Recent observations by electron microscopy have shown that a dislocation-free zone (DFZ) exists between the crack tip and the pile-up of dislocations in the plastic zone. Shang, S. J., Ohr, S. M. and Majumdar, B. S., ...Recent observations by electron microscopy have shown that a dislocation-free zone (DFZ) exists between the crack tip and the pile-up of dislocations in the plastic zone. Shang, S. J., Ohr, S. M. and Majumdar, B. S., Burns, S. J. have discussed the problem of the plastic zone at a crack tip in isotropic elastic medium. We know that the hard second phase, which neither causes very large stress concentration nor leads to micrographic split, can improve the bearing capacity of the materials. Therefore, it is necessary to discuss the problem of the plastic zone at a crack tip while the hard second phase exists.展开更多
The microstructures and mechanical properties of the Mg-7.68Gd-4.88Y-1.32Nd-0.63A1-0.05Zr magnesium alloy were investigated both in the as-cast condition and after homogenization heat treatment from 535 to 555 ℃ in t...The microstructures and mechanical properties of the Mg-7.68Gd-4.88Y-1.32Nd-0.63A1-0.05Zr magnesium alloy were investigated both in the as-cast condition and after homogenization heat treatment from 535 to 555 ℃ in the time range 0-48 h by op- tical microscopy, scanning electron microscopy and hardness measurement. The as-cast alloy consisted of ct-Mg matrix, Mgs（Y0.5Gd0.5） phase which is a eutectic phase, strip of Al2（Y0.6Gd0.4） phase, little A13Zr and Mg（Y3Gd） phase. With the increasing of homogenization temperature and time, the Mgs（Y0.5Gd0.5） phase was completely dissolved into the matrix. The Al2（Y0.6Gd0.4） phase was almost not dissolved which impeded grain boundaries motion making the grain size almost not changed in the process of ho- mogenization. The optimum homogenization condition was 545 ℃/16 h. The tensile strength increased, yield strength decreased and the plasticity improved obviously after 545 ℃/16 h homogenization treatment.展开更多
文摘Recent observations by electron microscopy have shown that a dislocation-free zone (DFZ) exists between the crack tip and the pile-up of dislocations in the plastic zone. Shang, S. J., Ohr, S. M. and Majumdar, B. S., Burns, S. J. have discussed the problem of the plastic zone at a crack tip in isotropic elastic medium. We know that the hard second phase, which neither causes very large stress concentration nor leads to micrographic split, can improve the bearing capacity of the materials. Therefore, it is necessary to discuss the problem of the plastic zone at a crack tip while the hard second phase exists.
基金Project supported by National Natural Science Foundation of China(51204020)National Basic Research Program of China(2013CB632202,2013CB632205)Key Projects in the National Science&the Technology Pillar Program during the Twelfth Five-year Plan Period(2011BAE22B01)
文摘The microstructures and mechanical properties of the Mg-7.68Gd-4.88Y-1.32Nd-0.63A1-0.05Zr magnesium alloy were investigated both in the as-cast condition and after homogenization heat treatment from 535 to 555 ℃ in the time range 0-48 h by op- tical microscopy, scanning electron microscopy and hardness measurement. The as-cast alloy consisted of ct-Mg matrix, Mgs（Y0.5Gd0.5） phase which is a eutectic phase, strip of Al2（Y0.6Gd0.4） phase, little A13Zr and Mg（Y3Gd） phase. With the increasing of homogenization temperature and time, the Mgs（Y0.5Gd0.5） phase was completely dissolved into the matrix. The Al2（Y0.6Gd0.4） phase was almost not dissolved which impeded grain boundaries motion making the grain size almost not changed in the process of ho- mogenization. The optimum homogenization condition was 545 ℃/16 h. The tensile strength increased, yield strength decreased and the plasticity improved obviously after 545 ℃/16 h homogenization treatment.
