Abstract
Most Severe Plastic Deformation (SPD) processes lack both the capability for continuous process and the homogeneity of tailored material properties in processed samples. These challenges have limited the adaptation of SPD technology to process titanium alloys for biomedical and structural applications. This thesis presents microstructural and mechanical characterization of Ti6Al4V titanium alloy processed by a Constrained Bending and Straightening (CBS) SPD technique. The proposed CBS method was intended for a continuous process of titanium sheets with improved magnitude and homogeneity of the entailed strain, hardness and tensile properties. The CBS process tool was designed and fabricated in the University of Johannesburg workshop. The tool was used to process Titanium Alloy Grade 5 (Ti6Al4V) sheets at a combination of (2, 4, 6) passes (N) and (6 mm, 12 mm) feeds (F) designated as N2F6, N4F6, N6F6, N2F12, N4F12 and N6F12. Sub-samples were cut from the processed sheets. The samples were prepared, and their respective microstructural analysis, hardness and tensile tests were performed. A numerical model for the CBS process was built and simulated with ABAQUS Standard Finite Element Analysis (FEA) method. The model was used to predict the magnitude and the homogenity of the Effective Plastic (EP) strain, the tensile yield strength and the hardness of the material. The simulation results were validated with the experimental data. The experimental results showed that...
Ph.D.(Mechanical Engineering Science)