V. Balasubramanian

Effect of Tool Pin Profile and Tool Rotational Speed on Mechanical Properties of Friction Stir Welded AA6061 Aluminium Alloy

AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to many of the fusion welding processes that are routinely used for joining structural aluminium alloys, the Friction Stir Welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a nonconsumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force, etc., and tool pin profile play a major role in deciding the joint properties. In this investigation, an attempt has been made to study the effect of rotational speed and tool pin profile on mechanical properties of AA6061 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular, and square) have been used to fabricate the joints at five different tool rotational speeds (800–1600 RPM). Tensile properties, microhardness, and microstructure of the joints have been evaluated. From this investigation it is found that the joints fabricated using square pin profiled tool with a tool rotational speed of 1200 RPM exhibited superior mechanical properties compared to other joints.

Application of Response Surface Methodolody to Prediction of Dilution in Plasma Transferred Arc Hardfacing of Stainless Steel on Carbon Steel

The application of response surface methodology was highlighted to predict and optimize the percentage of dilution of iron-based hardfaced surface produced by the PTA (plasma transferred arc welding) process. The experiments were conducted based on five-factor five-level central composite rotatable design with full replication technique and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was also used to optimize the process parameters that yielded the lowest percentage of dilution.

Modelling of process parameters in explosive cladding of mildsteel and aluminium

Abstract Explosive cladding is best known for its capability to join a wide variety of both similar and dissimilar combinations of metals that connot be joined by other methods. To make effective use of explosive cladding it is essential that a high degree of confidence be achieved in predicting the wavy interface geometry (amplitude and wave length) to attain an acceptable bonding. Factorial technique has been used to design the experiments. Regression analysis is used to develop the models and Analysis of variance method is used to study the main and interaction effect of process parameters on wavy interface geometry. The adequacy of the developed models have been checked by calculating correlating co-efficient. These models can be effectively used to predict the wavy interface geometry in terms of process parameters.

Effect of Autogenous Arc Welding Processes on Tensile and Impact Properties of Ferritic Stainless Steel Joints

The effect of autogeneous arc welding processes on tensile and impact properties of ferritic stainless steel conformed to AISI 409M grade is studied. Rolled plates of 4 mm thickness have been used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure, and fracture surface morphology of continuous current gas tungsten arc welding (CCGTAW), pulsed current gas tungsten arc welding (PCGTAW), and plasma arc welding (PAW) joints are evaluated and the results are compared. It is found that the PAW joints of ferritic stainless steel show superior tensile and impact properties when compared with CCGTAW and PCGTAW joints, and this is mainly due to lower heat input, finer fusion zone grain diameter, and higher fusion zone hardness.

Effect of Heat Input on Mechanical and Metallurgical Properties of Friction Stir Welded AA6061-10% SiCp MMCs

Metal matrix composites (MMCs) reinforced with SiC particles combine the matrix properties with those of the ceramic reinforcement, leading to higher stiffness and superior thermal stability with respect to the corresponding unreinforced alloys. However, their wide application as structural material needs proper development of a suitable joining process. In this investigation, an attempt was made to study the effect of heat input on the evolution of microstructure in weld region of friction stir welded AA6061-10% SiCp MMCs. The tensile properties of the joints were evaluated and they are related with microstructure and heat input of the process. The microstructure characterization of the weld zone shows evidence of a substantial grain refinement of the aluminum matrix and fracturing of reinforcement particles due to dynamic recrystallization induced by the plastic deformation and frictional heating during welding.

Influences of Welding Speed on Tensile Properties of Friction Stir Welded AZ61A Magnesium Alloy

This article reports the influences of welding speed on tensile properties of the friction stir welded AZ61A magnesium alloy. Five different welding speeds ranging from 30 to 150xa0mm/min were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the stir zone microstructure and hardness. From this investigation, it is found that the joint fabricated with a welding speed of 90xa0mm/min exhibited the acceptable tensile properties compared to other joints. The formation of fine grains in the stir zone is the main reason for the higher hardness and acceptable tensile properties of these joints.

Microstructure, Tensile and Impact Toughness Properties of Friction Stir Welded Mild Steel

Microstructure, tensile and impact toughness properties and fracture location of friction stir welded AISI 1018 mild steel were revealed. The AISI 1018 mild steel plates with thickness of 5 mm were friction stir welded by tungsten based alloy tool with tool rotational speed of 1000 r/min and welding speed of 50 mm/min. Tensile strength of stir zone is higher (8%) compared to that of the base metal. This may be due to the formation of finer grains in the weld nugget region under the stirring action of the rotating tool. The ductility and impact toughness of the joints are decreased compared to those of the base metal owing to the inclusion of tungsten particles in the weld region.

Understanding the Parameters Controlling Plasma Transferred Arc Hardfacing Using Response Surface Methodology

Control of dilution is important in hardfacing, where typically low dilution is desirable. At present, majority of the fabrication industries use shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and submerged arc welding (SAW) processes for hardfacing purposes. In these processes, the percentage of dilution level is higher, ranging between 10–30%. In plasma transferred arc (PTA) hardfacing, a solidified metallurgical bond between deposit and substrate is obtained with minimum dilution (less than 10%). This article highlights the application of response surface methodology (RSM) to predict and optimize the percentage of dilution of nickel based hardfaced surface produced by PTA process. The experiments were conducted based on five-factor, five levels central composite rotatable design with full replications technique and mathematical model was developed using RSM. Further, the RSM is used to optimize the process parameters that yield the lowest percentage of dilution.

Predicting Grain Size and Tensile Strength of Friction Stir Welded Joints of AA7075-T6 Aluminium Alloy

This article reports empirical relationships to predict grain size and tensile strength of friction stir welded (FSW) AA7075-T6 aluminium alloy joints. Six-factor, five-level, central composite rotatable design matrix is used to optimize the experimental conditions. The empirical relationships are developed by response surface methodology (RSM) incorporating tool and process parameters. A linear regression relationship is also established between grain size of weld nugget and tensile strength of FSW joints.

Comparison of Electron Beam and Friction Stir Weldments of Modified 12 wt% Ferritic Stainless Steel

This article presents the comparative evaluation of microstructural features and mechanical properties of electron beam welded (high energy density fusion welding) and friction stir welded (FSW) (solid-state welding) 409 M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarser ferrite grains in the base material are changed to finer grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure of alpha ferrite with grain boundary martensite was observed in fusion zone of electron beam welded (EBW) joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The EBW joint exhibited superior impact toughness compared to the base metal and FSW joint.