Papers by Keyword: Compressive Torsion Processing

Abstract: 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.

Abstract: The present study is aiming at investigating the possibility of producing a magnesium foam from machined chips. To produce highly porous magnesium foam, precursor producing process was investigated by hot extrusion and compressive torsion processing (CTP). The CTP could realize well-consolidated precursors and homogeneous distribution of a blowing agent. The precursor made of machined chips satisfactorily expanded, and the porosity were comparatively high by optimizing processing parameters of the CTP.

Abstract: A compressive torsion processing (CTP) was applied to hypereutectic Al-Si alloy in order to raise ductility and formability by microstructure refinement of the alloy. The CTP is a unique severe plastic deformation process and it can easily apply large strain to a work piece without change in shape. In the present work, influence of compressive torsion processing temperature on microstructure refinement and tensile property of hypereutectic Al-Si alloy is dealt with. When the CTP was applied on the Al-Si alloy, primary and eutectic Si particles were refined more effectively at lower processing temperature. Total tensile elongation of CTPed alloy was four times as large as that of non CTPed one. Distribution of the total elongation was quite uniform in the whole CTPed specimen.

Abstract: Compressive torsion combined loading that uses relatively low compressive pressure has a great advantage of microstructure refinement of cylindrical metal blocks without changing their shape while processing. In the present work, effects of processing temperature and rotation times on homogeneity of the refined microstructure were investigated for Al-5%Mg alloy. Although lower processing temperature was effective to obtain fine grains, it was difficult to obtain homogeneous refinement at lower temperature. Higher processing temperature was favorable to obtain homogeneous microstructure, for instance, in the cylindrical specimen of φ25×10 mm the homogeneous refinement could be obtained at higher temperatures than 373K. Increasing rotation times was also effective to obtain homogeneous refined microstructure for thicker specimens.

Abstract: 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.