Creep and microstructural stability of dispersion strengthened AlFeVSiEr alloy

Abstract

A planar flow cast AlFeSiV alloy modified with 0.75 wt.% Er was evaluated in terms of creep response and elevated temperature stability. Creep tests were conducted at temperature and stresses ranging from 291 to 426 °C and 71.86 to 186.4 MPa respectively. In addition, isothermal coarsening was assessed at temperatures of 375, 475 and 525 °C for times up to 456 h. Steady state creep rates, at 375 °C were in the range 1.7 × 10 −10 to 1.2 × 10 −5 s −1. Creep properties were analyzed in terms of Arrheninius-type equations and the creep response was found to be controlled by the self diffusion of aluminium. Coarsening was monitored by hardness measurements and dispersoid size and was found to be insignificant at 375 °C. At 475 and 525 °C the average precipitate size increased from 0.087 μm to 0.163 μm and 0.195 μm respectively after 456 h; this resulted in softening of the alloy. The measured coarsening rates were in good agreement with the rates predicted by the Lifshitz-Slyozov-Wagner (LSW) theory.