Changes of the elastic constants of V, Nb, and Ta by hydrogen and deuterium

By ultrasonic methods the elastic constants of V, Nb, and Ta are determined at room temperature after loading with hydrogen and deuterium. For Nb and Ta also the change of the temperature dependence of the elastic constants on alloying are determined up to 300°C. All measurements are performed in the cubic α-phases. The three alloy systems show qualitatively the same behaviour: The bulk moduli are nearly unaffected whereas the shear constants C44 increase. These changes are independent of the hydrogen isotope. The shear constants (C11–C12)/2 decrease as a function of alloy concentration and these decreases are isotope-dependent, being stronger for hydrogen than for deuterium.