Microstructural evolution of a forged 2XXX series aluminum powder metallurgy alloy

Abstract

The microstructural response to hot upset forging was studied for a commercially relevant 2000-series aluminum powder metallurgy alloy. Sufficiently large specimens were produced such that the tensile property development was recorded for true compressive forging strains 0 mm/mm to 1.55 mm/mm. Full theoretical density values were obtained and up to a four-fold improvement in tensile ductility was observed. The tensile strength of a sintered-T6 component was measured at 357 MPa, while forging to 1.40 mm/mm increased that to 418 MPa. Microstructural reinforcement was found to be predominantly S-phase precipitates. Prior particle boundaries (PPB) of an unforged specimen were found to be continuously decorated with MgO and Mg2Sn crystallites. Such boundaries in hot forged specimen were discretized into clusters, producing regions of PPB devoid of oxides or other secondary phases. Improvements to mechanical properties were largely attributed to this effect.