STRENGTH AND DUCTILITY UNDER DYNAMIC LOADING IN FINE-GRAINED IN905XL ALUMINUM-ALLOY

Three IN905XL aluminum alloys with fine grain (1 mu m), intermediate grain (3 mu m), and coarse grain (5 mu m) have been developed by a combination of mechanical alloying (MA) and conventional extrusion in order to investigate their mechanical properties at dynamic strain rates of 1 X 10(3) and 2 X 10(3) s(-1) and a quasi-static strain rate of 10(-3) s(-1). Flow stresses are found to increase with decreasing grain size for all the strain rates tested. Negative strain-rate sensitivity of flow stress is observed up to 1 X 10(3) s(-1) in both intermediate- and coarse-grained IN905XL. At the highest strain rate of 2 x 10(3) s(-1), however, all samples showed a positive strain-rate sensitivity of strength. Total elongation at high strain rates is generally larger than that at low strain rates. Total elongation also decreases with grain size for all the strain rates. This decrease in elongation results from an initiation of microcracks at interfaces between the matrix and pal-tides finely dispersed near grain boundary regions, introduced during MA processing; then, this initiation leads elongation of alloys to small limited values.