HVOF微粒撞击诱导镁合金表面纳米化工艺研究

研究了超音速火焰喷涂(HVOF, high velocity oxygen-fuel flame)微粒撞击诱导Mg-15Gd-3Y镁合金表面纳米化新工艺，分析了不同工艺参数对表层变形及纳米化的影响规律。发现撞击钢丸粒径大小、轰击距离和处理时间对表层组织和硬度分布具有重要影响。通过光学显微镜和透射电镜观察了表面自身纳米化处理后镁合金样品表层组织的形变特征和纳米化效果；利用显微硬度仪测试了样品从表面至基体的硬度分布；采用X射线衍射仪分析了纳米化处理前后样品表层的物相变化情况。检测结果显示，该工艺在镁合金材料表面成功实现了自身纳米化，表层晶粒细化至20 nm左右，显微硬度提高至2倍以上，处理后样品表层没有出现氧化

Research on a New Technology of Surface Nanocrystallization in Mg Alloy Induced by HVOF Microparticles Impact

A new technology for surface self-nanocrystallization of Mg-15Gd-3Y magnesium alloy induced by HVOF (high velocity oxygen-fuel flame) microparticles impact at low temperature was investigated, and the influencing rule of the surface layer deformation and nanocrystallization with different processing parameters were analyzed. It is found that diameter size of the impacting steel shots, bombardment distance and treating time have an important influence on the microstructure of deformed layer and microhardness distribution with depth. The deformation characteristics and nanocrystallization effect of the top surface layer of magnesium alloy specimen with the surface self-nanocrystallization were investigated by optical microscopy (OM) and transmission electron microscopy (TEM), respectively. Meanwhile, the microhardness distribution from the topmost surface to the matrix of the specimen was tested by a microhardness tester. The phase of surface layer in the specimen before and after treatment was analyzed using X-ray diffractometer (XRD). Results show that surface self-nanocrystallization of the magnesium alloy is realized by the new technology, verified by the TEM testing results, and grain size of the top surface layer is refined to about 20 nm. The microhardness of the most top surface layer is increased up to above twice as that of the substrate. No oxide of the magnesium alloy is found in top surface layer of the treated specimen.