Depth Resolved Strain and Phase Mapping of Dissimilar Friction Stir Welds Using High Energy Synchrotron Radiation

R V Martins,V Honkimäki

doi:10.1080/07303300310001628625

Abstract

The strain and phase distribution in a dissimilar friction stir weld of AA6082-T6 to AA2024-T3 is investigated non-destructively. The measurements are performed using a novel depth resolved strain and phase mapping technique. The technique is based on the use of a focussed high energy synchrotron beam, a novel spiral slit system, and an area detector system. Through thickness measurements of the residual strain along the weld centre show strong variations with changes of sign. The strain scans across the weld exhibit a strong asymmetry in particular for the longitudinal strain component. A depth resolved strain mapping across the weld shows for the dominant longitudinal strain component variations in depth, especially on the AA6082 side of the weld. Results from the strain measurements are related to the depth resolved map of the material distribution in the weld zone.

Highlights

Friction stir welding (FSW) is a welding technique that was developed in the early 90s at The Welding Institute (UK) (Thomas et al, 1991)
The second scan ran along the weld centre with a step size of 15 mm
Steep gradients are observed in scans along the weld centre at the beginning and the end of the welds

Summary

INTRODUCTION

FSW is a solid state welding process in which a spinning tool is forced along the joint line, heating the abutting material from the two components. It bears a high potential for larger applications in the automotive and aerospace industries (Thomas and Nicholas, 1997). In general the stress component parallel to the weld line is the dominant one, being tensile with around 150 MPa in the weld region. These are balanced by compressive stresses further away from the weld. The present investigation aims to determine the residual stress field in a FSW of a specific dissimilar material combination (AA6082-T6 to AA2024-T3) and to relate these results to observations about the material distribution in the weld zone

SAMPLE

EXPERIMENTAL TECHNIQUE

RESULTS AND DISCUSSION

SUMMARY