Microstructural-micromechanical correlation in an Al–Cu–Mg–Ag–TiB2 (A205) alloy: additively manufactured and cast

Abstract

In this paper, the processing-structure-property correlation of a high-strength titanium-modified aluminum-copper alloy, i.e., Al–Cu–Mg–Ag–Ti–B (A205), in the laser powder-bed fusion (LPBF) and casting conditions are studied. The as-fabricated and heat-treated materials were considered for this study. As A205 is a heat-treatable aluminum alloy, the effects of different post-fabrication heat-treatment processes, (i) solution heat-treatment (SHT: 520°C for 2 h) and (ii) over-aging and stabilizing treatment (T7), were also assessed. To test the stated relationship in LPBF and cast conditions depth-sensing indentation testing and extensive structural analyses were performed. The morphology and distribution of precipitates and nanoparticles in the microstructure were analyzed using optical, scanning electron, and transmission electron microscopy. The average nanoindentation hardness at as-fabricated, SHT, and T7 conditions are 1.48 ± 0.04, 1.50 ± 0.03, and 1.56 ± 0.06 GPa for the LPBF samples and 1.34 ± 0.04, 1.52 ± 0.10, and 1.72 ± 0.09 GPa for the cast samples. Detailed microstructural analyses confirmed the presence of precipitates and reinforced particles and revealed their morphology. The fine equiaxed grains with the average grain size of 1.1 ± 0.4 μm in the as-built condition highly enhanced the mechanical properties compared to the cast counter material, where the average grain size was measured as 46.4 ± 10.5 μm. Heat treatment played a more effective role on the cast samples and the strength of the cast material exceeded the LPBF material considerably after T7 treatment. This study offers a new compositional window for the additive manufactured lightweight high-strength material categories for various applications including automotive and aerospace industries. Besides, our findings demonstrate the significance of controlling the precipitates through the post-fabrication heat treatment processes.