The current work investigates the viability of utilizing a friction stir deposition (FSD) technique to fabricate continuous multilayer high-performance, metal-based nanoceramic composites. For this purpose, AA2011/nano Al₂O₃ composites were successfully produced using AA2011 as a matrix in two temper conditions (i.e., AA2011-T6 and AA2011-O). The deposition of matrices without nano Al₂O₃ addition was also friction stir deposited for comparison purposes. The deposition process parameters were an 800 rpm rod rotation speed and a 5 mm/min feed rate. Relative density and mechanical properties (i.e., hardness, compressive strength, and wear resistance) were evaluated on the base materials, deposited matrices, and produced composites. The microstructural features of the base materials and the friction stir deposited materials were investigated using an optical microscope (OM) and a scanning electron microscope (SEM) equipped with an EDS analysis system. The worn surface was also examined using SEM. The suggested technique with the applied parameters succeeded in producing defect-free deposited continuous multilayer AA2011-T6/nano Al₂O₃ and AA2011-O/nano Al₂O₃ composites, revealing well-bonded layers, grain refined microstructures, and homogeneously distributed Al₂O₃ particles. The deposited composites showed higher hardness, compressive strengths, and wear resistance than the deposited AA2011 matrices at the two temper conditions. Using the AA2011-T6 temper condition as a matrix, the produced composite showed the highest wear resistance among all the deposited and base materials.

In the current study, a 2 mm thick low-carbon steel sheet (A283M—Grade C) was joined with a brass sheet (CuZn40) of 1 mm thickness using friction stir spot welding (FSSW). Different welding parameters including rotational speeds of 1000, 1250, and 1500 rpm, and dwell times of 5, 10, 20, and 30 s were applied to explore the effective range of parameters to have FSSW joints with high load-carrying capacity. The joint quality of the friction stir spot-welded (FSSWed) dissimilar materials was evaluated via visual examination, tensile lap shear test, hardness test, and macro- and microstructural investigation using SEM. Moreover, EDS analysis was applied to examine the mixing at the interfaces of the dissimilar materials. Heat input calculation for the FSSW of steel–brass was found to be linearly proportional with the number of revolutions per spot joint, with maximum heat input obtained of 11 kJ at the number of revolutions of 500. The temperature measurement during FSSW showed agreement with the heat input dependence on the number of revolution. However, at the same revolutions of 500, it was found that the higher rotation speed of 1500 rpm resulted in higher temperature of 583 °C compared to 535 °C at rotation speed of 1000 rpm. This implies the significant effect for the rotation speed in the increase of temperature. The macro investigations of the friction stir spot-welded joints transverse sections showed sound joints at the different investigated parameters with significant joint ligament between the steel and brass. FSSW of steel/brass joints with a number of revolutions ranging between 250 to 500 revolutions per spot at appropriate tool speed range (1000–1500 rpm) produces joints with high load-carrying capacity from 4 kN to 7.5 kN. The hardness showed an increase in the carbon steel (lower sheet) with maximum of 248 HV and an increase of brass hardness at mixed interface between brass and steel with significant reduction in the stir zone hardness. Microstructural investigation of the joint zone showed mechanical mixing between steel and brass with the steel extruded from the lower sheet into the upper brass sheet.

Bobbin tool friction stir welding (BT-FSW) is characterized by a fully penetrated pin and double-sided shoulder that promote symmetrical solid-state joints. However, control of the processing parameters to obtain defect-free thick lap joints is still difficult and needs more effort. In this study, the BT-FSW process was used to produce 10 mm AA1050-H14 similar lap joints. A newly designed bobbin tool (BT) with three different pin geometries (cylindrical, square, and triangular) and concave shoulders profile was designed, manufactured, and applied to produce the Al alloy lap joints. The experiments were carried out at a constant tool rotation speed of 600 rpm and a wide range of various welding travel speeds of 200, 400, 600, 800, and 1000 mm/min. The generated temperature during the BT-FSW process was recorded and analyzed at the joints’ center line, and at both advancing and retreating sides. Visual inspection, macrostructures, hardness, and tensile properties were investigated. The fracture surfaces after tensile testing were also examined. The results showed that the pin geometry and travel speed are considered the most important controlling parameters in BT-FSW thick lap joints. The square (Sq) pin geometry gives the highest BT-FSW stir zone temperature compared to the other two pins, cylindrical (Cy) and triangular (Tr), whereas the Tr pin gives the lowest stir zone temperature at all applied travel speeds from 200 to 1000 mm/min. Furthermore, the temperature along the lap joints decreased with increasing the welding speed, and the maximum temperature of 380 °C was obtained at the lowest travel speed of 200 mm/min with applying Sq pin geometry. The temperature at the advancing side (AS) was higher than that at the retreating side (RS) by around 20 °C. Defect-free welds were produced using a bobbin tool with Cy and Sq pin geometries at all the travel welding speeds investigated. BT-FSW at a travel speed of 200 mm/min leads to the highest tensile shear properties, in the case of using the Sq pin. The hardness profiles showed a significant effect for both the tool pin geometry and the welding speed, whereas the width of the softened region is reduced dramatically with increasing the welding speed and using the triangular pin.

Friction stir welding (FSW) as a solid-state process is an excellent candidate for high softening temperature materials welding; however, extending the tool life is required to make the process cost-effective. This work investigates the use of a high pin to shoulder ratio (65%) tungsten carbide (WC) tool for friction stir welding of 5 mm thick 2205 DSS to extend the tool life of this low-cost tool material. In addition, the effect of FSW parameters in terms of rotational rates, travel speeds, and downward forces on the microstructural features and mechanical properties of the welded joints were investigated. Characterization in terms of visual inspection, macro and microstructures, hardness, and tensile testing was conducted. The obtained results indicated that the combined rotational rate, travel speed, and downward force parameters govern the production of defect-free joints. The 2205 DSS friction stir welds show an enhancement in hardness compared to the base material. The stir zone showed a significantly refined grain structure of ferrite and austenite with the reduction in the average grain size from 8.8 µm and 13.3 µm for the base material to 2.71 µm and 2.24 µm, respectively. Moreover, this joint showed higher yield strength and ultimate tensile strength compared to the DSS as-received material.

Light-weight metal matrix composites, especially magnesium-based composites, have recently become more widespread for high-efficiency applications, including aerospace, automobile, defense, and telecommunication industries. The squeeze cast AZ91 base material (AZ91-BM) and its composites having 23 vol.% short carbon fibers were fabricated and investigated. The composite specimens were machined normal to the reinforced plane (Composite-N) and parallel to the reinforced plane (Composite-P). All the as-casted materials were subjected to different tests, such as hardness, compression, and wear testing, evaluating the mechanical properties. Dry wear tests were performed using a pin-on-disk machine at room temperature under different applied wear loads (1–5 N) and different sliding distances ($0.4461\times {10}^4$–$3.12\times {10}^4$ m). The microstructures and worn surfaces of the fabricated AZ91-BM and the two composite specimens were investigated using a scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS) advanced analysis system. The wear debris was collected and investigated also under the SEM. The results showed significant improvement in hardness, compressive strength, and wear resistance of the composite specimens (Composite-N and Composite-P) over the AZ91-BM. The compressive strength and wear resistance are more fibers orientation sensitive than the hardness results. When the fiber orientation is parallel to the sliding direction (Composite-N), the weight loss is somewhat lower than that of the fiber orientation perpendicular to the sliding direction (Composite-P) at a constant wear load of 2 N and the sliding distances of $0.4461\times {10}^4$, $1.34\times {10}^{4 },$ and $2.23\times {10}^4$ m. In contrast, the weight loss of Composite-P is lower than Composite-N, especially at the highest sliding distance of $3.12\times {10}^4$ m due to the continuous feeding of graphite lubricant film and the higher compressive strength. Plastic deformation, oxidation, and abrasive wear are the dominant wear mechanisms of AZ91-BM; in contrast, abrasive and delamination wear are mainly the wear mechanisms of the two composites under the applied testing conditions.

In this study, AZ91/23 vol.% short carbon fiber composite was produced by a squeeze casting technique using a cylindrical pre-form of treated carbon fibers, in which the fibers are randomly oriented in the horizontal plane. Cylindrical specimens (height = 9 mm and diameter = 6 mm) were machined from the as-cast AZ91 matrix and its composite. The full behavior of the produced composite was studied through the test specimens machined in two directions, namely parallel to the reinforced plane (in the radial direction of the cast cylinder) and normal to the reinforced plane (in the axial direction of the cast composite). The microstructures of the produced composite specimens were investigated using SEM equipped with EDS analysis. Density, hardness, compressive, and wear behavior were also investigated. For comparison, the AZ91 matrix was evaluated as a reference. The microstructure of the produced AZ91 matrix alloy and its composite revealed dense materials without casting defects. Both composite specimens show improvement in hardness, compressive strength, and wear properties over the AZ91 matrix. The compressive and wear properties are more fiber orientation-dependent than the hardness results. The parallel composite specimen depicts the highest compressive properties in terms of yield compressive strength (311 MPa) and ultimate compressive strength (419 MPa), compared to that shown by the AZ91 matrix and the normal composite specimen. This improvement in compressive strength was at the expense of ductility. The parallel composite specimen shows the lowest ductility (R = 3.8%), compared to that given by the normal composite specimen (R = 7.1) and the AZ91 matrix alloy (R = 13.6). The wear testing results showed that at the highest wear load of 5 N, the material weight loss of the parallel composite specimen decreases by 44% and 64% compared to the AZ91 matrix and the normal composite specimen, respectively.