室温力学性能
(西北工业大学 材料科学与工程学院，西安 710071)
摘 要: 研究了砂型铸造Mg-5Zn-3Al-0.2Mn合金的显微组织，发现其主要相组成为δ-Mg基体相和τ(Mg32(Al, Zn)49)化合物相， τ相以半连续网状骨骼形态沿δ相的晶界分布。 实验合金中加入少量Sr, Ti, B元素后， 合金组织细化， τ相形态转变为断续的短条状或粒状， 并且分布更加均匀。 在本实验条件下，当炉前加入0.06%Ti、 0.012%B、 0.1%Sr时， 合金的组织形态得到显著改善， 合金的室温力学性能最佳。 不同温度下对Mg-5Zn-3Al-0.2Mn合金进行的固溶处理实验发现，在335 ℃固溶17 h淬火后， 合金的室温抗拉强度和塑性得到了大幅度提高； 在343 ℃固溶17 h淬火后，合金组织完全转变为单相固溶体， 合金的室温力学性能较好， σb为245 MPa, δ为12%。
关键字: 铸造镁合金； 显微组织； 室温力学性能； 变质； 固溶处理
mechanical properties of
Mg-5Zn-3Al-0.2Mn casting alloy
（ College of Materials Science and Engineering,
Northwestern Polytechnic University, Xi′an 710071, China）
Abstract: The as-cast microstructures of sand-casting magnesium alloys Mg-5Zn-3Al-0.2Mn were studied, which was found to contain δ-Mg and τ(Mg32(Al, Zn)49) phases. By adding trace elements Sr, Ti and B into the melt of the alloys, the primary grain of δ-Mg is refined, meanwhile the morphology of τ phase is changed from semi-netted shape to short rods or spheres, and the distribution of τ phase tends to be more homogeneous. In the case of additions of 0.06%Ti, 0.012%B, and 0.1%Sr, δ-Mg grain is greatly refined and the best room temperature mechanical properties are gotten. It is also found that the ultimate strength and the elongation of Mg5-Zn3-Al0.2-Mn alloy greatly increase when the alloy is quenched after annealed at higher temperature. The microstructure of Mg5-Zn3-Al0.2-Mn alloy is transformed from binary phase microstructure into δ-Mg solid solution due to the dissolution of τ phase after annealed at 343 ℃ for 17 h, and meanwhile the mechanical properties reach the maximum values, i.e., σb 245 MPa, δ12%.
Key words: casting magnesium alloy; microstructures；room temperature mechanical properties；refinement; solid solution treatmen
