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通过光学显微镜、扫描电镜、X射线分析等手段研究了Mg-4Al-1RE-xCa镁合金的铸态和压缩蠕变态组织,测试了其室温、高温拉伸性能和高温抗蠕变性能。结果表明,Mg-4Al-1RE合金为树枝晶结构,晶粒粗大且分布不均匀,强化相为针状Al11Nd3相。随着Ca含量的增加,晶粒明显细化,生成的骨骼状Al2Ca相和颗粒状Al2Nd相逐渐增加,而Al11Nd3相数量减少、尺寸变短。室温时,随着Ca含量的增加,铸态合金屈服强度和硬度有所提高,抗拉强度和塑性显著下降;150℃条件下合金的强度较室温时低,而塑性明显提高。Ca含量为0.8%时合金的瞬时高温抗拉强度最高,为138 MPa。沿晶分布的Al2Ca相热稳定性好,有利于合金抗蠕变性能的提高,一旦呈封闭网状,会对基体产生割裂作用,降低力学性能。
The as-cast and compressive creep microstructure of Mg-4Al-1RE-xCa magnesium alloy was studied by means of optical microscope, scanning electron microscope and X-ray analysis. The tensile properties at room temperature, high temperature and creep resistance at high temperature were tested. The results show that the Mg-4Al-1RE alloy has a dendritic structure with coarse grains and uneven distribution, and the reinforcing phase is an acicular Al11Nd3 phase. With the increase of Ca content, the grains are obviously refined, the formed Al2Ca phase and the granular Al2Nd phase are gradually increased, while the Al11Nd3 phase number is reduced and the size is shortened. At room temperature, with the increase of Ca content, the yield strength and hardness of the as-cast alloy increased, while the tensile strength and plasticity decreased significantly. The strength of the alloy at 150 ℃ was lower than that at room temperature, but the plasticity obviously increased. When the content of Ca is 0.8%, the instantaneous high temperature tensile strength of alloy is 138 MPa. Al2Ca phase distribution along the crystal thermal stability, is conducive to improve the creep resistance of the alloy, once a closed mesh, the substrate will have a split effect, reduce mechanical properties.