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Friction stir welding and processing are widely used for joining of aluminum alloys and composites and fabrication of aluminum matrix composites. However, the friction stirred plates possess different microstructural zones which create significant difference in local properties and heat treatment is required to establish uniformity. In this article, the state-of-the-art of heat treatment on FSWed/FSPed aluminum alloys is discussed. The effects of heat treatment time and temperature on microstructural appearances and mechanical properties are examined thoroughly. Special attention is provided on the change in the state of precipitates by different heat treatment processes. Also, the effects of different heat treatment techniques are compared. Finally, some ideas regarding direction of new research related to current topic are addressed.

Despite the high strength-to-weight ratio, the poor tribological behavior and sea water corrosion performance of aluminum alloy limit its engineering applications. In this investigation, an attempt is made to obtain good wear and corrosion resistance by fabricating MoS2 and CeO2 reinforced aluminum 7075 matrix hybrid composites through friction stir processing. The microstructural observation suggests intermetallic free uniformly distributed composites are formed. The specific wear and corrosion rates of the fabricated composites are analyzed. The reason behind variation of the responses is investigated. The processing conditions such as rotational speed, traverse speed, tilt angle and mixing ratio of reinforcement powder are optimized for low specific wear rate and low corrosion rate using Taguchi optimization method. The effects of the processing conditions on individual responses are also investigated. Gray relation approach is also adopted for optimizing the processing conditions while considering equal importance of both the output responses.

The extensive use of aluminum matrix composites as structural material urges it to possess good surface properties such as wear and corrosion resistance. To achieve that, mixture of MoS2 and CeO2 powder was reinforced in Al7075 alloy through friction stir processing with different processing speed and multi-pass approach. The microstructural image analysis by optical microscope and scanning electron microscope revealed reduction of matrix grain size and improvement of particle distribution for lower processing speed and multi-pass processing. The elemental analysis indicated well dispersion of reinforcement particles in matrix along with the presence of compounds of aluminum alloy. The microhardness and tensile strength were increased with reduction of processing speed and increase of number of pass. The friction coefficient and the wear loss were also low for composites produced with low processing speed and multi-pass. A combined abrasive and adhesive wear was observed in all the processed composites. With increase of processing speed and number of pass, the corrosion behavior of the composites in 3.5% NaCl solution deteriorated. The composite produced with 30 mm/min and 2 pass exhibited best particle distribution, microhardness and wear resistance. However, the composite fabricated with 30 mm/min and 1 pass yielded best corrosion resistance.

The Cu–SS welded structures are widely used in nuclear and power generation industries. Various solid state and fusion welding techniques have been experimented for welding Cu–SS with resultant phenomena of low joining strength in solid state and generation of crack in fusion. Of late application of induction heating as a joining technique is gaining momentum in view of its low maintenance, high production rate and cost effectiveness. In consideration of the above facts, in this study, induction heating for welding Cu–SS is experimented in ambient condition under varied settings of load and current. Although few micro-cracks were observed in SEM images, successful joining between copper and stainless steel was achieved. Some compounds like FeCu4, Cr3Fe, Cu(Fe2O4) and CrO were detected by XRD near the weld interface. The microhardness increased near the interface in comparison to the base metals. The interface microhardness was increased with current and load. Similarly, the tensile strength was also increased for higher values of process parameters. Highest strength of 220 MPa was obtained at 2 kg load and 650 A current. Failure of welded joint under tension took place by ductile–brittle fracture mode.

Aluminium alloys, a structural material owing to the great specific strength, are often subjected to extensive wear and corrosive environment. Considering the situation, in this article, a hybrid composite was made by integrating MoS2 and CeO2 powder in Al7075 alloy by friction stir processing. The SEM image of the microstructure of the composite reveals well dispersion of the powder particles in aluminium matrix. During sliding contact against WC ball, a significant decrease in friction coefficient of the composite is observed due to the presence of lubricating MoS2 powder. The SEM micrographs of the worn surfaces indicate that the oxidation and severe adhesive type of wear in aluminium are changed to a combination of abrasion and adhesion type of wear in the composite. The specific wear loss of around 8 × 10−4 mm3/N-m of the aluminium alloy is reduced to nearly 4 × 10−4 mm3/N-m by incorporating micro-reinforcements. In a solution of 3.5% NaCl, the corrosion current density is drastically reduced to 8.18 × 10−7 A/cm2 from 2 × 10−6 A/cm2 of unreinforced alloy. Also, the corrosion potential is increased from −863.962 to −672.192 mV due to the addition of hybrid reinforcement. Moreover, the rapid corrosion of aluminium alloy is reduced, and secondary passivation due to the presence of CeO2 is observed. Therefore, it is evident that the wear resistance and corrosion resistance of the Al7075 alloy are improved by the addition of MoS2 and CeO2 powder.

In the present study, Induction welding was carried out to achieve the joining between dissimilar metals such as mild steel (AISI 1015) and copper (Cu) in open atmosphere with different loads and different current settings. Microstructural evaluation of the welded joints was done by optical microscope and scanning electron microscope (SEM). The study showed that Cu was well bonded with mild steel (MS) without any crack near diffusion line. The X-Ray Diffraction (XRD) analysis was carried out and it revealed the presence of FeCu4 and Cu(Fe2O4) along with Cu and Fe. Joint quality was examined by measuring ultimate tensile strength (UTS) and microhardness. The UTS of the welded specimens was found to be increasing with the increase of load and current. The maximum UTS was obtained for specimen welded at 650 A with 2.5 kg load applied during welding. Microhardness distribution of the welded specimens showed that microhardness at interface line was more than that of copper and less than that of mild steel. The maximum microhardness on the copper side was at the interface line and attained base metal microhardness 1 mm onward from the interface. However the microhardness on mild steel side increased nearly upto 6 mm from the interface line.