微米尺度钼丝的力学性能及其尺寸效应

Size Effect on Mechanical Property for Cold-Draw Micron-sized Molybdenum-Wires

对直径分别为125 mm、140 mm和160 mm的钼丝(模型材料)进行拉伸实验和应力控制的拉-拉疲劳实验,研究了微米尺度体心立方结构的钼丝的力学性能及其尺寸效应。在扫描电镜下观察钼丝的拉伸断口和疲劳断口,分析了金属钼丝的拉伸和疲劳断裂行为。结果表明,微米尺度体心立方拉拔态钼丝的拉伸断裂强度和应力控制下的疲劳强度都随着钼丝直径的减小而下降。微米尺度钼丝的疲劳性能尺寸效应,来源于丝中径向方向的拉长晶粒数目不同。结果丝的直径越小钼丝对表面所萌生的疲劳裂纹或缺陷越敏感,疲劳扩展寿命越短。

Cold-draw molybdenum wires with diameters of 125, 140 and 160 mm were selected as a model material. Tensile tests and tension-tension fatigue tests under stress control were conducted to investigate mechanical performance of the micron-sized Mo wires. While the fractured surfaces of the wires were examined by scanning electron microscopy. The experimental results show that both of tensile and fatigue strengths under stress control decrease with the decreasing wire diameter. The size effect on fatigue performance of the Mo wire can be attributed to the difference of the quantity of grains along the radial direction, which leads to that the smaller the wire diameter the more sensitive to the fatigue crack or defect on the Mo wire surface, and thereby, the shorter the fatigue life.