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采用激光熔凝技术处理镁合金,系统分析了激光熔凝处理后熔凝层组织变化特征。研究结果表明,激光熔凝处理后,熔凝层相组成仍为α-Mg和β-Mg17Al12,其中β相含量较原始镁合金有所提高。熔凝层组织呈明显的树枝晶形貌特征,较原始镁合金晶粒显著细化,且沿熔凝层深度增加,枝晶尺寸逐渐增大。透射电镜分析进一步证明了熔凝层由密排六方结构的α-Mg和体心立方结构的β-Mg17Al12组成,其中β相呈板条状、短柱状和六棱柱状多种形态析出。另外,当激光功率从2 kW增加到5 kW时,熔凝层中β含量和枝晶尺寸均增加,且枝晶长度方向的增加幅度约为宽度方向上增加幅度的10倍。在枝晶细化和沉淀强化综合作用下,熔凝层的耐磨性较原始镁合金有显著提高。
The laser melting technology was used to treat the magnesium alloy. The microstructure change characteristics of the fused layer after the laser melting treatment were systematically analyzed. The results show that the phase composition of fused layer is still α-Mg and β-Mg17Al12 after laser fusion treatment, and the content of β phase is higher than the original magnesium alloy. The microstructure of dermabrasion showed obvious dendritic morphology, which was significantly refined than that of the original magnesium alloy. The depth of the fused layer increased and the size of dendrite increased gradually. Transmission electron microscopy (TEM) analysis further confirmed that the fused layer consisted of α-Mg with hexagonal close-packed hexagonal structure and β-Mg17Al12 with cubic structure. The β phase was lath, short and hexagonal. In addition, when the laser power is increased from 2 kW to 5 kW, the content of β and the dendrite size both increase and the dendrite length increases by about 10 times of the width increase. Under the combination of dendritic refinement and precipitation strengthening, the wear resistance of the fused layer is significantly higher than that of the original magnesium alloy.