Study of Pore Closure Mechanism of Aluminium Composite Processed through Powder Metallurgy Route A. Rajeshkannan 1, a , Bibhya Sharma 2,b 1 Mechanical Engineering, School of Engineering & Physics, 2 School of Computing, Information and Mathematical Sciences, Faculty of Science, Technology & Environment, The University of the South Pacific, Laucala Campus, Suva, Fiji. a ananthanarayanan_r@usp.ac.fj, b bibhya.sharma@usp.ac.fj Keywords:Porosity; Strain; Density; Composites. Abstract. Hot swaging experiments were carried out on as-sintered Al composite preforms in order to evaluate its pore closure characteristics. The effect of tungsten carbide and iron carbide in plain aluminium has been investigated under triaxial stress state condition. Cylindrical preforms with 0.5 aspect ratio and 88% fractional theoretical density have been produced for pure Al, Al-2WC and Al-2WC-4Fe 3 C through classical powder metallurgy route. Then, the as-sintered preforms are hot swaged to various height strains to further enclose the residual porosities; thereby to enhance density and mechanical properties. It is observed that induced strain substantially helped to close the porosities; however this largely depends on the reinforcing carbide particles in the Al-matrix. Introduction Aluminium matrix composites are in the state of much developing yet possess high potential to research on, especially to reveal its structural, chemical, electrical and their associated properties. These composites are having wide scope in electrical, electronics, aerospace, chemical industries etc., due to a unique combination of its properties [1]. Composites are artificially synthesis material that possess combination of matrix and dispersed phase’s properties. This expected to serve for the intended properties much better than a monolithic alloys. One of the challenging tasks in producing composites is the processing route, it is identified P/M is a promising route that can potentially produce component with desired geometry and properties [2]. However it is necessary to design process parameters for novel composites before to take onto actual production. The deformation characteristics are essential to formulate the workability of a material. It is well known that through classical P/M route (pressing-sintering) achieving up to 1-2% porosity range is farfetched. Mostly it demands for further processing, it is well established that conventional forging on sintered product substantially reduces porosities with the increased mechanical properties [3]. Besides it has merits of achieving final shape and size with single blow, meaning thereby the operation is simple and economical. Thus, in this investigation hot deformation technique has been considered. Before executing hot deformation the preforms are produced with predetermined density so as to evaluate its pore closure mechanism during hot deformation. Porosities in P/M components complicate the plasticity theory. For conventionally produced material the theory was developed based on volume constancy principle. But in P/M, on account of deformation porosities close and so bulk volume changes, thus applying mass constancy principle to evaluate the plasticity theory. A new yield function for compressible materials was derived by Doraivelu et al. the derivation of yield function was based on a yield criterion and it was experimentally verified for uniaxial compressive stress for P/M Al alloy [4]. However, this function was not further verified for other states of stress. Sowerby et al. [5] made an attempt to establish the effective use of hoop and axial strains at the free surface for an upsetting preform and from which the associated stress have been derived for multi-stress state. A new generalized yield criterion for P/M material was derived elsewhere by considering an anisotropic parameter; in which a new flow rule was also proposed [6]. The objective of present work is to establish the pore closure mechanism against the deformation induced through hot swaging on the considered Al matrix composites. The Advanced Materials Research Vol. 911(2014) pp50-54 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.911.50