Abstract:
The structure-property relations and creep behavior of powder metallurgy
processed and hot rolled commercially pure Al and its composites with 5, 10, 15 and
20 vol.% SiC particulate reinforcements, have been studied. The results of uninterrupted
tests at 623 K under a stress of 21 MPa show the presence of distinct primary, secondary
and tertiary stages of creep. Both the creep resistance and Young’s moduli of the
composites are deteriorated with increase in particulate volume fraction due to cracking
and debonding of SiC particles during rolling. The stress exponents for both Al and Al-
SiCp composites, determined using stress jump tests at 623 K, are found to be between 4
and 5, suggesting the predominance of dislocation creep. The creep threshold stress has
been found as ≤ 3 MPa, which is attributed to back stress and detachment stress caused
by interactions of dislocations with Al2O3 and Fe-rich dispersoids present in both pure Al
and Al-SiCp composites. The activation energy estimated from temperature change tests
at 11 and 21 MPa is reasonably close to that for grain boundary and lattice self diffusion
of Al at low and high stresses, respectively. Pure Al and Al-5 or 10 volume percent SiC
particulate composites, has been also evaluated after subjecting to 0, 2 and 8 thermal
cycles between 773 and 273 K with rapid quenching.
