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In the present work, localised heating has been adopted at the damage site of the cold upset materials and the role of this mechanism on the workability has been analysed. Cylindrical specimens containing 96% aluminium and 4% titanium were prepared through powder metallurgy technique with an aspect ratio (height to diameter) of 1 by suitable pressures. A series of cold upsetting test was conducted and the material properties for various preforms initial relative densities (80%, 85% and 90%) were determined under the stable strain rate. The flow of metals was analysed using a finite element tool and it was observed that the metal flow starts from near the centre zone to the equatorial zone and the damage happens in the outer position because of more amount of accumulated stresses and the pores. These stresses and pores decrease the workability of the final component. Hence, the present research is intended to reduce the stresses and minimize the pores by applying a localized heating (100 °C–250 °C) at the equatorial sites of the components and thereby increasing the workability of the material. Also, heating selectively at the equatorial site of the workpiece improves the workability due to change in grain size and it was noticed that the grain size of the developed porous preforms was high for the higher heating conditions due to the growth of the grains. Therefore, the localized heating adopted in this work is a superior method to enhance the workability of the powder samples and this novel technique could be useful in improving the workability of the structural components that have extensive applications in the automobile and aerospace industries.

In the metal forming process, the understanding of metal flows and the fracture strains are most significant to the failure/damage of the components. Usually, in metalworking, damage occurs because of nucleation, growth and coalescence of the void into a small fracture. These small fractures increased in the circumferential path due to the existence of stresses and the pores which leads to failure at the equatorial position during the upsetting of porous samples. Hence, the fracture of the workpieces strongly depends on the stresses and the pores. Such form of stresses and pores if relieved will give a better damage limit of the material. Therefore, in this research, a novel scheme of localised heating is adopted at the equatorial position of the compressed samples to enhance the critical damage parameter. The powder metallurgy route was used to prepare the required compacts with different relative densities (80%–90%) and 1 aspect ratio by applying suitable powder forming pressures. The upsetting test was performed on the obtained porous samples for various weight percentages of titanium (2%–6%) in the aluminium at the stable strain rate (0.1 s−1) and the damage location was noticed for various components. After the identification of damage position, various temperatures (100 °C–250 °C) of localised heating were attempted on the failure site of the specimens after some incremental stages of upsetting tests. The experimental results were analysed using various damage criteria and it was found that the initiation of failure is delayed and increased the critical damage value by selectively heating the samples because of relieving the stresses, reduction in porosity and changes in microstructure.

Friction stud welding process is a suitable candidate in joining stud fasteners for steel structure buildings, military vehicles, automobiles, aircraft, ocean liners, bridges, ship buildings, etc., The peak temperature for welding is achieved by converting mechanical energy to thermal energy at the sample interface without the use of electric energy from other sources because it is a solid-state process. The study of the thermal behavior of different metals during friction stud welding is very important since it is a thermal energy process. However, there is no good thermal model for the friction stud welding process. In this work, the generation of heat flux at the interfacial area of two distinct metals, namely aluminum and mild steel, is calculated using a mathematical model. The temperature at the interfacial region, which plays a significant role in the quality and strength of the weld component, is particularly focused on experimentation and analytical modeling. In the experimentation, a noncontact type infrared thermometer is used to measure temperature directly. The temperature profile was determined by the finite difference method based on thermal resistance and capacitance formulation at transient conditions. The obtained mathematical results are compared with the experimental results at the distance of 5 and 10[Formula: see text]mm from the welded interface. The computed temperature profile is in good agreement with the experimental data on the heating side and with a minimum degree of deviation in the cooling part. The maximum percentage of error for the 5[Formula: see text]mm interface is 3.349 and for the 10[Formula: see text]mm interface is 2.857. This deviation is due to the zero-axial shortening assumption in the analytical model. Besides, the temperature characteristics of the welded are analyzed at various time increments by numerical simulation. As a result, the predicted temperature is more on the aluminum side compared to the mild steel due to a change in thermal properties. This proposed thermal model would be helpful to improve the design and manufacture of welding machines.

A study on workability, densification and failure characteristics of porous aluminum–titanium components has been performed by adopting a selective heating method under triaxial stress state condition. The required specimens were made using the powder metallurgy method with 90% of initial relative density and an aspect ratio of 1 through the appropriate compaction pressures. A sequence of upsetting has been executed on the powder metallurgical compacts using a hydraulic press for different titanium compositions (2-6%). In the upsetting process, the damage of the specimens mainly relies on the accumulation of stresses at the damage site. Hence, the damage site of the compacts was identified for various specimens using finite element simulation software. Once the damage position was identified, the compacts were heated at the damage sites (selective heating) for different temperatures, namely 100, 140, 195, 220 and 250 °C using a portable gas cartridge. As a result, the failure initiation is arrested thereby increasing the workability and densification. Selectively heating the damage zone of the components has relieved the accumulated stresses and has reduced the porosity (from 11.385 to 6.702% for Al-2%Ti, from 12.797 to 7.920% for Al-4%Ti and from 13.215 to 8.611% for Al-6%Ti) of the preforms. Thus, the damage limit of the components can be increased during upsetting by the selective heating process.

In the present scenario, aerospace and automobile industries depend on lightweight materials such as magnesium and aluminum alloys because of their great balance between mechanical properties and weight ratio. Despite these benefits during the joining process of these dissimilar materials by welding, many challenges arises. The prominent one is related to the low melting points of these lightweight metals which make it almost impossible the joining using conventional arc welding techniques. To tackle this challenge, Friction Stir Welding (FSW) can be considered as a promising candidate tool. In this study, to demonstrate the FSW performances of joining two dissimilar materials we have investigated the joining of AA 6061 and Mg AZ 31 B using a built-in house a modified milling machine. The dissimilar combinations of AA 6061 and Mg AZ 31 B joints were successfully joined by embedding different welding conditions and varying the offset distance. The mechanical performances were evaluated by conducting specific mechanical tests such as micro-hardness, tensile, and impact tests, respectively. To explain the mechanical results, we have applied optical microscopy observation on the microstructure associated with the bonding location. The results prove that the strength of the Friction Stir Welded joints is much higher as compared to other techniques especially in terms of dissimilar metals.

An investigation on strain-based formability and pore closure rate of selectively heated sintered powder metallurgical aluminum–titanium composites has been carried out to evaluate the role of heating on the curing of stresses accumulated during mechanical working. Samples with an initial relative density of 90% and an aspect ratio of 1 were prepared through the powder metallurgy technique by applying suitable powder compaction pressures with different titanium contents such as 2%, 4% and 6%. A series of upsetting tests have been carried out on the prepared porous specimens using a 0.5 MN capacity hydraulic press and the failure zone was identified through the experimental work. It was found that failure occurs in the equatorial region of the workpiece due to the accumulation of stresses and the presence of higher amounts of pores. The magnitude of these accumulated stresses and the level of pores affect the formability of the components during cold upsetting. Therefore, there is a need to relieve the accumulated stresses and reduce the pores at the failure zone of the metals. Hence, this work is aimed at relieving the accumulated stresses, reducing the porosity amounts by adopting a novel mechanism of heating in the equatorial region of the samples for various temperatures such as 100 °C, 140 °C, 195 °C, 220 °C and 250 °C. As a result, the forming limit and pore closing rate were found to improve by selectively heating the specimens at locations where stresses have accumulated. Selectively heating this location relieves the accumulated stresses and decreases the number of pores present in the preforms, thereby enabling the metal to reach still higher strain levels before the onset of failure.

In the upsetting process, flow of metal starts from centre region to outer region and failure occurs due to nucleation of void, growth of void and finally void coalescence into micro-crack. These micro-cracks extend in the hoop direction and fracture occurs at the equatorial region due to the presence of accumulated stresses. Hence, the failure of the components strongly depends on the stress accumulated on the failure zone. In the present work, the failure zone was identified through upsetting experiments on powder metallurgical Al–4 wt% Ti composites that have different initial relative densities and an aspect ratio of 1. It was found that the failure occurs at the equatorial region due to accumulation of maximum principal stresses. These accumulated stresses affect the failure limit of the work piece during cold upsetting. Hence, it is necessary to relieve these accumulated stresses for better failure limit in various engineering applications. Thus, this work is aimed at relieving the accumulated stresses on the failure zone by heating selectively on the region where more work hardening has taken place during the deformation stage. As the heating has been performed only at selected locations, the mechanical properties of the samples are not expected to deteriorate due to the heating step. As a result, initiation and progression of failure can be delayed by selective heating before the onset of failure initiation. Selective heating relieve the accumulated stresses and delay the failure onset, thereby increasing the failure limit of the metal.

In this work, a new method of selective heating is proposed to increase the deformation behaviour of cylindrical sintered aluminium preforms during the process. Initially, cold upsetting is carried out using 0.5 MN hydraulic press machine at 0.1 s−1 strain rate and the failure locations of the preforms are predicted for various initial relative densities with the aspect ratio of 1 during the deformation process. After the prediction of this failure location, various conditions of selective heating are attempted uniformly on the deformed preforms after a certain stage of deformation before the onset of the failure initiation, using portable gas cartridge at a different temperature and time to assess their consequence on formability behaviour. The detailed experimental results are evaluated for the formability of the selectively heated preforms under different variables such as flow stress, relative density, axial strain, formability stress index and stress ratio parameter. As a result, the initiation of failure and its progression can be delayed by selectively heating the samples before the onset of the failure initiation. Selective heating of the failure location may relieve the accumulated stresses and delay the onset of failure to a later strain level thereby increasing the formability of the metal.

Friction stud welding, a recent variant of friction welding process, is ideally suited for naval applications, short-term emergency repairs, submarine rescue, aerospace applications and automotive applications. In all these critical applications, there is a need for joining of dissimilar materials in general and aluminium matrix composites/steel joints in particular as in the case of recent aerospace and automotive applications. The strength of the dissimilar joint is a major concern in all these applications. Due to the variation in thermal properties and inhomogeneous temperature distribution, heat-affected zones are formed that lead to deterioration in strength in the dissimilar joints. In the present work, a new procedure is disclosed that can increase the strength of the dissimilar joint. The design of the specimen is modified and ceramic slurry is introduced at the interface in order to achieve increase in joint efficiency and higher joint strength.

The use of boron carbide-reinforced aluminium matrix composites has grown rapidly in critical applications of aerospace industries, automotive sectors, military, and nuclear engineering. However, boron carbide reinforcement within AA6061 alloy is worthy of investigation in terms of its mechanical and tribological properties. Novel aluminium matrix composites were developed with three different reinforcements (i.e. 5, 10, and 15 wt% of B4C) by using the stir casting process. The developed samples were then tested for performance in terms of mechanical properties (i.e. tensile strength, bending strength, impact strength, shear properties, and micro-hardness). The microstructure of the developed samples was analysed using a scanning electron microscope. By adding 5% B4C reinforcement, the samples display enhanced mechanical properties (high bending, increased resistance to impact test, and shear strength). The micro-hardness tends to increase by increasing the percentage of reinforcement. The novel composites have superior wear resistance due to an increase in the content of B4C particles. The measurements indicate that the wear rate resistance is significantly higher for the composite material with a large amount of B4C particles when was compared with AA6061 alloy. The patterns of surface analysis reveal a homogeneous distribution of ceramic reinforcements in 5 and 15 wt% of B4C samples, as well as a low agglomeration of embedded particles.

The present work investigates the densification and forming limit of sintered porous aluminium–titanium preforms for various relative densities and titanium particles. The compacts of 1 aspect ratio with 2–6% of titanium contents in aluminium matrix for various relative densities were prepared through powder metallurgy route by applying suitable powder forming pressures. A sequence of the cold upsetting test has been carried out using 0.5 MN capacity of hydraulic press machine at 0.1 s−1 strain rate. The relation between true axial strain and preforms relative density was plotted, and the influence of titanium and relative density on the densification curve was investigated at various compaction pressures. The specimen properties like apparent strain hardening exponent (na) and apparent strength coefficient (Ka) was determined through stepwise incremental deformation tests. The critical transition density (CTD) vide forming limit diagram was determined from the plot of na and Ka concerning the preforms relative density, and it was found to be 85.9%, 87.7% and 88% for 2%, 4% and 6% of titanium in the aluminium matrix. The CTD values of porous aluminium–titanium preforms were compared with those of the previous work of porous aluminium–copper preforms under the same compositions. Also, the average grain size of the components was determined and it is observed that 2% of titanium contains a larger grain size compared to other compositions. Hence, a higher forming limit was obtained in 2% of titanium reinforced with aluminium matrix.

Aluminium matrix composites (AMCs) have great potential for critical applications within aerospace, automotive, defence, marine, agriculture and nuclear engineering sectors. The composite materials are very attractive because of their good balance between lightweight versus high strength and machinability. Depending on the particular application, these properties can be further enhanced by adding silicon carbide, boron carbide and graphite, respectively. These reinforcements help to upscale the physical/mechanical properties in order to meet the novel industrial demand. In the present work, a novel hybrid composite is developed through stir cast welding technique. The novel materials manufactured are of great importance, because they exhibit higher mechanical properties and better wear resistance with respect to classical materials (i.e. pure aluminium). The results of mechanical test showed that the addition of 5% boron carbide content to aluminium matrix permits to enhance the tensile properties, shear strength and hardness values; 6% silicon carbide and 4% graphite allow to improve the flexural strength and wear rate, respectively. The best performance was obtained for aluminium composite with 5 wt% boron carbide. The correlation between industrial requirements and the findings from this research indicates that the newly developed composite is an excellent candidate material for structural neutron absorber, armour plate and as a substrate material for computer hard discs.

Friction welding is a solid state joining technique used for joining similar and dissimilar materials with high integrity. This new technique is being successfully applied to the aerospace, automobile, and ship building industries, and is attracting more and more research interest. Owing to the significance, thermal analysis on friction stud welding of mild steel and aluminium combination is carried out in the present work. In this study the temperature profiles at different locations are predicted mathematically by using one dimensional finite element method.

Friction welding is a solid state joining technique used for joining similar and dissimilar materials with high integrity. This new technique is being successfully applied to the aerospace, automobile, and ship building industries, and is attracting more and more research interest. The quality of Friction Stud Welded joints depends on the frictional heat generated at the interface. Hence, thermal analysis on friction stud welding of stainless steel (AISI 304) and aluminium silicon carbide (AlSiC) combination is carried out in the present work. In this study, numerical simulation is carried out using ANSYS software and the temperature profiles are predicted at various increments of time. The developed numerical model is found to be adequate to predict temperature distribution of friction stud weld aluminium silicon carbide/stainless steel joints.

Owing to high strength to low weight ratio, Aluminium matrix composites are widely used in diverse applications of many industries. This lucrative property is achieved by reinforcing the brittle ceramic particles in the aluminium matrix. Aluminium matrix composites are produced by liquid processing methods and solid processing methods. Nevertheless, liquidprocessing techniques stand out because of its simplicity and its suitability for mass production. In this review article, the production of aluminium matrix composites by different liquid processing technique is discussed and a comparative study is carried out.

Friction welding is the most suitable candidate for joining the dissimilar materials such as AA 6063 T6 alloy/Alumina for critical situations in high temperature and high corrosion resistance applications. In the present work, the numerical simulation was carried out to understand the mechanism of joining of AA 6063 T6 alloy/ Alumina rod by friction welding process. The developed thermo mechanical model is a highly nonlinear due to the interaction between the temperature fields and time dependent of the material properties. The developed numerical tool could be used to predict the temperature distribution, stress, strain and deformation of the dissimilar joints.