Effect of Plane Strain Compression and Subsequent Recrystallization Annealing on Microstructures and Phase Transformatio
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Effect of Plane Strain Compression and Subsequent Recrystallization Annealing on Microstructures and Phase Transformation of NiTiFe Shape Memory Alloy Yulong Liang, Shuyong Jiang, Yanqiu Zhang, and Chengzhi Zhao (Submitted September 24, 2017; in revised form March 12, 2018) The effect of plane strain compression and subsequent recrystallization annealing on microstructures and phase transformation of NiTiFe shape memory alloy (SMA) is investigated. Inhomogeneous plastic deformation at various deformation degrees occurs in NiTiFe SMA during plane strain compression. Nanocrystalline phase and amorphous phase increase as the deformation degree increases. B2 austenite, B19¢ martensite, nanocrystalline and amorphous phases coexist in the NiTiFe samples subjected to large plastic strain. The static recrystallization mechanisms depend on the microstructures of the deformed NiTiFe samples. The static recrystallization mechanisms deal with nucleation and growth of the recrystallized grains, growth of nanocrystalline phase and crystallization of amorphous phase. Grain size, subgrain boundaries, geometrically necessary dislocation density and Schmid factor are captured on the basis of electron backscattered diffraction data. The process of recrystallization annealing cannot eliminate the deformation texture completely. The slip direction [110] is the most favorable slip direction in the recrystallized NiTiFe sample. Plane strain compression along with subsequent recrystallization annealing changes the phase transformation path of as-rolled NiTiFe SMA, and it results in the decreasing martensite transformation start temperature. The three annealed NiTiFe samples exhibit the similar phase transformation behavior since complete recrystallization annealing leads to the similar microstructures. Keywords
NiTiFe alloy, plastic deformation, phase transformation, shape memory alloy, static recrystallization
1. Introduction The near-equiatomic binary NiTi alloy is well known as shape memory alloy (SMA) due to good shape memory effect and superelasticity (Ref 1, 2). However, the engineering application of NiTi SMA is restricted by its limitation of the transformation temperature (Ref 3). The addition of the third element to binary NiTi SMA can change the phase transformation temperatures, which extends the application field of SMAs (Ref 4-6). The addition of Fe element to binary NiTi SMA contributes to lowering the martensitic transformation temperature, and consequently, NiTiFe SMA is extensively used in the aerospace engineering (Ref 7). The mechanical properties of SMAs can be enhanced by means of thermomechanical treatment including cold working and subsequent annealing (Ref 8-10). As we know, the properties of metal materials are closely related to the microstructures, which are influenced by the processing
Yulong Liang, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001, China; and College of Materials Science and Chemical Engineering, Harbin Enginee
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