The effect of solution treatment on aging behavior and mechanical properties of AA2024-TiB2 composite synthesized by semi-solid casting

Abstract

AA2024 reinforced with varying amounts of titanium boride (TiB2) was developed using stir rheocasting to study the effect of solution heat treatment on aging behavior and mechanical properties. The developed specimens were subjected to solution heat treatment at 490 °C for 1, 2.5, and 5 h, followed by artificial aging at 190 °C for an aging duration of 1–12 h. The metallurgical characterization was done by x-ray diffraction, optical microscopy, and field emission scanning electron microscope and mechanical characterization by Vickers hardness tester and universal testing machine. Microstructural observation showed the formation of globular grains and fairly uniform particle distribution. Up on peak aging, the AA2024/2 wt% TiB2 composite has shown better improvement in yield strength (YS = 230 MPa), tensile strength (UTS = 342 MPa), and Vickers hardness (VH = 147) amongst other developed specimens. The improvement in mechanical properties of AA2024/2 wt% TiB2 composite up on peak aging was nearly 83%, 77%, and 20%, respectively, over their as-cast states. However, the percent elongation has decreased by 51% for the AA2024/2 wt% TiB2 composite against its as-cast state. The optimum solution heat treatment time was found to be 2.5 h that led to the fastest aging kinetics and peak hardness. Due to incomplete dissolution of precipitates at a solution treating time less than 2.5 h, the hardness decreased, and the aging kinetics decelerated. The aging kinetics further accelerated with increasing solution heat treating time beyond 2.5 h, but the hardness decreased due to grain growth of the matrix.