热处理温度对NiTiNb_5相变温度和组织的影响

Influence of Heat Treatment Temperature on Phase Transformaition Temperature and Microstructure of NiTiNb_5 Alloy

采用差式扫描量热仪(DSC)、扫描电镜(SEM)和金相显微镜,研究了新型材料NiTiNb5合金经200～900℃热处理后的相变温度、相变滞后(As-Ms)、相变焓以及微观组织的变化。结果表明,当热处理温度低于700℃时,不论是锻态还是轧态,合金都没有出现马氏体及其逆相变,表明铸态NiTiNb5形状记忆合金经锻造或轧制后不再具有形状记忆效应,转变成结构材料;当热处理温度提高到800℃后,NiTiNb5合金锻态或轧态又出现较明显的马氏体及其逆相变,表明NiTiNb5合金经过合适的热处理,恢复了形状记忆效应。组织分析表明,800℃后的再结晶是NiTiNb5合金恢复"功能材料"特性的主要原因。

Influence of heat treatment at 200~900 ℃ on phase transformation temperature,phase hysteresis(As-Ms),phase transformaition enthalpy(ΔH)and microstructure of NiTiNb5 shape memory alloy was investigated by DSC,OM and SEM.The results show that the absence of martensite or reverse phase transformation can be observed at both forged NiTiNb5 alloy and rolled one with heat treatment at below 700 ℃,which shows the NiTiNb5 alloy transforms into structural material.However,with increasing heat treatment temperature to higher than 800 ℃,the martensitic phase and its reverse transformation can be observed in forged NiTiNb5 alloy or rolled one,showing the recovery of shaped memory effects.The microstructure analysis exhibits that the recrystallization in NiTiNb5 alloy is mainly responsible for its recovery functional materials performance after heat treatment at more than 800 ℃.