In order to produce metal-matrix-composites by a simple method, it has been attempted to fabricate an Al/Ti composite by pressing alternately multilayered pure Al and Ti foils at room temperature. The thickness of Ti foil used, was 10, 25 or 102 μm for the constant thickness, 92μm, of Al foil to fabricate Al/Ti composites with various volume fraction. Effect of Ti foil thickness on fabrication and bending properties of multilayered Al/Ti composites has been examined. Three inflection points are detected on nominal compressive stress-displacement curves for alternately multilayered Al/Ti foils. Joining of the multilayered Al/Ti foils is attained after the 3rd inflection point. Stress at the 3rd inflection point rises with increasing thickness of the multilayered Ti foils and is proportional to the volume fraction of Ti phase. Multilayered Al/Ti composite with Ti flakes of 52.1 volume percent could be fabricated at nominal compressive stresses higher than 3 GPa at room temperature. The bending strength of multilayered Al/Ti composites obtained increases with the volume fraction of Ti phase.

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The tensile strength of dissimilar friction welds between 6061 aluminum alloy and S45C carbon steel at high rates of loading is evaluated using a tensile version of the split Hopkinson bar. Round tension specimens are machined from 30 mm diameter friction welded butt joints. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. All quasi-static and impact tests on the as-welded tension specimens having the weld interface in the middle of the gage length are conducted at room temperature. The test results indicate that the joint tensile strength decreases considerably with increasing loading rate. Macroscopic observations of the fracture surfaces of broken tension specimens reveal that the static fracture takes place in the 6061 aluminum alloy region close to the weld interface, while the impact fracture occurs at the weld interface. The microindentation hardness tests are performed across the weld interface in an attempt to investigate the extent of the heat-affected zone (HAZ) due to friction welding. The microstructure and the distributions of aluminum and iron at the weld interface region are examined with the help of a scanning electron microscope and an electron probe micro-analyzer. The decrease in joint tensile strength with increasing loading rate may be attributed to the presence of very thin brittle intermetallic compounds formed at the weld interface during the friction welding operation.

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Cast 99.7 mass% aluminum strips were produced using the open type, heated mold continuous casting (Ohno Strip Casting) process at casting speeds of 1.7, 5.0 and 8.3 mm/s. The effects of casting speed on the solidified structures and crystal orientations of the strips were investigated. All strips were constituted macroscopically of unidirectionally solidified structures and microscopically of aligned primary and secondary cell grains extending parallel to the casting direction. At the starting end, the crystal orientation of the strip parallel to the casting direction was distributed from [001] to [011]. At 1400 mm away from the starting end, particularly at slow casting speed (1.7 mm/s), the crystal orientations of the strip tended to be [001], It was found that all primary cell grains had mixed boundary which consisted of tilt and twist angles. As the casting speed of the strips increased, tilt and twist angles of the primary cell grains increased. Higher casting speed also resulted in primary cell grain growth parallel to the casting direction with some slight twisting.

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Intergranular corrosion (IGC) behavior of 6061 aluminum alloy extrusions was investigated. After IGC test in accordance with ISO/DIS 11846 (method B), heavy IGC was observed and the corrosion reached about 300 μm deep from the surface. However, it became clear that the IGC did not propagate more than 300 μm deep from the surface during IGC test for a long period. It was considered that the IGC was caused by the existence of PFZs because PFZs were clearly observed on the surface layer of the extrusion but were not observed in the center position of the extrusion thickness. Furthermore, it was considered that the formation of PFZs was associated with the grain boundaries characteristics. That is, it was suggested that most of the grain boundaries had random high angle in the extrusion surface, but had small angle in the center plane of the thickness. To verify this hypothesis, the center plane which was cold rolled and recrystallized was examined by the IGC test. As a result, heavy IGC was observed because the center plane had random high angle boundaries and PFZs.

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Effect of inclination of faying surface on the mechanical properties of 5052 aluminum alloy joints, which were welded by a brake type friction welding machine, has been investigated. The inclination angle of faying surface to the specimen axis was 0° to 25°. The axial shortening increases at first rapidly and then slowly with increase in the welding time. It is found that the initial axial shortening speed increases with increasing the inclination angle. Regardless of the friction time, both burn off length and total loss increased with increasing inclination angle. Heat affected zone of welded joints became narrower with increasing inclination of faying surface. The inclination of faying surface had no effects on the microstructures of joint. Hardness of weld zone was lower than that of the base metal. The width of softening zone tended to decrease with increase in the inclination angle. Tensile strength of the welded joints was 84% as large as that of the base metal independent of the inclinatin angle of faying surface. Regardless of both welding condition and inclination of faying surface, the elongation of welded joints was 81% as large as that of the base metal. All joints fractured at the heat affected zone.

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Comparatively thick pipes of 6061 aluminum alloy and S25C carbon steel were friction welded under a preferable welding condition and the strength distribution on the weld interface was investigated. The results obtained are as follows; (1) According to a decrease of the thickness ratio 0.30, 0.16, 0.15, 0.14, 0.13 and 0.12, the joint efficiency decreased 73.9%, 68.1%, 63.8%, 55.8%, 39.9% and 21.6%, respectively. (2) Friction welding of thin pipe having less thickness ratio t/D₀ than 0.11 was difficult to produce a sound weld (D₀: outer diameter, t: thickness of pipe). (3) The tensile strength of each 11.1% area from inner and outer edges of the weld interface was low, and the joint efficiencies were 30∼50%. (4) The joint efficiency of the joint removed inner and outer areas of the weld interface was about 95%.

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