| Two Equal-channel angular (ECA) pressing facilities have been set-up at USC. One facility offers the possibility to control the pressing speed and record the load during pressing while the other offers a high pressing stress at a high temperature.; The technique was applied to two high ductility and low strength two-phase alloys, the eutectic Pb-62%Sn and the eutectoid Zn-22%Al. The mechanical properties were not dramatically enhanced.; The processing of pure Al and Al-5%Zn allowed the study of the effect of some of the parameters, such as the number of passes, the processing route and the pressing speed on the prepared material. It was also helpful in understanding the mechanisms taking place during the ECA deformation, and led to a model that is a variation on the low energy dislocation structure theory and models for rolling of aluminum alloys. The concept of a critical ECA strain was also derived from this study on Al alloys.; The effect of a small addition of Sc into Al alloys was observed, through a comparison of results on Al-3%Mg, Al-0.2%Sc and Al-3%Mg-0.2%Sc, to be very beneficial to the superplastic properties after ECA deformation. This was related to the large enhancement in thermal stability introduced by the presence of the stable intermetallic Al3SC particulates.; The technique was also applied to commercial alloys such as Al-6061, Al-1420, Al-1421, Al-1460, and Al-2004. The results on Al-6061 pressed at 298 K showed the importance of the dislocation network reorganization and was in excellent agreement with the model developed for Al alloys. The other alloys processed at higher temperature proved that a submicron grained structure was achievable via ECA deformation. Furthermore, the tensile tests showed a very strong superplastic effect occurring at relatively low temperatures and high strain rates, with elongations to failure as high as 2000% in one of the commercial Al alloys. |
