Single-crystal elastic constants of Fe-15Ni-15Cr alloy

Resonant ultrasound spectroscopy (RUS) and pulse-echo (PE) superposition techniques have been used to determine the three independent elastic-stiffness constants C(11), C(12), and C(44) as a function of temperature for single crystals of 70Fe-15Ni-15Cr alloy. The values of the elastic moduli determined using RUS and PE are in very good agreement within the range of uncertainties. This particular ternary composition of Fe, Ni, and Cr undergoes an fcc-bcc structural phase transformation near 190 K resulting in a low-temperature ferromagnetic phase. The Debye characteristic temperature was determined to be 447 K from PE and 451 K from RUS measurements. The Zener elastic anisotropy A = 2C(44)/(C(11)-C(12)) is nearly constant: A = 3.53 +/- 0.16 in Fe-Ni-Cr alloys with similar compositions. For these alloys, only small variations are observed in the Griineisen parameter, gamma approximate to 2.08, and in the Poisson ratio, nu([hkl]) = 0.293 +/- 0.013.