Processing, Microstructure and Mechanical Behaviour of Al6262-4wt. % B4C Composites

Metal matrix composites play an important role in automobiles, aerospace, sports and marine sector. In the present investigation, an attempt has been made to investigate the mechanical properties of Boron Carbide (B4C) particulates reinforced Al6262 alloy composites. Al6262 alloy was used as the base matrix. B4C particulates were used as reinforcement. The composites containing 4 wt. % of B4C particulates were fabricated by using liquid metallurgy route. The microstructures of the composites were examined by scanning electron microscopy. Further, tensile behaviour of as cast Al6262 alloy and 4 wt. % B4C composites were studied. Mechanical properties like hardness, ultimate tensile strength, yield strength and percentage elongation were evaluated as per ASTM standards. Microstructural observation revealed the uniform distribution of particles in the Al6262 alloy matrix. Further, it was found that the hardness, ultimate tensile strength and yield strength of composites were increased due to presence of boron carbide particle in the Al6262 alloy matrix. Percentage elongation of the composites decreased with addition of 4 wt. % of B4C particulates in soft Al alloy.

a critical size, particles no longer rupture. Statistically larger flaws and other defects are more likely to exist because of the larger particles size and weaken the strength of composites when compared with the composites containing smaller size of the particles. Shisheng and co-authors [8] studied the mechanical behaviour of in situ carbon nano tube and silicon carbide reinforced Al6061 aluminium matrix composites. Results show that significant improvement in tensile properties with the SiC size to be 7 microns, which has ductility of 8.5% and Young's modulus of 98 GPa, and tensile strength of 428 MPa. Ibrahim et al. [9] investigated the impact toughness of Al-15 vol. % B 4 C composites produced using powder injection method. Aluminium based composites exhibited better toughness. The composite impact toughness was controlled by the precipitation and coarsening of hardened phase particles. Xin Gao et al. [10] reported the mechanical properties of graphene reinforced aluminium framework composites. Graphene strengthened aluminium lattice composites were set up by powder metallurgy course. The outcomes demonstrate that with expanding the graphene substance, a definitive elasticity of the composites at first increments and later reductions. In any case, the extension to crack of the composite steadily diminishes. From the writing overview, it can be presumed that the vast majority of the studies are given to miniaturized scale measure particulates. However, the utilization of nano estimated clay particulates is moderately restricted. So, the present work aims to develop high strength and low density composites for structural and transport applications by usage of micro sized B 4 C particles. With the development of new processing techniques stir casting process has evidenced to be comparatively economical and easy to use. The preparation of the composites focuses on B 4 C ceramic particulates that are reinforced in steps of two into the vortex formed in molten metal Al6262 alloy by liquid metallurgy stir casting.

II. MATERIALS USED AND EXPERIMENTAL DETAILS A. Matrix material
In the present experimental investigation, Aluminium Alloy 6262 is used as the matrix material and its chemical composition is shown in Table 1. Al6262 alloy is one of the wrought aluminium alloy containing magnesium as the major element and it is combined with silicon and copper. The density of Al6262 is 2.70 g/cm 3 and the melting point is considered as 660 ˚C.

B.
Reinforcement material The main benefit of introducing the reinforcement material to the matrix is to enhance both mechanical and tribological properties. In the current research, micro B 4 C particulates is been used because the micro-particles of B 4 C are water dispersion is having high hardness and good dimensional, phase stability and it also is used to improve fatigue resistance, smoothness, fracture toughness, and creep resistance. The density of B 4 C is 2.52 g/cm 3 , is less than that of base alloy. So, the reinforcement material is added in steps of two during the preparation of the composites to have proper mixing with the base matrix and to avoid the difficulty of agglomeration.

C.
Fabrication Procedure In the present research, the composites of micro B 4 C and Al6262 is mostly arranged by two phase fluid metallurgy mix throwing process and an endeavour has done to examine the tractable properties of Al6262 amalgam and Al6262 -4 wt. % micro B 4 C composites. Firstly, the micro B 4 C particulates were preheated for 400˚C to make their surface oxidized and enhance the wettability, then the required measure of Al6262 is kept in a graphite pot which was set in electric furnace at a working temperature of 750˚C.The furnace temperature was raised up completely to soften the bolster stock totally. Once the Al6262 is totally liquefied then the degassing tablet i.e. Solid Hexa Chloroethene (C 2 Cl 6 ) was acquainted with the liquid dissolve and blended for 4 to 8 minutes, which helps in the expulsion of undesirable adsorbed gases from the soften [11]. Next the prewarmed particles are likewise brought into the liquid liquefy of Al6262 amalgam novelty which incorporates two phase expansion of the fortification into the framework. The two-phase options incorporate isolating the 4wt. % of micro B 4 C particles in two equivalent weights and after that individual weights of particles are included two phases rather including at the same time. Fig. 1a and b shows the stir casting set up and the prepared composites with the cast iron die which used in the present study.

D. Chara
The  [14]. Fig. 4 demonstrates the 18 % change in a definitive elasticity of Al6262 compound in the wake of including 4 wt. % of B 4 C particulates.

Al6262
Al626+4% It can be seen that by adding 4wt. % of B 4 C particulates yield strength of the Al6262 alloy increased from 121 MPa to 146 MPa. This increase in yield strength is in agreement with the results obtained by several researchers, who reported that the strength of the particle reinforced composites is more strongly dependent on the weight fraction of the reinforcement [15]. Fig. 6 demonstrating the impact of B 4 C content on the elongation (ductility) of the composites. It can be seen from the chart that the flexibility of the composites diminishes essentially with the 4 wt. % B 4 C fortified composites. This diminishing in rate prolongation in correlation with the base amalgam is a most usually happening detriment in particulate fortified metal lattice composites. The lessened pliability in composites can be ascribed to the nearness of B 4 C particulates which may get broke and have sharp corners that make the composites inclined to restricted split start and proliferation. The fragile impact that happens because of the nearness of the hard-artistic particles bringing on expanded neighbourhood stretch focus locales may likewise be the reason.