激光熔化镁合金凝固组织及腐蚀行为

采用Nd:YAG毫秒脉冲激光器,在高纯氩气保护下扫描AZ91D镁合金样品,采用X射线衍射仪(XRD),光学显微镜,扫描电镜(SEM),原子力显微镜(AFM)等对处理后镁合金表面形貌、组织、成分进行研究。使用模拟改性体液和质量分数为3.5%的NaCl溶液对实验样品进行腐蚀,观察腐蚀表面并计算材料腐蚀率。结果表明:在相同腐蚀时间下,与未被处理样品相比,激光处理后镁合金由于其显微组织中细化的α-Mg相与β-Mg_(17)Al_(12)相,及选择性气化现象和基体合金化学成分共同导致表面Al元素富集提高了表层的抗腐蚀性能;通过测算激光熔化区枝晶晶胞尺寸与冷却速率的关系得到其凝固方程。

Solidified Structure and Corrosion Behavior of Laser-melt Magnesium Alloy

The AZ91D magnesium alloy samples were scanned by millisecond pulse Nd :YAG laser un-der high pure argon protection .The surface morphology ,microstructure and composition of the trea-ted magnesium alloy were studied by X-ray diffraction ,optical microscopy ,scanning electron micros-copy ,atomic force microscopy .In addition ,the corrosion surface which was corroded using simulated body fluid and the mass fraction of 3 .5% NaCl solution was observed and material corrosion rate was calculated .The results show that ,at the same corrosion time ,compared with the untreated samples , the surface corrosion resistance is improved by the enrichment of Al at the irradiated surface by the joint effect of the combination of refined homogeneous microstructure of α-Mg phase and β-Mg17 Al12 phase and the selective vaporization and the chemical composition of base metal in the laser-treated AZ91D alloy ;the solidification equation is obtained by calculating the relation between the size of the dendrite cell and the cooling rate in laser melting zone .