The effects of high strain rates on superplastic forming

In this study, the effects of high strain rates on superplastic forming through the deep drawing process were investigated experimentally and through finite-element analysis. Ti6Al4V sheet was used as the material and experimental studies were conducted at a high strain rate of 10⁻² s⁻¹ and a forming pressure of 25 bar. In the first phase of the study, the characterization of the experimental material was performed by subjecting the material to hot tensile tests at 870 °C and a deformation rate of 10⁻² s⁻¹, resulting in an elongation of 1489%. The mechanical properties obtained from the experimental results were then defined as creep parameters for the analysis of the superplastic process in the ABAQUS software. From the analysis, the optimal mold depth for a 40 mm forming diameter was determined to be 40 mm, with a blank diameter of 120 mm. The experimental study revealed that the Ti6Al4V alloy could be successfully formed at a 3.0 limit drawing ratio (LDR) without tearing. However, surface-forming defects resembling orange peel were observed due to grain coarsening in the microstructure of the deep-drawn sample. Thickness analysis of the formed specimen's cross-section showed a thickness distribution that was 98% consistent with the results of numerical analysis and the experimental study.