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Cast AlFe alloys containing several percent iron have low ductility because of their brittle precipitates. Therefore, precipitate refinement is very important for improving their mechanical properties. In recent decades, severe plastic deformation processes have been developed to achieve this grain refinement. For example, our previously proposed severe plastic deformation process, called compressive torsion, is quite effective for not only grain refinement but also precipitate refinement even in brittle materials. In the present work, precipitate refinement of cast Al—Fe alloys by compressive torsion and the resulting improvements in their tensile properties were investigated. Compressive torsion with various numbers of revolutions was applied to Al—Fe alloys at 373 K. Then, the alloys were subjected to tensile testing at room temperature, 473 K, and 573 K. The obtained experimental results indicated that the initial eutectic microstructure of the alloys disappeared after the compressive torsion processing. All large precipitates with sizes of more than 200 μm were refined, and their sizes were reduced to several tens of micrometers. Furthermore, these refined precipitates were dispersed homogenously in the alloy microstructure. In result, the tensile properties of the alloys, namely, their strength and elongation, were improved remarkably. In particular, the elongation reached more than 30% at room temperature.

Compressive torsion process (CTP) which was developed by authors is effective process for grain and precipitates refinement of metallic materials with a severe plastic deformation. In the CTP, a cylindrical specimen is subjected to simultaneous compressive and torsional loading without change in its shape. However, metal flow and strain distribution in the processed specimen are not cleared, because the deformation is very large and complicated. In the present work, visualization of internal deformation of specimen processed by CTP was investigated using dual alloy etching technique. Two kinds of aluminum alloy were prepared by cutting on fan-like shape and alternately placed to a cylindrical shape. After CTPing, contrasts in the specimen were observed by polishing and etching. The internal distribution of shear strain was quantified by measuring the displacement of interface between the alloys. As a result, the visualization and quantification of internal deformation was successfully carried out using the technique. The internal strain distribution was varied not only in radial direction but also in longitudinal direction because of frictional constraint on the lateral face. A laminate contrast of the alloys observed on the vertical cross section was well related with the strain distribution in the specimen.

A compressive torsion process, which is one of severe deformation processes, is applied to AZ61 magnesium alloy to control microstructure. This process is composed of relatively low compressive pressure and axial rotation, and can apply huge strain to a work piece without changing in shape during processing. Effect of processing temperature on grain refinement and texture change was investigated. The alloy with initial 10~200 μm grains was refined under 10 μm by this process. The initial grains were refined smaller with lower process temperature, but the refinement was not enough at inner parts of a cylindrical specimen because of geometric strain gradient due to rotational loading. In the case of relatively higher temperature processing, though the refined grains became larger, the grain refinement were uniform all over the specimen even the geometric strain gradient. Axisymmetrical texture of (0002) crystal planes in the starting alloy was changed to the orientations parallel to the basal plane of a cylindrical specimen after this process.

The compressive torsion process (CTP) is applied for consolidation of aluminum machined chip wastes to investigate a possibility of a new solid state recycling for aluminum alloy. The machined chips were consolidated by the CTP under the different temperatures and rotation times, and then the microstructure and tensile properties were investigated. It was possible to consolidate aluminum chips sufficiently into a cylindrical specimen by the CTP even at room temperature. The tensile strength of the specimen processed by the CTP was higher than that of annealed alloy made from an ingot metallurgy process. The tensile strength increased as the processing temperature decreased. The enough elongation over 15% was also obtained all over the specimen processed at room and elevated temperatures. It was concluded that the CTP had the availability of a new solid state recycling process with upgrading of aluminum alloy.

A Compressive Torsion Processing (CTP) is a unique severe plastic deformation process which can easily apply very large strain without shape change to a work piece. Hypereutectic Al-Si alloys have good properties such as low thermal expansion and high wear resistance. It is important for the alloys to control the size of second phase particles (primary and eutectic silicon, intermetallic compounds) as well as grain size of aluminum matrix. In the present work, the CTP was applied to hypereutectic Al-Si alloy (AA390) to investigate the possibility of microstructure refinement of the alloy and the mechanical property of processed alloy was also investigated by tensile test.

A compressive torsion process that is one of the severe plastic deformation processes was applied to a commercial pure aluminum in order to obtain fine grain. In the compressive torsion processing the material was subjected to simultaneous compressive and torsional loading without change in its shape. The possibility of grain refinement and the effects of process conditions on the refinement were investigated by changing deformation temperature, compressive pressure, torsional cycle and torsional speed. Very fine grains around several microns were obtained by the compressive torsion process. However the grain refinement was not uniform in the specimen, the fine-grained region was concentrated in peripheral parts of the operating die. Decreasing processing temperature and increasing torsional cycle are effective to decrease grain size and extend finer grain area. The compressive pressure does not influence grain size and finer grain area. Increasing torsional speed enlarges grain size because of rise in temperature due to deformation heat generated in processing.