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 properties and fracture mode of a wrought Ti-47Al-Mn-2Nb alloy. For both alloys with and without boron, sigma(0.2) and (b) show non-monotonous strain rate sensitivity at intermediate temperatures, positive strain rate sensitivity at low and high temperatures, delta fluctuates with the change of the strain rate at low and intermediate temperatures, but decrease monotonically at high temperatures. Brittle-to-ductile transition (BDT) was found in the alloys. BDT temperature, T-BD rises with the increase of strain rate. The fractography analysis and theoretical calculation using the Nabarro model added up to the speculation that the BDT of the alloys is controlled by dislocation climbing. The addition of 1.0% B increased sigma(0.2) and (b) substantially, as well as, although to a less degree, at low and intermediate temperature. 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) 2000 Elsevier Science Ltd. All rights reserved.