激光沉积修复ZL114A铝合金的显微组织及显微硬度研究

Microstructure and micro-hardness of laser deposition repair ZL114A aluminum alloy

为了研究激光沉积技术修复ZL114A铝合金构件的工艺及性能,采用多参数组合激光沉积工艺实验制备了单道单层试样,在分析了其表面形貌、气孔等缺陷产生的原因的基础上,得到了一组相对优化的工艺参数,制备了无缺陷的块状修复试样,并对试样进行了组织分析及硬度检测。结果表明:铝合金修复试样修复区与基材形成良好的冶金结合,沉积层底部为以熔池边缘为起点外延生长的柱状树枝晶,且一次枝晶间距18.38μm,二次枝晶间距9.55μm,在沉积层顶层顶部出现α-Al柱状枝晶转变为等轴枝晶现象。层带区域Si相脱溶析出并趋于粒状化。由于晶粒细化和固溶强化作用,沉积区显微硬度较基材提高25.8%。

To study the process and properties of laser deposition repair （LDR） ZL114A aluminum alloy samples, the basic process experiment of multi parameter combination was accomplished by laser singlepass process, on the basis of analyzing surface features, the reasons of gas porosity, a set of optimized process parameters were obtained, and defect-free block specimens were prepared, microstructure analysis and hardness testing of the samples were carried out. Results show that the repair area and the substrate form a good metallurgical combination, α-A1 columnar dendrites took melt pool edge as a starting point at the bottom of the deposition layer. The primary dendrites arm spacing was 18.38 μm and the distance between dendrite crystal was 9.55 μm. On the top of the deposited layers, α-Al dendrite columnar crystal was changed into equiaxed dendrite microstructure. Si phase was precipitated and tended to be spheroidize in the layer band of the repaired zone. Due to the function of grain refinement and solution strengthening, the micro-hardness of the deposited area was 25.8% higher than that of the substrate.