摘要
本论文以轻质Mg-Li合金材料为研究对象,以均化处理、时效处理等热处理手段和Li对MgLiAlZn镁合金的微观组织和力学性能影响为主要研究内容。以具有代表性的Mg-8Al-0.5Zn、Mg-2.94Li-8Al-0.5Zn、Mg-3.25Li-8Al-0.5Zn、Mg-4.2Li-8Al-0.5Zn合金为基础,对镁锂合金成分-组织结构-机械性能之间的相互关系和作用规律进行了系统的研究。
用电阻炉配制了合金,对实验合金进行了不同条件下的热处理工艺,结合SEM、OM及拉伸实验等手段观察分析热处理前后,铸态和热处理态试验合金的组织变化和力学性能变化,分析热处理和Li对合金性能的影响。
研究结果表明,加入Li的MgLiAlZn合金的铸态显微组织由基体α-Mg固溶体、β-Mg17Al12相和AlLi相组成,只是β相数量减少,且基体组织明显细化,铸态合金的宏观硬度值随着Li的加入量的增加而增加。室温抗拉强度和抗压强度提高。经过固溶处理后,合金的晶粒尺寸没有太大的变化,β相几乎完全固溶于基体中,经过时效处理后,合金组织中重新析出β相,但其数量、尺寸与形貌有所不同。经过固溶处理后,合金的硬度降低,压缩强度和压缩率提高,时效处理后,合金硬度提高,抗拉强度和延伸率降低。
Mg-Li alloy were choosed as experiment alloys in this paper. Influence of Li amounts and heat treatments such as homogenizing and aging on microstructure and mechanical properties of MgLiAlZn alloys were studied. Mg-8Al-0.5Zn, Mg-2.94Li-8Al-0.5Zn, Mg-3.25Li-8Al-0.5Zn, Mg-4.2Li-8Al-0.5Zn were investi-gated systematically to obtain the relationship and interaction of compositon, microstructures and mechanical properties.
The alloys are prepared in electrical resistance furnace, and then heat-treated under different conditions. SEM and OM, combined with tensile test are used to analyze the influnce of Li amoutns and heat treatments on microstructure and mechanical properties of Mg-Li alloys.
The result shows that: the as-cast microstructure of MgLiAlZn alloy with Li addition are consisted of matrixα-Mg sosoloid,β-Mg17Al12 phases and AlLi phases, the fraction ofβphase decreases andα-Mg matrix is refined. With the increase of Li, the tensile strength and compression strength are increased. After solution treatment the grain size of alloys shows no obvious change and theβphases dissolve into the matrix. After aging treatment theβphases precipitate again, but the amount, size and morphology changes. The hardness values decrease after solution treatment, the compression strength and condensation improve. The hardness values improve after aging treatment, the tensile strength improve, and the ductility of alloy reduce.
引文
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