Optimization of casting parameters for improved mechanical properties of eggshell reinforced composites

The tensile strength, hardness and toughness of any materials are the most important mechanical properties in the selection of materials for varied industrial applications. In the development of aluminum based composite material, tensile strength and hardness were significantly improved by adding various ceramic reinforcement particles. However, toughness was reduced. In this research work, an attempt was made to enhance tensile strength, hardness and toughness simultaneously by using carbonized eggshell as reinforcement material developed via electromagnetic stir casting. The process parameters used in this study are the matrix pouring temperature, wt.-% of the reinforcement; preheat temperature, stirring current and stirring time. Response surface methodology (RSM) is used for conducting the experiment. The multi-objective optimization technique utility theory is employed to optimize the combined mechanical properties viz. tensile strength, hardness and toughness. Microstructure results show that at the optimum level of process parameters, eggshells are uniformly distributed. Confirmation tests are conducted to validate the experimental results. Experimental results revealed that at optimum process parameters, hardness and tensile strength are significantly improved without affecting the toughness property of the composite. The optimum level of process parameters to enhance all mechanical properties (tensile strength, hardness and toughness) were found to be a reinforced preheating temperature of about 448.32 °C, a stirring current of about 11.64 A, a stirring time of about 63.64 s, a maximum pouring temperature of about 800.24 °C and a percentage of eggshells of about 9.16 %. The novelty of this work lies in the fact that no attempt was made to optimize these electromagnetic process parameters. Corrosion loss, thermal expansion behavior and a wear test were investigated to observe the effect of adding eggshell at optimum electromagnetic stir casting parameters.

Fabrication and characterization of Al6063/SiC composites using electromagnetic stir casting process

In this work, metal matrix composites were fabricated using the electromagnetic stir casting process by adding 5 and 10 wt% silicon carbide in Al6063 alloy. Hardness, ultimate tensile strength, and yield strength of the developed Al6063/SiC/5p metal matrix composites have been improved by 17%, 18%, and 37%, respectively, in comparison with Al6063 alloy. Further, an improvement of 25%, 37%, and 71% in hardness, ultimate tensile strength, and yield strength, respectively, have been noted for Al6063/SiC/10p metal matrix composite in comparison with the Al6063 alloy. Results revealed that the hardness and strength of metal matrix composites were increased with silicon carbide addition in Al6063 alloy. The presence of different elements in metal matrix composites was identified by energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Energy-dispersive X-ray spectroscopy was used for elemental mapping observation of the metal matrix composites. Uniform distribution of reinforcement particles in the matrix with improved mechanical properties of metal matrix composites proved the adequacy of the electromagnetic stir casting process. The presence of facets and dimples in fractographs indicated the mixed mode of fracture. The average percentage porosity presented in Al6063/silicon carbide/5p and Al6063/SiC/10p metal matrix composites was found to be 4.68% and 5.22%, respectively.

Influence of precipitation hardening parameters on the microstructure and mechanical properties of extruded AA2014/eggshells green composites

The AA2014/5 wt. % carbonized eggshells metal matrix composite used in this study was fabricated by electromagnetic stir casting technique and immediately extruded on universal testing machine at 60 MPa using cylindrical H13 tool steel die coated with graphite to avoid upper flow of eggshells particles and to improve wettability of eggshells with AA2014 alloy. Microstructures of composites show some agglomerations in non-extruded samples while uniform distribution of carbonized eggshell particles. Optimum combination of precipitation hardening parameters achieved using response surface methodology to further improve the properties of AA2014/5 wt. % eggshell composites. Optimum values of solutionizing time, aging temperature and aging time were found to be 4.5 h, 250℃ and 13.5 h, respectively. More grain refinement of extruded AA2014/5 wt. % eggshell composites were observed after heat treatment at optimum precipitation hardening parameters. After heat treatment, fractographs of the AA2014/5 wt. % eggshells composite showed that fracture is dominated by trans-granular type. Density of the AA2014 is 5% higher than AA2014/5 wt. % eggshells metal matrix composite. It is observed that mechanical properties improve when carbonized eggshell particles are reinforced in matrix AA2014 aluminium alloy. After the heat treatment at optimum precipitation hardening parameters, mechanical properties are further improved.