Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation beh...Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation behavior and microstructure evolution of millimeter-grade coarse grains(MCGs)in the as-cast Ti-6Cr-5Mo-5V-4Al(Ti-6554)alloy were studied,and a hot processing map was established.Under compression along the rolling direction(RD),continuous dynamic recrystallization(CDRX)ensues due to the progressive rotation of subgrains within the MCGs.Along the transverse direction(TD),discontinuous dynamic recrystallization(DDRX)resulting from grain boundary bulging or bridging,occurs on the boundaries of the MCGs.With decreasing strain rate,increasing temperature,and higher deformation degree,dynamic recrystallization becomes more pronounced,resulting in a reduction in the original average grain size.The optimal processing parameters fall within a temperature range of 1050-1150℃,a strain rate of 0.01 s^(-1),and a deformation degree between 40%and 60%.展开更多
Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of...Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.展开更多
The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average...The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.展开更多
To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceol...To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceolata) and poplar (triploid Populus tomentosa Carr) under different conditions was conducted. The results indicate that the residue rate decreases with the increase of liquefaction temperature, liquefaction time, catalyst content or liquid ratio. It is also found that the optimum condition of liquefaction for poplar is estimated as: the reaction temperature of 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4.5 and catalyst content of 8%, and 4.2% residue rate could be obtained. Under the processing parameters of temperature 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4 and catalyst content of 10%, the residue rate of Chinese fir can reach 5.6%.展开更多
As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet t...As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet transition are critical to high quality figuration. The effects of various processing parameters on figuration quality were studied in the experiment of GMA W rapid prototyping using the wire of ERSO-6 , including welding voltage, wire feeding rate, welding speed and so on. The optimal parameters for ERSO-6 are obtained. Simultaneously, it is verified that the rapid prototyping parts with favorable structures and quality can be achieved under the conditions of low heat input and stable droplet transition.展开更多
The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying th...The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.展开更多
The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testin...The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testing was performed in various Zn and Mg contents under different annealing and cold-rolling conditions. In the results, the stress drop and reloading time of serrations increase with increasing plastic strain and exhibit a common linear relationship. The increase rates of stress drop and reloading time increase with increasing Mg or Zn content. The alloys with a greater intensity of serrated yielding generally exhibit a greater elongation. The stress drop and reloading time of serrations decrease with increasing grain size in the case of the annealed samples. The cold-rolled sample exhibits the most severe serra- tion because it initially contains a large number of grain boundaries and dislocations.展开更多
Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot ...Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.展开更多
Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to pr...Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to produce porous Mg degradable implants.However,the microstructure evolution and mechanical properties of the SLMed NZ30K Mg alloy were not yet studied systematically.Therefore,the fabrication defects,microstructure,and mechanical properties of the SLMed NZ30K alloy under different processing parameters were investigated.The results show that there are two types of fabrication defects in the SLMed NZ30K alloy,gas pores and unfused defects.With the increase of the laser energy density,the porosity sharply decreases to the minimum first and then slightly increases.The minimum porosity is 0.49±0.18%.While the microstructure varies from the large grains with lamellar structure inside under low laser energy density,to the large grains with lamellar structure inside&the equiaxed grains&the columnar grains under middle laser energy density,and further to the fine equiaxed grains&the columnar grains under high laser energy density.The lamellar structure in the large grain is a newly observed microstructure for the NZ30K Mg alloy.Higher laser energy density leads to finer grains,which enhance all the yield strength(YS),ultimate tensile strength(UTS)and elongation,and the best comprehensive mechanical properties obtained are YS of 266±2.1 MPa,UTS of 296±5.2 MPa,with an elongation of 4.9±0.68%.The SLMed NZ30K Mg alloy with a bimodal-grained structure consisting of fine equiaxed grains and coarser columnar grains has better elongation and a yield drop phenomenon.展开更多
Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained co...Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.展开更多
The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of th...The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.展开更多
In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in construct...In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.展开更多
The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6A...The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6Al-2Zr-1Mo-1V alloy were investigated in this work.The result shows that laser power acts a dominant role in determining the relative density in comparison with scanning speed and hatch space.The optimal SLM process window for fabricating relative density>99%samples is located in the energy density range of 34.72 J·mm^(-3)to 52.08 J·mm^(-3),where the laser power range is between 125 W and 175 W.An upward trend is found in the micro-hardness as the energy density is increased.The optimum SLM processing parameters of Ti-6Al-2Zr-1Mo-1V alloy are:laser power of 150 W,scanning speed of 1,600 mm·s^(-1),hatch space of 0.08 mm,and layer thickness of 0.03 mm.The highest ultimate tensile strength,yield strength,and ductility under the optimum processing parameter are achieved,which are 1,205 MPa,1,099 MPa,and 8%,respectively.The results of this study can be used to guide SLM production Ti-6Al-2Zr-1Mo-1V alloy parts.展开更多
Al-3Ti-1B master alloys were prepared at different processing parameters by the reaction of halide salts,and the grain refining response of Al-7Si alloy was investigated with Al-3Ti-B master alloy.The microstructure o...Al-3Ti-1B master alloys were prepared at different processing parameters by the reaction of halide salts,and the grain refining response of Al-7Si alloy was investigated with Al-3Ti-B master alloy.The microstructure of master alloy and its grain refining effect on Al-7Si alloy were investigated by means of OM,XRD and SEM.Experimental results show that,the size of Al3Ti particles presented in Al-3Ti-1B master alloys increases with the increase of reaction temperature and decreases with the increase of cooling rate.The grain refining efficiency of Al-3Ti-1B master alloy on Al-7Si alloy is mainly attributed to heterogeneous nucleation of Al3Ti particles,and the morphology ofα(Al)changes from coarse dendritic to fine equiaxed.As a result,Al-3Ti-1B master alloy is prepared by permanent mold,and holding at 800 ℃for 30min,which has better grain refining performance on Al-7Si alloy.展开更多
The influence of processing parameters on the coating surface roughness of LD10 aluminum alloy treated by the power source with positive and negative pulse in the alkaline electrolyte was discussed.Lots of experiments...The influence of processing parameters on the coating surface roughness of LD10 aluminum alloy treated by the power source with positive and negative pulse in the alkaline electrolyte was discussed.Lots of experiments were done with different processing parameters including the positive final voltage,the negative final voltage,the frequency,the duty ratio,the processing time and electrolyte temperature.And the surface roughness tester TR200 was used to measure the coating surface roughness.The influence of the processing time on the surface roughness is the smallest,less than 0.2μm.The surface roughness decreases gradually with the duty ratio decreasing or the frequency increasing;it decreases gradually with each of the other parameters increasing,and then increases gradually after achieving the minimum value.Appropriately by selecting processing parameters,the coating with Ra 0.6 can be obtained.展开更多
In order to investigate the effects of powder materials and processing parameters on thermal and stress field during laser powder deposition （LPD）, a finite element model was developed with the help of ANSYS softwar...In order to investigate the effects of powder materials and processing parameters on thermal and stress field during laser powder deposition （LPD）, a finite element model was developed with the help of ANSYS software. The finite element model was verified by the comparison between the experimental results and computed results. Then LPD processes with different powder materials and processing parameters were simulated by using the FE model. The results show that less difference of thermal conductivity and thermal expansion coefficient between powder material and substrate material produces lower residual stress; higher laser power, laser scanning speed and smaller laser beam diameter can lead higher peak temperature and higher residual stress. The research opens up a way to rational selection of the powder materials and processing parameters for ensured quality.展开更多
The investigating of the hot press process parameters on the flexural properties of LVL （Laminated Veneer Lumber） reinforced composites derived from rubber wood veneer reinforced with fiber glass woven and epoxy adh...The investigating of the hot press process parameters on the flexural properties of LVL （Laminated Veneer Lumber） reinforced composites derived from rubber wood veneer reinforced with fiber glass woven and epoxy adhesive were performed via the DOE （design of experimental） approach. It was discovered that pressure was the most significantly and negatively effect on the product properties. Enhancing in the mechanical properties was related to decrease the processing pressure. Beside, press time was also significantly and positively effect. Although time was not clearly reflect from the mechanical results, but it was detected from the ANOVA （analysis of variance）results. The mechanical properties were increased with increasing compression time. From the results, the optimal condition to maximize mechanical properties was assumed at low pressure, 15 bars, low temperature, 70℃, and long time, 60 mins. The durability testing including screw nail withdrawal strength, water absorption, and termite resistance of LVL reinforced composite were also studied. The results are shown that the LVL wood has superior properties when compare with solid woods. It was found the withdrawal strength of LVL reinforce composite was higher than the solid woods. As expected that solid woods, except eucalyptus, had low water absorption resistance as it more hygroscopic corresponded to LVL reinforced wood. Also solid woods, except teal（, had low resistance to termite attack. Therefore, LVL reinforced was the best candidate by mean of durability properties compared to solid wood.展开更多
We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the sur...We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the surface of samples due to LSP. The maximum compressive residual stress at the surface by two LSP impacts on one side is higher than that by one LSP impact. The maximum value of tensile residual stress is found at the mid-plane of samples subjected to two-sided LSP. Compared with fatigue lives of samples treated by single-sided LSP, lives of those treated by two-sided LSP are lower. However, these are higher than untreated ones.展开更多
The unique properties of bulk metallic glass(BMG)render it an excellent material for bone-implant applications.BMG samples are difficult to produce directly because of the critical cooling rate of molding.Advancements...The unique properties of bulk metallic glass(BMG)render it an excellent material for bone-implant applications.BMG samples are difficult to produce directly because of the critical cooling rate of molding.Advancements in additive manufacturing technologies,such as selective laser melting(SLM),have enabled the development of BMG.The successful production of materials via SLM relies significantly on the processing parameters;meanwhile,the overall energy density affects the crystallization and,thus,the final properties.Therefore,to further determine the effects of the processing parameters,SLM is performed in this study to print Fe-based BMG with different properties three dimensionally using selected processing parameters but a constant energy density.The printed amorphous Fe-based BMG outperforms the typical 316 L stainless steel(316 L SS)in terms of mechanical properties and corrosion resistance.Moreover,observations from nanoindentation tests indicate that the hardness and elastic modulus of the Fe-based BMG can be customized explicitly by adjusting the SLM processing parameters.Indirect cytotoxicity results show that the Fe-based BMG can enhance the viability of SAOS2 cells,as compared with 316 L SS.These intriguing results show that Fe-based BMG should be investigated further for orthopedic implant applications.展开更多
Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping cap...Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping capabilities based on photopolymerization.However,owing to differences in the curing behavior and physical properties of different materials,multimaterial DLP 3D printing faces challenges such as insufficient interfacial bonding strength and unstable mechanical properties.In this study,two resins were integrated by multimaterial DLP 3D printing technology,and the effects of different layer thicknesses and exposure times on the interfacial bonding strength and morphology of the multimaterials were systematically investigated.The interfacial bonding mechanisms of the two resins was analyzed.It was found that increasing the exposure time can improve the interfacial bonding strength between materials,but certain limitations exist.A mathematical model relating the interfacial bonding strength to the exposure time and layer thickness was developed,and optimal process parameters were determined using optimization algorithms.A variable-parameter printing strategy for the interface was proposed to further improve the performance of printed parts.The maximum tensile strength of the multimaterial samples(44.43 MPa)using this strategy reached that of single-material parts(45 MPa),validating the feasibility of this strategy.This provides guidance for multimaterial DLP 3D printing processes and offers valuable insights for the future additive manufacturing of high-performance multimaterial components.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3706901,2022YFB3706903)the National Natural Science Foundation of China(No.52274382)。
文摘Hot compression experiments were conducted under conditions of deformation temperatures ranging from 950 to 1150℃,strain rates of 0.001-10 s^(-1),and deformation degrees ranging from 20%to 80%.The hot deformation behavior and microstructure evolution of millimeter-grade coarse grains(MCGs)in the as-cast Ti-6Cr-5Mo-5V-4Al(Ti-6554)alloy were studied,and a hot processing map was established.Under compression along the rolling direction(RD),continuous dynamic recrystallization(CDRX)ensues due to the progressive rotation of subgrains within the MCGs.Along the transverse direction(TD),discontinuous dynamic recrystallization(DDRX)resulting from grain boundary bulging or bridging,occurs on the boundaries of the MCGs.With decreasing strain rate,increasing temperature,and higher deformation degree,dynamic recrystallization becomes more pronounced,resulting in a reduction in the original average grain size.The optimal processing parameters fall within a temperature range of 1050-1150℃,a strain rate of 0.01 s^(-1),and a deformation degree between 40%and 60%.
基金Projects (50905144, 50875216) supported by the National Natural Science Foundation of ChinaProject (09-10) supported by the State Key Laboratory of Materials Processing and Die & Mould Technology, ChinaProject (JC201028) supported by the Northwestern Polytechnical University Foundation for Fundamental Research, China
文摘Thin-walled aluminum alloy tube numerical control （NC） bending with small bending radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element （FE） simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC bending d50 mm×1 mm×75 mm and d70 mm×1.5 mm×105 mm （initial tube outside diameter D0 × initial tube wall thickness t0 × bending radius R）, and qualified tubes are produced.
基金supported by the National Natural Science Foundation of China (No. 50274021)
文摘The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.
基金Supported by the Key Research Program Foundation of Ministry of Education of China (Grant No.02021) and the Development Plan Foundation of Beijing Forestry University
文摘To clarify the influencing factors of liquefaction of wood in phenol using phosphoric acid as a catalyst and get its liquefaction technology, a study on the liquefaction technology of Chinese fir (Cunninghamia lanceolata) and poplar (triploid Populus tomentosa Carr) under different conditions was conducted. The results indicate that the residue rate decreases with the increase of liquefaction temperature, liquefaction time, catalyst content or liquid ratio. It is also found that the optimum condition of liquefaction for poplar is estimated as: the reaction temperature of 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4.5 and catalyst content of 8%, and 4.2% residue rate could be obtained. Under the processing parameters of temperature 180 C, the reaction time of 2.5 h, liquid ratio (phenol/wood ratio) of 4 and catalyst content of 10%, the residue rate of Chinese fir can reach 5.6%.
文摘As a deposition technology, gas metal arc welding （GMAW） has shown new promise for rapid prototyping of metallic parts. During the process of metal forming using the arc of GMA W, low heat input and stable droplet transition are critical to high quality figuration. The effects of various processing parameters on figuration quality were studied in the experiment of GMA W rapid prototyping using the wire of ERSO-6 , including welding voltage, wire feeding rate, welding speed and so on. The optimal parameters for ERSO-6 are obtained. Simultaneously, it is verified that the rapid prototyping parts with favorable structures and quality can be achieved under the conditions of low heat input and stable droplet transition.
基金the Tertiary Education Support Program (TESP) of ESKOM for financial support
文摘The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy （AA5754） and commercially pure copper （C11000） was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.
基金financially supported by the National Natural Science Foundation of China(No.51301017)the Fundamental Research Funds for the Central Universities of China(No.FRF-TP-13-034A)
文摘The effects of alloying elements and processing parameters on the mechanical properties and Portevin-Le Chatelier effect of A1-Mg alloys developed for inner auto body sheets were investigated in detail. Tensile testing was performed in various Zn and Mg contents under different annealing and cold-rolling conditions. In the results, the stress drop and reloading time of serrations increase with increasing plastic strain and exhibit a common linear relationship. The increase rates of stress drop and reloading time increase with increasing Mg or Zn content. The alloys with a greater intensity of serrated yielding generally exhibit a greater elongation. The stress drop and reloading time of serrations decrease with increasing grain size in the case of the annealed samples. The cold-rolled sample exhibits the most severe serra- tion because it initially contains a large number of grain boundaries and dislocations.
基金financially supported by the National Key Research and Development Program of China(Grant No.2020YFB2008300)。
文摘Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.
基金financial supports from the National Natural Science Foundation of China(52130104,51821001)High Technology and Key Development Project of Ningbo,China(2019B10102)。
文摘Mg–3Nd–0.2Zn–0.4Zr(NZ30K,wt.%)alloy is a new kind of high-performance metallic biomaterial.The combination of the NZ30K Magnesium(Mg)alloy and selective laser melting(SLM)process seems to be an ideal solution to produce porous Mg degradable implants.However,the microstructure evolution and mechanical properties of the SLMed NZ30K Mg alloy were not yet studied systematically.Therefore,the fabrication defects,microstructure,and mechanical properties of the SLMed NZ30K alloy under different processing parameters were investigated.The results show that there are two types of fabrication defects in the SLMed NZ30K alloy,gas pores and unfused defects.With the increase of the laser energy density,the porosity sharply decreases to the minimum first and then slightly increases.The minimum porosity is 0.49±0.18%.While the microstructure varies from the large grains with lamellar structure inside under low laser energy density,to the large grains with lamellar structure inside&the equiaxed grains&the columnar grains under middle laser energy density,and further to the fine equiaxed grains&the columnar grains under high laser energy density.The lamellar structure in the large grain is a newly observed microstructure for the NZ30K Mg alloy.Higher laser energy density leads to finer grains,which enhance all the yield strength(YS),ultimate tensile strength(UTS)and elongation,and the best comprehensive mechanical properties obtained are YS of 266±2.1 MPa,UTS of 296±5.2 MPa,with an elongation of 4.9±0.68%.The SLMed NZ30K Mg alloy with a bimodal-grained structure consisting of fine equiaxed grains and coarser columnar grains has better elongation and a yield drop phenomenon.
文摘Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.
文摘The Mg_(2)Si-matrix thermoelectric material was synthesized by low temperature solid-state reaction.This paper studies the effects of holding time and reaction temperature on the particle size and the properties of the material,and also studies effects of doping elemental Sb,Te and their doping seqence on the properties of the material.The result shows that excessively high temperature and elongated holding time of solid-state reaction are harmful,there is a range of particle size to ensure optimum properties and the doping sequence of Sb or Te without influencing the properties.
基金supported by Major Special Science and Technology Project of Yunnan Province 202002AB080001-3the National Natural Science Foundation of China(no.51704088)Fundamental Research and Development Program of China(Grant no.JCKY2017205B032)。
文摘In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.
基金supported by Liaoning Doctoral Research Start-up Fund project(Grant No.2023-BS-215).
文摘The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6Al-2Zr-1Mo-1V alloy were investigated in this work.The result shows that laser power acts a dominant role in determining the relative density in comparison with scanning speed and hatch space.The optimal SLM process window for fabricating relative density>99%samples is located in the energy density range of 34.72 J·mm^(-3)to 52.08 J·mm^(-3),where the laser power range is between 125 W and 175 W.An upward trend is found in the micro-hardness as the energy density is increased.The optimum SLM processing parameters of Ti-6Al-2Zr-1Mo-1V alloy are:laser power of 150 W,scanning speed of 1,600 mm·s^(-1),hatch space of 0.08 mm,and layer thickness of 0.03 mm.The highest ultimate tensile strength,yield strength,and ductility under the optimum processing parameter are achieved,which are 1,205 MPa,1,099 MPa,and 8%,respectively.The results of this study can be used to guide SLM production Ti-6Al-2Zr-1Mo-1V alloy parts.
文摘Al-3Ti-1B master alloys were prepared at different processing parameters by the reaction of halide salts,and the grain refining response of Al-7Si alloy was investigated with Al-3Ti-B master alloy.The microstructure of master alloy and its grain refining effect on Al-7Si alloy were investigated by means of OM,XRD and SEM.Experimental results show that,the size of Al3Ti particles presented in Al-3Ti-1B master alloys increases with the increase of reaction temperature and decreases with the increase of cooling rate.The grain refining efficiency of Al-3Ti-1B master alloy on Al-7Si alloy is mainly attributed to heterogeneous nucleation of Al3Ti particles,and the morphology ofα(Al)changes from coarse dendritic to fine equiaxed.As a result,Al-3Ti-1B master alloy is prepared by permanent mold,and holding at 800 ℃for 30min,which has better grain refining performance on Al-7Si alloy.
基金The work was supported by the Innovation Fund for Small Technology-based Firms for Harbin DS Numerical Control Equipment Co.,Ltd.Samples,the micro-arcoxidation equipment and chemicals were provided by thecompany。
文摘The influence of processing parameters on the coating surface roughness of LD10 aluminum alloy treated by the power source with positive and negative pulse in the alkaline electrolyte was discussed.Lots of experiments were done with different processing parameters including the positive final voltage,the negative final voltage,the frequency,the duty ratio,the processing time and electrolyte temperature.And the surface roughness tester TR200 was used to measure the coating surface roughness.The influence of the processing time on the surface roughness is the smallest,less than 0.2μm.The surface roughness decreases gradually with the duty ratio decreasing or the frequency increasing;it decreases gradually with each of the other parameters increasing,and then increases gradually after achieving the minimum value.Appropriately by selecting processing parameters,the coating with Ra 0.6 can be obtained.
文摘In order to investigate the effects of powder materials and processing parameters on thermal and stress field during laser powder deposition （LPD）, a finite element model was developed with the help of ANSYS software. The finite element model was verified by the comparison between the experimental results and computed results. Then LPD processes with different powder materials and processing parameters were simulated by using the FE model. The results show that less difference of thermal conductivity and thermal expansion coefficient between powder material and substrate material produces lower residual stress; higher laser power, laser scanning speed and smaller laser beam diameter can lead higher peak temperature and higher residual stress. The research opens up a way to rational selection of the powder materials and processing parameters for ensured quality.
文摘The investigating of the hot press process parameters on the flexural properties of LVL （Laminated Veneer Lumber） reinforced composites derived from rubber wood veneer reinforced with fiber glass woven and epoxy adhesive were performed via the DOE （design of experimental） approach. It was discovered that pressure was the most significantly and negatively effect on the product properties. Enhancing in the mechanical properties was related to decrease the processing pressure. Beside, press time was also significantly and positively effect. Although time was not clearly reflect from the mechanical results, but it was detected from the ANOVA （analysis of variance）results. The mechanical properties were increased with increasing compression time. From the results, the optimal condition to maximize mechanical properties was assumed at low pressure, 15 bars, low temperature, 70℃, and long time, 60 mins. The durability testing including screw nail withdrawal strength, water absorption, and termite resistance of LVL reinforced composite were also studied. The results are shown that the LVL wood has superior properties when compare with solid woods. It was found the withdrawal strength of LVL reinforce composite was higher than the solid woods. As expected that solid woods, except eucalyptus, had low water absorption resistance as it more hygroscopic corresponded to LVL reinforced wood. Also solid woods, except teal（, had low resistance to termite attack. Therefore, LVL reinforced was the best candidate by mean of durability properties compared to solid wood.
基金supported by the National Natural Science Foundation of China under Grant Nos. 50705038and 50735001
文摘We address the effects of processing parameters on residual stresses and fatigue properties of LY2 Al alloy by laser shock processing （LSP）. Results show that compressive residual stresses are generated near the surface of samples due to LSP. The maximum compressive residual stress at the surface by two LSP impacts on one side is higher than that by one LSP impact. The maximum value of tensile residual stress is found at the mid-plane of samples subjected to two-sided LSP. Compared with fatigue lives of samples treated by single-sided LSP, lives of those treated by two-sided LSP are lower. However, these are higher than untreated ones.
基金National Natural Science Foundation of China(Grant Nos.51875379,52105342)China Scholarship Council via a research collaboration with National University of Singapore Additive Manufacturing Centre.
文摘The unique properties of bulk metallic glass(BMG)render it an excellent material for bone-implant applications.BMG samples are difficult to produce directly because of the critical cooling rate of molding.Advancements in additive manufacturing technologies,such as selective laser melting(SLM),have enabled the development of BMG.The successful production of materials via SLM relies significantly on the processing parameters;meanwhile,the overall energy density affects the crystallization and,thus,the final properties.Therefore,to further determine the effects of the processing parameters,SLM is performed in this study to print Fe-based BMG with different properties three dimensionally using selected processing parameters but a constant energy density.The printed amorphous Fe-based BMG outperforms the typical 316 L stainless steel(316 L SS)in terms of mechanical properties and corrosion resistance.Moreover,observations from nanoindentation tests indicate that the hardness and elastic modulus of the Fe-based BMG can be customized explicitly by adjusting the SLM processing parameters.Indirect cytotoxicity results show that the Fe-based BMG can enhance the viability of SAOS2 cells,as compared with 316 L SS.These intriguing results show that Fe-based BMG should be investigated further for orthopedic implant applications.
基金supported by National Key R&D Program of China(Grant No.2022YFB4600103)National Youth Talent Support Program,China Postdoctoral Science Foundation(Grant No.2021M692555)+1 种基金Shaanxi Province Qinchuangyuan'Scientists+Engineers'Team Building Project(Grant No.2023KXJ-266)Fundamental Research Funds for the Central Universities(Grant No.xzy012023145)。
文摘Multimaterial digital light processing(DLP)three-dimensional(3D)printing technology provides unique advantages in the field of multi material additive manufacturing(MM AM)with its high resolution and rapid shaping capabilities based on photopolymerization.However,owing to differences in the curing behavior and physical properties of different materials,multimaterial DLP 3D printing faces challenges such as insufficient interfacial bonding strength and unstable mechanical properties.In this study,two resins were integrated by multimaterial DLP 3D printing technology,and the effects of different layer thicknesses and exposure times on the interfacial bonding strength and morphology of the multimaterials were systematically investigated.The interfacial bonding mechanisms of the two resins was analyzed.It was found that increasing the exposure time can improve the interfacial bonding strength between materials,but certain limitations exist.A mathematical model relating the interfacial bonding strength to the exposure time and layer thickness was developed,and optimal process parameters were determined using optimization algorithms.A variable-parameter printing strategy for the interface was proposed to further improve the performance of printed parts.The maximum tensile strength of the multimaterial samples(44.43 MPa)using this strategy reached that of single-material parts(45 MPa),validating the feasibility of this strategy.This provides guidance for multimaterial DLP 3D printing processes and offers valuable insights for the future additive manufacturing of high-performance multimaterial components.
