添加Si粉对AZ91D镁合金激光表面改性

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.

Laser surface modification of AZ91D magnesium alloy with Si powder

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.