Friction Stir Processing Technique Research Articles

Microstructure, mechanical and corrosion study of friction stir processed Inconel 625 additive layers deposited via wire arc direct energy deposition

This study explores the application of friction stir processing (FSP) as an effective post-deposition surface treatment technique for improving the mechanical and corrosion properties of wire arc direct energy deposited (WA-DED) Inconel 625 additive layers. The coarse and cube-oriented microstructure observed in as-built Inconel 625 components results in anisotropic mechanical properties. The non-equilibrium solidification in WA-DED Inconel 625 leads to severe micro-segregation of alloying elements, forming large Nb and Mo-rich Laves and carbide phases in the inter-dendritic areas. This causes a heterogeneous distribution of vital alloying elements within the γ-Ni matrix of the material, adversely affecting its mechanical properties and corrosion resistance, thereby restricting the utility of this manufacturing technique in critical applications. The incorporation of FSP has been observed to successfully eradicate the presence of typical coarse and highly oriented microstructure through grain refinement, achieving a more uniform microstructure. Through severe plastic deformation (SPD), coarse eutectic phases are broken down and redistributed within the γ-Ni matrix, enhancing the uniformity of material properties. The research thoroughly investigates the changes in microstructure, mechanical performance, and corrosion resistance of both WA-DED and FSP-enhanced WA-DED Inconel 625 samples. A Thermo-Calc simulation using the classical Scheil model was conducted to understand the solidification pathway and the formation mechanism of the Laves phase in the WA-DED sample. The grain size was significantly reduced by 98.23%, from 138 µm in the WA-DED sample to 2.44 µm in the stir zone (SZ) of the FSP-treated area, due to dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and the Zener pinning effect. This grain refinement led to remarkable enhancements in the yield strength (YS) by approximately 113%, ultimate tensile strength (UTS) by about 37% and micro-hardness by around 60% compared to the WA-DED sample. In a 3.5 wt% NaCl solution, the FSP-treated sample demonstrated superior corrosion resistance by forming a stable, thicker passive film than the as-built sample. The results of this study will offer valuable insights into utilizing the FSP technique as post-weld surface treatment of WA-DED deposited IN625 superalloy.

Exploring Microstructural, Interfacial, Mechanical, and Wear Properties of AlSi7Mg0.3 Composites with TiMOVWCr High-Entropy Alloy Powder.

This study explored the impact of varying weight percentages of TiMoVWCr high-entropy alloy (HEA) powder addition on A356 composites produced using friction stir processing (FSP). Unlike previous research that often focused on singular aspects, such as mechanical properties, or microstructural analysis, this investigation systematically examined the multifaceted performance of A356 composites by comprehensively assessing the microstructure, interfacial bonding strength, mechanical properties, and wear behavior. The study identified a uniform distribution of TiMoVWCr HEA powder in the composition A356/2%Ti2%Mo2%V2%W2%Cr, highlighting the effectiveness of the FSP technique in achieving homogeneous dispersion. Strong bonding between the reinforcement and matrix material was observed in the same composition, indicating favorable interfacial characteristics. Mechanical properties, including tensile strength and hardness, were evaluated for various compositions, demonstrating significant improvements across the board. The addition of 2%Ti2%Mo2%V2%W2%Cr powder enhanced the tensile strength by 36.39%, while hardness improved by 62.71%. Similarly, wear resistance showed notable enhancements ranging from 35.56 to 48.89% for different compositions. Microstructural analysis revealed approximately 1640.59 grains per square inch for the A356/2%Ti2%Mo2%V2%W2%Cr processed composite at 500 magnifications. In reinforcing Al composites with Ti, Mo, V, W, and Cr high-entropy alloy (HEA) particles, each element imparted distinct benefits. Titanium (Ti) enhanced strength and wear resistance, molybdenum (Mo) contributed to improved hardness, vanadium (V) promoted hardenability, tungsten (W) enhanced wear resistance, and chromium (Cr) provided wear resistance and hardness. Anticipating the potential applications of the developed composite, the study suggests its suitability for the aerospace sector, particularly in casting lightweight yet high-strength parts such as aircraft components, engine components, and structural components, underlining the significance of the investigated TiMoVWCr HEA powder-modified A356 composites.

Optimizing friction stir processing parameters for aluminium alloy 2024 reinforced with SiC particles: A taguchi approach of investigation

The present investigation focuses on the microstructural behavior and mechanical properties of Aluminium alloy 2024 reinforced with SiC nanoparticles by applying the Friction Stir Processing (FSP) technique. Taguchi L9 orthogonal array was used to find the optimal process parameters. The experiment used the expected best process parameters, which confirmed the predicted highest value for the mechanical characteristic. Traverse speed, axial load, and rotating speed are the main factors affecting aluminum metal matrix composite. Hence, this experiment examined the effects of five different tool spinning speeds, specifically 800, 900, 1000, 1100, and 1200 rpm. Weld samples are fabricated wherein the stir zone contains SiC nanoparticles. The results of the study indicate that the optimal welding rotational speed of 1000 rpm has a significant impact on the microstructure, wear rate, and microhardness. Specifically, it was observed that the stirred zone exhibited enhanced wear resistance compared to other zones. The study's findings revealed that after implementing friction stir processing (FSP), a well-defined shear zone was observed on the advancing side of the stir zone. Additionally, it is found that the uniform dispersion and strong bonding of SiC particles with an aluminium matrix further enhance wear resistance.

Influence of magnetic field on the mechanical behavior of friction stir processed paramagnetic alloy

The study investigated the influence of an externally applied static magnetic field (MF) on the mechanical behavior of a friction stir processed paramagnetic 1100 aluminum (Al 1100) alloy. The aim was to take advantage of the solid-state friction stir processing (FSP) technique to modify the microstructure and further improve the properties by testing in the presence of MF. Al 1100 was tested in tension under different static MFs (B = 0, 150, 1000, 1400, 1800, and 2200 Gauss) perpendicular to the stress axis. The strong effect of a comparatively weak static MF was observed on the elongation of both base and processed Al 1100 alloy, in both rolling and transverse directions, attributed to the magneto-plasticity effect (MPE) where the motion of dislocations in crystals is influenced in the presence of magnetic fields. Amongst the different mechanisms associated with MPE, the major effect in the current study was observed from the magnetization force, spin transition, and increase in strain energy of dislocations. This knowledge will open new lanes to improve the properties of a processed sample by exposing it to an MF which is a non-contact, pollution-free route; saving time and cost by avoiding in-between thermo-mechanical steps to break the cast microstructure.

Effect of Yttria-Stabilized Zirconia addition along with Cu in development of titanium based metal matrix composite via FSP technique for the application in biomedical devices

ABSTRACT The present study investigated the effect of incorporating Yttria-Stabilized Zirconia (YSZ) and copper (Cu) in the development of Titanium-Based Metal Matrix Composites (TMCs) using the Friction Stir Processing (FSP) technique. The macrostructure of the TMCs, after adding 5% YSZ and 2% Cu, displayed a defect-free, crack-free, and porosity-free surface, indicating the precision of the FSP method. Microstructure analysis revealed a uniform distribution of reinforcement particles and proper dispersion of grains, key for enhancing mechanical properties. The interfacial bonding between titanium and YSZ was exceptionally strong, devoid of cracks and porosity, attributed to the copper additive’s role. The increase in the number of grains per square inch for the Ti/5% YSZ/2% Cu composite (1176.26 grains per square inch at 500×) signified finer grain structure, contributing to a remarkable 48.04% improvement in tensile strength compared to pure titanium. The uniform distribution of reinforcement and strong bonding between titanium and YSZ are the driving forces behind the 46.34% increased in hardness. Additionally, the wear resistance of the composite improved by approximately 76.66%, a vital characteristic for applications facing abrasive conditions. The corrosion testing demonstrated an 8.33% enhancement in corrosion resistance with the Ti/5% YSZ/2% Cu composite.

AA5754–Al2O3 Nanocomposite Prepared by Friction Stir Processing: Microstructural Evolution and Mechanical Performance

The utilization of Al2O3 nanopowder to reinforce AA5754 aluminum alloy through blind holes employing the friction stir processing (FSP) technique to produce an aluminum matrix nanocomposite is explored in this paper. Motivated by the necessity to enhance the strength and ductility of welded joints, the impacts of varying the tool rotational speed (rpm) and blind hole diameter on the microstructure and mechanical properties of the joints are investigated. Experimental characterization techniques including SEM, optical microscopy, microhardness, and tensile tests were employed to analyze the welded joints produced under different processing parameters (tool rotational speeds of 910, 1280, and 1700 rpm, and blind hole diameters of 0, 1, 1.5, and 2 mm). Comparative analyses were conducted against base metal properties and joints without reinforcement powder. It was found that the addition of nanopowder resulted in a decrease in the maximum generated heat during FSP, while also reducing the stir zone size compared to samples without nanopowder. Moreover, enhancements in both the strength and ductility of the joints were observed with the incorporation of Al2O3 nanoparticles. The optimal combination of welding conditions, observed at 1280 rpm rotational speed and 1.5 mm hole diameter, yielded a remarkable ultimate tensile strength of 567 MPa, accompanied by a hardness of 45 HV. These results underscore the potential of nano-Al2O3 reinforcement in significantly improving the mechanical properties of the produced nanocomposite, with implications for advancing the performance of welded structures in various engineering applications.

Tribological and corrosion behaviour of Al-Mg-CeO2 metal matrix surface composites

In this work, multiple-passes of friction stir processing (FSP) technique was utilized to fabricate Al-Mg-CeO2 surface composites (SCs). Microstructural studies revealed that 5-pass FSP showed a better dispersion of CeO2 nano-particles and enhanced grain refinement compared to 1-pass FSP. The results indicated that the Al-Mg-CeO2 SCs exhibit enhanced tribological characteristics viz; load bearing capacity, improved resistance to wear (34.48% decreased wear rate in 5-pass SCs) and corrosion resistance in respect to the non-reinforced Al-Mg matrix. The analysis of mechanical, tribological, and corrosion behaviour strongly correlates with microstructural evolution.

Synthesis and characterization of magnesium-titanium carbide nanocomposites via friction stir processing: An in-depth parameter investigation

Magnesium Metal Matrix Composites (MMMCs) possess remarkable mechanical and metallurgical properties that have garnered the interest of researchers worldwide. The current research endeavors to synthesize nanocomposites based on magnesium (Mg), specifically AZ31B, by employing Friction Stir Processing (FSP) and integrating nano-titanium carbide (TiC) as a reinforcing element. Additionally, the impact of various FSP parameters, encompassing transverse speeds (35 and 70 mm/min) and tool rotation speeds (850 and 1700 rpm), on the metallurgical, wear, and mechanical properties of the developed MMMCs was investigated. The microstructural analysis revealed that employing the FSP technique led to a uniform dispersion of nano-TiC reinforcement particles within the base matrix of the AZ31B Mg alloy. This concurrent distribution played a crucial role in both refining and evolving the grain sizes, subsequently leading to improvements in the composites’s mechanical and wear characteristics. To be more specific, the grain size witnessed a reduction by nearly 18 times, the microhardness increased by approximately 2.54 times, and the ultimate tensile strength (UTS) showed a 2.08-fold increase when compared to the base alloy. Furthermore, in contrast to the base material characterized by an adhesive wear mechanism, the presence of scratches indicates that the abrasive wear mechanism predominated in the case of the AZ31B/TiC nanocomposite. The outcome of the results depicts that the nanocomposite fabricated at a tool rotation speed of 1700 rpm and 70 mm/min transverse shows better mechanical and tribological characteristics than other developed composites and the base alloy.

Al-5052/SiC + CeO2 hybrid surface composites: Achieving improved microstructural and mechanical behaviour via friction stir processing

In the present work, hybrid surface composites (HSCs) were fabricated using aluminium 5052 alloy as base matrix and silicon carbide (SiC) and cerium oxide (CeO2) as reinforcement particles via friction stir processing (FSP) technique. Varying reinforcement ratios of SiC and CeO2 nano-powders, viz 100:0, 75:25, 50:50, 25:75, and 0:100 was used. Multi-pass FSP was employed to obtain improved dispersion of reinforcement particles. Results revealed the collaborative impact of SiC and CeO2 particles on the mechanical properties of the SCs, shedding light on the optimal ratios for achieving superior mechanical performance. The hybrid ratio of (SiC: CeO2) 75:25 was predominant in tensile strength enhancements with an ultimate tensile strength of 283 MPa compared to 269 MPa of BM while the percentage elongation increased to 21.6 as compared to 18.8 in BM. The average microhardness also improved to 92 HV compared to 85 HV. These results emphasised on the importance of HSC fabricated using 75:25 ratio of SiC:CeO2 reinforcing particles.

Enhanced toughness and tear resistance of thin-walled High-Pressure Die-Cast aluminum alloys through Friction stir processing

In this study, we investigate the toughness and resistance to tear of thin-wall high-pressure die-cast (HPDC) aluminum alloys in two different orientations following the implementation of friction stir processing (FSP). The FSP technique was applied to two different HPDC Al-Si alloys: the recyclable-grade, high iron, A380 alloy and the premium-quality, low iron, Aural-5 alloy. Our findings reveal significant tear resistance and strength enhancements for both alloys after FSP modification. Specifically, FSPed A380 alloy requires 126% higher energy to tear, and it has 49% higher tear strength than the HPDC counterpart. Similarly, the tear energy and tear strength of the Aural-5 alloy witness enhancements of 69% and 21%, respectively. These findings emphasize the capability of FSP to improve the toughness of HPDC aluminum alloys, creating new possibilities for preventing cracks in a variety of engineering applications.

Influence of tool plunge depth and multiple passes on the microstructure, texture evolution and hardness of age-hardenable aluminium 7075 alloy

In this study, the surface properties of AA7075 were modified through the solid-state friction stir processing technique using a hexagonal-shaped H13 pin. Single pass friction stir processing was conducted at two different shoulder plunge depths at constant tool rotation and linear speeds with the resulting cross-sections being examined using optical macroscopy. Six friction stir processing passes were then carried out intermittently at optimal shoulder plunge depth and the corresponding microstructural evolution along the nugget was investigated using advanced microstructural characterization techniques such as electron backscatter diffraction and high-resolution transmission electron microscopy. Bulk texture examination was conducted using the neutron diffraction method, while hardness measurements were taken using Vicker's hardness testing machine. Single pass friction stir processing conducted at a shoulder plunge depth of 0.25 mm produced defect-free material consolidation with a refined grain structure along the nugget. Minimum grain size averaging 3.78 μm was observed at the top, while slightly increased grain sizes were noticed at the middle and bottom regions of the nugget. After 6 friction stir processing passes, grain size was reduced significantly averaging 1.84 μm at the top, while size at the pin-driven zone exhibited an increasing trend due to heat input and strain rate variations. Both, single-pass and 6 pass specimens exhibited a weaker texture along the nugget due to randomness in grain orientation and the effect of particle-stimulated nucleation mechanism. In the single-pass specimen, hardness decreased along the nugget, with a maximum of 85.2 HV at the top, while 6-pass specimen exhibited an improved hardness of 133.5 HV due to the strengthening caused by grain refinement, precipitates and dislocations.

Effect of friction stir processing on mechanical, in vitro degradation, and biocompatibility behaviour of stir casted Mg-Zn-rare earth oxide composites for biodegradable implant applications

The current work takes the benefit of utilizing a composite approach by reinforcing Mg with Zn, Cerium oxide - a rare earth and bone-friendly ceramic, and bioactive hydroxyapatite to develop magnesium-based MMCs for high structural integrity and low degradation inside the human body via stir casting technique in a protective Ar-SF6 environment. The friction stir processing (FSP) technique was employed to tailor the properties of as-cast Mg composites, resulting in further grain refinement and better dispersion of reinforced materials. Phase and microstructure analysis were analyzed via XRD, FESEM, and optical microscopy. During tensile tests, as-cast Mg-5Zn-1HA-1.5CeO2 improved 68.6% in yield strength and 16.3% in ultimate tensile strength. After FSP, the same composite resulted in an overall improvement of 114.6% in yield strength and 31.9% in ultimate strength compared to as-cast pure Mg. Dispersion of inert bioceramics within the Mg matrix results in higher polarization resistance as per Electrochemical impedance spectroscopy (EIS). At the same time, a remarkable 81.6% reduction in H2 emission and an 84.4% decrement in corrosion rate were found during the immersion study for Mg-5Zn-1HA-1.5CeO2 composites. All Mg-based composites exhibited no cytotoxicity as cell viability evaluated via MTT assay was found to be greater than 80% for 50% and 25% extract concentrations. The composite’s hemolysis rate was below 5%, indicating acceptable hemocompatibility. This work provides insight into developing rare earth oxide-incorporated Mg composites with better mechanical capabilities and degradation resistance while avoiding the long-term cytotoxicity of rare-earth materials.

Development and characterization of Cu-Ni- Al2O3 surface composite developed by friction stir process technique

In this study, a copper-based composite reinforced with Al2O3 and Ni with different weight percent was produced using the Friction Stir Processing (FSP) technique. The macrostructure and microstructure of the composite were characterized to understand the arrangement and distribution of the reinforcement particles. The wettability of the composite was evaluated to determine its ability of reinforcement to interact with the matrix material. Uniform distribution and fair interaction of Al2O3 and Ni particles were found in the Cu-based matrix material Tensile and hardness tests were conducted to measure the mechanical properties of the composite and assess its strength and resistance to deformation. The hardness and tensile strength of copper after the addition of 5 % Al2O3 and 2 % Ni was improved by about 43.33 % and 50.45 % respectively. The number of grains was found to be about 2740.07 per square inch for Cu/5 % Al2O3/2 % Ni processed composite with FSP per square inch at 500 magnifications. Additionally, wear analysis was carried out to investigate the wear behavior of the composite under specific loading conditions. XRD analysis was performed to examine the crystallographic behavior and integrity of the composite. The identified phases of the Cu/Al2O3/Ni composite after XRD analysis were Cu, Al2O3, Ni, and Cu2O. The results obtained from these various analyses provided valuable insights into the structural, mechanical, and wettability properties of the copper-based composite reinforced with Al2O3 and Ni, fabricated using the FSP technique.

Effect of CeO2–Ni addition on the behavior of AZ91- A356 based composite fabricated by friction solid state technique

This study aims to investigate the behavior of AZ91- A356 alloy after the addition of CeO2 and Ni using the friction stir processing (FSP) technique. The Macrostructure of AZ91- A356/2 % Ni/5 % CeO2 showed a crack-free and defect-free composite. The microstructure image showed fair distribution for AZ91- A356/2 % Ni/5 % CeO2 composite. The interfacial layer analysis aimed to determine the formation and characteristics of the layer between the processed alloy and the reinforcement. A strong interfacial layer between A356-AZ91, CeO2, and Ni was found for AZ91- A356/2 % Ni/5 % CeO2 composite. The addition of 5 % CeO2 and 2% Ni showed a 44.78% improvement in tensile strength and a 38.84% improvement in hardness. The number of grains was found to be about 2521.38 per square inch at 500 magnifications for AZ91- A356/2 % Ni/5 % CeO2 processed composite with FSP. The formations of Al, Mg, NiAl3, CeO2, and Ni phases were observed in XRD. The wear rate of AZ91- A356 alloy decreased by about 68.85% after the addition of the 2% Ni- 5% CeO2 particles. The results of this study will contribute to a better understanding of the processing-structure-properties relationship in the A356-AZ91 alloy and guide the development of improved dissimilar materials and processing techniques.

Exploring the mechanical, metallurgical, and fracture characteristics of hybrid-reinforced magnesium metal matrix composite synthesized via friction stir processing route

Low-cost hybrid-reinforced magnesium metal matrix composite (HMMC) materials present a revolutionary category of materials achieved by combining two or more distinct reinforcing elements within the magnesium (Mg) matrix. The main focus of this research is to fabricate Mg-based HMMCs with exceptional mechanical and other characteristics by utilizing Mg substrate AZ61A as the base material. To achieve this, nano-titanium carbide (TiC), nano-silicon carbide (SiC), and fly ash (FA) were selected as hybrid reinforcements, and the friction stir processing technique was employed for their incorporation. The microstructural, thermal, mechanical, wear, and fracture properties of synthesized HMMCs were carefully examined using a conventional testing approach. The findings demonstrate that the grain size of the base AZ61A alloy was measured at 32 µm, whereas the AZ61A/FA/TiC/SiC composite exhibited a remarkable reduction to 3.5 µm. Notably, this reduction in grain size leads to simultaneous enhancement in mechanical properties. The microhardness, ultimate tensile strength, and ultimate compressive strength of the developed HMMC showed an impressive increase, measuring 2.09 times, 2.75 times, and 2.10 times higher, respectively, compared to their initial values of the base material. Moreover, a significant enhancement in wear resistance was also observed, attributed to the increased hardness and homogenous hybrid reinforcement dispersion into the HMMCs. In addition, it was evident that the synergistic combination of different reinforcement particulates in Mg-based alloy improves overall fracture resistance and catastrophic failure and mitigates crack propagation.

Effect of nano-TiO2 particles addition on dissimilar AA2024 and AA2014 based composite developed by friction stir process technique

Aluminum composite materials have gained immense popularity in the construction and aerospace industries as these materials are lightweight, durable, and exhibit a high strength-to-weight ratio. The present study aims to develop dissimilar AA2024 and AA2014-based composite materials using nano-TiO2 reinforcement particles via Friction Stir Processing (FSP) techniques. The FSP technique is a solid-state processing method that is used to modify the properties of metal alloys without altering their chemical composition. The samples were prepared by placing a nano-TiO2over AA2024 and AA2014 aluminum alloys sheet and subjected to FSP process parameters. The microstructure, hardness, and tensile properties of the composite samples were assessed using scanning electron microscopy (SEM), Vickers hardness tester, and tensile testing machine respectively. The results showed that the FSP technique led to the formation of a homogeneous and fine-grained microstructure in the composite samples. The nano-TiO2 reinforcement also provided additional strengthening to the AA2024 and AA2014 aluminum alloys matrix resulting in improved hardness and tensile properties of the composites. The resulting composites exhibited enhanced wear resistance properties. The FSP method presented in this study has implications for extending the properties of other metal alloys, opening up new avenues for research in the field of materials science.

An innovative and alternative approach toward gear fabrication

In this paper, we present the first demonstration of single-step gear manufacturing via an innovative in-situ friction stir forging approach. This novel process is a natural extension to the friction stir processing technique and relies on shear and normal stresses to form the complex shapes. Friction stir welding pin tool with shoulder is plunged at high revolutions per minute (rpm) into the sample to heat it to the desired temperature and enable plastic flow. Then, the tool is forged at high plunge rate to form the desired structurally-sound and defect free complex shapes. To better visualize the process the experiments are complemented by a 3D thermomechanically coupled, smoothed particle hydrodynamics (SPH) model to understand the material flow pattern both radially and through thickness in the gear teeth, plastic strain distribution, and temperature profile. We have demonstrated application of I-FSF to inherently poor formable AZ31 Mg, AA 7075-T6, and AA5083–10 vol% TiB2 composite and fabricated 14-tooth spur gears from these materials with minimal farther machining. Microstructure of the forged gears exhibited a directional material flow pattern due to the normal forging action and refinement of grains to 6–13 μm through dynamically recrystallization across the radial, through-thickness direction, which is in good agreement with the corresponding SPH simulation results.

Development and characterization of grinding sludge-reinforced aluminum-based composite by friction stir process technique

Purpose The quantum of metal particle waste generation in manufacturing industries is posing a great concern for the environment. The iron forging industries generate a huge amount of grinding sludge (GS) waste, which is disposed into the earth. The accumulation of this waste in dump yards causes an increase in soil and air pollution levels. Design/methodology/approach In the current investigation, an effort was made to use this waste GS for the progress of aluminum-based composite. To maintain uniform distribution of reinforcing material, the friction stir processing technique was used. Findings The characterization based on the SEM image of the Al/GS composite revealed that uniform dispersal of reinforcement content can be attained in a single tool pass. Number of grains/inch was approximately 2,402. XRD of GS powder confirmed the presence of SiO2, Fe2O3, Al2O3 and CaO phases. These phases proved GS to be a better reinforcement with aluminum alloy. Tensile strength and hardness were significantly improved in comparison to the aluminum alloy. Thermal expansion and corrosion weight loss were evaluated to observe the influence of GS addition. Originality/value The studies proved that the use of GS as reinforcement material can help in curbing the menace of soil pollution to a large extent.

Surface Modification on Magnesium Alloys’ Hardness and Microstructure Using Friction Stir Processing – A Review

Low density of magnesium-based alloy is one potential as the lightest structural material for light weight-high strength applications for automotive and aerospace. Severe plastic deformation (SPD) together with thermomechanical processing are proved to be a successful method for attaining desired microstructural modifications through achieving fine and highly misoriented microstructures and creating various structures to the bulk properties of magnesium alloy. The material's deformation can result in an altered microstructure that is gainful to the material's requirements. However, the poor deformability of magnesium and its alloys limits the application of the thermomechanical approach. Controlling over temperature and deformation rate is hard to achieve. Among the thermomechanical processes, friction stir processing (FSP) offers an easy way to achieve process stability and mechanical properties enhancement by heat treatment which results in the closure of porosity and refined grain size. During this process, heat is generated by the rotation of the FSP processing tool. Few process parameters such as rotational and traverse speeds should be controlled to make FSP stay within the defined processing condition. It is critical to set the right tool rotational speed as well as traverse speed to ensure adequate heat generation. As there are no established standards for operating the FSP, the only solution is to experiment with different settings to find the best parameter which will produce better quality on processed magnesium alloy workpiece. This paper explores earlier studies on surface modification via FSP technique to improve the mechanical properties strengthening of magnesium alloy mainly on grain size and hardness. The surface modification was done mostly on popular series of magnesium alloy (AZ series) using different tool material, tool geometry and different parameters combination. A comprehensive view of surface modification on magnesium alloys which includes the FSP tool and workpiece material used, variations of FSP parameters settings as well as the effect on hardness and microstructure analysis will be discussed.

Selective alloying of pure aluminum with varying amounts of magnesium using friction stir processing for improved mechanical and corrosion-resistant properties

This study investigates the effects of adding different amounts of Mg to the surface of pure Al substrate using friction stir processing (FSP) technique to prepare Al–Mg solid solutions. For this purpose, machined grooves on the surface of the pure Al plates were filled by bulk Mg blocks and FSPed to form Al–Mg solid solution layers with ∼2.0, 4.5, and 33.9 at.% Mg. The chemical composition, microstructure, and surface Volta potential of the surface alloyed layers were studied by SEM/EDS, XRD, and SKPFM, respectively. The results revealed that incorporating Mg into the Al substrate causes a considerable refinement of the microstructure, resulting in a significant increase in Vickers hardness number from 25 to 208.4 HV (∼734% increase). As the Mg content in the alloyed layer increased, a transition from a single-phase solid solution structure to a dual-phase structure was observed. Based on the potentiodynamic polarization results, it is evident that the corrosion resistance of the single-phase alloyed layer can match that of marine-grade aluminum alloys.