Microstructural evolution and strengthening mechanisms in a heat-treated additively manufactured Al-Cu-Mn-Zr alloy

The microstructural and strength evolution of an additively manufactured Al-8.6Cu-0.5Mn-0.9Zr alloy upon aging at 300, 350, and 400? is investigated. The strengthening phases of the alloy evolve significantly upon aging, with breakdown and spheroidization of the interconnected theta'-Al2Cu network, dissolution of metastable theta'-Al2Cu precipitates, and precipitation of nanometric L1(2)-Al3Zr from a matrix supersaturated in Zr. In the peakaged states, the alloy displays a favorable combination of strength and ductility, with a room-temperature yield strength of 314-341 MPa and ductility of 11-13%. The measured yield strengths for microstructures with different aging treatments are compared to predictions of yield strengths from grain boundary, solid solution, and particle strengthening contributions. The observed strain hardening behavior is related to fundamental precipitate and dislocation interactions. Comparison between predicted and measured strength values indicates a continued need for strengthening models specifically developed for the heterogeneous microstructures of additively manufactured alloys.

Automated summary

The microstructural and strength evolution of an additively manufactured alloy were investigated at different temperatures. The results showed significant changes in the strengthening phases upon aging, indicating the need for specific strengthening models for additively manufactured alloys.