The influence of mechanical surface treatments on fatigue behavior of extruded AZ61 magnesium alloy

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• 作者：Md. Shahnewaz Bhuiyan^a ; Yoshiharu Mutoh^b ; ^{mutoh@mech.nagaokaut.ac.jp} ; A.J. McEvily^c
• 关键词：Shot peening ; Micro peening ; Barrel processing ; Fatigue limit ; Surface roughness ; Compressive residual stress ; Magnesium alloy
• 刊名：Materials Science and Engineering ; A
• 出版年：2012
• 期刊代码：61_09215093
• 类别：ms
• 出版时间：15 July, 2012
• 卷：549
• 期：Complete
• 页码：69-75
• 文件大小：1631 K

摘要

Surface treatments such as shot peening which introduce compressive residual stresses into the near surface region can have a beneficial effect on fatigue behavior. In the present study, tension-compression fatigue tests were carried out to understand the influence of three different mechanical surface treatments on fatigue properties of extruded AZ61 magnesium alloy at a stress ratio of 鈭? and frequency of 20 Hz under ambient environment. The mechanical surface treatments used in the present study were: (a) shot peening, (b) micro-peening and (c) barrel processing. It was found that the fatigue strength of shot-peened specimens actually degraded by about 30%as compared to the specimens which had not been shot peened. In the shot peened specimens cracks were nucleated at shot-peened induced surface defects which then propagated to failure, a direct indication that the shot-peening induced compressive residual stresses were not able to offset the detrimental effect of process-induced high surface roughness and surface defects. On the other hand, both micro-peened and barrel processed specimens exhibited an improvement in fatigue strength of about 15%. In these latter two instances, even though cracks were nucleated at sites of specimen surface roughness, the process-induced compressive residual stress retarded fatigue crack propagation, thereby resulting in the observed improvement in fatigue strength.