alloying in theβ-Ti unit,based on the originalβformula[Al-Ti14](V2Ti)of Ti-6Al-4V alloy.The microstructures of the as-cast alloys by copper-mold suction-casting change from pureα(n=1)toα+α’martensite(n=7).When n is 6,Ti-5.6Al-6.8V-8.1Zr alloy reaches the highest ultimate tensile strength of 1,293 MPa and yield strength of 1,097 MPa,at the expense of a low elongation of 2%,mainly due to the presence of a large amount of acicularα’martensite.Its specific strength far exceeds that of Ti-6Al-4V alloy by 35%.
基金supported by the Key Discipline and Major Project of Dalian Science and Technology Innovation Foun-dation(No.2020JJ25CY004).
文摘Superalloys feature multi-elements and complex elemental ranges,which makes the proper composition selection difficult.In fact,more strict composition standards generally apply in practical productions.The objective of this paper is to understand and eventually to renew the composition standard via example of the most common grade Inconel 718.We have recently shown that t he alloy chemistry originates from a nearest-neighbor cluster[center-shell]plus a few next-neighbor glue atoms,or expressed in cluster for-mula[center-shell](glue atoms).By grouping the elements into Ni=(Ni,Co,Cu,Fe),Cr=(Cr,Mn,Si,Mo),and Nb=(Nb,Al,Ti),it is found that the reported alloys fall within a narrow composition zone Ni_(11.0-13.0)-Cr_(3.5-4.5)-Nb_(1) confined by cluster formulas of 16 and 18 atoms.This composition zone is also expressed in terms of 288-atom supercluster formulas,Ni_(198-208)-Cr_(63-72)-Nb_(16-18),which leads to coordi-nated elemental variations in wt.%:69.0≤Ni+Co+Cu+Fe≤72.7;19.8≤Cr+Mn+1.7 Si+0.6 Mo≤22.8;8.7≤Nb+3.2 Al+1.9 Ti≤9.8.Within this composition zone,Ni_(206)-Cr_(65.5)-Nb_(16.5) is further pinpointed and validated by our own experiments to possess the optimal match of strength and plasticity both at room and at 923 K.
基金support from the National Natural Science Foundation of China(No.52071052).
文摘The segregation of Sn and discontinuous precipitation at grain boundaries are detrimental to the strength,ductility,and machinability of the Cu−Ni−Sn alloy.A strategy to solve the above problems is multi-component composition design by introducing strong enthalpic interaction element.In this work,a series of Cu_(80)Ni_(15)Sn_(5−x)Ti_(x)(at.%)alloys were designed by cluster-plus-glue-atom model,and the effects of Ti content on the microstructure and properties of the alloys were systematically investigated using TEM and other analysis methods.The results demonstrate that Ti can effectively inhibit the segregation and discontinuous precipitation while promoting continuous precipitation to improve the high-temperature stability of the alloys.As the Ti content increases,the distribution of Ti changes from uniform distribution to predominant precipitation.The hardness and conductivity of the alloy exceed those of the C72900(Cu−15Ni−8Sn(wt.%))commercial alloy and the Cu_(80)Ni_(15)Sn_(5)(at.%)reference alloy when Ti is in the solution state.
基金supported by the National Key Research and Development Program of China(No.2016YFB1100103)the Key Discipline and Major Project of Dalian Science and Technology Innovation Foundation(No.2020JJ25CY004).
文摘A novel Ti-6.38Al-3.87V-2.43Mo alloy was designed with a cluster formula of 12[Al-Ti12](V0.75Mo0.25Ti2)+4[Al-Ti12](Al3)by replacing Ti with Mo/V on the basis of the Ti-Al congruent alloy.The effects of laser power and scanning speed on the molten pool size,surface roughness,relative density,microstructure,and micro-hardness of single-track and bulk Ti-6.38Al-3.87V-2.43Mo samples prepared via laser additive manufacturing(LAM)were investigated.The results show that processing parameters significantly affect the formability,microstructure,and micro-hardness of the alloy.With decreasing laser power from 1,900 W to 1,000 W,the relative density is decreased from 99.86%to 90.91%due to the increase of lack-of-fusion;however,with increasing scanning speed,the relative density does not change significantly,but exceeds 99%.In particular,Ti-6.38Al-3.87V-2.43Mo samples of single-track and bulk exhibit a good formability under an input laser power of 1,900 W and a scanning speed of 8 mm·s_(-1),and display the lowest surface roughness(Ra=13.33μm)and the highest relative density(99.86%).Besides,the microstructure of LAM Ti-6.38Al-3.87V-2.43Mo alloy coarsens with increasing laser power or decreasing scanning speed due to the greater input energy reducing the cooling rate.The coarsening of the microstructure decreases the microhardness of the alloy.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB1100103)the Science Research Project of Liaoning Province Education Department(Grant No.JDL2019023)+1 种基金the Natural Science Foundation of Liaoning Province(Grant No.2020-BS-208)the Open Project of Key Laboratory of Materials Modification by Laser,Ion and Electron Beams(Grant No.KF2006)。
文摘Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpreting Ti-6A1-4V and other popular dual-phaseα+βTi alloy s with well-established chemical compositions.Our model identifiedαmolecule-like structural unit that covers onlyαnearest-neighbor cluster along withαfew next-neighbor glue atoms,which can be represented as"[cluster](glue atoms)x".The structural units of theαandβphases in Ti-6Al-4V,α-[Al-Ti_(12)](AlTi_(2)),andβ-[Al-Ti_(14)](V2Ti),were derived first and were in an unusual unit ratio of about 2.33:1.To obtain an alloy composition formula that satisfied this unit ratio,the two clusters were treated as hard spheres of different radii and packed according to the clusterplusglueatom model.Our calculations determined that the Ti-6A1-4V alloy unit is composed of 12α-[Al-Ti_(12)](AlTi_(2))and 5β-[Al-Ti_(14)](V2Ti)units(Ti-6.05A1-3.94V wt.%),with the fractional volume of theβphase being 32.5 vol.%,which is in agreement with experimental data.Finally,we describe how the chemical formulas of theαand p phases explain the high temperature near-a alloys(such as Ti-1100,[Al-(Ti_(0.97)Zr_(0.03))_(12)](Al_(0.67)Si_(0.12)Sn_(0.18)Mo_(0.03))_(1.01)Ti_(1.99))and high-strengthβ-Ti alloys(such as Ti-5553,[Al-Ti_(14)](Al_(0.24)Fe_(0.03)Cr_(0.20)-Mo_(0.18)V0.35)_(2.45)Ti_(0.55)),respectively.
基金supported by the National Natural Science Foundation of China(51801017)the Key Discipline and Major Project of Dalian Science and Technology Innovation Foundation(2020JJ25CY004)+3 种基金the Subject Development Foundation of Key Laboratory of Surface Physics and Chemistry(XKFZ201706)the State Key Lab of Advanced Metals and Materials(2018-Z03)the Scientific Challenge Program for National Defense Basic Scientific Research(TZ2016004)supported by the US National Science Foundation under Contract DMR-0905979。
文摘Each conventional alloy has its own specific compositions but the compositional origin is largely unknown due to our insufficient understanding about chemical shortrange ordering in the alloy,in particular,in the solid-solution state.In the present paper,the compositions of metallic alloys are discussed and formulated,by unveiling the basic moleculelike structural units in solid solutions.Friedel oscillation theory,which describes the partial charge screening behavior in solid solutions,and henceforth the origin of short-range ordering,is applied to pin down the ideal chemical compositions of conventional metallic alloys.We propose that,at a specific composition,atoms self-assemble into an ideally ordered structure consisting of atoms residing in the nearestneighbor shell(denoted as cluster)plus those in the next outer shell(denoted as glue atoms),which can be formulated as[cluster](glue atoms).This simplified version of short-rangeorder structure represents the smallest charge-neutral and mean-density zone(termed as“chemical units”)and can be regarded as the‘molecules’of solid solutions.Accordingly,the chemical units and the corresponding molecule-like formulas for face-centered-cubic(FCC),hexagonal close-packed(HCP),and body-centered cubic(BCC)structures are analyzed and equations are obtained to identify the chemical formulas for FCC solid solutions.For instance,well-knownα-brass Cu-30 Zn alloy is formulated as[Zn-Cu_(12)]Zn4.Examples of aluminum alloys,superalloys and stainless steels are also illustrated,demonstrating the versatility of the present model to interpret chemically complex alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos. 51131002 and 51171035)the Fundamental Research Funds for the Central Universities(Grant No. DUT12LAB08)
文摘Bulk amorphous formation in Ti-Cu-based multicomponent alloys, free of Ni, Pd and Be elements, were studied using the cluster-plus-glue-atom model. The basic cluster formula was revealed as [Ti9Cu6]Cu3 to explain the best binary glass forming composition Ti50Cu50=Ti9Cu9, where the CN14 rhombi-dodecahedron Ti9Cu6 was the principal cluster in the devitrification phase CuTi. This basic cluster formula was further alloyed with Zr and Sn and a critical glass forming ability was reached at （Ti7.2Zr1.8）（Cus.72Sn0.28） and （Ti7.2Zr1.8）（Cu8.45Sn0.55） up to 5 mm in diameter by suction casting, which was the largest in Ti-Cu- based and Ni-, Pd- and Be-free alloys.
基金supported by the Science Challenge Program (JCKY2016212A504)the National Natural Science Foundation of China(11674045)
文摘It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. Here it is revealed that the same order is just hidden in the atomic global packing modes of the crystalline phases relevant to bulk metallic glasses. Among the multiple nearest-neighbor dusters devel- oped from all the non-equivalent atomic sites in a given phase, there always exists a principal duster, centered by which the spherical periodicity, both topologically and chemically, is the most distinct. Then the principal dusters plus specific glue atoms just constitute the cluster-plus-glue-atom structural units shared by both metallic glasses and the corresponding crystalline phases. It is further pointed out that the spherical periodicity order represents the common structural homology of crystalline and amorphous states in the medium-range through scrutinizing all binary bulk-glass-relevant phases in Cu-（Zr, Hf）, Ni-（Nb, Ta）, Al-Ca, and Pd-Si systems.
