The corelation between creep resistance and microstructure in AA6111 alloy strengthened by synergistic Er, Zr addition

Abstract

In this research work, the creep behavior of AA6111 alloy strengthened by Er, Zr microalloying was investigated at 473–573 K/70–90 MPa. The results showed that the improvement on creep resistance induced by synergistic Er, Zr addition was better than the only Er addition, which can be attributed to the formation of Ll2-ordered Al3(Er, Zr) precipitates with special core-shell structure. The outer shell composed of slowing-diffusing Zr could act as a diffusion barrier, decreasing the coarsening rate and maintaining the thermal stability of Al3(Er, Zr) nanoprecipitates at high temperature. Thus, these nanosized Al3(Er, Zr) precipitates could hinder the movement of dislocations as well as pin grain boundaries effectively during creep process. Besides, coarse intermetallics embedded on grain boundaries were also refined to tiny pieces assisted by Er, Zr modification, which is an important reason for such prominent creep performance. Based on the modified power-law equation, the true stress exponents for all experimental alloys were measured to be 5, indicating the creep deformation was dominated by dislocation climbing mechanism.