The present authors have realized that cutting chips may be identified utilizable for the strengthening of materials due to large plastic strain accumulated during cutting. The authors have proposed upgrade recycling techniques in which severe plastic deformation in room temperature air is utilized to cutting chip mixture of dissimilar materials, thereby consolidation and further accumulation of strain are simultaneously achieved. In this study, such composite materials are produced and evaluated with combinations of 6061 aluminum/IF steel and 6061 aluminum/pure copper. It is clarified that appropriate second phase cutting chip is a BCC metal. The ultimate tensile strength of the 6061 alloy is improved approximately up to 500 MPa (about 1.6 times that of the material before cutting) when the volume fraction of the IF steel is 20%. To predict the attainable maximum tensile strength by the current method, the Eshelby equivalent inclusion model is employed. The present method is identified to have a potential of realizing 713 MPa (about 2.3 times that of the material before cutting) in the case of the 6061 alloy/20%IF steel composite by eliminating production defects adjusting the matrix/second phase combination and conditions for cutting and plastic working.

The present authors have proposed in situ composites in which cold working was applied to the cutting chip mixture of dissimilar materials. The composites have exhibited superior strength together with ultra fine grain structure. In this study, such composite materials are produced by combining 6061 aluminum alloy and IF steel chips. Microstructural evolution processes are visualized by means of the microtomography as well as the TEM observation. It has been clarified that ultra fine grains with a large fraction of high angle boundaries are obtained due to the effects of severe plastic deformation during cutting. Grain size of the matrix aluminum alloy is reduced to about 220 nm by applying swaging strain of only 1.9. It should be noted that the significant strain hardening of the chips occurs during initial deformation stage where strain applied by swaging seems to be consumed mostly for consolidation. The chips gradually change their orientation in the material at this stage. It can be inferred that the rapid development of ultra fine structure in the matrix is also attributed to gradual change in deformation axis thereby realizing effective multi axial deformation. Overall, the utilization of chips is identified as a highly effective way of grain refining compared to the other uniand multi axial deformation processes.