Precipitated phase characteristics and fracture behaviour of cast Al-Cu-Mn alloy

The cast Al4.4Cu0.6Mn alloy samples were subjected to quenching at 530 degrees C for 14 h, followed by aging treatment at 170 degrees C for 6, 8, 10, and 12 h. The effects of aging treatment time on the mechanical properties including the tensile strength (sb), yield strength (s0.2), elongation (d5), hardness (HB), and microstructure morphology of the alloy were investigated using metallographic microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, tensile-property, and hardness tests. The highest tensile strength of the alloy was 481.4 MPa when the aging time was 8 h. The size of precipitates increased gradually with the increase in aging time, and their morphology developed gradually from granular and bundle to reticulation. The main strengthening phases of the alloy were the q- and T-phases as determined by X-ray diffraction and energy dispersive spectroscopy. Dimples and tear ridges were observed in the fracture morphology of four samples after different aging times, indicating that the fracture mode for the studied alloy is quasi-cleavage fracture. The T-phase has better thermal stability. Therefore, the mechanical properties of the alloy under the heat treatment conditions in this paper were stable and were not significantly affected by the aging time.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study investigated the effect of heat treatment on the mechanical properties and microstructure of cast Al4.4Cu0.6Mn alloy. The results showed that the aging treatment time had an impact on the alloy's mechanical properties and microstructure. With increasing aging time, the tensile strength of the alloy increased gradually, and the size of precipitates also increased. The fracture mode was quasi-cleavage fracture.