Synthesis and Properties of Elevated Temperature P/M Aluminum Alloys.
Annual technical rept. 1 Oct 82-30 Sep 83,
NORTHWESTERN UNIV EVANSTON IL DEPT OF MATERIALS SCIENCE AND ENGINEERING
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High temperature alloys in order to maintain thier strength during long time exposure at high temperatures must have stable microstructures. The dispersed phase coarsening rates in the A1-7.5Fe-3.5Ce and A1-10Fe-1.5Mo-1V alloys, developed for high temperature applications, were compared at 475 and 575 C. To the extent that the average intercept length cubed, L3, is a linear function of time during isothermal aging, after an initial transient, the particle coarsening obeys the Lifshitz-Slyozov-Wagner theory. The interfacial energies estimated from the coarsening rates using the theory of particle coarsening show that the interfaces between the particles and matrix are high energy incoherent interfaces. The dispersed particles in the A1-10Fe-1.5Mo-1V alloy coarsen faster at both temperatures than the particles in the A1-7.5Fe-3.5Ce showing that the latter alloy is more stable at these temperatures. Since the diffusion in diffusion controlled coarsening usually occurs by a vacancy mechanism, plastic deformation should increase the rate of particle coarsening since plastic deformation increases the vacancy concentration. This has been confirmed in combined creep and coarsening studies with the A1-7.5Fe-3.5Ce alloy.
- Properties of Metals and Alloys