分散強化型合金のOrowanループによる加工硬化の温度依存性

Abstract

The temperature dependence of work-hardening of dispersion-hardened alloy, which is due to Orowan loops formed around dispersed particles, has been calculated using a model that Orowan loops climb and annihilate through a pipe diffusion of vacancies along the loops during the deformation. Assuming a uniform distribution of Orowan loops around each particle, the rate of their annihilation was obtained by considering the total vacancy flux in a whole distribution of loops, and the amount and rate of work-hardening were finally given as a function of deformation temperature and particle size. These expressions were extended to the case in which there was a distribution of particle size.The calculation fairly well accounted for the temperature dependence and particle-size dependence of work-hardening rate in an Al-1.2%Si alloy containing silicon particles, when reasonable values of the diffusion coefficient of pipe diffusion, that is, D0p=10−3 cm2/s, Qp=58.6 kJ/(mol·K) or D0p=10−2 cm2/s, Qp=66.9 kJ/(mol·K), were used, where D0p and Qp mean a frequency factor and an activation energy for pipe diffusion, respectively. However, the work-hardening rate calculated decreased rapidly with increasing deformation temperature in a narrow temperature range compared to the measurements on the Al-1.2%Si alloy. This discrepancy has been ascribed to the fact that although the rate of climb of the Orowan loop depends on its position lying on particle interface, the position was not taken into account in the present calculation.