Intergranular strain accumulation in a near-alpha titanium alloy during plastic deformation

摘要

Neutron diffractometry has been used to characterise the evolution of intergranular lattice strains during the tensile loading of the near-α titanium alloy Ti-834. The measurements were made on tensile testpieces in directions both parallel and perpendicular to the applied load. To rationalise the observations, and elastic-plastic self-consistent model for the α phase is used, in which the three basal and two non-basal slip systems observed in titanium alloys are invoked; its is found that it is possible to reproduce successfully the observed trends and magnitudes of the microstrains in both the longitudinal and transverse directions. Unfortunately, no reflection was found for which intergranular strain accumulation is small, i.e. less than 1 * 10~(-4). This situation should be recognised when making measurements of residual strains and stresses in large-scale engineering components, since intergranular strains must be distinguished from the macro-scale engineering strains. To circumvent this difficulty a novel method is proposed whereby the results of two or more peaks are combined to form a synthetic 'actor' which accumulates near-zero intergranular strain in both the parallel and perpendicular directions.