Relationship between cooling rate, microstructure evolution, and performance improvement of an Al-Cu alloy prepared using different methods

Abstract

The relationship between the cooling rate and microstructure evolution and the performance improvement of an Al-4.5 wt% Cu alloy prepared using different casting methods was investigated. The microstructure evolution, solute element distribution, and mechanical properties of specimens prepared using different cooling rates were systematically investigated using multi-scale optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile testing, and hardness testing. Upon increasing the cooling rate from 1.65 to 117.3 K s-1, the average grain size, secondary dendrite arm spacing, and width and area fraction of eutectic phases significantly decreased, and the density of the precipitated phase, super-saturation degree of solute elements, and mechanical properties improved. Through a combination of grain-boundary, solid-solution, and precipitation strengthening, the cooling rate indirectly affected the mechanical properties of the heat-treated alloy sheets. The Al-4.5 wt% Cu alloy prepared by twin-roll casting under a cooling rate of 117.3 K s-1 exhibited a strength between 145.33 and 321.79 MPa and an elongation of 11.65%, demonstrating its potential as a high-performance aluminium alloy.