(西北工業(yè)大學(xué) 凝固技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安 710072)
摘 要: 利用激光表面快速熔凝技術(shù)對(duì)Nd13.5Fe79.75B6.75過包晶合金的凝固組織及其變化規(guī)律進(jìn)行研究。結(jié)果表明：當(dāng)掃描速度大于2 mm/s時(shí)，包晶反應(yīng)(γ+L→T1)被抑制，包晶T1相可直接從液相中析出(L→T1)。根據(jù)最高界面生長(zhǎng)溫度判據(jù)及KGT模型計(jì)算了T1相領(lǐng)先析出的臨界生長(zhǎng)速度為0.34 mm/s，理論預(yù)測(cè)值略小于實(shí)驗(yàn)確定值；另在100~500 mm/s掃描速度范圍內(nèi)觀測(cè)到粗胞晶→細(xì)胞晶→平界面的不同凝固形態(tài)的高速帶狀組織，理論預(yù)測(cè)此合金形成高速帶狀組織的速度范圍為148~7 800 mm/s，理論預(yù)測(cè)下限值與實(shí)驗(yàn)結(jié)果吻合較好。
關(guān)鍵字: Nd13.5Fe79.75B6.75；包晶合金；激光表面快凝；相轉(zhuǎn)變；帶狀組織
（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
