Structure and properties of rapidly-solidified Al-rich Al-Mn-Si alloys : Part II : Atomized powder, its extrudate and the effect of blended-in SiC

Argon atomized Al-5 Mn-3 Si (wt%) powder has been extruded with and without 15 vol% added SiC particulate at 425 degree C and characterized both as extruded and after 100 and 1000 h at 425 degree C. As extruded matrix microstructure of discrete alpha AlMnSi particles of mean diameter 60 nm in an alpha Al matrix was similar to that for comparable melt-spun ribbon after 2 to 5 h at 425 degree C and coarsening of alpha AlMnSi in 100 and 1000 h at 425 degree C was also comparable. Hardness and proof strength of the matrix as extruded and their decrease on heat treatment matched predictions of a combined Orowan and Hall-Petch model as for the melt-spun condition. Initial hardness and tensile properties of the matrix were similar to those of extruded Al-Fe-V-Si with the same (approx. 15) vol per cent of silicide. Increment in Young's modulus of approx. 30 GPa when SiC was present was similar to that for Al-Fe-V-Si/SiC MMC, while increments in strength and decrements in elongation to fracture were smaller for the Al-Mn-Si/SiC MMC.