Influence of Er content on microstructural evolution and mechanical properties of Al-2Fe alloy

Abstract Herein, Al-10 wt. % Er master alloy (Er) is used to modify the Al-2Fe alloy, and the effect of physical state of Er during solidification and homogenous annealing is systematically examined by using XRD, SEM, TEM and EDS. The results reveal that the addition of Er can refine α-Al secondary dendrite spacing and reduce the length of Al3Fe phase. For instance, the secondary dendrite spacing of α-Al decreased from 30~60 μm to 14~19 μm with the increase of Er content. Moreover, the L12-structured Al3Er particles preferentially formed in the liquid alloy can be used as heterogeneous nucleation core for α-Al grains. The granular Al3Er is formed between dendrites during solidification and hinders the growth of α-Al grains and Al3Fe phases. Furthermore, the lamellar Al+Al3Er eutectic is formed with an increase of Er content. In addition, Al10Fe2Er is formed at the Al/Al3Fe phase boundary in Al-2Fe alloys with 0.7 wt.% and 0.9 wt.% Er. The Al3Er within grains and among dendrites partially dissolved in the matrix after annealing at 480 oC for 24 h. The micron-sized Al10Fe2Er particles are formed around eutectic Al3Fe in Al-2Fe alloys with 0.3 wt. % and 0.5 wt. % Er. The size of Al10Fe2Er, which already exists in as-cast Al-2Fe alloys with 0.7 wt. % and 0.9 wt. % Er, is increased due to atomic diffusion, which compromised mechanical properties.