STRAIN RATE DEPENDENCE IN 6061 AND 2024 ALUMINUM MATRIX COMPOSITES

The effects of loading rate on the deformation and fracture behaviors of two cast composites under the as-worked (AW) and AW+T6 conditions have been examined over the strain rates from 5×10^-4 to 1×10³ s^-1. The results showed that the peak load, specimen deflection, specimen lateral expansion fraction, crack initiation energy, propagation energy, total fracture energy, and deformation zone all tended to increase with increasing strain rate. Under quasi-static loading, the composites failed predominantly by matrix/reinforcement interface decohesion. As the loading rate increased, reinforcement failure became the major failure mechanism. In comparing the fracture modes in the AW and AW+T6 specimens, the latter showed a higher tendency toward particle cracking. The AW composites exhibited a higher strain-rate dependence. The T6 specimens, due to their intrinsic more brittle nature, appeared to be less influenced by loading rate over the strain rate range examined.