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

摘要

The effects of temperature from 77 to 1375 K,strain rate from 10~(-5) to 10~(-1)s~(-1) and 1.0 at percentboron were systematically investigated on tensile properties andfracture mode of a wrought Ti-47Al-2Mn-2Nb alloy. For bothalloys 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 andintermediate temperatures, but decrease monotonically at hightemperatures. Brittle-to-ductile transition (BDT) was found inthe alloys. BDT temperature, T(BD) rises with the increase ofstrain rate. The fractography analysis and theoretical calculationusing the Nabarro model added up to the speculation that theBDT of the alloys is controlled by dislocation climbing. Theaddition of 1.0 percent B increased #sigma#_(0.2) and _bsubstantially, as well as, although to a less degree, at low andintermediate temperature. It was found that the boron additioncan lower the T_(BD) more than 100 deg C under differentstrain rate from 10~(-5) to 10~(-1)s~(-1).