Deformation of titanium alloy Ti-6Al-4V under dynamic compression

Deformation localisation is the main reason for material failure in cold forging of titanium alloys and is thus closely related to the production yield of cold forging. Recent research has revealed that the width of shear band of titanium alloys after dynamic compression is related with their static and dynamic mechanical properties and processing parameters. To explore the influences of these factors on titanium alloys in dynamic compression, the distributions of stress, strain, strain rate and temperature of the specimens over the macro and microscales have been systematically studied. This work can be beneficial to process parameter optimisation and material designing for cold forging. In the study of the influence of process parameters on dynamic compression, considering material constitutive behaviour, physical parameters and process parameters, a numerical dynamic compression model for titanium alloys has been constructed. The entire dynamic compression process is simulated and a good agreement with experiments is observed. By extracting and comparing the stress, strain and temperature distribution under prescribed conditions, the effects of friction and compression velocity on the macrostate and distribution of strain and stress of compression samples are studied. Friction and compression rate are important factors influencing the spread and the stress state of deformation localisation zone. When friction is reduced to a certain level, deformation localisation can be effectively alleviated. The increase of friction and compression rate can lead to early appearance of tension stress in the deformation localisation zone, which may explain the experimental finding that crack tendency increases with higher compression rate and poorer lubrication. By adjusting the process parameters, the severity of strain localisation and stress state in the localised zone can be controlled thus enhancing the compression performance of titanium alloys. (C) 2010 Elsevier B.V. All rights reserved.