(西北工业大学 凝固技术国家重点实验室，西安 710072)
摘 要: 利用激光表面快速熔凝技术对Nd13.5Fe79.75B6.75过包晶合金的凝固组织及其变化规律进行研究。结果表明：当扫描速度大于2 mm/s时，包晶反应(γ+L→T1)被抑制，包晶T1相可直接从液相中析出(L→T1)。根据最高界面生长温度判据及KGT模型计算了T1相领先析出的临界生长速度为0.34 mm/s，理论预测值略小于实验确定值；另在100~500 mm/s扫描速度范围内观测到粗胞晶→细胞晶→平界面的不同凝固形态的高速带状组织，理论预测此合金形成高速带状组织的速度范围为148~7 800 mm/s，理论预测下限值与实验结果吻合较好。
关键字: Nd13.5Fe79.75B6.75；包晶合金；激光表面快凝；相转变；带状组织
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract: Laser rapid solidification experiments were performed on Nd13.5Fe79.75B6.75 hyperperitectic alloy to investigate microstructure evolution. The results show that at scanning velocity higher than 2 mm/s, peritectic T1 phase directly precipitates from the liquid instead of by peritectic reaction. Using KGT model and the maximum growth temperature criterion, critical velocity for the transition from primary γ-Fe phase to T1 phase is calculated to be 0.34 mm/s, which approaches the experimental value of 2 mm/s. High velocity banding structure, showing oscillatory plane front and cellular microstructures, is firstly detected in Nd13.5Fe79.75B6.75 peritectic alloys. The growth velocity for banding structure is deduced to be in the range of 100−500 mm/s. The experimental appearance of the banding structure agrees well with the theoretical prediction.
Key words: Nd13.5Fe79.75B6.75; peritectic alloy; laser rapid solidification; phase transition; banded structure
