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Microstructure and martensitic transformation in quaternary NiTiHfV alloy

Microstructure and martensitic transformation in quaternary NiTiHfV alloy

SHUITCEV Aleksandr
REN Yi
ZHANG Ze-zhong
VASIN Roman
SUN Bin
LI Li
TONG Yun-xiang
400

The effect of age hardening on the microstructure, martensitic transformation behavior, and shape memory properties of the (Ni50Ti30Hf20)95V5 alloy was investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, microhardness, and bending tests. The results demonstrate a significant influence of V addition on the microstructure of the alloy. V addition leads to the formation of a (Ni,V)2(Ti,Hf)-type Laves phase, which coexists with B19'''' martensite at room temperature. Aging at 550 °C results in precipitation hardening due to the formation of nano-scale orthorhombic H-phase, with the peak hardness observed after 3 h of aging. The alloy at peak hardness state exhibits higher transformation strain and lower unrecovered strain compared to the solution-treated sample. The aged sample achieves a maximum transformation strain of 1.56% under 500 MPa.

shape memory alloysNiTiHfVH-phaseLaves phasemartensitic transformation