Effect of heating rate on the microstructure and fatigue properties of 2524 aluminum alloy

The 2524 aluminum alloy was cold rolled to 70% reduction and then annealed at 500℃ for 0.5h in an air furnace with a heating rate of 5℃/min and in a salt bath with a heating rate of 75℃/s, respectively. The effect of heating rate on the microstructure, tensile properties and fatigue crack growth (FCG) rate of the alloy was investigated. In the case of slow heating the alloy exhibited a coarse elongated grain structure (~75μm), while a fine equiaxed grain structure (~13μm) was obtained in the case of rapid heating. The sheet annealed with rapid heating has slightly higher tensile strength and yield strength, but a slightly lower elongation than the sheet annealed with slow heating. The FCG rate of the sheet annealed with slow heating is 20% lower than the sheet annealed with rapid heating.