V. Anandakrishnan

Multi-objective optimization of upsetting parameters of Al–TiC metal matrix composites: A grey Taguchi approach

This work is a novel attempt to identify the optimum process parameters in cold upsetting of Al–TiC metal matrix composites with multiple responses using grey Taguchi approach. The formation of barrel and workability are the important attributes that greatly influence the process of upsetting. Three independently controllable process variables, namely, aspect ratio, friction factor and load, each at four levels are considered to find their optimum levels which yields maximum barrel radius and workability simultaneously. Grey Taguchi analysis has been performed to optimize the levels of input parameters. Both the quality characteristics are improved significantly at the optimal process condition as verified by the confirmation test. The effect of individual process variables on the responses is determined using analysis of variance.

Determination of Optimum Parameters for Multi-Performance Characteristic in Turning of Al 6061-6% ZrB2 in-situ Metal Matrix Composite Using Grey Relational Analysis

In-situ aluminum matrix composite is the innovation of high performance material technology and it has superior interfacial integrity and thermodynamic stability between the matrix and reinforcement. During synthesis, the ZrB2 particle is formed by exothermic reaction within the aluminum melt. As a result, small, fine and oxide free reinforcements are formed. Excessive temperature released from in-situ chemical reaction will facilitate the homogeneous distribution of particles in entire shape of the composites. Making the engineering components from this composite material require machining operations. Therefore, addressing the machinability issues of the composite is very important. This paper proposes an approach to optimize the machining parameters in turning of Al 6061-6% ZrB2 in-situ Metal Matrix Composite (MMC) with multiple performance characteristics by using grey relational analysis. The effect of in-situ ZrB2 reinforcement particles on machinability behavior need to be studied. The machining parameters, namely cutting speed, feed rate and depth of cut are optimized with considerations of multiple performance characteristics including surface roughness, tool wear and cutting force. It is concluded that the feed rate has the strongest effect. The confirmation experiment indicates that there is a good agreement between the estimated value and experimental value of the Grey relational grade.

Optimization of welding parameters to attain maximum strength in friction stir welded AA7075 joints

Abstract Selection of welding parameters is very important to increase the weld strength. Friction stir welding parameters affect the weld strength of aluminum alloy, such as high strength AA7075 plates. This paper presents an application of Taguchi method to friction stir welding strength of AA 7075 plates. An orthogonal array, the signal-to-noise ratio (S/N), and the analysis of variance (ANOVA) are employed to investigate friction stir welding parameter effects on the weld strength. From the ANOVA and the S/N ratio response graphs, the significant parameters and the optimal combination level of welding parameters were obtained. Confirmation experiments have been conducted to validate the optimized parameters.

Workability studies on Al+2.5%TiO2+Gr powder metallurgy composites during cold upsetting

Al+2.5%TiO2+Gr composites were synthesized through powder metallurgy technique and their workability behavior has been studied under tri-axial stress state condition. The powders were compacted using suitable punch and die in 400 kN hydraulic press and sintered at a temperature of about 590 oC for a period of 3 hours in an electric muffle furnace. The sintered preforms were characterized by XRD and SEM analysis. Then the preforms were subjected to incremental compressive loading of 10 kN until the cracks found at the free surface. The true axial stress (σz), true hoop stress (σ}), true hydrostatic stress (σσm) true effective stress (σeff), formability stress index (β) and stress ratio parameters [(σz/σeff), (σm/σeff), (σ}/σeff)] were calculated for all the preforms and these are correlated with the true axial strain (ez). It is inferred that, the addition of TiO2 and Gr to the Al matrix material increases the stress ratio parameters and formability stress index (β). A hardness test was also conducted for sintered and cold forged preforms and results are reported.

Synthesis and forming behavior of aluminium-based hybrid powder metallurgic composites

Aluminium-based metal matrix composites were synthesized from Al-TiO2-Gr powder mixtures using the powder metallurgy technique and their forming characteristics were studied during cold upsetting. Green cylindrical compacts of pure Al, Al-5wt%TiO2, Al-5wt%TiO2-2wt%Gr, and Al-5wt%TiO2-4wt%Gr were made using a 400-kN hydraulic press equipped with suitable punch and die and by sintering at (590 ± 10)°C for 3 h. Cold upset forging tests were carried out, the true axial stress (σz), the true hoop stress (σθ), and the true hydrostatic stress (σm) were evaluated and, their behavior against the true axial strain (ɛz) was also analyzed. It is observed that the addition of 5wt% TiO2 into the Al matrix increases σz, σθ, and σm. The addition of both TiO2 and Gr reinforcements reduces the densification and deformation characteristics of the sintered preforms during cold upsetting. Microstructure analyses of the as-sintered and cold upset forged specimens also were carried out to substantiate the experimental results.

Synthesis and Forming Behavior of In Situ AA 7075 - TiC Composites

The forming behavior of a particulate reinforced AA 7075-TiC composite produced by in-situ stir casting process was investigated with cold upsetting test using graphite as lubricant. The prepared composites containing 0%, 4% and 8% of TiC reinforcement was completely investigated under tri-axial stress state condition. The various stress parameters were evaluated for all the above said composites and its variation with respect to axial strain was plotted, studied and discussed. Microstructural characterization of the composites was also done to study the distribution of the reinforcement in the metal matrix composite.

Hot Upset Studies on Sintered (Al–TiO2–Gr) Powder Metallurgy Hybrid Composite

Aluminum hybrid composites were synthesized using powder metallurgy process from ball milled powders to yield the compositions like: Al+0%TiO2, Al+5%TiO2, Al+5%TiO2+2%Gr and Al+5%TiO2+4%Gr. SEM and EDAX analysis of sintered preforms show the uniform distribution of the reinforcements. Hot upset process was carried out after heating the preforms at 450°C, and the densification and deformation characteristics were studied by correlating the true axial stress with the true axial strain, lateral strain, and theoretical density. Addition of TiO2 to the unreinforced Al and Gr reinforcements to the Al–TiO2 composite increase the induced stresses during hot upset process. The microstructures of hot upset samples are analyzed.

Synthesis and forming characteristics of Al–TiO2 powder metallurgy composites during cold upsetting under plane stress state conditions

Aluminum-based metal matrix composites with various weight percentages of TiO2 reinforcement were synthesized by powder metallurgy technique and their forming characteristics were completely studied during cold upsetting under plane stress state conditions. The milled powders were characterized by scanning electron microscope, X-ray diffraction (XRD), and energy dispersive analysis using X-ray (EDAX) analysis. Green cylindrical compacts were made using a 400 kN hydraulic press using suitable punch and die, sintered at (590 ± 10)℃ for a period of 3 h, furnace cooled, and machined to obtain samples with 0.5 aspect ratio. The cold upset tests were carried out in steps of 10 kN and the true axial stress (σ z ), the true hoop stress (σθ), the true hydrostatic stress (σ m ), and the true effective stresses (σeff) were determined, and their behavior against the true axial strain (ɛ z ) was thoroughly analyzed. It was observed that, the addition of TiO2 to the Al matrix material increases the strength coefficient (K) and decreases the strain hardening index (n). The decrease in densification and deformation characteristics was observed for the addition of more weight percentages of TiO2. The microstructure analysis was done for the cold upset samples and reported.

Development of carbide intermetallic layer by electric discharge alloying on AISI-D2 tool steel and its wear resistance

Abstract Electrical discharge alloying was performed on AISI-D2 steel using Ni–W powder mixed dielectric in order to improve the hardness and to reduce the specific wear rate. The alloyed layer was characterized using optical microscopy, scanning electron microscopy, X-ray diffraction analysis and energy-dispersive spectroscopy. Wear tests were conducted based on L9 orthogonal array in a pin-on-disc tribometer and the alloying parameters were optimized using Taguchis technique. Hard intermetallics based on Fe7C3, Cr3C2 and Ni2W4C were formed by electric discharge alloying, which primarily contributed to the improvement in hardness up to 600 HV0.5. The specific wear rate of the alloyed layer was subsequently reduced by around a factor of eight compared to that of the base material. The pulse off-time was found to be predominant in obtaining higher hardness and lower specific wear rate among the alloying parameters, peak current, pulse on-time and off-time.

Taguchi Grey Relational Analysis of Dry Sliding Wear Behaviour of Annealed AA7075-TiC Metal Matrix Composites

The optimization of dry sliding wear process parameters of in-situ aluminium based metal matrix composites to obtain multiple objectives to minimize wear rate, specific wear rate, co-efficient of friction and maximize wear resistance was attempted by Taguchi Grey Relational Analysis. Moreover to identify the significance of the parameters, a statistical analysis was performed using analysis of variance. Based on the analysis, the sliding speed was identified as the major contributor with 71.41% followed by percentage of reinforcement with 8.13% and other parameters load and sliding distance are found to be insignificant. The optimum parameters identified by the Grey Relational Analysis are verified through experimental confirmation test.