title: Phase transformation evolution in NiTi shape memory alloy under cyclic nanoindentation loadings at dissimilar rates.
abstract: Hysteresis energy decreased significantly as nanocrystalline NiTi shape memory alloy was under triangular cyclic nanoindentation loadings at high rate. Jagged curves evidenced discrete stress relaxations. With a large recovery state of maximum deformation in each cycle, this behavior concluded in several nucleation sites of phase transformation in stressed bulk. Additionally, the higher initial propagation velocity of interface and thermal activation volume, and higher levels of phase transition stress in subsequent cycles explained the monotonic decreasing trend of dissipated energy. In contrast, the dissipated energy showed an opposite increasing trend during triangular cyclic loadings at a low rate and 60 sec holding time after each unloading stage. Due to the isothermal loading rate and the holding time, a major part of the released latent heat was transferred during the cyclic loading resulting in an unchanged phase transition stress. This fact with the reorientation phenomenon explained the monotonic increasing trend of hysteresis energy.
authors: 1] Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, VIC 3010, Australia [2] frontierTECH, Melbourne, VIC 3141, Australia.
authors: Abbas
authors: A
authors: Amini
authors: Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055, P. R. China.
authors: Chun
authors: C
authors: Cheng
authors: School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, P. R. China.
authors: Qianhua
authors: Q
authors: Kan
authors: Institute for Frontier Materials (IFM), Deakin University, Waurn Ponds, VIC 3217, Australia.
authors: Minoo
authors: M
authors: Naebe
authors: Wuhan National Laboratory for Optoelectronics (WNLO) and the School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.
authors: Haisheng
authors: H
authors: Song