Powder Metallurgy Fabrication of Multimodal-Grained AA2024 Aluminum Alloy and Microstructural Response to Powder Size Control

Abstract

In order to break the limitations of traditional homogeneous material modification, this paper proposes the preparation of homogeneous and heterogeneous bimodal structural materials by powder metallurgy. AA2024 aluminum alloy powder was mixed with different particle sizes in a certain proportion by ball milling, and the homogeneous mixed crystal material was prepared by hot-press sintering. The results indicate that, by adjusting the ratio of coarse and fine powder, the precise control of the mixed crystal structure composed of coarse and fine crystals is realized. The mixed crystal structure causes additional hardening, which increases the strength and malleability of the mixed crystal material. When the mass ratio of coarse to fine powder is 5:5, the tensile strength is ~ 201.83 MPa, the yield strength is ~ 157.45 MPa, and the elongation is ~ 15.86%, which is ~ 10.45% higher than the fine crystal strength and 1.15 times higher than the elongation. The introduction of a mixed crystal structure breaks the limitation of single modification, the coarse and fine grains coordinate with each other, the soft domain represented by the coarse crystals delays the crack expansion and improves the plasticity, and a hard domain represented by the fine crystals disperses the stress and ensures the strength of the material.