高电导率Mg-Al-Sr耐热镁合金的研究

Heat Resistant Mg-Al-Sr Alloys with High Electrical Conductivity

摘要:

采用普通铸造法制备了Mg-3Al-xSr (x=0.1~0.9，质量分数，%)系列合金。利用金相显微镜、XRD、SEM、电导率测量仪和显微硬度仪等手段对该系列合金的金相组织、显微结构、电导率及维氏显微硬度等性能进行了测试。结果表明，在Mg-3Al合金中添加少量Sr元素 (<0.1%)会生成Al4Sr相，而继续增加Sr后 (>0.1%)合金中开始出现Mg-Al-Sr相 (τ相)，Mg-Al-Sr铸态合金的电导率因此随着Sr含量的增加而不断提高；经高温热处理后 (400 ℃)，热处理态Mg-Al-Sr合金的电导率均随着热处理时间的延长而不断增加，这主要是由τ相逐渐分解并转变为Al4Sr相引起的；添加少量的Sr (<0.1%)会降低Mg-3Al合金的显微硬度，而随着Sr元素的继续添加 (>0.1%)，合金的显微硬度先增大后减小，并在Sr含量达到0.6%时达到峰值；此外，高温热处理会降低Mg-Al-Sr铸态合金的显微硬度。

Abstract:

Mg-3Al-xSr (x=0.1~0.9 wt%) alloys were prepared by a traditional cast method. Microstructures, electrical conductivities and micro-hardness of the present alloys in as-cast and as-heat treated states were studied by means of optical microscope, SEM, XRD, electrical conductivity meter and micro-hardness measuring instruments. The results show that Al4Sr phase is formed with little addition of Sr (<0.1 wt%). With increasing content of Sr, the electrical conductivity of as-cast Mg-Al-Sr alloys increases, and Mg-Al-Sr ternary phase (τ phase) is formed. After high temperature heat treatment at 400 oC, τ phase would decompose to Al4Sr phase, and the corresponding electrical conductivity of Mg-Al-Sr alloys increases with the heating time increasing. Vickers hardness of the as-cast alloy decreases slightly with a small amount of Sr addition (<0.1 wt%). With the increasing content of Sr (>0.1 wt%), the hardness of the alloys increases first, reaching the peak hardness at 0.6 wt% Sr and then decreases. Moreover, the high temperature treatment would decrease the corresponding hardness for as-cast alloys.