(1. 南昌航空大學(xué) 輕合金加工科學(xué)與技術(shù)國防重點學(xué)科實驗室，南昌 330063；
2. 江西省航空制造業(yè)協(xié)同創(chuàng)新中心，南昌 330063；
3. 西北工業(yè)大學(xué) 凝固技術(shù)國家重點實驗室，西安 710072)
摘 要: 采用差熱分析與階梯銅模噴鑄技術(shù)，研究不同冷卻速率作用下Cu70Zr30 合金初生相尺寸、形貌以及包晶層厚度等的演化規(guī)律，討論相選擇與包晶轉(zhuǎn)變的形成機理。結(jié)果表明：近平衡凝固條件下，差熱分析試樣中初生相形成與包晶轉(zhuǎn)變的發(fā)生溫度分別為1042 ℃和957 ℃，均滯后于平衡相圖中相應(yīng)的溫度。由于包晶相兩側(cè)成分區(qū)間相差不大，且固態(tài)中原子擴散系數(shù)較小，因此，平均包晶層厚度僅為5 μm，并存在殘余的Cu51Zr14 初生相。銅模噴鑄條件下，非平衡凝固組織中初生相結(jié)構(gòu)未發(fā)生改變，但包晶轉(zhuǎn)變得到有效抑制。隨冷卻速率提高，過冷度的增加有利于形核發(fā)生，初生相形貌從定向束狀向等軸晶發(fā)生轉(zhuǎn)變。
關(guān)鍵字: Cu-Zr 合金；冷卻速率；非平衡凝固；相選擇；包晶轉(zhuǎn)變
（1. National Defense Key Discipline Laboratory of Light Alloy Processing Science and Technology,
Nanchang Hangkong University,Nanchang 330063,China;
2. Collaborative Innovation Center for Aviation Manufacturing Industry of Jiangxi Province,Nanchang 330063,China;
3. State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072,China）
Abstract:The effects of cooling rate on the size and morphology of primary phase in Cu70Zr30 alloy,as well as the thickness of peritectic layer were investigated by differential thermal analysis and step copper mould spray casting techniques. The formation mechanisms of phase selection and peritectic transformation were discussed. The results show that the measured temperatures for primary phase and peritectic transformation are respectively 1042 ℃ and 957 ℃ in near-equilibrium solidification,which are smaller than the values from equilibrium phase diagram. Due to slight composition interval between the adjacent regions of peritectic phase and sluggish solute diffusion rate in solid,the average thickness of peritectic layer is merely 5 μm with the presence of residual primary phase Cu51Zr14. The structure of primary phase is not changed by copper mould spray casting,while peritectic transformation is suppressed effectively. With increasing cooling rate,undercooling is enhanced to activate more nucleation events,which generates the morphology transition of primary phase from directionally bundle to equiaxed-grain microstructure.
Key words: Cu-Zr alloy; cooling rate; non-equilibrium solidification; phase selection; peritectic transformation
