MC碳化物非平衡凝固生长形态选择规律研究

TiC carbide reinforced intermetallic matrix in-situ composite coatings were fabricated by laser surface alloying and laser cladding. New morphologies of radial-branching facet dendritic and three-dimensionally inter-comnected frame-like dendrite of rapidly and quasi-rapidly solidified TiC carbide were observed in the under laser processed in-situ intermetallic matrix composite coatings with a solidification cooling rate ranging from 10-103K/s. It is demonstrated that free surfaces of TiC carbide, irrespective of the growth morphologyies, are with strong faceted features, indicating that the solid/liquid interface is atomically smooth and the growth mechanisms are lateral growth. Results of this research also indicate that the theoretical predication of lateral to continuous growth with increasing kinetic undercooling for a typical faceted phase is not applicable for those faceted phase with very high entropy of melting.

通过分别对联10-10C/s冷却速度范围内MC碳化物由缓冷近平衡凝固“汉字书写体”向快速凝固“梅花状”生长形态及时性10-10C/s冷却速度范围内快速凝固MC碳化物由“梅花状”向“花草状”生长形态的生长形态演化过程及微观机制的研究，完整地获得从缓冷近平衡凝固到快速凝固宽广非平衡凝固冷却速度范围内、MC碳化物“小面相”非平衡凝固生长形态演化一般规律的理论新认识。