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The microstructure and texture of friction stir welded joints of hot mill stock 5754 and 5182 aluminium alloy sheets were examined after a commercial joining process. The as received sheet was cut into two pieces, one piece was cold rolled with 20% reduction in thickness, whereas the other was subsequently aged at 230uC for 100 h after the 20% prestrain. These two pieces with different thermal pretreatments were joined by friction stir welding (FSW). On FSW, a uniform fine grained microstructure in the through thickness of the sheet having a width corresponding to the diameter of tool shoulder was observed in both the 5754 and 5182 joints. Moreover, the microhardness profile did not reveal a softened heat affected zone between the weld and the base metal. An X-ray pole figure study showed that the 5754 and 5182 weld zones were not highly textured and both comprised of similar texture components. The calculated average sheet formability of the weld zones predicts a more isotropic behaviour than that for the start materials. Orientation image mapping of the weld zone in 5182 and semi-automatic electron backscatter pattern linescan analysis of the 5754 weld zone showed that most of the grain boundaries were high angle ones. This determination affirms that the weld zones in AA 5754 and AA 5182 joints undergo homogeneous dynamic recrystallisation throughout the thickness resulting in uniform mechanical properties.MST/4840

We report an x-ray diffraction study of interdiffusion and strain relaxation in (SimGen)p short-period superlattices. An interdiffusion coefficient Dλ was determined by monitoring, as a function of time, the decay upon annealing of the first order 000 satellite peak arising from the compositional modulation of the superlattice. Strain relaxation was obtained from the shift of the 400 superlattice peak on annealing. In the early stage of annealing the low angle satellite exhibited a rapid nonexponential decay after which a slower exponential decay was observed indicating a larger initial interdiffusion coefficient. This enhancement was correlated with the presence of strain and it disappeared upon relaxation. Diffusion was faster in structures alternating thin Si and thick Ge layers suggesting that migration of Si into Ge is the dominant diffusion process.

The variation of electrical resistivity with deformation, as a function of purity and orientation, has been studied for Cu single crystals deformed in tension and fatigue. In stage I the rate of increase of resistivity depends very strongly on the impurity content, decreasing with increasing purity. In stage II the resistivity increases quadratically with stress, the rate of increase depending on orientation. The resistivity produced by dislocations appears not to be strongly anisotropic. The value of resistivity per unit dislocation is about 1 × 10−19 ΩSi-cm.

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