Analysis of friction stir welded 6061 aluminum using an X-ray microbeam Laue technique.

摘要

Using microbeams from high brilliance third generation synchrotron X-ray sources and advanced X-ray optics, an emerging differential-aperture X-ray microscopy (DAXM) technique is used to investigate friction stir welded aluminum 6061. The process of friction stir welding uses a cylindrical tool piece with a projecting threaded nib. This tool piece is rotated and the nib is plunged into the joint line of the metal to be welded. As the tool piece is rotated, it also traverses the length of the joint line. With a constant downward force driving the plunge of the tool piece, the nib and the shoulder contact the work piece interface and surface creating frictional and deformational heat. The result is a solid state weld which involves the plastic flow of metal along the interface of the metals to be joined.; By employing polychromatic X-ray microbeams and a virtual pinhole camera method, called differential aperture microscopy, crystallographic orientation with submicron resolution in three-dimensions is attained. In an effort to characterize the local texture in the polycrystalline material, analysis of the [100] direction is performed with respect to the advancing direction of the friction stir welds. Emphasis is placed on the analysis of the Laue patterns and Laue spots from the diffraction experiments in an effort to characterize the local distortion at various points in the weld. Analysis is provided for the advancing and retreating sides of the welds.