Research on the Hot Deformation Behavior of the Casting NiTi Alloy.

Chengchuang Tao,Ge Zhou,Hongjun Huang,Bowen Zheng,Xiaoguang Yuan,Lijia Chen,Xiaojiao Zuo

doi:10.3390/ma14206173

Abstract

The hot deformation behavior and processing maps of the casting NiTi alloy were studied at the deformation temperature of 650–1050 °C and the strain rate of 5 × 10−3–1 s−1 by Gleeble-3800 thermal simulating tester. The variation of the strain rate sensitivity exponent m and the activation energy Q under different deformation conditions (T = 650–1050 °C, = 0.005–1 s−1) were obtained. The formability of the NiTi alloy was the best from 800 °C to 950 °C. The constitutive equation of the casting NiTi alloy was constructed by the Arrhenius model. The processing map of the casting NiTi alloy was plotted according to the dynamic material model (DMM) based on the Prasad instability criterion. The optimal processing areas were at 800–950 °C and 0.005–0.05 s−1. The microstructure of the casting NiTi alloy was analyzed by TEM, SEM and EBSD. The softening mechanisms of the casting NiTi alloy were mainly dynamic recrystallization of the Ti2Ni phase and the nucleation and growth of fine martensite.

Highlights

Materials 2021, 14, 6173. https://The NiTi shape memory alloy was firstly discovered at the US Navy Ordnance Laboratory
The NiTi alloy possesses the advantage of shape memory effect (SME), super elastic (SE) and excellent corrosion resistance [1,2,3], which is widely used in automotive, aerospace, and other fields [4,5,6,7,8,9]
The sample was selected in the axial direction

Summary

Introduction

The NiTi shape memory alloy was firstly discovered at the US Navy Ordnance Laboratory. Chang et al [10] found the optimal shape memory effect of the NiTi alloy was obtained at 300 ◦ C × 100 h through studying the influence of aging process on the shape memory effect and superelastic properties. Fan et al [11] investigated the phase transformation behavior of the Ni51.1-Ti (at.%) alloy by thermodynamic and experimental methods. Takeda et al [12] researched the influence of creep conditions on the volume fraction of the martensitic phase of the NiTi alloy by studying the thermodynamic properties of the NiTi alloy. The NiTi binary alloy has become one of the hottest topics

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Conclusion