混合稀土变质对A356合金组织及力学性能的影响

Effects of Mixed Rare Earth Modification on Microstructure and Mechanical Properties of A356 Alloy

研究了不同含量混合稀土RE对A356合金组织及力学性能的影响。结果表明:当RE加入量为0.5wt%时,合金中共晶硅由粗大的板片状变成细颗粒状,且均匀分布于合金基体中,合金抗拉强度为200.8MPa,伸长率为4.52%,布氏硬度为58.6HBW。该铸造合金的拉伸断裂是以韧窝为主的韧性断裂+解理脆性断裂的混合断裂。当混合RE的添加量为0.9wt%时,合金组织中开始出现轻微的过变质,此时,共晶Si开始略有粗化和长大,局部区域有偏聚倾向,但其形貌仍为颗粒状。

The effects of mixed rare earth RE on the microstructure and mechanical properties of A356 alloy were studied. The results show that when the RE adding amount is 0.5 wt%, the eutectic silicon of the alloy changes from coarse schistose to fine granular, and is distributed evenly in the alloy matrix, the tensile strength of the alloy is 200.8MPa,the elongation is 4.52%,and the Brinell hardness is 58.6HBW. The tensile fracture mode of the cast alloy is mixed fracture with ductile fracture dominated by dimples and cleavage brittle fracture. When the addition amount of RE is 0.9%, slight over-modification begins to appear in the alloy. At this time, the eutectic Si begins to coarsen and grows up slightly, and there is a tendency of segregation in some regions, but the morphology is still granular.