激光熔铸修理航空铝合金LY12CZ组织与疲劳性能

为修复腐蚀损伤的飞机铝合金构件,使用铝基稀土合金粉末,对预置模拟腐蚀损伤的铝合金(LY12CZ)试样进行激光熔铸修复,分析试样修复后熔铸层的显微组织结构,并对熔铸修理试样和无损试样进行疲劳对比试验。结果表明:熔铸层内为尺寸较小的等轴晶粒,尺寸为3~4μm;靠近熔铸界面处为具有定向凝固特征的柱状枝晶,晶轴垂直于界面,轴向尺寸可达30~40μm;激光熔铸修复的试样疲劳性能较完好试样大幅下降,主要原因为熔铸层内的熔铸加工缺陷形成了裂纹源,熔铸层底部的柱状枝晶具有较强的应力开裂倾向,熔铸残余拉应力加速裂纹的萌生与扩展。

Microstructure and fatigue properties of aviation aluminum alloy LY12CZ repaired by laser melt casting

Corrosion damaged aluminum alloy(LY12CZ) was repaired by laser melt casting with Al based rare-earth alloy powder.The microstructure of melt casting zone was investigated,and comparison test of fatigue life was carried out between repaired specimens and no-damage specimens.It is found that fine equiaxed crystals distribute in the casting layer and the crystal size is about 3-4 μm.The columnar crystals,axial direction size of which reaches 30-40 μm,exist near the substrate with its crystallographic axis perpendicular to the interface.The fatigue life of specimens repaired by laser melt casting is much shorter than that of no-damage specimens,due to the origin of crack resulting from flaws in the casting layer;the columnar grains in the bottom of casting zone are easy to crack under the tensile stress;the residual stress after melt casting accelerates the initiation and growth of crack.