ICT2014 Abstracts

The intermetallic half-Heusler (HH) compound ZrNiSn is of interest as a thermoelectric material for waste heat recovery applications. This is the first comprehensive study of the dependence of the elastic moduli and hardness of ZrNiSn on porosity and the powder processing technique. In this study, eleven polycrystalline ZrNiSn specimens were prepared from arc melted ingots that were subsequently powder processed (by mortar and pestle or planetary milling) and then densified by pulsed electric current sintering (PECS). Powders for four additional specimens were prepared by vibratory milling and then densified by PECS. Using a range of sintering temperatures between 800^oC and 1025^oC, the volume fraction porosity, P, of the specimens was intentionally varied from 0.01 to 0.24. The room temperature Young’s modulus, shear modulus and Poisson’s ratio were determined by resonant ultrasound spectroscopy (RUS) and the room temperature hardness was measured by Vickers indentation. Both porosity dependence of the elastic moduli and the hardness can be described well by the empirical exponential relationship A(P) = A₀exp(-b_AP) where A is the porosity-dependent mechanical property, A₀ is the value of A at P = 0, and b_Ais a measure of the rate of decrease in A with increasing P.  Differences in the elastic moduli for specimens fabricated from the vibratory and planetary milled powders may be related to antisite defects in the ZrNiSn.