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This paper aims to investigate the modification of surface of a copper alloy by friction stir surface processing (FSSP).

The metallographic condition of the surface modification was observed using microscopy. Electrochemical corrosion tests were carried out on the modified surface and the corroded surface was observed by scanning electron microscopy (SEM).

The test results showed that FSSP resulted in refinement of the surface grains of the copper alloy. The degree of refinement was increased with rotation speed and increased in the descending distance of the stirring tool. The corrosion resistance of the modified surface was superior to the base metal except for the surface generated by a rotation speed of 800 rpm and a descending distance 0.1 mm. For the surface modification of the rotation speed of 800 rpm, its corrosion resistance was lower than for the other two rotation speeds. When the rotation speed is specified, the corrosion resistance is improved with increased descending distance. When the descending distance is specified, the corrosion resistance is improved with the rotation speed.

In this study, it was confirmed that the corrosion resistance of the surface modification was best at the rotation speed 1200 rpm and descending distance 0.2 mm.

This study aims to investigate and present the tribological behaviour of recursively friction stir processed 7075 aluminium alloy.

In this work, aluminium 7075 alloy is friction stir processed recursively by varying the tool rotational speed, traverse speed and the number of passes. Wear pins for testing were extracted from the processed zone and the surfaces were prepared. Wear tests were conducted as per the standard on a pin-on-disc wear testing machine at constant testing conditions and the corresponding tribological properties were analysed. The worn surface and the debris were analysed using a field-emission scanning electron microscope with energy dispersive spectroscopy analysis and elemental mapping to identify the mode of wear mechanism.

The experimental results indicate that the specimen fabricated at 1,150 rpm of tool rotation speed and 60 mm/min of traverse speed with 4 passes had the highest wear resistance and the minimum friction coefficient.

This paper details the effect of recursive friction stir processing on the surface of AA 7075 to improve the tribological properties.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0070/

In-situ aluminum metal matrix composites (AMMC) have taken over the use of ex-situ AMMC due to the generation of finer and thermodynamically stable intermetallic compounds. However, conventional processing routes pose inevitable defects like porosity and agglomeration of particles. This paper aims to study current state of progress in in-situ AMMC fabricated by Friction Stir Processing.

Friction stir processing (FSP) has successfully evolved to be a favorable in-situ composite manufacturing technique. The dynamics of the process account for a higher plastic strain of 35 and a strain rate of 75 per second. These processing conditions are responsible for grain evolution from rolled grain → dislocation walls and dislocation tangles → subgrains → dislocation multiplication → new grains. Working of matrix and reinforcement under ultra-high strain rate and shorter exposure time to high temperatures produce ultra-fine grains. Do the grain evolution modes include subgrain boundaries → subgrain boundaries and high angle grain boundaries → high angle grain boundaries.

Further, the increased strain and strain rate can shave and disrupt the oxide layer on the surface of particles and enhance wettability between the constituents. The frictional heat generated by tool and workpiece interaction is sufficient enough to raise the temperature to facilitate the exothermic reaction between the constituents. The heat released during the exothermic reaction can even raise the temperature and accelerate the reaction kinetics. In addition, heat release may cause local melting of the matrix material which helps to form strong interfacial bonds.

This article critically reviews the state of the art in the fabrication of in-situ AMMC through FSP. Further, FSP as a primary process and post-processing technique in the synthesis of in-situ AMMC are also dealt with.

This paper aims to determine the optimum parametric settings for yielding superior mechanical properties, namely, ultimate tensile strength (UTS), yield strength (YS) and percentage elongation (EL) of AZ91D/AgNPs/TiO₂ hybrid composite fabricated by friction stir processing.

An empirical model has been developed to govern crucial influencing parameters, namely, rotation speed (RS), tool transverse speed (TS), number of passes (NPS) and reinforcement fraction (RF) or weight percentage. Box Behnken design (BBD) with four input parameters and three levels of each parameter was used to design the experimental work, and analysis of variance (ANOVA) was used to check the acceptability of the developed model. Desirability function analysis (DFA) for a multiresponse optimization approach is integrated with response surface methodology (RSM). The individual desirability index (IDI) was calculated for each response, and a composite desirability index (CDI) was obtained. The optimal parametric settings were determined based on maximum CDI values. A confirmation test is also performed to compare the actual and predicted values of responses.

The relationship between input parameters and output responses (UTS, YS, and EL) was investigated using the Box-Behnken design (BBD). Silver nanoparticles (AgNPs) and nano-sized titanium dioxide (TiO₂) enhanced the ultimate tensile strength and yield strength. It was observed that the inclusion of AgNPs led to an increase in ductility, while the increase in the weight fraction of TiO₂ resulted in a decrease in ductility.

AZ91D/AgNPs/TiO₂ hybrid composite finds enormous applications in biomedical implants, aerospace, sports and aerospace industries, especially where lightweight materials with high strength are critical.

In terms of optimum value through desirability, the experimental trials yield the following results: maximum value of UTS (318.369 MPa), maximum value of YS (200.120 MPa) and EL (7.610) at 1,021 rpm of RS, 70 mm/min of TS, 4 NPS and level 3 of RF.

This paper aims to summarize the microstructure characterization of parts that were produced using a hybrid manufacturing process consisting of laser metal deposition (LMD) and friction stir processing (FSP). This research was conducted to investigate the evolution of the microstructure following FSP and LMD and to study the possibility of producing or repairing parts with a forged-like microstructure using this hybrid technique.

The microstructure of the nugget regions obtained in the substrate weld, stir over deposit and deposit over stir experiments was investigated.

Highly refined grain size in the order of 1-2 μm was observed where FSP was performed over laser-deposited Ti–6Al–4V. Large equiaxed grains were observed in the experiment where subsequent deposition was carried over the stir. A decreasing grain size was also observed in the dilution zone (DZ) inside the nugget from the stir surface to the bottom of the DZ.

A highly refined microstructure formed from FSP is able to increase the fatigue life by delaying the fatigue crack initiation. Peters et al. (1980) reported that reducing the grain size from 12-15 μm to 1-2 μm in an equiaxed Ti–6Al–4V alloy corresponded with about 25 per cent increase in fatigue strengths at 10,000,000 cycles.

This proposed technical approach is a novel and effective method to produce forged-like parts using a metal additive manufacturing process.

Friction stir processing (FSP) as a solid-state process has the potential for the production of effective aluminum matrix composites (AMCs). In this investigation, various ceramic particles including B₄C, TiC, SiC, Al₂O₃ and WC were incorporated as the dispersed phase within AA6082 aluminum alloy by FSP. The wear rate of the composite is then investigated experimentally by making use of a design of experiments technique where wear rate is evaluated as the output parameter. The input parameters considered include tool rotational speed, traverse speed, groove width and ceramic particle type. An artificial neural network (ANN) simulation was then used to describe the wear rate of the surface composites. The weights of the network were adjusted to minimize the mean squared error using a feed forward back propagation technique. The effect of the individual input parameters on wear rate was then inferred from the ANN models. Trends are presented and related to the associated microstructures observed. The TiC infused AMC displayed the lowest wear rate whereas the Al₂O₃ infused AMC displayed the highest, within the scope of the current investigation. The paper aims to discuss these issues.

The paper used ANN for the research study.

The finding of this paper is that the wear rate of AA6063 aluminum surface composites is influenced remarkably by FSP parameters.

Original work of authors.

The deposition of particles onto a substrate during the cold spraying (CS) process relies on severe plastic deformation, so there are various micro-defects induced by insufficient deformation and severe crushing. To solve the problems, many post-treat techniques have been used to improving the quality by eliminating the micro-defects. This paper aims to help scholars and engineers in this field a better and systematic understand of CS technology by summarizing the post-treatment technologies that have been investigated recently years.

This review summarizes the types of micro-defects and introduces the effect of micro-defects on the properties of CS coating/additive manufactured, illustrates the post-treatment technologies and its effect on the microstructure and performances, and finally outlooks the future development trends of post-treatments for CS.

There are significant discoveries in post-treatment technology to change the performance of cold spray deposits. There are also many limitations for post-treatment methods, including improved performance and limitations of use. Thus, there is still a strong requirement for further improvement. Hybrid post-treatment may be a more ideal method, as it can eliminate more defects than a single method. The proposed ultrasonic impact treatment could be an alternative method, as it can densify and flatten the CS deposits.

It is the first time to reveal the influence factors on the performances of CS deposits from the perspective of microdefects, and proposed corresponding well targeted post-treatment methods, which is more instructive for improving the performances of CS deposits.

This study aims to analyse the changes in mechanical and wear performance of aluminium alloy when yttrium oxide particles are incorporated. The microstructures are studied to analyse the change in the grain structures. Worn surfaces are observed via scanning electron microscope to study the wear mechanism in detail.

Stir casting is used to incorporate varying composition of yttrium particles, having an average particle size of 25 micrometer, in aluminium alloy 6063 matrix. Wear testing is carried out by DUCOM manufactured high temperature rotatory tribometer, and an indentation test is used for analysing the microhardness of the fabricated samples.

Microhardness of the material is increased with the increasing content of particulate addition. With the increasing content of reinforcement, more refined grains are produced. The load is transferred from the matrix to more rigid yttrium oxide particles. These factors contributed to escalated microhardness of the reinforced samples. Particulate addition enhanced the wear performance of the material; this might be attributed to increased microhardness and formation of an oxide layer.

Aluminium composites are finding wide applications in various industries, and there is always a requirement of material with enhanced tribological properties. Yttrium oxide particles exhibit improved mechanical properties, and their interaction with the aluminium matrix has not been studied much in the past. So, in this work, yttrium oxide incorporated aluminium matrix is studied.

This study aims to examine the corrosion and flexural behaviour of advanced hybrid aluminium matrix nanocomposites (HAMNCs) made with a vacuum-assisted stir die casting (two-layer feeding) and reinforced with titanium oxide (TiO₂) and yttrium oxide (Y₂O₃) nanoparticles. The previous researchers have shown that TiO₂ and Y₂O₃ nanoparticles make aluminium composites much more resistant to corrosion and wear.

Salt spray corrosion tests were done on the samples over time as well as the pre-and post-corrosion morphology of the test samples was also investigated. The density, porosity and energy dispersive X-ray of the fabricated samples were observed.

It was observed that a lower corrosion rate of 0.127 mils/year and 0.573 mils/year was seen in the Al/5 Wt.%TiO₂/5 Wt.%Y₂O₃ (HAMNC1) and Al/7.5 Wt.%TiO₂/2.5 Wt.%Y₂O₃ (HAMNC3), respectively. It was evident from the results that the pores and densities of the samples varied with the filler concentrations and matrix filler wettability. HAMNC1 has the lowest values of density and porosity at 2.568 g/cm³ and 9.91%, respectively. At the same time, a significant improvement in the flexural strength of 72 N/mm² was also seen in the HAMNC1 configuration.

The proposed hybrid samples are well suited for aerospace and automobile structural components such as brake drums, discs, engine cylinders and fins.

The mixed influence evaluation of TiO₂ and Y₂O₃ nanoparticles with pure Al on composite samples has not been studied. This research aims to examine the combined influence of nanoparticles on the corrosion aspects of two-step feeding vacuum stir casted products, as well as their morphology.

Friction stir processing (FSP) is overviewed with the process variables, along with the thermal aspect of different metals.

With its inbuilt advantages, FSP is used to reduce the failure in the structural integrity of the body panels of automobiles, airplanes and lashing rails. FSP has excellent process ability and surface treatability with good corrosion resistance and high strength at elevated temperatures. Process parameters such as rotation speed of the tool, traverse speed, tool tilt angle, groove design, volume fraction and increase in number of tool passes should be considered for generating a processed and defect-free surface of the workpiece.

FSP process is used for modifying the surface by reinforcement of composites to improve the mechanical properties and results in the ultrafine grain refinement of microstructure. FSP uses the frictional heat and mechanical deformation for achieving the maximum performance using the low-cost tool; the production time is also very less.

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