SUPERPLASTIC-LIKE BEHAVIOR IN AS-EXTRUDED AL-ZN-MG ALLOY MATRIX COMPOSITES REINFORCED WITH SI3N4 WHISKERS

For as-extruded AlZnMg alloy without reinforcement of Si3N4ω, a maximum elongation is 140%, which was measured near a relatively high strain rate 2 × 10-2s-1 at 818 K. On the other hand, a maximum elongation of 160% for α-Si3N4ω/AlZnMg composites, whose grain size was less than 4 μm, was obtained at 798 K and at the highest end in strain rate range of 8 × 10-1s-1 evaluated in this work, and for β-Si3N4ω/AlZnMg composites with grain size of about 4 μm, a maximum elongation of 230% was obtained at 818 K and a high strain rate of 2 × 10-1s-1. In these AlZnMg system alloys the composites reinforced with α-Si3N4ω exhibited a high superplastic elongation at higher strain rates than the composites reinforced with β-Si3N4ω. © 1991.