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

The integration of additive manufacturing and severe plastic deformation has produced an Al-Si alloy with superior mechanical properties. The novel processing pathway effectively avoids strength-ductility trade-off, resulting in an elongation increase of three times while maintaining a comparable yield strength to that of the original condition. The implementation of an intermediate annealing heat treatment (HT) before the subsequent equal channel angular pressing (ECAP) processing resulted in the most favorable combinations of strength and ductility. The ECAP process transformed the ultrafine interconnected eutectic network into ultrafine particles. This process also led to the formation of a heterogeneous grain size and the transformation of the 3-dimensional network of aluminides (Al2Cu) and Si-enriched precipitates into particles with varying sizes, ranging from 4nm to 500nm. In contrast, the ECAP processing without an intermediate annealing heat treatment led to a maximum yield strength increment of 22%. Notably, this enhancement in strength was achieved while preserving comparable levels of elongation to those observed in the as-built material. Hence, achieving the optimal combination of yield strength and ductility ratio demands a careful balance between various strengthening mechanisms, including subgrains and precipitates.