姜庆伟刘印王尧晁月盛李小武
金属学报
通过差示扫描量热仪(DSC)和显微硬度测试研究了等通道转角挤压(ECAP)制备的超细晶铜在退火条件下的热稳定性和硬度变化, 同时利用扫描电镜电子通道衬度(SEM--ECC)技术和透射电镜(TEM)研究了超细晶铜在室温到300 ℃的温度范围内分别在单向压缩和循环变形后的微观结构变化. 结果表明: 超细晶铜即使在低于再结晶温度退火条件下也会以缓慢渐进的方式发生逐步的再结晶和晶粒粗化, 该结构软化过程通过DSC随退火时间的响应曲线探测不到. 高温压缩下晶粒的粗化行为与应变速率有关, 应变速率越大, 粗化的局部化越明显; 应变速率越小, 更多的晶粒发生整体粗化. 高温循环加载促使晶粒粗化发生得更为显著、均匀, 在粗化的晶粒内可观察到一些典型的位错组态, 如墙结构和胞结构等. 另外, 利用最大晶粒尺度(Dmax)与平均晶粒尺度(Daver)的比值V定量讨论了不同高温变形情况下晶粒粗化的不均匀性.
关键词:
超细晶铜
,
cyclic deformation
,
uniaxial compression
,
temperature
,
microstructure
,
grain coarsening
夏月波
,
张天宜
,
费广涛
,
周星
金属学报
本文报道了不同取向Al单晶体在循环形变过程中的应力响应、内耗和超声衰减的变化及它们之间的关系,试验结果表明,循环应力σ、内耗Q~(-1)和超声衰减△α对晶体取向有明显的依赖性,单滑移取向和多滑移取向晶体之间,上述三量的差别很大,对同一取向晶体,σ增加对应着Q~(-1)减少和Δa增加,但Δa达到最大值需要的循环周次少于σ达到最大值所需的循环数,而Q~(-1)与σ则基本上同时达到最低值和最大值。
关键词:
晶体取向
,
cyclic deformation
,
stress response
,
internal friction
,
ultrasonic attenuation
杨继红
,
张新平
,
Y.W.Mai
,
李勇
金属学报
利用扫描电镜电子通道衬度(SEM--ECC)技术观察了循环变形饱和阶段Cu单晶样品中近表面区域的位错微结构. 在样品边缘一些条带状或斑点状呈黑色的位错组织区, 利用离散位错动力学方法模拟了该区的位错微观结构, 并计算了与此位错微结构相对应的内应力分布. 模拟和计算结果表明, 黑色区是内应力出现最大值区,即应力集中区, 它与驻留滑移带(PSB)中的不均匀变形有关,是疲劳裂纹萌生最可能的位置.模拟和计算结果很好地解释了这一现象.
关键词:
Cu
,
cyclic deformation
,
crack
nucleation
,
null
SUN Zhengming
,
WANG Zhongguang
,
AI Suhua Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China. To whom correspondence should be addressed.
材料科学技术（英文）
Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-% martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.
关键词:
cyclic deformation
,
null
,
null
林栋梁
,
吴建生
,
陈贤芬
金属学报
本文系统地研究了Nb单晶循环变形的应力-应变关系及位错组态。和单向变形相比较,单晶在循环变形后都有应力不对称现象,拉伸时的应力小于压缩时的应力。循环硬化曲线可以分成三个阶段:初始阶段、快速硬化阶段和饱和阶段。初始阶段位错组态为密集的位错网络和碎块状的位错圈。快速硬化阶段出现条带状的位错缠结。饱和阶段的位错组态为条带和条带之间的螺位错,塑性变形主要通过条带间的螺位错往复运动来实现。
关键词:
铌单晶
,
cyclic deformation
,
dislocation
林栋梁
,
吴建生
金属学报
用光学显微镜和扫描电镜观察了〔321〕和〔110〕位向的铌单晶在循环变形时的表面形貌变化.研究了圆形试样经过循环变形到饱和阶段表面出现的皱褶.本文用形变带这个词来表示材料经不均匀变形后产生的这种皱带,它不同于有特定位向的扭折带.根据表面形貌细节把形变带分成五类,并对形变带的形成过程进行了讨论.形变带所在平面和轴向夹角均在≈45°,说明宏观应力状态对形变带的形成起重要作用.
关键词:
铌单晶
,
cyclic deformation
,
deformation bands
JIN Nengyun Shanghai Jiaotong University
,
Shanghai Jin Nengyun
,
Department of Materials Science
,
Shanghai Jiaotong University
,
Shanghai 200030
,
ChinaPresent address:Max-Planck-Institut für Metallforschung-Institut für Physik
,
Stuttgart 80
,
FRG
金属学报(英文版)
Cyclic stress-strain responses and dislocation structure of copper single crystals with various tensile axes were systematically studied and compared with each other.Experimental results reveal that the evolution of microscopic dislocation configurations in a crystal and, accordingly,its macroscopic cyclic behaviours are closely related with its orientation.Re- markable secondary slip has been observed in some crystals with orientations well inside the crystallographic triangle, which are usually considered as single-slip ones.Their cyclio behaviours and dislocation structures at saturation are similar to those of their neighbouring multi-slip crystals.These results have constructed the experimental basis for the newly pro- posed dislocation interaction model Jor cyclic deformation of fee crystals,which will be des- cribed in the second part of this article.
关键词:
Copper
,
null
,
null
,
null
,
null
,
null
,
null
