选区激光熔化成形Al-Si合金及其裂纹形成机制研究

Selective laser melting Al-Si aluminum alloy and the crack formation mechanism

为了得到性能良好的Al-Si合金零件,对选区激光熔化成形Al-Si合金的成形特性以及成形试样中裂纹进行了研究,得到了成形样致密度和工艺参量的关系以及裂纹的形成机制。在合适的工艺区间内,随着激光能量密度的增大,致密度先上升后下降;大部分试样底部存在沿熔覆层扩展的冷裂纹;其形成机制是Al-Si合金粉末成形过程中,生成大量共晶Si相,使材料的抗裂性能不足以抵抗成形过程中的高温度梯度导致的残余应力所致。结果表明,通过调整成形工艺参量,可以得到无裂纹的性能良好的成型零件。

To get A1-Si alloy parts with high performance, the formation and cracking behaviors of A1-Si alloy parts fabricated by selective laser melting were studied. The relationship between process parameters and fabrication densification, and the mechanism of crack formation were revealed. The results show that the density of the fabricated samples increases at first and then decreases with the increase of laser power density. The cold cracks are formed in most of the samples which expand along the cladding layer. Its formation mechanism is that a large number of eutectic Si is formed during the process and eutectic Si reduces crack resistance strength of A1-Si aluminum alloy, and crack resistance cannot be enough to resist the high temperature gradient during the forming process, and the generated residual stress is the cause of cold cracks. By improving the process parameters, A1-Si alloy parts with high performance and without cracks could be formed.