【作者】 李婷；

【导师】 王存山；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2010， 硕士

【摘要】 镁、铝合金因其密度小、比强度高、导电导热性能好成为理想的工程材料。但镁、铝合金较低耐腐蚀性能和力学性能制约了其在生产中的应用。因此采用激光熔覆技术提高轻合金表面性能具有深远的研究意义和应用价值。钛基合金不仅具有良好的耐蚀性能、耐磨性能,还具有很高的强度和硬度,而且与镁、铝合金有较好的物化相容性,是轻合金表面改性的理想材料。本文基于团簇线判据原理,在二元团簇结构附近二元深共晶点,通过加入第三组元的方式设计一系列合金成分,并通过组织、性能测试等进行了成分优化,可知,当Al含量为7.5at.％时,所得合金成分晶粒最细小,熔点低,硬度高且有优良的耐腐蚀性能,成为轻合金表面良好的熔覆材料。在镁合金表面激光熔覆Ti70.3 Ni22.2Al7.5合金,由于镁合金的稀释作用,使涂层中还有少量的镁元素存在。激光功率和光斑直径一定时,涂层主要是由Ti2Ni金属间化合物和β-Ti相组成,激光扫描速度为6mm／s时,获得的涂层具有组织细小,硬度最大,高的耐磨性和耐腐蚀性能。再次,在上述实验优化的工艺参数基础上,在铝合金表面进行了激光熔覆Ti70.3Ni22.2Al7.5合金的实验,获得了具有优良冶金结合的涂层。合金涂层组织是由Ti2Ni金属间化合物和β-Ti相组成。随着激光扫描速度的增加,合金涂层的组织有明显变化,在扫描速度为6mm／s时,组织为细小的锯齿状树枝晶；受晶粒大小的影响,激光扫描速度为6mm／s时涂层获得最大的显微硬度和良好的抗摩擦磨损能力；不同扫描速度下的涂层均具有良好的抗腐蚀能力。比较了在镁合金基体和铝合金基体上激光熔覆的涂层组织与性能,可见,在铝合金基体上获得的涂层组织更为细小,涂层的硬度也有较大提高,而基体材料的变化对涂层合金的耐磨性和耐蚀性影响并不显著。更多还原

【Abstract】 Magnesium (Mg) alloy and Aluminum (Al) alloy as the ideal engineering material for there low density, high specific strength and good thermal conductivity properties. However, the poor corrosion resistance and the mechanical properties of Light alloy restricted there application in production. Therefore, the laser cladding technology used to improve the surface properties of Light alloy with great research significance and application prospect.Titanium(Ti)-based alloy becomes the ideal surface modification of Light alloy material because of its good corrosion resistance, wear resistance, high strength and hardness, and also has better physical and chemical compatibility with Mg alloy and Aluminum alloy.Based on the cluster line criterion theory, binary clusters in the vicinity of the binary eutectic point, by adding the third element in the way of designing a series of alloy composition, which is optimizated by structure analysis and performance tests. The results show that when the Al content was 7.5at.%, the proceeds of the smallest grain of alloy composition, low melting point, high hardness and excellent corrosion resistance have become well-Light alloys cladding material.The study of the laser clad Ti70.3 Ni22.2Al7.5 alloy coating on the Mg alloys show that, due to the dilution effect of Mg alloy, there also have a small amount of Mg alloy compounds. When the Laser power and spot diameter have no change, and the scanning speed is 6mm/s, the clad layer has small organization, which also has the maximum hardness, high wear resistance and corrosion resistance.Based on the laser cladding of Mg alloy, we get the optimal process parameters, then in aluminum surface by laser cladding Ti70.3Ni22.2Al7.5 experimental, obtained with excellent metallurgical bonding of the coating alloys. the microstructure of the coating is composed of Ti2Ni intermetallic andβ-Ti phase; With the increase of scanning speed, alloy coating significantly changes, in the scan speed of 6mm/s, the organization is the small jagged dendrite; by the size of the grain, when speed is 6mm/s, the coating has good wear resistance ability; different scanning speeds of the coating have good corrosion resistance.Comparing the coating alloy between the magnesium alloy and aluminum alloy, the results show that, the microstructure of coating was smaller in the aluminum alloy substrates, the hardness has improved. The coating alloy’s corrosion resistance and wear resistance is no significant change with difference of the substrate materials.更多还原