Overcoming the strength-ductility tradeoff of a 3D-printed Al-Si alloy by equal channel angular pressing

Abstract

The integration of additive manufacturing and severeplastic deformation has produced an Al-Si alloy with superior mechanicalproperties concerning its as-built condition and its conventionallymanufactured counterparts. The novel processing pathway effectively resolves theinherent conflict between strength and ductility, resulting in elongationenhancements of 240% while maintaining a comparable yield strength to that ofthe original condition. The implementation of an intermedia annealing heattreatment (HT) before to the subsequent equal channel angular pressing (ECAP)processing resulted in the most favorable combinations of strength andductility. The ECAP process transformed the ultrafineinterconnected eutectic network into ultrafine particles. This process also led to the formation of aheterogeneous grain size and the transformation of the 3-dimensional network ofaluminides (Al2Cu) and Si-enriched precipitates into particles withvarying sizes, ranging from 4 nm to 500 nm. Incontrast, the implementation of ECAP processing without an intermediateannealing heat treatment led to a maximum yield strength increment of22%. Notably, this enhancement in strength was achieved while preservingcomparable levels of elongation to those observed in the as-builtmaterial. Hence, achieving the optimal combination of yield strength andductility ratio demands a careful equilibrium between various strengtheningmechanisms, including subgrains and precipitates.