Investigating the Synergistic Strengthening in Additively Manufactured CuCrZr Alloys: An In-situ Study of Heterogeneous Microstructure Deformation and CPFEM Analysis

Abstract

Additive manufacturing of CuCrZr alloys produces unique heterogeneous microstructures of co-existing coarse and fine grains, leading to high room-temperature strength. However, the specific mechanisms governing this enhancement are not yet well understood. Here, we combine in-situ micromechanical testing with CPFEM to analyze the deformation behavior. In-situ DIC reveals that the soft, coarse grains accommodate initial plastic strain, while the hard, fine grains constrain deformation and contribute to the overall strength. This strain incompatibility drives the formation of high-density GNDs at the interfaces between coarse and fine grains, as observed through in-situ EBSD and quantified by CPFEM. We demonstrate that the resulting long-range back stresses from these GNDs produce a potent HDI hardening effect, which our CPFEM model quantifies as an additional back-stress contribution of approximately a ~16% increment in yield strength. This HDI effect acts as a secondary strengthening contribution that complements traditional grain-boundary effects. This work examines the interaction within heterogeneous structures and offers a strategy for designing advanced additively manufactured alloys.