工业纯镁内部疲劳微裂纹的热扩散性愈合  

DIFFUSIVE HEALING OF INTERNAL FATIGUE MICROCRACKS IN PURE MAGNESIUM

作　　者：杨君刚[1] 张海龙[1] 孙军[1] 

机构地区：[1]西安交通大学材料科学与工程学院金属材料强度国家重点实验室

出　　处：《金属学报》2005年第8期819-823,共5页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目59889101国家杰出青年科学基金项目59925104资助

摘　　要：采用单向对称拉压低周疲劳方法在具有等轴晶的工业纯镁试样中引入了微米级的内部裂纹.裂纹主要位于晶内和穿晶位置,宽度为0.5—1.5μm,长宽比分布在10～35之间.在623 K对疲劳试样进行2,4和6.5 h的真空退火处理. SEM观察表明:晶内疲劳微裂纹纵剖面二维形态发生了主要由表面扩散控制的形态变化,由初始的扁椭圆形演化成多个球洞定向排列的形态;穿晶疲劳微裂纹纵剖面二维形态则在表面和晶界扩散的耦合作用下首先在晶界处分隔成两部分,并在晶界上留下了一个空洞在退火处理的后期阶段,空洞收缩消失,引起空洞间距的增大并引起试样密度少量恢复.Micron-sized internal cracks were introduced into pure magnesium specimens with equiaxial grains by uniaxial symmetric tension-compression plastic-strain-controlled fatigues at room temperature. These cracks are within the grains or across the grain boundaries, and their widths are within the range of 0.5 1.5 #m, and the aspect ratios of length-to-width are within the range of 10-35. The as-fatigued specimens were then annealed in vacuum at 623 K from 2 to 6.5 h.SEM observations show that the two-dimensional longitudinal section of the intragranular microcracks evolves from the original thin=ellipse shape into the several aligned spherical voids dominated by surface diffusion. The transgranular microcracks break into two parts at the site of grain boundary dominated by surface diffusion coupled with grain boundary diffusion, and a single void was left on the grain boundary. During the late annealing, the shrinkage of the resultant voids brings an increase in the void-to-void spacing and further a somewhat recovery in the sample density.

关 键 词：工业纯镁 内部疲劳微裂纹 扩散愈合 

分 类 号：TG111.8[金属学及工艺—物理冶金] TG146.2[金属学及工艺—金属学]