A microstructural and mechanical property investigation of a hot upset forged 2xxx series aluminum powder metallurgy alloy reinforced with AlN

Abstract

Abstract Metal-matrix composites (MMC) of a 2000-series aluminum alloy coupled with AlN were fabricated through a commercially-relevant aluminum powder metallurgy (APM) approach. Cylindrical preforms containing 0–5 vol% AlN were produced to investigate the mechanical properties and microstructure evolution through hot upset forging. Specimen were deformed to a maximum strain of 0.15–1.55 mm/mm at rates of 0.1–1.0 s−1. TEM observations of forged products indicated the Al–AlN interfaces were free of defects and of high quality. Near-full (>99.5% theoretical) densities were observed at 1.40 mm/mm. At this strain, a substantial increase in all tensile properties was observed. An elastic modulus of 77 GPa was realized in a forged product with 5% AlN, accompanied by a 0.2% offset yield strength of 325 MPa and a UTS of at least 400 MPa. Versus an undeformed sample, forged MMC’s exhibited up to a five-fold increase in tensile ductility. Likewise, improvements of up to 98 MPa (57%) in fatigue strength were recorded. Mechanical gains were a result of densification and residual oxide disruption, as well as the enhanced dispersion of the AlN phase.