A STUDY OF SHEAR DEFORMATION AND WORK-HARDENING OF METALS UNDER PRESSURES TO 2100-MPA

Work-hardening curves have been obtained from thin disks being sheared unidirectionally between Bridgman anvils under normal pressures up to 2100 MPa (= 300 000 lbf in-2 + 21 kbar). The materials tested were hard-rolled aluminum alloy 2124-T6 and the same alloy reinforced with 20% chopped SiC fibers with the fibers initially both parallel to and normal to the disks. Averaged shear strains in excess of 100, i.e. 10(4)%, were routinely achieved. Selected samples were subsequently examined by scanning electron microscopy. Negative work-hardening rates were observed in the mechanical tests of both the unreinforced matrix alloy and the composite but not the aluminum, and the micrographs showed the concentration of deformation into shear bands which is to be expected from such work softening. The results obtained permit conclusions among others regarding the tribological behavior of these materials. The equivalent coefficients of friction, which would have been observed had these materials been used as solid lubricants, ranged from 0.25 at 700 MPa pressure to 0.14 at 2100 MPa.