激光沉积修复ZL114A铝合金组织及力学性能

Microstructure and mechanical properties of laser deposition repair casting ZL114A aluminium alloy

摘要:

采用6 kW光纤激光器对预制槽损伤的ZL114A铸造铝合金进行激光沉积修复实验研究,分析了热处理前后激光修复区组织形貌及分布规律,并对试样的显微硬度和室温拉伸性能进行了测试。结果表明修复区与基材形成良好的冶金结合,沉积区底部为近似平行于熔合线法线外延生长的柱状树枝晶,一次枝晶间距约15.7 μm,二次枝晶间距约5.2 μm,共晶组织呈分叉棒状或块状连续分布于枝晶间隙,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。热处理后修复区柱状枝晶的二次枝晶臂因高温原子扩散作用，连成一片，且共晶Si相粒状化明显,粒径约4.93 μm,部分颗粒均匀分散分布于一次枝晶臂的两侧。热处理后修复区硬度较基材平均提高55.5%,且修复试样的室温拉伸力学性能优于铸造基材。

Abstract:

ZL114A casting aluminum alloy with pre-groove damage was repaired by laser deposition repair (LDR). Microstructure and distribution law of laser deposition repaired zone before and after heat treatment were analyzed, and then microhardness and room temperature tensile properties of the sample were tested. The results showed that the repaired parts and the substrate formed a good metallurgical combination, at the bottom of the deposition layer were α-Al columnar dendrites which approximately paralleled to the normal directions of the fusion line with epitaxial growth feature. The primary dendrite arm spacing is about 15.7 μm,and the distance between secondary dendrites is about 5.27 μm. Eutectic structure presented as bifurcated rod or block in shape, and continuously distributed in the gaps among dendrite crystals, and α-Al columnar dendrites transformed into equiaxed crystal at the top of the last deposition layer. After the heat treatment, secondary dendrite arm of columnar dendrite is expansive because of atomic diffusion, and eutectic Si granulation were clear to be observed, the particle size is about 4.93 μm, and part of them distributed uniformly on both sides of primary dendritic arm. The hardness of repair area increased by an average of 55.5% than substrates after heat treatment, and the room temperature tensile properties were better than casting parts.