在AA7075基体上激光同质熔覆AA7075粉末的热处理和残余应力.pdf

在AA7075 基体上激光同质熔覆AA7075 粉 末的热处理和残余应力 R. Cottam • V. Luzin • Q. Liu • Y. C. Wong • J. Wang • M. Brandt 摘要：在AA7075 基体上激光同质熔覆AA7075 粉末旨在评估热处理的效果和测量熔覆层 和基体的残余应力，并以此加深对激光熔覆的理解。熔覆区的微结构具有很典型的快速凝固 特征。在和基体比较时可以看出，由于激光热作用的影响，热影响区显示出粗大的析出相。 固溶热处理以及随后的时效处理被用来恢复热影响区的强度。通过测量整个熔覆层和基体的 纳米硬度，发现7075 熔覆层的硬度在热处理前和热处理后都是低于基体的，这可能是由于锌 元素和镁元素蒸发引起的。利用中子衍射测量热处理前和热处理后的残余应力。熔覆层的残 余应力为50MPa 量级的拉应力；热处理后残余应力增长到大约100MPa。 关键词：AA7075 ，激光熔覆，残余应力，中子衍射 Investigation into Heat Treatment and Residual Stress in Laser Clad AA7075 Powder on AA7075 Substrate R. Cottam• V. Luzin• Q. Liu• Y. C. Wong• J. Wang• M. Brandt Abstract The laser cladding of AA7075 powder onto a AA7075 substrate was conducted to evaluate the effect of heat treatment and to measure residual stress between the clad layer and substrate to better understand the effect of laser cladding. The microstructure formed in the clad region was characteristic of a high cooling rate, which is typical for laser cladding. The heat-affected zone (HAZ) showed coarser precipitates when compared with the substrate and was attributed to the heating from the laser. A solution heat treatment followed by aging was employed to restore the strength in the HAZ. Nanohardness traverses of the clad and substrate was performed and it was shown the hardness in the 7075 clad layer was lower than the substrate both pre- and post-heat treatment and was attributed to the vaporization of zinc and magnesium. Neutron diffraction was employed to measure the residual stress both before and after heat treatment. The residual stresses formed in the clad layer were tensile and about 50 MPa i n magnitude; heat treatment increased the stress level to approximately 100 MPa. Keywords AA7075 Laser cladding Residual stress Neutron diffraction 简介 目前，复杂机械的经营成本几乎相当于其购置价格，而如何能够减少这笔花销对其使用 方非常有吸引力。对受到磨损或腐蚀