Stage Stir Casting Research Articles

Effects of graphene nano particles on interfacial microstructure and mechanical properties of Al7150/B4C hybrid nanocomposite fabricated by novel double ultrasonic two stage stir casting technique

In the present research, an Al7150 alloys-based hybrid nanocomposite was fabricated by incorporating boron carbide and graphene nanoparticles through a novel fabrication method of double ultrasonic two-stage stir casting. Initially, the Al-B4C nanocomposite was optimized based on better microstructural and mechanical properties, and then a hybrid nanocomposite was prepared by incorporating graphene nanoparticles into the optimized Al-B4C nanocomposite. Homogeneous dispersion of graphene and boron carbide nanoparticles in Al7150 matrix was successfully achieved due to the double ultrasonic effect analyzed by Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM) analysis. Significant dispersion of nanoreinforcements with enhanced interfacial bonding and dislocation strengthening improved the microstructural and mechanical properties of the Orovan reinforced hybrid nanocomposite. The Vickers microhardness and ultimate tensile strength were improved by 19 % and 47 %, respectively, for the optimized Al-B4C nanocomposite compared to base metal. However, the Vickers microhardness and ultimate tensile strength were significantly improved by 36 % and 57 %, respectively, for the optimized hybrid nanocomposite compared to the base material (BM). The hard AlB2, Al3BC and Al4C3 phases are formed due to the reaction between the matrix and reinforcement during solidification and act as reinforcement within the matrix and resist dislocation movements, resulting in a significant improvement in the mechanical properties of the nanocomposite. Fractography analysis by SEM also confirms the enhanced bonding of graphene nanoparticles as it deforms/slips during fracture and supports the effect of double ultrasonication on the tearing of boron carbide nanoparticles.

Mechanical behavior and fractography of graphite and boron carbide particulates reinforced A356 alloy hybrid metal matrix composites

The present work shows the mechanical behavior of as-cast A356 alloy and A356-4 wt% graphite (Gr)-12 wt% boron carbide (B4C) hybrid composites. The hybrid composite samples were developed by two stage stir casting technique. The developed hybrid composites were subjected to scanning electron microscope (SEM) and energy dispersive spectroscope to analyze its microstructure followed by physical and mechanical tests like density, hardness, and tensile tests. The SEM analysis showed almost uniform distribution of particulates; also, hardness and tensile properties improved upon addition of reinforcement viz., graphite and B4C. The density of hybrid composite decreased upon addition of reinforcement when compared with base A356 alloy. Fractography of tensile specimens were carried out for analysis of fractured surfaces.

Mechanical and tribological behaviours of aluminium hybrid composites reinforced by CDA-B4C

This study focuses on fabricating aluminium hybrid metal matrix composites reinforced with eco-friendly agro waste, cow dung ash and boron carbide by two stage stir casting. Weight percentage of cow dung ash and boron carbide were added in ratios of 2.5:7.5, 5:5, and 7.5:2.5. The effects on mechanical properties like hardness, tensile strength, impact strength, flexural strength and wear behaviour were studied. SEM and EDX analysis were employed to study the fracture mechanism for tensile, impact and wear specimens. Optical microstructure images reveal uniform distribution of particles and XRD analysis confirms the presence of reinforcements. Increasing CDA particles has reduced the density of the hybrid composite up to 8%. A maximum increase in hardness, tensile strength and wear resistance was up to 30%, 56% and 56% respectively, and then a slight decrease in impact was found in increasing the CDA particles. Dimples, transgranular cleavage facets, cracks and micro ploughing, micro cuttings are revealed from the fractured specimens of tensile, impact and wear respectively.

Studies on micro structural characteristics, mechanical and tribological behaviours of boron carbide and cow dung ash reinforced aluminium (Al 7075) hybrid metal matrix composite

This study focuses on the influence of reinforcements in microstructure, mechanical and tribological properties when compared to the base material (Al 7075). Boron carbide (B4C) and cow dung ash (CDA) were reinforcements by varying the weight percentage from 0 to 10 using two stage stir casting technique. Micro structural analysis and phase identification were investigated by optical microscope, SEM with EDX and XRD respectively. Mechanical and tribological testing was carried out and fracture mechanisms for tensile, impact and wear were analysed. Micro structural images reveal uniform distribution of reinforcements in matrix and XRD confirms the presence of reinforced B4C - CDA particles in the samples. It is concluded that the mechanical and tribological properties have increased while adding B4C - CDA reinforcements yet impact strength has slightly reduced. Dimples, transgranular cleavage facets, cracks and micro ploughing, micro cuttings are revealed from the fractured specimens of tensile, impact and wear respectively.

Microstructure and Mechanical Characteristics of CDA–B4C Hybrid Metal Matrix Composites

This study focuses on fabricating aluminium hybrid metal matrix with eco-friendly agro waste, cow dung ash and boron carbide by two stage stir casting. Weight percentage of cow dung ash and boron carbide were reinforced in ratios of 2.5:7.5, 5:5, and 7.5:2.5. The fabricated samples were subjected to optical microscope, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) to identify micro structural analysis and phase identification of the reinforcements respectively. The effects on mechanical properties like density, hardness, tensile strength, impact strength and flexural strength properties were studied, and the results are compared to the base alloy (Al 7075). Fracture mechanisms for tensile and impact specimens were analysed through SEM and EDX. Micro structural and SEM images reveal uniform distribution of particles in the matrix. Increasing CDA particles has reduced the density of the hybrid composite up to 8%. A maximum increase in hardness and tensile strength was up to 30% and 56% respectively, and then a slight decrease was found in increasing the CDA particles. The flexural strength has increased to a maximum of 12% at 7.5% CDA and decrement in impact strength was inferred in all the hybrid composites when compared with base alloy. Dimples, transgranular cleavage facets and cracks are revealed from the fractured specimens of tensile and impact specimens.

Development and mechanical-wear characterization of Al2024-nano B4C composites for aerospace applications

In the current research, the production of composites, characterization, mechanical and wear behavior of 5 and 10 wt.% of nano composites have been investigated by reinforcing the nano B4C ceramic particulates into Al2024 alloy. The composites were prepared by using two stage stir casting technique containing Al2024 alloy as a matrix phase and nano B4C particulates as reinforcement. After the composite preparation, the prepared composite material was examined by using various techniques such as SEM, EDS and XRD for characterizing the chemical elements and microstructures of reinforced and unreinforced material. Later, the mechanical properties and wear behavior of as cast Al2024 alloy and Al2024 −5 and 10 wt.% nano B4C composites were studied. Different mechanical properties such as hardness, percentage elongation, ultimate and yield strength were evaluated as per the ASTM standards. The dry sliding wear tests were conducted by using pin on disc equipment. The experiments were conducted for the sliding distance of 3000 m by varying the sliding speed and load. It was found that due to the addition of nano B4C ceramic particles in the Al2024 alloy matrix, the hardness, ultimate tensile strength and yield strength of the prepared composites were increased and the percentage elongation was decreased. Furthermore, there was an improvement in the volumetric wear loss with respect to the speed, load, and sliding distance for all the prepared composite materials. However, with the addition of nano B4C ceramic particulates in the base Al2024 matrix, the volumetric wear loss was decreased. The scanning electron microscope was used to study and analyze the fractography and different wear mechanisms for various test conditions of different compositions, tensile fractured surfaces and worn surfaces.

Mechanical Characterization of Ceramic Nano B4C- Al2618 Alloy Composites Synthesized by Semi Solid State Processing

ABSTRACTAl2618 alloy composites containing 6 wt% nano B4C were prepared by liquid metallurgy two stage stir casting process. Characterization was performed using scanning electron microscope to validate the homogenous distribution of nano B4C particles in the Al2618 alloy matrix. The presence of B and C elements was confirmed by EDS analysis in the nano B4C reinforced metal composites. The mechanical behavior of the prepared nano composites were evaluated as per the ASTM standards, and it was noted that the tensile strength (ultimate strength and yield strength) and compression strength increased with the addition of 6 wt% nano B4C particles. Finally, to understand the failure mechanisms the fractography analysis was conducted on the broken tensile specimens by using SEM images.

Effect of bagasse ash reinforcement on Al356 matrix composite manufactured by two stage stir casting process

In the present work Al356-Bagasse ash composites are produced by two stage stir casting method and subsequently various properties like compression strength, tensile strength, hardness of Al356 are studied. Al356 alloy is reinforced with bagasse ash particles of the various weight percentage (2,4 and 6% wt.). An experimental result shows uniform distribution of the bagasse ash particles in the matrix of the Al356 leading to increase in the mechanical strength of the composites. The tensile and compression tests are carried out with the help of Universal Testing Machine and it was observed that ultimate tensile strength, yield strength and compression strength increases with increase weight percentage of bagasse ash in the composite, while percentage elongation decreases. The hardness of the composites are measured by brinell hardness tester and it was observed that hardness of the composite material increases with increase in weight percentage of bagasse ash particles.

Mechanical characterization of precipitation hardened Al7075-grey cast iron powder reinforced metal matrix composites

Al7075 alloy is the most commonly used by the aerospace industry. Al7075 alloy is characterized by its improved properties such as higher toughness, specific strength and hardness. The current work focuses on the preparation and characterization of age hardened Al7075-Grey cast iron composites. Two stage stir casting technique is used for the preparation of the composite. Age hardening treatment is imparted to enhance the mechanical characteristics. The variation of hardness and tensile strength with respect to aging temperature and percentage of reinforcement is analyzed. The composites exhibit higher hardness and tensile strength as the reinforcement percentage is increased at an aging temperature of 1000C.

Study on fracture behaviour of Hybrid Aluminium Composite

This work makes an attempt to study of fracture behaviour of hybrid Composite reinforced with hard ceramic Boron carbide as primary phase and secondary phase as soft solid lubricant Molybdenum Disulphide with base matrix Al2219 by two stage stir casting method is incorporated. Compact tension type specimen was utilized for test and dimensions are conformity to ASTM E-647.Fatigue crack growth and fracture toughness test conducted as per ASTM Standard E-399 and E-1820. This study discloses that reinforcing the hard ceramic Boron Carbide of constant 3wt% and soft solid lubricant Molybdenum Disulphide with increasing wt% of 3%, 4%, 5% to Al2219, results increase in energy required to open the crack front to create two new crack surfaces during mode-I type failure and also significantly variation of fracture toughness. Surface of fractured specimens were study under scanning electron microscope and observes that pulled regions tiny dimples results in balance between ductility and strength of prepared hybrid composite.

Property Enhancement During Artificial Aging of Al6061- Silicon Oxide Metal Matrix Composites

In the current work Al6061- Silicon oxide (SiO2) composites are produced by two stage stir casting method and subsequently studied various properties. Microstructure, hardness, tensile and wear properties of Al6061 based composite having 2, 4 and 6% wt.% of SiO2 is analyzed and presented. The aging behavior and tensile properties of the cast material were studied. Experimental results show homogeneous dispersal of the SiO2 particles in the matrix leading to substantial improvement in the mechanical properties. Presence of SiO2 particulate in aluminium matrix alloy hastening the aging kinetics and thus attains improvement in strength. These particulates offer short circuit path for nucleation of fine precipitates to hinder the movement of dislocation and thus increases hardness as well strength of materials. After aging at 100°C for Al6061/6% wt. SiO2 composite , highest strength is observed at longer duration of aging. Comparison of the characteristics study before and after heat treatment was done and it is revealed that there is an enhancement in hardness, ultimate tensile strength and wear resistance of both Al6061 alloy and its composites after precipitation hardening treatment

Mechanical characterization of precipitation hardened Al7075-grey cast iron powder reinforced metal matrix composites

Al7075 alloy is the most commonly used by the aerospace industry. Al7075 alloy is characterized by its improved properties such as higher toughness, specific strength and hardness. The current work focuses on the preparation and characterization of age hardened Al7075-Grey cast iron composites. Two stage stir casting technique is used for the preparation of the composite. Age hardening treatment is imparted to enhance the mechanical characteristics. The variation of hardness and tensile strength with respect to aging temperature and percentage of reinforcement is analyzed. The composites exhibit higher hardness and tensile strength as the reinforcement percentage is increased at an aging temperature of 100°C.

Influence of Artificial Aging on the Stir Cast Al6061-SiC Metal Matrix Composites under Different Aging Conditions

The present work aims to improve the microstructure and hardness related properties of age hardened Al6061-SiC reinforced composites produced by a two stage stir casting method. Three composites with 2, 4, and 6wt. % (35-40μm) of SiC reinforcement are subjected to microstructural examination and hardness test at different locations to analyse the uniform distribution of the reinforcements in the matrix. As-cast composites are solution-treated at 558°C, followed by an aging treatment conducted at 100, 150, and 200°C, during which peak hardness values are noted. The peak aged samples are subjected to hardness and wear tests. In line with the objectives, ranges from 80-100% and 120-145% additional increase in hardness values are observed over as-cast alloy during the aging treatment conducted at 100, 150 and 200°C, respectively. Lower temperature aging shows substantial improvement in hardness and wear resistance over high temperature aging in each respective group. Also higher weight percentages of reinforced composites show excellent wear resistance, due to the presence of eroded iron particles from the counter surface which is regarded as a beneficial effect during the wear test. The presence of SiC particles provides more sites for the nucleation of fine precipitates. These fine precipitates hinder the movement of dislocation and thus increases hardness as well as wear resistance after the precipitation hardening treatment

Effect of Weight Percentage and Cutting Parameter on Surface Finish of SiC Reinforced Aluminium Composite

In the present work, aluminium alloy of series 1100 is selected as a matrix material and SiC of 45 microns as reinforcement. The composites are synthesized by 2 stage stir casting route, by varying a weight % of reinforcement from 6 % and 10%. The surface roughness of prepared composite were examined after plain turning operation. The machining parameters like speed, feed, DOC, SiC Wt. % are varied at 3 different levels. In order to minimize the time, cost and material a taguchi L9 orthogonal array was used for experiment. From the studies it was observed that the roughness value will increase with the increasing in reinforcement percentage.

Experimental evaluation onto the damping behavior of Al/SiC/RHA hybrid composites

In the present study, the damping behavior of hybrid composites has been investigated using dynamic mechanical analyzer (DMA). The composites were fabricated with 2, 4, 6, and 8% by weight of rice husk ash (RHA) and SiC in equal proportions using two stage stir casting process. Damping measurements of all the specimens were obtained by dynamic mechanical analyzer (DMA) at different frequencies in air atmosphere. Scanning electron microscope (model JSM-6610LV) was used to study the microstructural characterization of the hybrid composites. It was observed that the dislocation density, which results from the thermal mismatch between the reinforcement and the matrix and the porosity of composites, has a great influence on the damping capacity of hybrid composites. The dislocation damping mechanisms were discussed with regards to the Granato–Lucke theory.

Influence of dislocation density on the residual stresses induced while machining Al/SiC/RHA hybrid composites

The present study aims at finding the residual stresses on aluminum hybrid composites during turning operation. The composites with varying percentage by weight reinforcement of 2, 4, 6 and 8 RHA and SiC in equal proportions were fabricated using two stage stir casting process. X-ray diffraction was used to study the residual stresses on the surface layer of the machined surface. It was observed that the residual stresses generated during casting were considerably larger when compared to the stresses generated during machining of composites. It was also noticed that the residual stresses were found to decrease with the increase in the reinforcement and increases with the increase in cutting speed. The related mechanisms are explained and presented in this work.