Grain Size Effects On Young'S Modulus And Hardness Of Nanocrystalline Niti Shape Memory Alloy

In this paper, the effects of grain size on the Young's modulus and hardness of nanocrystalline NiTi are investigated by macroscopic isothermal tension and microscopic nanoindentation. Amorphous NiTi with nanocrystalline debris is fabricated through 50% thickness reduction cold-rolling. Polycrystalline NiTi with average grain size of 10-100 nm are obtained by annealing and subsequent water quenching. It's shown that as the grain size decreases in the nano region (below 100 nm), hardness of the nanocrystalline NiTi consistently increase but the change of modulus is non-monotonic with a minimum value at around 60 nm.