Manickam Ravichandran

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.

Experimental investigations of Al-TiO2-Gr hybrid composites fabricated by stir casting

Abstract Al-TiO2-Gr composites containing different weight percentages of TiO2 and graphite (Gr) particles were produced by stir casting method. The samples were prepared by adding TiO2 and Gr particles to the molten aluminum, then the resulting slurry was stirred at a specified temperature for a predetermined time. SEM and EDAX analyses were carried out for the as cast samples. The effects of the addition of reinforcement content on mechanical properties and workability behavior of the composites were investigated. Microstructural investigation of the final products proved that synthesized composites with well-distributed reinforcing particles could be fabricated by stir casting method. Tensile fracture analyses of the composites were conducted using SEM. The results show that the tensile strength of the composites increased with increasing weight fraction of TiO2 and Gr particles. Workability studies show that, the addition of reinforcements increases the true axial stress (σz), true hoop stress (σθ), true hydrostatic stress (σm) and stress ratio parameters [(σz/σeff), (σθ/σeff) and (σm/σeff)] during cold upsetting.

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.

Synthesis, Characterization and Wire Electric Erosion Behaviour of AA7178-10 wt.% ZrB2 Composite

In this work, AA7178-10 wt.% ZrB2 Metal Matrix Composite was produced using stir casting route and the mechanical properties of the composites were studied. The microstructure and elemental verification were done by using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Among the various non-traditional machining processes, Wire Electrical Discharge Machining (WEDM) is an important process for machining MMCs. The objective of this work is to investigate the effect of Peak current (I), Pulse On-Time (PTOn), Pulse Off Time (PTOff) and Wire feed rate (WF) on the combined objective of maximum Metal Removal Rate (MRR) and minimum Surface Roughness (SR) during machining of AA7178-10 wt.% ZrB2 composite using Taguchi based Grey Relational Analysis (GRA). L16 orthogonal array, for the four machining parameters at four levels each, was opted to conduct the experiments. Analysis of variance (ANOVA) was performed to find the validity of the experimental plan followed in the present work. Results show that, maximum MRR and minimum SR can be achieved for the peak current (11 A), Pulse On-Time (112 μs), Pulse Off Time (45 μs) and Wire feed rate (7 m/min).

Synthesis, properties and EDM behavior of 10 wt.-% ZrB2 reinforced AA7178 matrix composites

Abstract The present study outlines the optimization of process parameters in the EDM of AA7178-10 wt.-% ZrB2 composites. The composites were fabricated by using stir casting and the mechanical properties are evaluated. The mechanical properties of AA7075, AA7178 and AA7178-10 wt.-% ZrB2 composites were reported. Scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) analysis were used to characterize the composites. The fabricated composite material was machined using different process parameters based on Taguchis L9 orthogonal array. Parameters such as current (I), pulse on time (PT-on) and pulse off time (PT-off) were varied. The response variables measured for the analysis are material removal rate (MRR) and surface roughness (SR). From the SN Ratio (SNR) analysis, it was observed that, current is the significant factor affecting both MRR and SR. ANOVA analysis was carried out to determine the percentage contribution of each factor to the responses. Further, a verification experiment was performed to confirm the performance of optimum parameters.

Microstructure and Properties of Hot Extruded Al-TiO2 Powder Metallurgic Composites

Aluminium metal matrix composites reinforced with TiO2 were synthesized using powder metallurgy route. The compositions such as Al-2.5%TiO2, Al-5%TiO2, Al-7.5%TiO2 and Al-10%TiO2 were milled using ball mill for 1 hour. The green compacts were prepared using 400 kN hydraulic press. The sintering was done by using electric muffle furnace at a temperature of 550°C for 1 hour. Hot extrusion was carried out for the sintered composite samples with suitable punch and die. The mechanical properties such as ultimate tensile strength, yield strength, percentage elongation and hardness have been studied for the hot extruded samples. The microstructures of the extruded composites were analyzed using optical microscope and reported. The high compressive strength was obtained for the Al-5%TiO2 composite.

Parametric optimization of seam welding of stainless steel (SS 304) sheets

Abstract In the present study, seam welding process parameters were optimized for joining 306 stainless steel plates. Welding pressure, welding speed and welding temperature combinations were carefully selected with the objective of producing a weld joint with maximum impact strength and hardness. Taguchi technique was applied for optimizing the selected welding parameters. The factors used in this study consisted of pressure, welding speed and welding temperature, each of which had three levels in the study. L27 orthogonal array and corresponding levels were selected according to the aforementioned factors and experimental tests were performed. Signal-to-noise (S/N) ratio was used to evaluate the experimental results. The results indicate that the welding speed has the greatest influence on impact strength, followed by welding pressure and temperature. Experiments have also been conducted to validate the optimized parameters.