【作者】 赵永；

【导师】 黄安国；

【作者基本信息】 华中科技大学 ， 数字化材料成型， 2007， 硕士

【摘要】 铝及铝合金是工业中用量最大的有色金属,在航空、航天、汽车、铁路运输业及动力机械等行业中得到了广泛应用。但由于硬度低,耐磨性较差,限制了其进一步应用。激光熔覆是近二十年来发展起来的一种表面强化技术,它具有许多常规方法无法比拟的优势,它可有效地提高铝及铝合金表面的硬度和耐磨性。本文采用CO₂激光器在铝及铝合金基体上涂覆了Y和Y-Al粉末涂层,采用预置粉末涂层法将粉末涂覆于基体表面,采用氩气保护激光熔池,加入一定量CaF2、LiF和MgF2作为造渣剂,在一定的激光熔覆处理工艺参数下,可以获得均匀连续、界面为冶金结合的致密涂层。涂层底部和中下部基相组织为胞状枝晶,中上部和顶部为细小枝晶或等轴晶。以稀土元素Y为熔覆材料的研究在国内目前不多。因为Y和Al的熔点相差很多,在激光熔覆加工过程中Y元素过渡比较困难。本文计算了激光熔覆深度和激光功率、光斑直径和涂层厚度的定量关系,探讨了在铝及铝合金2034表面熔覆铝钇合金涂层的可行性,并利用SEM、XRD、EDS、硬度实验、金相实验等方法研究了制备的熔覆层的组织及性能,同时比较了纯铝及2034铝合金激光熔覆后的涂层的组织和性能,结果表明,涂层硬度较纯铝提高了一倍多,但较2034要低,表明仅依靠激光熔覆Al-Y涂层对提高铝合金2034的表面性能有一定的局限性更多还原

【Abstract】 Al and its alloy have a wide scope of applications in the field of aerospace, auto industries, transportation and power machine and so on due to its low density, high specific strength , etc. But its surface properties such as poor corrosion resistance and wear resistance restrict its wider application in the modern industries. Laser cladding can improve the surface properties of aluminum alloy, which is a new technique has been developed for about twenty years. It has some unique advantages compared with the general material processes.Al-Y alloys coatings have been obtained by CO₂ laser cladding in this paper. The first stage, we placed a layer of Y or Al+Y powers on base metal before laser irradiating, in process, Argon used as shielding gas and CaF2、LiF and MgF2 as slagging, both can protect the melting pool. The coatings have smooth and continuous surface, and get metallurgical bond to the substrate. In the bottom and near the base metal of the clad, the matrix grains are finely cellular or cell-dendrite. we get dendritic and equiaxial grains In middle and top of the clad zone.There is few research about the cladding materials like yttrium at home and abroad. The melting point of Y is much more the Al’s, so Y element transfer to the cladding zone is very difficult. In this paper we calculate the depth of the cladding zone, and discuss the feasibility of creating Al-Y alloys on the Al and Al2034. The microstructure, hardness and component of the cladding coatings zone have been analyzed and tested by use of a series of modern physical test means , such as SEM, XRD, EDS etc. and make a compare between the cladding zone of Al and Al2034. The result is the hardness of cladding zone on Al surface is one times than Al-base. But less than Al2034. The research show that it is limitative to improve the surface properties by cladding Al+Y power on Al2034.更多还原