The NiTi alloys are generally considered hard-to-deform materials when processing by equalchannel angular pressing (ECAP) at room temperature. Nevertheless, it is shown by experiment that a NiTi alloy may be successfully processed by ECAP for up to two passes using a core-sheath configuration. Three-dimensional finite element simulations were used to more fully evaluate the flow behavior after the first and second pass of ECAP. The values of the microhardness were recorded across transverse directions within the cores and the results show that the imposed strain both decreases by comparison with the processing of conventional sheath-free NiTi billet and increases by increasing the dimensions of the core. The lower areas of the cores undergo less deformation than the upper areas after successful ECAP processing but the imposed strain, and thus the microhardness values, become homogeneously distributed on the longitudinal planes after two passes of ECAP.
A new design of billet, based on a core–sheath configuration, was used for the processing of Ni, Fe, and a NiTi alloy by equal‐channel angular pressing (ECAP) at room temperature. This configuration involves inserting metal cores within Fe sheaths prior to processing and it is designed especially for use with hard‐to‐deform materials. Billets were processed through one or two ECAP passes at room temperature and the microhardness values were recorded across the transverse directions within the cores to evaluate the flow process. As in conventional ECAP, the hardness increased significantly after the first pass and there were regions of lower hardness along the bottom surfaces of each core. The gradient of hardness decreased with increasing core diameter but the average microhardness values remained unchanged. Three‐dimensional finite element simulations were used to evaluate the flow behavior after one pass of ECAP using different core metals. These simulations show the lower areas of the cores undergo less deformation than the upper areas and the homogeneity increases with increasing levels of friction at the core–sheath interface.
A composite containing A356 Al alloy as matrix and ZrB2 particles was made in an induction furnace by mixing Al-15Zr and Al-8B master alloys with Zr:B weight ratio of 9:2. The microstructures and tensile properties of the extruded composite were studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis before and after T6 heat treatment. XRD results showed the presence of ZrB2 phase in the microstructure. Tensile test results showed an increase in ultimate tensile strength (UTS) and elongation values of the extruded composite in comparison with the matrix alloy. Further investigation showed an increase in UTS, but reduction in elongation values of the composite after T6 heat treatment.
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