摘要:
通过光学显微镜、X射线衍射仪(XRD)、描扫电镜(SEM)、微分扫描量热仪(DSC)和力学性能测试等手段,研究了加入质量分数为0%、1%、3%和5%混合稀土对Mg-9Y-0.6Zr(WK90)镁合金组织及性能的影响.结果表明:铸态WK90合金组织由α-Mg基体及少量的共晶组织构成,添加混合稀土后,晶界处的共晶组织明显增多,并由单一共晶形式转变为层状共晶和离异共晶并存;随着混合稀土添加量的增大,共晶组织的种类及数量增多,合金DSC曲线的低熔点吸热峰总面积增大并最终发生分离;混合稀土为3%铸态合金及含混合稀土为1%的挤压态合金分别具有最高的断裂强度,影响合金强度的因素除了晶粒尺寸外,离异共晶组织的分布状态和形貌也是重要的因素.
Abstract:
The effects of 0%, 1%, 3% and 5% mish-metal additions on the microstructure and properties of an as-cast Mg-9Y-0.6Zr (WK90) alloy were investigated by optical microscope, X-ray diffractometer (XRD), scanning electron microscope (SEM), differential scanning calorimeter (DSC) and mechanical tester. The results indicate that the microstructure of the as-cast alloy is composed of α-Mg and little eutectic structure. After adding mish-metal, the eutectic structure increases markedly. When the mish-metal contents are 0%, 1% and 3%, the eutectic structure is in a single form, and there are the layered eutectic structure and the divorced eutectic structure when the mish-metal content is 5%. The areas of low temperature endothermic peaks in the DSC curves of WK90 alloy with different mish-metal contents increase and at last are separated with adding mish-metal, which is decided by the quantity and type of eutectic structure. The as-cast alloy with a mish-metal addition of 3% and the extruded alloy with a mish-metal addition of 1% have the best ultimate tensile strength under their own states. The influence reasons are not only grain size but also the distribution and the morphology of the divorced eutectic structure.
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