Stress exponent and threshold stress of in situ TiCp/LD7Al matrix composite in creep

Abstract

The elevated temperature creep behavior of in situ 20vol%TiCP/LD7Al matrix composite and LD7Al alloy was investigated under the condition of constant compressive stress at 523 K，573 K and 623 K，respectively. The stress exponents of the composite material and the matrix aluminium alloy were obtained by fitting the creep rate and the applied stress in log-log plot，respectively. By introducing an effective stress （σ-σ0） to the power equation and extroplating the linearly-regressed experemental data to zero creep rate，the threshold stresses were obtained. The results showed that both the stress exponents and the threshold stresses of the composite were higher than those of LD7Al，indicating that the presence of TiC particles significantly improved the elevated temperature creep property of LD7Al. By introducing a threshold stress，the high-temperature creep behavior of the composite can be explained by the cooperative effect of the dislocation-climbing and the particle hindrance to the matrix deformation.