The Elastic Constants of Ni3Al to 1.4 GPa.

NI3Al, having the L12 ordered structure, belongs to a class of intermetallic compounds which shows unusual mechanical behavior, namely a peak in mechanical strength with an increase in temperature. The peak temperature for Ni3Al is 922 K, where the yield stress value is four times its value at room temperature. A large number of investigations determining the dependence of different physical properties as a function of temperature have been done, but the pressure dependence of the properties of Ni3Al remains to be investigated in depth. The present report fills this gap in our information by determining the pressure dependence of the three elastic constants c11, c12, and c44 of single-crystal Ni3Al to 1.4 GPa at room temperature. The pressure derivatives of the elastic constants of single-crystal Ni3Al have been determined to 1.4 GPa by both superposition and pulse-echo overlap techniques. Measurements were made on single-crystal specimens of orientation 100 and 110, thus providing at least one cross-check. The values of c11, c12, and c44 at one atmosphere are found to be 223.5, 149.0, and 12.9 GPa, respectively. The pressure derivatives of the elastic constants have been determined. Keywords Ultrasonics.