The corrosion behavior of various clad sheets of aluminum alloys for the automotive radiator in a weakly acidic solution called OY water and a long-life coolant solution at pH10.0 was studied. The materials were Al-1.0Zn, Al1.0Zn-1.0Fe, Al-1.0Zn-1.0Ni and Al-1.0Zn-1.0Fe-0.5Ni alloys cladded on AA3003 core alloy. These materials were subjected to elevating-temperature immersion tests and polarization measurements in test solutions. These clad sheets showed good corrosion resistance in OY water because of the cathodic protection of cladding alloys. In the long-life coolant solution at pH10.0, a severe pitting corrosion occurred with the formation of a black-colored oxide film on Al-1.0%Zn clad sheet. On the other hand, the pitting corrosion on Al-1.0%Zn-1.0%Fe clad sheet was significantly reduced compared to that on Al-1.0%Zn clad sheet. There was no difference in polarization behavior between Al-1.0%Zn and Al-1.0%Zn-1.0%Fe clad sheets. The good corrosion resistance of Al-1.0%Zn-1.0%Fe clad sheet in the long-life coolant solution at pH10.0 was discussed in terms of the dispersion of intermetallic compounds such as Al₃Fe and Al₃Ni, and oxide film formation.

A commercial A5052 aluminum alloy was processed by multi-directional forging (MDF) to 6 passes in a total strain of 4.8 at room temperature. Microstructures and crystal orientations were examined by the electron back-scatter diffraction method. The change in crystal orientations was discussed from two models, the minimum work (Taylor) and the maximum resolved shear stress (Sachs). Ultra-fine grain structure below 1μm was developed in the specimen after the MDF for 6 passes. The analysis using crystal orientation index of ｛hkl｝<uvw> indicated that the main components of texture after MDF for 6 passes were ｛011｝ <100> and ｛011｝ <110>, which were parallel to the compression plane in the final pass of MDF and the compression axis before two passes, respectively, in the specimen coordinate system. Regardless of the number of MDF pass, the main component was ｛011｝<100>. The plastic deformation in MDF from 1 to 3 passes was mainly explained by the Sachs model, however this model could not apply to the formation of the texture after MDF for 6 passes.

We investigated the processability and aging characteristics of a selective laser melted (SLM) Al-Mg-Sc alloy. The Al-Mg-Sc SLM specimens were densified with increasing volume energy density in the SLM process. The Al-MgSc SLM specimen, fabricated under the optimum laser scan conditions for densification, had a relative density of more than 99.9%. The Vickers hardness significantly increased by aging heat treatment, and the peak-aging condition was found at 325°C for 4 h. Meanwhile, the hardness could be maintained even after prolonged aging, that is, robust aging behavior was confirmed for aging time. Both the as-fabricated and peak-aged Al-Mg-Sc SLM specimens showed mixed crystal grain microstructures with equiaxed and columnar crystals. The nanostructure of the peak-aged Al-Mg-Sc SLM specimen was dispersed single-nano-sized Al₃Sc precipitates in the α-Al matrix, which were generated by aging of the as-fabricated SLM specimen supersaturated with solid solution Sc. In the peak-aged Al-Mg-Sc SLM specimen, both the tensile strength and 0.2% proof stress significantly increased to 550 MPa and 500 MPa, respectively, equivalent to those of the heat-treated conventional extra-super duralumin. This strengthening was mainly attributed to precipitation hardening of the finely precipitated Al₃Sc phase (L1₂-type), coherent with the α-Al matrix.

Additive manufacturing technology has advantages in building free shape parts and simplification of manufacturing process. In order to manufacture high quality parts, it is important to investigate the influence of not only the fabrication conditions but also powder characteristics on the properties of parts. In this research, the influence of powder particle morphology on the density, microstructure and mechanical properties of Al-10%Si-0.4%Mg alloy fabricated by laser-based powder bed fusion process at high power and high scan speed was investigated using two types of powders, i.e. non-spherical and spherical powders. As a result, the density of the as-built specimen of spherical powder was higher than that of the alloy of non-spherical powder. In the case of spherical powder, the relative density of the as-built specimen was 100% even at the high power and high scan speed fabrication condition. The microstructure of the as-built specimens of both powders exhibited anisotropic parallel to the building direction. The as-built specimens of both powders fabricated normal to the building direction showed more than 400 MPa in tensile strength and 4% in elongation.