Fu-Yuan Dong
,
Peng Zhang
,
Jian-Chao Pang
,
Qi-Qiang Duan
,
Yi-Bin Ren
,
Ke Yang
,
Zhe-Feng Zhang
金属学报(英文版)
doi:10.1007/s40195-016-0370-9
Three high-nitrogen stainless steels with different N contents were successfully processed by equal-channel angular pressing for one pass, and their microstructures and mechanical properties were investigated. It was found that the microstructure of the billet was heterogeneous across the billet thickness, resulting in the difference in the mechanical properties due to the different deformation conditions. A relatively low strength, high uniform elongation, and high work-hardening rate for the samples at the bottom of the billet was achieved in comparison with those processed at the top. Meanwhile, it was observed that the density of deformation twins increased with the content of N; accordingly, the strength and elongation of the alloys increase with the content of N, resulting in a good strength-ductility combination.
关键词:
High-nitrogen
,
stainless
,
(HNS)
,
steels
,
Equal-channel
,
angular
,
pressing
,
(ECAP)
,
N
,
content
,
Twinning
,
Strength
,
Ductility
Ying Yan
,
Wan-Peng Deng
,
Zhan-Feng Gao
,
Jing Zhu
,
Zhong-Jun Wang
,
Xiao-Wu Li
金属学报(英文版)
doi:10.1007/s40195-016-0373-6
To explore the coupled effect of temperature T and strain rate ε˙ε˙ on the deformation features of AZ31 Mg alloy, mechanical behaviors and microstructural evolutions as well as surface deformation and damage features were systematically examined under uniaxial tension at T spanning from 298 to 523 K and ε˙ε˙ from 10-4 to 10-2 s-1. The increase in T or the decrease in ε˙ε˙ leads to the marked decrease in flow stress, the appearance of a stress quasi-plateau after an initially rapid strain hardening, and even to the occurrence of successive strain softening. Correspondingly, the plastic deformation modes of AZ31 Mg alloy transform from the predominant twinning and a limited amount of dislocation slip into the enhanced non-basal slip and the dynamic recrystallization (DRX) together with the weakened twinning. Meanwhile, the cracking modes also change from along grain boundaries (GBs) and at twin boundaries (TBs) or the end of twins into nearby GBs where the DRX has occurred. The appearance of a stress quasi-plateau, the formation of large-sized cracks nearby GBs, and the occurrence of continuous strain softening, are intimately related to the enhancement of the non-basal slip and the DRX.
关键词:
AZ31
,
Mg
,
alloy
,
Uniaxial
,
tension
,
Temperature
,
Strain
,
rate
,
Deformation
,
Damage
,
Twinning
Yongbo XU
,
M.A.Meyers
材料科学技术（英文）
Microstructures of the localized shear bands generated during explosion with a thick-walled cylinder specimen in Ti-6Al-4V alloy, were characterized by TEM and SEM. The results show that the twinning is a major mode of deformation, and the distortion-free grains in the bands with the size of 10 µm in diameter were proposed to be the re-crystallization during dynamic explosion. The further observations show that the α→α2 phase transformation may occur in the bands, and this kind of transformation could be confirmed by its dark field image and electron diffraction analysis. Analysis shows that there is specified orientation between the α→α2 Phases.
关键词:
Shear localization
,
null
,
null
,
null
Yafang GUO
金属学报(英文版)
The deformation behavior in magnesium single crystal under c-axis tension is investigated in a temperature range between 250 K and 570 K by molecular dynamics simulations. At a low temperature, twinning and shear bands are found to be the main deformation mechanisms. In particular, the {1012} tension twins with the reorientation angle of about 90° are observed in the simulations. The mechanisms of {1012} twinning are illustrated by the simulated motion of atoms. Moreover, grain nucleation and growth are found to be accompanied with the {1012} twinning. At temperatures above 450 K, the twin frequency decreases with increasing temperature. The {1012} extension twin almost disappears at the temperature of 570 K. The non-basal slip plays an important role on the tensile deformation in magnesium single crystal at high temperatures.
关键词:
Atomistic simulations
,
镁
,
孪晶
,
拉伸
