Pure aluminum powder with grain sizes of 45 to 10μm preformed on aluminum (A1050) and mild steel (SPCC)substrates were rolled to form cladding materials at room temperature in air. The partial rolling reduction of the Al cladding layer was smaller than that of the A1050 substrate in an Al powder/A1050 cladding sheet. In contrast, the partial rolling reduction of the Al cladding layer was larger than that of the SPCC substrate in an Al powder/SPCC cladding sheet. The difference in the partial rolling reduction of the cladding layers and SPCC substrates became smaller with increasing total rolling reduction of the Al powder/SPCC cladding sheets. The shear adhesion strength of the Al powder/SPCC cladding sheet was about 40MPa, which decreased to about 10MPa after heat treatment at 773K for 3.6ks. The intermetallic compounds were formed between the cladding layer and the substrate after heat treatment at 773K for 3.6ks. Also, the cladding layer showed excellent oxidation resistance compared with cast iron after heat treatment at 1073K for 36ks in air, though light oxidation occurred in specimens after heat treatment at 773K for 36ks in air.
The newly developed extrusion process for Mg-Al-Mn-Ca magnesium alloys using rapidly solidified powders produced very fine grains. The uniaxial tensile and compressive anisotropic stress-strain curves in the extrusion direction and the transverse directions were identified by finite element (FE) analysis based on the measured force-displacement relation. Compared with the cast ingot magnesium alloys, the extruded magnesium alloys have higher strength and weaker anisotropic material properties. Using the identified anisotropic material properties of the extruded magnesium alloys and anisotropic yield function Hill48, the deformation behaviors of magnesium under three-point bending tests and a ball-on-plate indentation test were accurately predicted.
As a demonstration of the production process of thermoplastic carbon fiber reinforced plastic (CFRTP) parts by press forming, a varying-cross-section beam has been press formed using thermoplastic carbon fiber composite sheets. The shape of a front side member in an automobile has been applied as the formed shape 800mm long, 170mm wide in front, 270mm wide in the rear and 50mm high. Deformation of the fiber during the press forming has been investigated. Inserting sheets with fiber orientations corresponding to the corner line in the varying width part had an effect on the uniformity of the mechanical strength in the formed beam. Two beams are joined to a closed beam and a drop impact test has been carried out. The results showed that the beam has the favorable characteristic that a constant destruction load is maintained from the front to the distance in which the impact energy is absorbed. The constant destruction load depended on the combined strength of the sheets in the press-forming process.
Environment issues have restricted the industry-wide trend to reduce the amount of Cl or P additive used for lubrication in metal forming. Diamond like carbon （DLC） has superior tribological properties such as low friction and wear resistance under poor lubrication. However, DLC has never been applied to severe forging in metal forming. Thus, we focused on a Si-containing DLC （DLC-Si） coating with high adhesion strength, which has been used in the sliding parts. The combination of DLC-Si and polymer-containing oil without S or P additive, was evaluated by the ball penetration test. An observation of the workpiece and the DLC-Si coated ball also indicated a high lubrication performance of the combination. The low friction working of the combination is probably different from that due to the high viscosity of polymer-containing oil. We found that DLC-Si coatings with polymer-containing oils have a great potential to reduce friction and wear. It would suggest that strong adsorption on DLC-Si coatings is effective for lubricating for the combination of DLC-Si coatings and polymer-containing oils.
In this study, the ductile fracture limit at low stress triaxiality was examined．Spheroidized medium-carbon steel JIS-S55C was adopted as the test material. Notched-bar combined torsion tests were carried out so as to control low stress triaxiality states. The stress triaxiality and equivalent plastic strain were calculated by the finite element method. The ductile fracture limit at low stress triaxiality could be expressed as a function of the stress triaxiality and equivalent plastic strain. It was not consistent with the ductile fracture limit at high stress triaxiality determined by notched-bar tensile tests. This result suggested that the ductile crack initiation mechanism differed between the tensile mode and the shear mode.