NON-EQUILIBRIUM STATE AND DIFFUSION CREEP IN CERAMET BODIES

Powder compacts of Cu, Ni, and Fe, and a mixture of these powders at initial porosities of 30 to 32% were subjected to tensile creep at temperatures up to 1250 C in a vacuum. The observed elongations were plotted as a function of time for various durations of time under isothermal conditions (1000 C) at a constant load (10 g/sq mm). For pure Cu powders, the initial strain rate as well as the total deformation in creep decreased as the duration of preliminary annealing was increased. For a 50/50 mixture of Cu and Ni powders, the initial (15 min or less) strain rate showed an increase which is postulated to result from a large quantity of excess vacancies because of the inequality of the partial diffusion coefficients of Cu and Ni. When the duration of preliminary annealing was prolonged (more than 1 hr), the creep strain of the mixture was reduced and became smaller than that of pure Cu. Specimens with different initial porosities had different initial creep rates, but after annealing the creep rates became identical. (Author) Trans. of Fizika Metallov i Metallovedeniye 8: pp. 766-776, 1959.