Product microstructure of Ti-Ni-Nb shape memory alloy (SMA) by high-temperature synthesis (SHS) of self-propagating

Experiments of the combustion synthesis of the Ti-Ni-Nb SMA have been done by SHS technique. The influences of powder particle size,purity and heating temperature on the microstructure of thermo-explosion synthesised products were investigated. It is found that the powders of higher purity, the fine niobium powders, and the titanium powders with moderate particle size (26 mum) are beneficial to the products of high-density and less impurity phase, such as (Ti,Nb)(2)Ni,etc. Regular reaction sintering occured only as the heating temperature is lower than 1 173 K for thermo-explosion reaction. At the thermo-explosion temperature, the synthesised products consist of the (Ti,Nb)Ni matrix phase,the (Ti,Nb)(2)Ni impurity phase and the eutectic phase beta-Nb(Ti,Ni) - (Ti,Nb)Ni. At the temperature higher than the thermo-explosion temperature, the eutectic phase nearly disapperaed, while the matrix grains are coarsened.