The novel idea of alloying,which is based on the utilization of multiple principal elements in high concentrations,has created a novel class of promising materials called high entropy alloys(HEAs).So far,several HEAs ...The novel idea of alloying,which is based on the utilization of multiple principal elements in high concentrations,has created a novel class of promising materials called high entropy alloys(HEAs).So far,several HEAs with outstanding properties beyond those of conventional alloys have been discovered,and new superior high-entropy alloys are still expected to be developed in the future.However,the fabrication process of HEAs through conventional manufacturing techniques suffers from significant limitations due to the intrinsic requirements of HEAs.Additive manufacturing(AM),on the other hand,has provided new opportunities for fabricating geometrically complex HEAs with the possibility of in situ tailoring of their microstructure features.Considering the growing interest in AM of HEAs during most recent years,this review article aims at providing the state of the art in AM of HEAs.It describes the feedstock requirements for laser based AM techniques.Thereafter,a comprehensive picture of the current state of nearly all HEAs processed by laser metal deposition(LMD),selective laser melting(SLM)and selective electron beam melting(SEBM)is presented.Special attention is paid to the features of AM derived microstructures along with their outstanding properties and underlying mechanisms for various material processing combinations.The AM of interstitial solute hardening HEAs,HEA matrix composites as well as non-beam based AM of HEAs will also be addressed.The post-AM treatments and the strategies to fabricate defect-free HEAs are summarized.Finally,a conclusion of current state and future prospects of additive manufacturing of HEAs will be presented.展开更多
The bonding of steel and mushy Al 28Pb alloy was studied. The relationship model about preheat temperature of steel plate, solid fraction of mushy Al 28Pb alloy, rolling speed and interfacial shear strength of the bon...The bonding of steel and mushy Al 28Pb alloy was studied. The relationship model about preheat temperature of steel plate, solid fraction of mushy Al 28Pb alloy, rolling speed and interfacial shear strength of the bonding plate was established by artificial neural network perfectly. This model can be optimized by a genetic algorithm, and the optimum bonding parameters for the largest interfacial shear strength are: 546 ℃ for preheat temperature of steel plate, 43.5% for solid fraction of mushy Al 28Pb alloy and 8.6 mm/s for rolling speed, and the corresponding largest interfacial shear strength of bonding plate is 70.3 MPa. [展开更多
The nonequilibrium diffusion of liquid aluminum atoms in cross direction in the innerpart of the solid steel base has been realized by using methods such as roughening steel plate surface, immersing flux on steel plat...The nonequilibrium diffusion of liquid aluminum atoms in cross direction in the innerpart of the solid steel base has been realized by using methods such as roughening steel plate surface, immersing flux on steel plate surface and short time diffusion, and the interface of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction was formed by using rapid solidification. The interfacial structure was studied by means of electron probe microanalysis. The results showed that the interfacial structure of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction is quite different from that of solid steel and liquid aluminum under conventional diffusion, that is, the interface of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction is made up of groups of Al 13 Fe 4 teeth (which grew from the contact surface to steel base inner) at the bulges of steel plate surface and Fe Al solid solution (whose Al content is less than 3.5%) at the concaves of steel plate surface between the groups of Al 13 Fe 4 teeth.展开更多
To obtain the billet with homogeneous and spheroidized primary grains is the key step in the semi- solid forming process. Among the semi-solid billet preparation methods, the process of low-superheat direct chill （DC...To obtain the billet with homogeneous and spheroidized primary grains is the key step in the semi- solid forming process. Among the semi-solid billet preparation methods, the process of low-superheat direct chill （DC） casting is simpler and more effective. In this study, the billets of AISi7Mg alloy were prepared by low- superheat DC casting at various withdrawal rates. The effect of withdrawal rate on the surface quality of the billets was investigated, and the evolution mechanism of the microstructural morphology in the billets was analyzed. The results show that the periodic corrugations and a large quantity of fine shrinkage pits appear in the billet surface when the withdrawal rate is 100 mm.min-1, and the above defects in the billet surface can be eliminated completely when the withdrawal rate is above 150 mm.min-1. But when the withdrawal rate is too fast （250 mm.min-1）, the primary a grains, except the ones in the billet center, have not enough time for ripening due to the high silidification rate, and will solidify as the dendrite structure. When the withdrawal rate is between 150 - 200 mm.min-1, the dendritic growth of the primary a grains is effectively inhibited, and a billet of AISi7Mg alloy with a smooth surface and homogeneous, fine, non-dendritic grains can be obtained.展开更多
The main difference of this work from Hiroshi Nagai’sis the integral of separating force on the roller-dles. A precise equation of the contact are is proposed and used in the integral so that an analytical solution o...The main difference of this work from Hiroshi Nagai’sis the integral of separating force on the roller-dles. A precise equation of the contact are is proposed and used in the integral so that an analytical solution of drawing force is obtained. Thus, as a different conclusion, the new solution is in connection with the friction coefficient. The meanvalue theorem and horizontal force equilibrium are used in determining the roller-die pressure. The solutions are compared with those from Hiroshi Nagai’s.展开更多
Ⅰ. INTRODUCTION Experimental data show that the larger the yield stresses of materials are, the smaller the coefficients of linear expansion will be, and the reverse is also true. In this note, we study whether there...Ⅰ. INTRODUCTION Experimental data show that the larger the yield stresses of materials are, the smaller the coefficients of linear expansion will be, and the reverse is also true. In this note, we study whether there is a certain relationship between yield stress and coefficient of linear expansion.展开更多
Hamilton and ZHOU Shan-you reported that, because the high strength aluminium alloy 7075 contains more Fe and Si impurities than the high strength aluminium alloy 7475 does, its superplastic elongation is lower than t...Hamilton and ZHOU Shan-you reported that, because the high strength aluminium alloy 7075 contains more Fe and Si impurities than the high strength aluminium alloy 7475 does, its superplastic elongation is lower than the maximum elongation 1200% of 7475 aluminium alloy. ZHOU Shan-you has obtained the maximum elongation 500% of展开更多
Since the slightly compressible method in R. P. FEM (Rigid Plastic Finite Element Method) was proposed by K. Mori, it has been used extensively in metal forming processes. One of the theoretical bases of R. P. FEM is ...Since the slightly compressible method in R. P. FEM (Rigid Plastic Finite Element Method) was proposed by K. Mori, it has been used extensively in metal forming processes. One of the theoretical bases of R. P. FEM is Markov’s variational principle which展开更多
Although several formulas for predicting the total elongation of the superplastic deformation have been reported, up to now, there is still no one which directly shows the relationship between gauge dimension, grain s...Although several formulas for predicting the total elongation of the superplastic deformation have been reported, up to now, there is still no one which directly shows the relationship between gauge dimension, grain size and superplastic elongation of a specimen. In consideration of the irregularity of the fracture surface of a superplastic tensile specimen which is approximately self-similar, a fractal model for the fracture of materials during展开更多
基金the Ministry of Science and Higher Education of the Russian Federation as part of the Project(No.FENU-2020-0020)。
文摘The novel idea of alloying,which is based on the utilization of multiple principal elements in high concentrations,has created a novel class of promising materials called high entropy alloys(HEAs).So far,several HEAs with outstanding properties beyond those of conventional alloys have been discovered,and new superior high-entropy alloys are still expected to be developed in the future.However,the fabrication process of HEAs through conventional manufacturing techniques suffers from significant limitations due to the intrinsic requirements of HEAs.Additive manufacturing(AM),on the other hand,has provided new opportunities for fabricating geometrically complex HEAs with the possibility of in situ tailoring of their microstructure features.Considering the growing interest in AM of HEAs during most recent years,this review article aims at providing the state of the art in AM of HEAs.It describes the feedstock requirements for laser based AM techniques.Thereafter,a comprehensive picture of the current state of nearly all HEAs processed by laser metal deposition(LMD),selective laser melting(SLM)and selective electron beam melting(SEBM)is presented.Special attention is paid to the features of AM derived microstructures along with their outstanding properties and underlying mechanisms for various material processing combinations.The AM of interstitial solute hardening HEAs,HEA matrix composites as well as non-beam based AM of HEAs will also be addressed.The post-AM treatments and the strategies to fabricate defect-free HEAs are summarized.Finally,a conclusion of current state and future prospects of additive manufacturing of HEAs will be presented.
文摘The bonding of steel and mushy Al 28Pb alloy was studied. The relationship model about preheat temperature of steel plate, solid fraction of mushy Al 28Pb alloy, rolling speed and interfacial shear strength of the bonding plate was established by artificial neural network perfectly. This model can be optimized by a genetic algorithm, and the optimum bonding parameters for the largest interfacial shear strength are: 546 ℃ for preheat temperature of steel plate, 43.5% for solid fraction of mushy Al 28Pb alloy and 8.6 mm/s for rolling speed, and the corresponding largest interfacial shear strength of bonding plate is 70.3 MPa. [
文摘The nonequilibrium diffusion of liquid aluminum atoms in cross direction in the innerpart of the solid steel base has been realized by using methods such as roughening steel plate surface, immersing flux on steel plate surface and short time diffusion, and the interface of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction was formed by using rapid solidification. The interfacial structure was studied by means of electron probe microanalysis. The results showed that the interfacial structure of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction is quite different from that of solid steel and liquid aluminum under conventional diffusion, that is, the interface of solid steel and liquid aluminum under nonequilibrium diffusion in cross direction is made up of groups of Al 13 Fe 4 teeth (which grew from the contact surface to steel base inner) at the bulges of steel plate surface and Fe Al solid solution (whose Al content is less than 3.5%) at the concaves of steel plate surface between the groups of Al 13 Fe 4 teeth.
基金supported by the Postdoctoral Foundation of Northeastern University and the National High Technology Research and Development Program of China(Grant No.2009BAE80B01)
文摘To obtain the billet with homogeneous and spheroidized primary grains is the key step in the semi- solid forming process. Among the semi-solid billet preparation methods, the process of low-superheat direct chill （DC） casting is simpler and more effective. In this study, the billets of AISi7Mg alloy were prepared by low- superheat DC casting at various withdrawal rates. The effect of withdrawal rate on the surface quality of the billets was investigated, and the evolution mechanism of the microstructural morphology in the billets was analyzed. The results show that the periodic corrugations and a large quantity of fine shrinkage pits appear in the billet surface when the withdrawal rate is 100 mm.min-1, and the above defects in the billet surface can be eliminated completely when the withdrawal rate is above 150 mm.min-1. But when the withdrawal rate is too fast （250 mm.min-1）, the primary a grains, except the ones in the billet center, have not enough time for ripening due to the high silidification rate, and will solidify as the dendrite structure. When the withdrawal rate is between 150 - 200 mm.min-1, the dendritic growth of the primary a grains is effectively inhibited, and a billet of AISi7Mg alloy with a smooth surface and homogeneous, fine, non-dendritic grains can be obtained.
文摘The main difference of this work from Hiroshi Nagai’sis the integral of separating force on the roller-dles. A precise equation of the contact are is proposed and used in the integral so that an analytical solution of drawing force is obtained. Thus, as a different conclusion, the new solution is in connection with the friction coefficient. The meanvalue theorem and horizontal force equilibrium are used in determining the roller-die pressure. The solutions are compared with those from Hiroshi Nagai’s.
文摘Ⅰ. INTRODUCTION Experimental data show that the larger the yield stresses of materials are, the smaller the coefficients of linear expansion will be, and the reverse is also true. In this note, we study whether there is a certain relationship between yield stress and coefficient of linear expansion.
文摘Hamilton and ZHOU Shan-you reported that, because the high strength aluminium alloy 7075 contains more Fe and Si impurities than the high strength aluminium alloy 7475 does, its superplastic elongation is lower than the maximum elongation 1200% of 7475 aluminium alloy. ZHOU Shan-you has obtained the maximum elongation 500% of
基金Project supported by the National Natural Science Foundation of China
文摘Since the slightly compressible method in R. P. FEM (Rigid Plastic Finite Element Method) was proposed by K. Mori, it has been used extensively in metal forming processes. One of the theoretical bases of R. P. FEM is Markov’s variational principle which
文摘Although several formulas for predicting the total elongation of the superplastic deformation have been reported, up to now, there is still no one which directly shows the relationship between gauge dimension, grain size and superplastic elongation of a specimen. In consideration of the irregularity of the fracture surface of a superplastic tensile specimen which is approximately self-similar, a fractal model for the fracture of materials during
