Surface and Near-Surface Analysis of Residual Stresses in Aluminium and Titanium Alloys — Examples of the Case for X-Ray Diffraction

Abstract

Three examples of the use of X-ray diffraction to measure surface and near-surface residual stresses in aluminium and titanium alloys are presented. The first example indicates that surface stresses in an Al-SiC metal-matrix composite may be significantly different from those that are measured in the bulk of the material by neutron diffraction. In cold-expanded holes in 7050 aluminium alloy plate, both X-ray and neutron diffraction results indicate a compressive stress field of -5mm depth, but differences in radial and hoop stresses values may be due to the different cold-expansion methods employed. The final example indicates that stress gradients as shallow as 40µm, in this case in a milled Ti-6Al-4V alloy plate, are readily measurable by the X-ray diffraction technique. The paper stresses the need for more combined X-ray and neutron diffraction investigations, to maximise information retrieval.