Improvement in compressive creep resistance of Al-0.2Zr alloy with L12 structured Sc-enriched precipitates

The influence of Sc microalloying on compressive creep behaviors of Al-0.2Zr and Al-0.2Zr-0.1Sc alloy have been studied. The steady state creep rate of Al-0.2Zr-0.1Sc alloy ranged from 1.124 x 10(-9) s(-1) to 1.926 x 10(-8) s(-1) at 90-150 degrees C/70 MPa. By contrast, the steady state creep rate of Al-0.2Zr alloy ranged from 6.862 x 10(-8) s(-1) to 8.560 x 10(-7) s(-1), indicating that Sc addition significantly improve the compressive creep resistance of Al-0.2Zr alloy. According to the TEM micrographs, except for Al-3(Zr,Sc) precipitates precipitated during aging, a large number of fine dispersed Al3Sc precipitates precipitated after creep for 70 h, which significantly hinder movements of dislocations and grain boundaries. As a result, the steady-state creep rate of Al-0.2Zr-0.1Sc alloy slightly decreases after 70 hat 150 degrees C/70 MPa. The critical creep stress value of Al-0.2Zr alloy is 47.2 MPa, and that of Al-0.2Zr-0.1Sc alloy is 68.4 MPa. The higher critical creep stress value indicates the more excellent compressive creep resistance.