Some aspects of workability studies on P/M sintered high strength 4% Titanium carbide composite steel preforms during cold upsetting

Workability is concerned with the extent to which a material can be deformed in a specific metal working process without the initiation of cracks. Ductile fracture is the most common failure in bulk forming process. The formability is a complicated phenomenon which depends on the friction between the preform and the die surface in cold upsetting. A complete experimental investigation on the workability behavior of the steel composite of 4%TiC was performed under different stress states, namely, plane and triaxial stress state conditions. Cold upsetting of the Fe-1.0%C-4%Ti steel composite preforms was carried out applying different lubricants, namely, graphite, zinc stearate and molybdenum disulphide, and without lubricant, and the formability behaviour of the same under plane and triaxial stress state conditions was determined. The curves plotted for different preforms were analysed and relationship was established between the axial strain and the formability stress index under plane and triaxial state conditions. A relationship between the relative density and the axial strain was also established. Various stress ratio parameters, namely, (σθ/σeff), (σm/ σeff) and (σz/σeff), under plane and triaxial stress state conditions were determined empirically as a function of the relative density. An attempt is also made to study the variation of slope of the relative density versus stress ratio parameters under plane and triaxial stress conditions with respect to the relative density to identify the pore closure mechanism. © Springer Science+Business Media, Inc. 2007.