Welding Metallurgy of

The relationships between residual stress relaxation and texture development in AZ31 Mg alloys via the vibratory stress relief technique

The textures and crystallographic orientations beneath the treatment area in AA 6061 aluminum alloy after vibratory stress relief (VSR) process were investigated by combining the electron backscatter diffraction analysis of the misoriented low- or high-angle boundaries, the (inverse) pole figures, the line scans and the various grain orientations. The relaxation effect caused by compressive residual stress in the intermediate region is superior to that of tensile residual stress on both sides of the cantilever by means of X-ray diffraction techniques. The residual stress relaxation that occurs due to vibrational stress excitation accompanies the “orientation of banding” disintegration, the decreases in the dislocation density, the strain energy, and the fraction of low-angle boundaries within each type of grain orientation, such as Copper {112} 〈111〉, S {123} 〈634〉, Goss {110} 〈001〉, and Brass {110} 〈112〉, excepting the Cube (or near-Cube) {100} 〈001〉 grain orientation. The maintained invariance in the Cube texture can be attributed to the maximum number of active primary slip systems, resulting in an interaction that results from hindered slip on intersecting families of the planes.

The effect of residual stress relaxation by the vibratory stress relief technique on the textures of grains in AA 6061 aluminum alloy

Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ-ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.

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Evolution of microstructure and residual stress under various vibration modes in 304 stainless steel welds.

Strength and fatigue crack growth behaviours of metal inert gas AA5083-H116 welded joints under in-process vibrational treatment

The study on the vertical and horizontal spot vibration welding of Inconel 690 alloy was carried out to observe the dendrite morphologies and estimate the temperature gradient G and growth rate R under different vibration conditions. The purpose is to further understand the mechanism of microstructure changes under vibration. Based on different temperature distributions along vertical and horizontal directions in the centre of a melting pool, it is found that vertical and horizontal vibrations induce the divergence of the nucleates site and grain growth rate then affect the grain morphologies. Vertical vibration welding creates a coarse dendrite structure with sturdy secondary and tertiary dendrite arms, and the X-ray diffraction (XRD) profile of this structure shows a strong (200) peak. Horizontal vibration welding results in grain refinement and a relatively disordered structure, which is reflected by its low XRD intensity. The study shows that vibration affects the weld structure by improving n...

S.-M. Yang

Papers

Study of vibration welding mechanism