An in situ Study of NiTi Powder Sintering Using Neutron Diffraction

Metals

Gang Chen²  Klaus-Dieter Liss¹  Peng Cao² 

[1] Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia; E-Mail:;Department of Chemical and Materials Engineering, the University of Auckland, Private Bag 92019, Auckland 1142, New Zealand

关键词: NiTi;    powder sintering;    dehydrogenation;    neutron diffraction;   

DOI  :  10.3390/met5020530

来源: mdpi

【 摘 要 】

This study investigates phase transformation and mechanical properties of porous NiTi alloys using two different powder compacts (i.e., Ni/Ti and Ni/TiH₂) by a conventional press-and-sinter means. The compacted powder mixtures were sintered in vacuum at a final temperature of 1373 K. The phase evolution was performed by in situ neutron diffraction upon sintering and cooling. The predominant phase identified in all the produced porous NiTi alloys after being sintered at 1373 K is B2 NiTi phase with the presence of other minor phases. It is found that dehydrogenation of TiH₂ significantly affects the sintering behavior and resultant microstructure. In comparison to the Ni/Ti compact, dehydrogenation occurring in the Ni/TiH₂ compact leads to less densification, yet higher chemical homogenization, after high temperature sintering but not in the case of low temperature sintering. Moreover, there is a direct evidence of the eutectoid decomposition of NiTi at ca. 847 and 823 K for Ni/Ti and Ni/TiH₂, respectively, during furnace cooling. The static and cyclic stress-strain behaviors of the porous NiTi alloys made from the Ni/Ti and Ni/TiH₂ compacts were also investigated. As compared with the Ni/Ti sintered samples, the samplessintered from the Ni/TiH₂ compact exhibited a much higher porosity, a higher close-to-total porosity, a larger pore size and lower tensile and compressive fracture strength.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.