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The creep behavior of Al-8Fe-4Ce powder metallurgy alloy produced by rapid solidification processing (RSP/PM alloy) was studied within the 623 to 773 K temperature range and at initial stresses ranging from 10 to 52 MPa. The activation energy, Q, for creep in RSP/PM Al-Fe-Ce alloy is 2.3QL, where Ql is the activation energy for lattice diffusion in pure aluminum and the stress exponent is 8.6. The high-temperature creep deformation is associated with deformation of matrix and Al13Fe4 incoherent particles. In addition, particle coarsening is an important factor in alloy degradation. The formation and growth of cavities during creep at all stress levels at 698 K is also a contributing factor.

The effect of prestraining at a fast strain rate (region III) on the subsequent superplastic behaviour (region II) of a 7475 AI alloy has been studied. The results show that prestraining causes a decrease in the elongation to failure as compared to the non-prestrained (as-received) samples. This decrease in elongation is postulated to be associated with the growth of cavities formed during prestraining as well as grain growth during deformation in region II. Prestraining in region III did not lead to any observable inhomogeneities in strain distribution during subsequent deformation.

The accumulation of cavitation damage in an aluminum-silicon eutectic alloy (Al-13%Si) during superplastic flow has been examined as a function of strain, strain-rate and temperature. Both cavitation damage and the microstructural changes occurring during deformation have been assessed. The role of grain size and its stability in affecting the level of cavitation damage has been identified. It has been found that the percentage cavitation is primarily controlled by the level of strain and at increasing grain-size results in continuous cavity nucleation. Similar evidence has also been obtained from fracture surfaces.

Segments of hot rolled Pyromet Alloy CTX-3 bar were solution treated at 1800°F and cooled to room temperature in various media, resulting in calculated cooling rates (from 1800°F to 1000'F) ranging from O.l"F/sec. to %66"F/sec. After subsequent overaging at 1425"F/1150"F, it was determined that both very slow and very rapid cooling after solution treatment resulted in extensive precipitation of the stable D phase and a decrease in y' content. Since rl contributes little to the strengthening of Alloy CTX-3, decreases in tensile and/or yield strength were associated with copiousrl precipitation. However, improvements in 1000°F notch stress rupture life were associated with abundant grain boundary rl precipitation. SEM fractography of notch rupture specimens revealed increasing evidence of cleavage in specimens containing higher volume fractions of rl phase, suggesting that rl may reduce grain boundary sliding. It was also noted that after long term (>5000h) exposure to rupture test conditions, dissolution of coarse y' and precipitation of a fine (