凝固生长形态及机制
(北京航空航天大学 材料学院， 北京 100083)
摘 要: 利用碳对TiAl金属间化合物合金进行激光表面合金化，制得了以TiC （MC碳化物）为增强相的复合材料涂层，研究了MC碳化物的凝固生长形态及生长机制。结果表明：在激光扫描速度为6.0mm/s的凝固条件下，MC碳化物呈现微观上具有“小片链状”生长特征的树枝状生长形态；当激光扫描速度增加至16.4mm/s时，其生长形态又转化为具有“三维网络”生长特征的发达树枝晶；TiC与Al3Ti共晶的动力学生长过程及MC碳化物所固有的侧向生长机制是影响MC碳化物凝固生长形态选择的重要因素。
关键字: MC碳化物； TiC；生长形态； 激光表面合金化
alloyed composite coating on substrate of TiAl intermetallics
（Laboratory of Laser Materials Processing and Surface Engineering,School of Materials, Beijing University of Aeronautics and Astronautics, Beijing 100083， China）
Abstract:TiC reinforced composite coating was fabricated by laser surface alloying on the substrate of TiAl intermetallics. The growth morphology and mechanism of the TiC carbide under rapid solidification conditions were investigated as a function of laser beam scanning speed. TiC carbide under a laser scanning speed of approximate 6.0mm/s is found to be dendritic having the necklace-like faceted growth characteristic on the dendritic arms. TiC carbide under a laser scanning speed of approximate 16.4mm/s is in well-developed dendrite having three-dimensional network growth characteristic. The intrinsic lateral growth of MC carbide and the growth kinetics of TiC and Al3Ti eutectic play an important role in controlling the growth morphology of MC carbide.
Key words: MC carbide; TiC; growth morphology; laser surface alloying
