The effects of temperature, strain rate and minor boron on tensile properties of wrought Ti-47Al-2Mn-2Nb alloy

The effects of temperature from 77 to 1375 K, strain rate From 10(-5) to 10 (-1)s(-1) and 1.0 at% boron were systematically investigated on tensile pro perties and fracture mode of a wrought Ti-47Al-Mn-2Nb alloy. For both alloy s with and without boron, sigma(0.2) and (b) show non-monotonous strain rat e sensitivity at intermediate temperatures, positive strain rate sensitivit y at low and high temperatures, delta fluctuates with the change of the str ain rate at low and intermediate temperatures, but decrease monotonically a t high temperatures. Brittle-to-ductile transition (BDT) was found in the a lloys. BDT temperature, T-BD rises with the increase of strain rate. The fr actography analysis and theoretical calculation using the Nabarro model add ed up to the speculation that the BDT of the alloys is controlled by disloc ation climbing. The addition of 1.0% B increased sigma(0.2) and (b) substan tially, as well as, although to a less degree, at low and intermediate temp erature. It was found that the boron addition can lower the T-BD more than 100 degrees C under different strain rate from 10(-5) to 10(-1)s(-1). (C) 2 000 Elsevier Science Ltd. All rights reserved.