Internal friction in an aluminum metal matrix composite during thermal cycling

摘要: The difference in coefficient of thermal expansion (CTE) between reinforcement and matrix metal composites (MMC) leads to large internal stresses following temperature changes. These may be sufficient generate plastic flow the softer phase lead, discontinuously reinforced MMC, a shape change during cycling even absence any applied stress. Dislocation anelasticity microplasticity aluminum have been extensively studied by mechanical spectroscopy. In low medium stress ranges for frequencies about 1 Hz, friction spectrum exhibits different maxima room 800 K associated relaxation mechanisms involving volume dislocations. At 0.4 T[sub M] (T[sub = melting point), peaks arising thermally activated movement dislocations are reported. 0.6-0.7 M], still arise longer dislocation loops inside grains, but now activation energies higher close those found two regimes creep that is, cross-slip climb. On other hand, arranged polygonization walls give an maximum at near Hz. these bases,more » spectroscopy has employed investigate properties composite, with short non-oriented alumina fibers, cycles 100 K.« less