Effect of DH treatment on microstructure and mechanical properties of an LM28-0.3wt.% Nd hypereutectic aluminum silicon alloy

In this article, a novel heat treatment method, deformation heat (DH) treatment (extrusion + aging), was employed on a hypereutectic aluminum silicon alloy (LM28-0.3wt.%Nd), and its effect on microstructure and mechanical properties of this alloy was investigated. It can be concluded that the eutectic microstructure disappears after the DH treatment, in the meantime the morphology of α(Al) solid solution was transformed from fir-tree and cellular to equiaxed, Si was refined with grain sizes of about 1-10 μm and distributed dispersedly, even some of them became globular shape, which can reduce stress accumulation effectively. Mechanical properties test indicated that the DH treatment could significantly improve the room-temperature strength and have little effect on the high-temperature strength of LM28-0.3wt.%Nd alloy. The fracture mechanism is ductile fracture by fracture morphology analysis.