钕对铸造Al-Si-Cu-Mg合金力学性能的影响

微量合金元素Nd的添加延缓了Al-Si-Cu-Mg合金的时效过程,细化了强化相,提高了合金时效硬度。当加入0.30%Nd,合金的强度提高了18%,但加入量继续增加,强度下降。分析显示,Nd的加入延缓了亚稳相的析出。富Nd相化合物,少量稳定相和过剩硅相质点的均匀析出,对合金起到了第二相强化的作用。在这两类析出相的共同作用下,合金获得了高的峰时效强度,但当合金中的Nd的含量超过一定量时,会形成一些富Nd的多元相和纯Nd质点相,这些相的出现导致了合金力学性能的下降。

Effect of Nd Addition on the Mechanical Property of Al-Si-Cu-Mg Cast Alloy

The addition of Nd postpones the age-hardening process of Al-Si-Cu-Mg alloy, increases the peak hardness. The UTS increases 18% when 0.30%Nd is added in, on the contrary, strength decreases if the content of Nd exceeds 0.30%. The SEM reveals that the addition Nd postpone nucleation of metastable particles and stable phases. At the same time, some larger Nd-rich particles and stable phases formed in the matrix, which strengthen alloys as second-phase. In the combined action of those two kinds of precipitates, the peak strength of alloy improve remarkably. However, when the content of Nd exceeds 0.30% some Nd-rich phases and pure Nd particles form, and those particles often grain boundary and result in the decrease of alloy strength.