Tsunemichi Imai

Joining of 5083 and 6061 aluminum alloys by friction stir welding

Friction stir welding (FSW) has emerged as a new solid state joining technique [1], especially for aluminum alloys [2–6]. In this process, a rotating tool travels down the length of contacting metal plates, and produces a highly plastically deformed zone through the associated stirring action. The localized heating zone is produced by friction between the tool shoulder and the plate top surface, as well as plastic deformation of the material in contact with the tool [1]. At the present time, FSW is used mainly for joining similar materials. For dissimilar welding, there have been few systematic studies aimed at clarifying the effect of material combination and welding conditions on weld properties [7, 8]. However, FSW of dissimilar materials will be required in the near future for advanced aircraft design. In the present research, we have tried to apply the FSW technique to dissimilar light metals such as 5083 and 6061 aluminum alloys. Then, we have examined the microstructure and the mechanical properties of the FSWed aluminum alloy joint. 3 mm thick plates of cold-rolled 5083 (0.4%Si, 0.4%Fe, 0.4%Mn, 4%Mg, balance Al) and 6061T6 (0.7%Si, 0.7%Fe, 0.1%Mn, 1.0%Mg, 0.4%Cu, 0.1%Cr, balance Al) aluminum alloys were used in this experiment. Fig. 1 shows a schematic illustration of the experimental apparatus. The test piece was fixed onto a steel plate horizontally. Welding direction was perpendicular to the rolled direction of the aluminum plates. The diameter of the tool shoulder was 10 mm. The diameter of the insert pin and height were 3.0 mm and 2.8 mm respectively. The tool rotation speeds were 890 rpm and 1540 rpm. The traverse speeds of the moving table were 118 mm/min and 155 mm/min. Fig. 2 shows combinations of test pieces. Following FSW, microstructures of the samples were observed by optical microscopy. Vickers microhardness profiles

Superplasticity in Mg–Li–Zn Alloys Processed by High Ratio Extrusion

Superplastic behavior of Mg-8.5Li-1Zn and Mg-8.5Li-3Zn alloys has been investigated. Dynamic recrystallization occurs in the Mg–Li–Zn alloys during extruding with high ratio after stir casting. Mg-8.5Li-1Zn alloy exhibits an elongation of about 400% at the high strain rate of 1.1 × 10−2 S−1 at 623 K, while the Mg-8.5Li-3Zn alloy shows maximum elongation of more than 540%. The apparent activation energy for superplastic flow of both Mg-8.5Li-1Zn and Mg-8.5Li-3Zn alloys at 573–673 K is about 86 kJ/mol and 79 kJ/mol, respectively, so that the dominant deformation mechanism in Mg–Li–Zn alloys is grain boundary sliding (GBS) controlled by grain boundary diffusion.

Severe Plastic Deformation of Commercially Pure Titanium by Rotary-Die Equal Channel Angular Pressing Method

The commercially pure titanium cylindrical samples with a diameter of 11.5mm and a length of 24mm were processed by a new severe plastic deformation process, called the rotary-die equal channel angular pressing (RD-ECAP), under the condition of 773K, 2.4mm/s punch. By the RD-ECAP, ECAP processes of 1-4 passes were possible without sample removal and the temperature of cp-titanium could be simply controlled. After the RD-ECAP process, the cp-titanium samples had no crack. Fine-grained microstructures were observed in the sample on Y plane. Therefore the samples processed by RD-ECAP were expected to have high mechanical strength.

Mechanical Properties of Low Young's Modulus Amorphous Carbon Reinforced Aluminum Composites

The XN-05C/2017, XN-05C/MESO-10 and BGC152/MESO-10 aluminum composites reinforced by low young’s modulus amorphous carbon fiber and particle, respectively, were fabricated by a PM route followed by hot extrusion and rolling in this study. The mechanical properties of the prepared composites were investigated subsequently. The XN-05C/2017 and XN-05C/MESO-10 were found to exhibit low elastic modulus of 50~60GPa within the fiber volume fraction of 0.10~0.15, while the BGC152/MESO-10 shows a data of 50GPa with a particle volume fraction of 0.10. The tensile strength of XN-05C/MESO-10 was evaluated to be 400~600MPa in the case of Vf=0.10~0.15, and become to decease with increasing fiber volume fraction. Damping application would be a potential consideration for the amorphous carbon fiber reinforced aluminum composites.