含晶界孔洞粗晶工业纯铁的循环变形及损伤特征

摘要

为了更好地了解体心立方（bcc）结构金属的循环变形机制,在恒总应变幅控制的条件下研究了含晶界孔洞粗晶工业纯铁的疲劳变形特征.结果表明,含晶界孔洞的粗晶工业纯铁在不同总应变幅＂εt/2下均发生不同程度的循环硬化现象,无循环饱和阶段出现.疲劳寿命与塑性应变幅的关系基本符合Coffin-Manson法则.循环变形的表面变形特征与外加总应变幅具有一定的相关性：随着总应变幅的增加,滑移变形及其导致的挤出侵入现象更为严重,滑移开裂更趋显著;越来越多的原来位于晶界上的微观孔洞发生扭曲变形、聚合、长大而产生裂纹,甚至导致沿晶开裂.在相对较高的总应变幅下,在表面还观察到了滑移扭折现象以及沿晶裂纹扩展进入晶粒内部的现象.在低应变幅＂εt/2=1.0×10-3下循环变形后发现了类驻留滑移带（PSB）楼梯位错结构,随着应变幅的增加,位错胞结构发展成为主要结构特征,其平均尺寸逐渐减小.%By means of ENVI 4. 8, the LANDSAT 5 RS image in 1994 and 2009 of Panjin City was interpreted and analyzed. And refer to the state standard of current land use classification taxonomy and the feather of the land utilization in the investigation area, the eight land use types were divided in the investigation area. Using ArcGIS 9.3 and Fragstats 3. 3, through format conversion and spatial analysis etc, the statistical data analysis and the indices of landscape patterns calculation were done to accomplish the analysis of the landscape pattern in the investigation area. The result is that the development trend of every type in the area is different, that the artificial landscape is more and more fragmented, but the natural landscape is good as a whole. Some problems should be paid more attention, such as the decrease of the mudflat, cropland and woodland.