High temperature mechanical and microstructural behavior of A35615 vol% SiCp and A356 alloy

作者：H.J. McQueen, М. M. Myshlyaev, E. V. Konopleva, A SAKARIS · 发表于：Canadian Metallurgical Quarterly · 年份：1998 · DOI：10.1016/s0008-4433(98)00007-x · 被引用次数：14 · 研究领域：Aluminum Alloys Composites Properties、Aluminum Alloy Microstructure Properties、Advanced ceramic materials synthesis

A metal-matrix composite (MMC, 15 vol% SiCp\A356 Al) and its matrix alloy were subjected to hot torsion over the range 300–540°C and 0.1–5.0 s−1. Flow stresses of the A356 MMC were found to be much higher than A356 alloy at low temperatures but the difference was quite small at higher temperatures. Flow stresses were found to depend on the strain rate through a sinh function and on temperature through an Arrhenius term with activation energies of 263 kJ\mol for the composite and 161 kJ\mol for the matrix ; the increased value for the composite suggests that the SiC particles cause the matrix to undergo additional strain hardening. The substructures in both materials increase in cell size and decrease in internal and wall density, as temperature T rises and strain rate ε falls ; the composite shows much greater and less uniform dislocation density to which the strengths of the two materials are related. Dynamic recovery seems to be predominant in A356 ; however, dynamic recrystallization likely nucleates in the vicinity of silicon carbide particles in 15 vol% SiCp\A356 Al. Ductility of the composite, about 25% below that of the alloy, rose by a factor of 4 between 400 and 500°C to become higher than many wrought alloy composites. The low ductility of A356 was shown to result from linking up of the cracks nucleated at coarse Si particles, whereas linkage of the decohesion voids at the SiC was associated with more plastic flow in the matrix which had much finer Si particles than...