Forging behaviour and properties of metal matrix composites based on mechanically alloyed Al-Mg-Li alloy

摘要

A range of Al-Mg-Li-C MMCs (25 vol.-% of 3μm SiC particles) were produced by mechanicalalloying and powder processing at Aerospace Metal Composites, Farnborough. Upset forging trialswere conducted at 350 and 550℃ and 0.01 and 0.1 s{sup}-1 No SiC particle cracking or wedgecracking at grain boundary triple points was observed. Forging at 550℃ caused some edge crackingand a coarser grain structure. Large billets of varying composition were forged to～15 mm thickplate at 350℃ and 0.01 s{sup}1 or 550℃ and 0.1 s{sup}-1 Monotonic testing showed the MMCsto exhibit high stiffnesses at moderate strength levels but rather low ductility and fracture toughness.Significant strengthening was found to accrue from dispersion hardening (C content) and solidsolution strengthening (Mg and Li solutes). A link was found between lower proof stress and coarsergrain structure after forging at 550℃. Fracture toughness K{sub}(1c) was found to decrease withincreasing yield strength which was attributed to higher strain concentrations in the smaller crack tipplastic zone.