THE INFLUENCE OF MATRIX MICROSTRUCTURE AND PARTICLE REINFORCEMENT ON THE CREEP-BEHAVIOR OF 2219 ALUMINUM

The influence of matrix microstructure and reinforcement with 15 vol p ct of TiC particles on the creep behavior of 2219 aluminum has been ex amined in the temperature range of 150-degrees-C to 250-degrees-C. At 150-degrees-C, reinforcement led to an improvement in creep resistance , while at 250-degrees-C, both materials exhibited essentially identic al creep behavior. Precipitate spacing in the matrix exerted the predo minant influence on minimum creep rate in both the unreinforced and th e reinforced materials over the temperature range studied. This behavi or and the high-stress dependence of minimum creep rate are explained using existing constant structure models where, in the present study, precipitate spacing is identified as the pertinent substructure dimens ion. A modest microstructure-independent strengthening from particle r einforcement was observed at 150-degrees-C and was accurately modeled by existing continuum mechanical models. The absence of reinforcement creep strengthening at 250-degrees-C can be attributed to diffusional relaxation processes at the higher temperature.