凝固生長形態(tài)及機制
(北京航空航天大學 材料學院， 北京 100083)
摘 要: 利用碳對TiAl金屬間化合物合金進行激光表面合金化，制得了以TiC （MC碳化物）為增強相的復合材料涂層，研究了MC碳化物的凝固生長形態(tài)及生長機制。結果表明：在激光掃描速度為6.0mm/s的凝固條件下，MC碳化物呈現(xiàn)微觀上具有“小片鏈狀”生長特征的樹枝狀生長形態(tài)；當激光掃描速度增加至16.4mm/s時，其生長形態(tài)又轉化為具有“三維網絡”生長特征的發(fā)達樹枝晶；TiC與Al3Ti共晶的動力學生長過程及MC碳化物所固有的側向生長機制是影響MC碳化物凝固生長形態(tài)選擇的重要因素。
關鍵字: MC碳化物； TiC；生長形態(tài)； 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
