Deformation mechanisms in commercial TI-5Al-2.5 Sn (0.5 At. pct Oeq) alloy at intermediate and high temperatures (0.3-0.6 tm)

The plastic flow of the commercial α-alloy Ti 5A1-2.5 Sn (0.5 at. pct Oeq) of 11 to 19 μm grain size was investigated in tension over the temperature range of 600 to 117.3 K (CPH structure) and strain rates of 3x10^-5 to 3 per s employing both constant strain rate and strain rate cycling tests. Dynamic strain aging (due to substitutional solutes) occurred in the temperature range of 600 to 850 K (0.31 to 0.44T _m)with an activation energy of 22.5 KcalJmole (94.1 KjJmol) derived from the start of serrations in the stress-strain curves. At temperatures above 850 K (0.46 to 0.60T _m), the deformation could be described by Dorn’s general equation for diffusion controlled mechanisms with an activation energy of 50 KcalJmole (209 KJJmol). M. D?NER was formerly with Department of Metallurgical Engineering and Materials Science, University of Kentucky, Lexington, Ky. 40506