CREEP AND MICROSTRUCTURAL STABILITY OF DISPERSION-STRENGTHENED AL-FE-V-SI-ER ALLOY

A planar flow cast Al-Fe-Si-V alloy modified with 0.75 wt.% Er was eva luated in terms of creep response and elevated temperature stability. Creep tests were conducted at temperatures and stresses ranging from 2 91 to 426-degrees-C and 71.86 to 186.4 MPa respectively. In addition, isothermal coarsening was assessed at temperatures of 375, 475 and 525 -degrees-C for times up to 456 h. Steady state creep rates, at 375-deg rees-C were in the range 1.7 x 10(-10) to 1.2 x 10(-5) s-1. Creep prop erties were analyzed in terms of Arrhenius-type equations and the cree p response was found to be controlled by the self diffusion of aluminu m. Coarsening was monitored by hardness measurements and dispersoid si ze and was found to be insignificant at 375-degrees-C. At 475 and 525- degrees-C the average precipitate size increased from 0.087 mum to 0.1 63 mum and 0.195 mum respectively after 456 h; this resulted in soften ing of the alloy. The measured coarsening rates were in good agreement with the rates predicted by the Lifshitz-Slyozov-Wagner (LSW) theory.