【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2mm/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0.34mm/s,理论预测值略小于实验确定值;另在100～500mm/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148～7800mm/s,理论预测下限值与实验结果吻合较好。更多还原

【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.更多还原