通过OM、SEM及布氏硬度分析,研究GWN751K镁合金在不同状态下的显微组织与性能,确定该合金的双级均匀化工艺参数.结果表明:合金经过440 ℃、6 h初级均匀化后,共晶组织开始发生分解,晶粒开始长大;经过535 ℃、16 h热处理后,合金晶粒明显长大,但元素分布较为均匀,晶界处仅明显残留含Y化合物;均匀化处理使合金的力学性能得到改善,合金断裂强度为245 MPa,屈服强度为192 MPa,伸长率为12%,较铸态合金的力学性能均有所提高;合金变形抗力较铸态合金的有所增加,这种特性在450 ℃仍保留下来,但差别减小.
The microstructures and properties of the as-cast and homogenized GWN751K magnesium alloy were investigated by optical microscopy, scanning electron microscopy and hardness measurement. The two-step homogenization parameters were determined. The results indicate that the eutectic structures in the as-cast alloy begin to decompose, and the grains begin to grow up after the alloy is homogenized at 440 ℃ for 6 h. After heat treatment at 535 ℃ for 16 h, the elements distribute uniformly and the grains grow up obviously, only yttrium element of intermetallic compounds leaves around boundary. The mechanical properties are improved after homogenization, with σ_b=245 MP_a, σ_(0.2)=192 MPa and δ=12%, which are better than those of the as-cast alloy. The flow stress of the homogenized alloy is higher than that of the as-cast alloy and this character is still retained until 450 ℃, but the difference decreases.
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