Papers by Author: P. Venugopal

Abstract: Groove pressing (GP) is a severe plastic deformation technique for producing ultra fine grain sized microstructures in metals and alloys. In the present study, groove pressing and a two-step process of groove pressing followed by cold rolling was used to investigate the potential of these processes to produce ultra fine grained copper with significantly enhanced strength. Mechanical and microstructure properties were evaluated after groove pressing and after groove pressing followed by cold rolling. The advantages conferred by groove pressing prior to cold rolling on producing copper with enhanced properties has been investigated.

Abstract: Equal channel angular extrusion (ECAE) is a processing method for introducing an ultrafine grain size into a material. In the present study, a two-step severe plastic deformation process was used to produce ultrafine grained copper with significantly enhanced strength. Equal channel angular extrusion was first used to refine the grain size of copper samples. The copper samples were further processed by cold rolling (CR) to a strain of 0.67 (about 50% reduction). This two-step process produced ultrafine grained copper with strengths higher than those of pure copper processed through ECAE only. This paper reports the microstructures and mechanical properties of the copper specimens processed by a combination of room temperature ECAE and CR. The effectiveness of initial processing by ECAE prior to cold rolling is discussed.

Abstract: Severe plastic deformation processes like equal channel angular extrusion (ECAE) have been widely investigated for their ability to produce nano/ ultra fine-grained microstructures. It is well known that submicron sized grains/ sub grains can be produced in most Al alloys using this technique. However, industrial applications of ECAE will depend heavily on the advantages conferred by this process when it is used as an intermediate processing step prior to conventional forming. In the current investigation, the influence of pre processing by ECAE on subsequent post processing by conventional cold extrusion has been investigated. ECAE extrusion was carried out on cylindrical specimens of AA 6101 using an ECAE die with a die angle of 120 degrees. Extrusion was carried out for three passes using two different processing routes. The ECA extruded specimens were subsequently subjected to conventional cold extrusion. The differences in extrusion pressures, which have a strong influence on industrial applications, were noted. Changes in microstructure and mechanical properties were also determined. The obtained results of mechanical properties and microstructure evaluation show that for high strains (strain ε ≈ 2.01), ECAE through some processing routes can be effectively used as an intermediate processing step prior to conventional cold extrusion to obtain a product with enhanced mechanical properties.