Effect of „Conventional‟ and „Severe Plastic Deformation‟ on 8 % TiB2 reinforced „In-situ‟ Aluminum composite

High specific strength of the material is critical for many structural applications in automotive and aerospace design. Among many other approaches for strengthening the materials, development of superfine and nano grained microstructure is becoming popular. Different techniques for producing ultra-fine-grained (UFG) materials have been introduced especially in the last decade. The advantages of fabricating materials with submicron size grained microstructure for structural components lie in their improved mechanical properties such as strength, hardness, ductility, fatigue resistance and low-temperature super plasticity. Severe plastic deformation (SPD) is one such process wherein simple shear stress is applied to a billet during multiple passages through an angled channel of constant cross section. The process is capable of generating very large plastic strains that significantly refines the microstructure without altering the external dimension of the billet. According to Hall-petch relation it is well known that refining the grain size increases the yield strength of a material. The concept of super plasticity is applied in super plastic forming. The super plastic forming is a very established industrial process for the fabrication of complex shapes in sheet metal. The present article is an attempt made to highlight the significance of severe plastic deformation over conventional extrusion technique of In-situ aluminum composite. The fabrication of insitu composite is through stir casting technique, a calculated amount of reaction mixture in certain proportions are mixed and added to the molten metal where exothermic reaction takes place due to the heat of the molten metal and the byproduct of the reaction is the reinforcement. The composite is then subjected to conventional extrusion and ‘equal channel angular processing’ techniques. The mechanical properties were evaluated and compared. An improvement in hardness of about 81% has been observed compared to the matrix metal and 40% more hardness when compared to extruded ones and an ultimate tensile strength of 565 Mpa was obtained exihibiting an enhancement of about 75% compared to base alloy. The Microstructure analysis reveals that dendritic coarse grains have been broken down to fine structured after ECAP. Keywords-Insitu composite, ultrafine grains, severe plastic deformation, equal channel angular processing