Transactions of Nonferrous Metals Society of China
JOURNAL OF RAILWAY SCIENCE AND ENGINEERING
|Vol. 16 No. 1 February 2006|
Ni-rich NiTi SMA prepared by SHS technique
（1. Department of Materials Science and Engineering, Southeast University, Nanjing 210096, China;
2. Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China）
Abstract:The effects of heat treatment on the microstructure and compressive properties of porous Ni-rich NiTi shape memory alloy (SMA) fabricated by self-propagating high-temperature synthesis (SHS) were investigated. The solution treatment at 1050℃ has little effects on stable Ti2Ni second phase, however, it decreases the amount of Ni4Ti3 phase derived from the SHS process and results in the improvement of the ductility of porous NiTi SMA. The subsequent aging treatment after solution treatment could lead to the precipitation of the discrete Ni4Ti3 phase in NiTi matrix grains, which increases the brittleness of porous NiTi SMA. Porous NiTi SMA presents a composite fracture behavior consisting of a ductile fracture of NiTi matrix and a cleavage fracture of second phase particles. Many cracks existing on the interfaces indicate that the bonding of the matrix with second phase particles is weak.
Key words: NiTi shape memory alloy; porous material; self-propagating high-temperature synthesis; microstructure; compressive properties