Tuning microstructure and mechanical properties of squeeze-cast whisker-reinforced 2024Al composites by hot forging process design

In order to minimize defects and obtain a uniform and consistent microstructure in Al-matrix composites, the hot forging process design, microstructure, and mechanical properties evolution in squeeze-cast 20 vol% Al18B4O33w/2024Al composites were investigated. Uniaxial cushioned forging was more effective than uniaxial free forging and uniaxial canned forging in increasing hot deformability and improving homogeneity of strain and microstructure in composites. Bi-directional forging accumulated larger strain in the microstructure, which produced alignment of whiskers and associated anisotropy in mechanical response. Both the strength factor and the whisker length affected composite strength. When loading parallel to whisker alignment, composites exhibited increased strength factor and greater distance between adjacent whiskers along the microcrack propagation direction, both of which resulted in higher strength and elongation. When loading normal to the whisker alignment, composite strength and ductility decreased due to a smaller strength factor, shorter microcrack propagation distance, and increased likelihood of interface debonding.