为提高镁合金的表面硬度,对预置Si粉的AZ91D进行高能CO2激光表面改性处理.采用光学显微镜、扫描电镜、电子探针微区分析和X射线衍射仪等方法研究了激光改性层的组织结构.结果表明:AZ91D表面改性层主要由α-Mg,Al12Mg17和Mg2Si组成.Si粉与镁合金完全发生反应形成金属间化合物Mg2Si,Mg2Si以树枝状分布.Al-Mn相由AZ91D基体中的团聚棒状变为激光改性层中的分散球状.激光表面改性后.由于Mg2Si相产生的强化和Mg17Al12产生的细晶强化,显微硬度从80 HV提高到324 HV.
To improve the hardness of AZ91D magnesium alloy,Si powder was preplaced on the surface of AZ91D magnesium alloy and then treated by a high power continuous wave CO2 laser.Mg2 Si reinforced Mg-based matrix composite were synthesized.The microstructure formed in laser surface modified layer were investigated by means of optical microscope (OM),scanning electron microscope (SEM),electron probe X-ray micro-analyzer (EPMA),and X-ray diffractometer (XRD) as well as Vickers microhardness tester.The main phases in the alloyed layer are alpha-Mg,Al12Mg17 and Mg2 Si.Mg2Si intermetallic compounds are distributed in dendrite shape.The morphology of Al-Mn phase changes from rod-like clusters in AZ91D substrate to spherical particles in the modified layer.The microhardness increased from 80 HV for as-received magnesium alloy to more than 324 HV for laser treated sample.The reasons can be explained by combining dispersion strengthening of Mg2Si and grain refining strengthening of Mg17Al12.
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