Microstructure and tensile properties of isothermally forged Ni–43Ti–4Al–2Nb–2Hf alloy

作     者：Xiao-Yun Song Yan Li Fei Zhang 

作者机构：State Key Laboratory of Nonferrous Metals & Processes General Research Institute for Nonferrous Metals Key Laboratory of Aerospace Materials and Performance (Ministry of Education) Beijing University of Aeronautics and Astronautics 

出 版 物：《Rare Metals》 (稀有金属（英文版）)

年 卷 期：2013年第32卷第5期

页      面：475-479页

核心收录：

学科分类：080503[工学-材料加工工程] 08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0802[工学-机械工程] 080201[工学-机械制造及其自动化] 

基　　金：supported by the National Natural Science Foundation of China (No. 51201016) 

主　　题：Intermetallics NiTi-Al alloy Isothermal forging Tensile property Microstructure 

摘      要：NiTi-Al-based alloys are promising high-tem- perature structural materials for aerospace and astronautics applications. A new NiTi-Al-based alloy Ni--43Ti-4AI- 2Nb-2Hf （at%） was processed via isothermal forging. The microstructure and mechanical properties at room temperature and high temperature were investigated through scanning electron microscope （SEM）, X-ray diffraction （XRD）, and tensile tests. Results show that the micro- structure of as-forged Ni-43Ti--4AI-2Nb-2Hf alloy con- sists of NiTi matrix, Ti2Ni phase, and Hf-rich phase. The simultaneous addition of Nb and Hf, which have strong affinities for Ti sites, promotes the precipitation of Hf-rich phases along the grain boundaries. The tensile strengths of Ni-43Ti-4A1-2Nb-2Hf alloy are dramatically increased compared with the ternary Ni-46Ti-4A1 alloy. At room temperature and 650℃, the yield stress of Ni--43Ti-4Al- 2Nb-2Hf alloy reaches 1,070 and 610 MPa, respectively, which are 30 % and 150 % higher than those of Ni--46Ti- 4Al alloy. The improved tensile property results from the solid solution strengthening by Nb and Hf, as well as the dispersion hardening of the Ti2Ni and Hf-rich phases.