Papers by Author: Hai Chang Jiang

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Authors: Hai Chang Jiang, Shu Wei Liu, Xiu Yan Li, Li Jian Rong
Abstract: One internal friction peak associated with the B2↔B19’ transformation appears on the cooling curve of porous NiTi shape memory alloy and the dense NiTi alloy shows the maximum peak. The tan δ value increased with the increasing of strain amplitude and the decreasing of frequency. Tan δ value of porous alloy mainly comes from the energy absorbing of the matrix at the small strain amplitude, however, if the strain amplitude is large, the tan δ value comes from the energy consumption that overcomes the friction between folds and the plastic contribution.
Authors: Qing Hua Wang, Hui Min Xie, Hai Chang Jiang, Yan Jie Li, Fu Long Dai, Peng Wan Chen, Qing Ming Zhang, Feng Lei Huang
Abstract: Martensitic phase transformation can greatly affect the mechanical behaviors and the stress-strain response of shape memory alloys (SMAs). In this study, the effect of martensitic phase transformation on the deformation of a single-crystal TiNi SMA specimen with a triangle crack was investigated experimentally by means of moiré interferometry method. A typical displacement field and the corresponding strain field in areas both around and far from the tip of the crack were measured in a certain time during the loading process in which the tensile load is coupled with the stress-induced martensitic phase transformation. Some characteristics of the deformation and the martensitic phase transformation of the specimen are revealed. These results may provide a reliable support for revealing the fracture mechanism of single crystal TiNi SMAs, and may enable further development in putting forward the failure criterion of SMAs.
Authors: Hai Chang Jiang, Li Jian Rong
Abstract: Porous Ti51Ni(49-x)Mox (x=0, 0.7, 1.0, 1.2) shape memory alloys were successfully fabricated by the self-propagating high-temperature synthesis (SHS) method. The effect of Mo content on microstructures, transformation characteristics and compressive properties of porous TiNiMo alloys was investigated systemically. It has been found that Mo doping into porous TiNi alloys will induce R phase transformation. A small amount of Mo addition (0.7at.%) improves compressive properties of porous TiNiMo alloy due to Mo solution strengthening and the obvious ductile fracture is observed on the fracture photography. However, the compressive strength and compressive strain of porous TiNiMo alloys with excessive Mo content decrease sharply and the failure manner turned into brittle fracture mode, which results from a large amount of Ti2Ni and Ti4Ni2O phases precipitated at grain boundary. Porous Ti51Ni48.3Mo0.7 alloy with suitable transformation temperature and high compressive strength is very promising for use as biomaterial and damping material.
Authors: Hua Du, Hui Min Xie, Hai Chang Jiang, Li Jian Rong, Qi Ang Luo, Chang Zhi Gu, Ya-Pu Zhao
Abstract: In this paper, a new technique for fabricating grating on the surface of porous TiNi SMA is proposed. The grating is directly written onto the surface of the specimen using the FIB milling. No photoresist is required during the lithography process. From the experimental results, it can be obviously seen that the grating fabricated by FIB milling has a better quality than that by electron beam lithography. Using the self-made FIB grating, the in-plane deformation of the porous TiNi SMA in microscale is studied by SEM moiré method. Moiré and the microscopical structures are synchronously observed, including microcracks, martensites and grain boundaries.
Authors: Qing Hua Wang, Hui Min Xie, Hai Chang Jiang, Bing Pan, Fu Long Dai
Abstract: TiNi/Al-12%Si alloy is a kind of prospective material used as special energy absorbers for eliminating undesirable noise and mechanical vibration. The investigation on the mechanical properties of this composite alloy is of great importance. In this study, the surface deformation of TiNi/Al-12%Si composite alloy under external loading was measured experimentally by means of DSCM method. Some deformation characteristics of TiNi/AlSi composite alloy under the effect of the tensile load and the interaction between TiNi and AlSi are discussed. In addition, the elastic modulus and the poisson ' s ratio of this alloy were measured as well. The results agrees well with the theory predicts.
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