Number Of Friction Stir Processing Passes Research Articles

Investigating the Impact of Friction Stir Processing on the Hydrogen Embrittlement in AA6082-T6 Heat-Treatable Aluminum Alloy

AbstractThis study investigates the impact of friction stir processing (FSP) on the hydrogen embrittlement (HE) in AA6082-T6 heat-treatable aluminum alloy. The effects of different number of FSP passes and different hydrogen cathodic charging (HCC) conditions on the material’s response to HE are examined through comprehensive mechanical testing, microhardness analysis, and microstructural characterization. The results revealed that FSP leads to a decrease in yield strength, ultimate tensile strength, and microhardness, accompanied by an increase in energy absorption. The introduction of hydrogen through HCC significantly reduces mechanical properties, particularly in non-FSPed specimens. Notably, specimens with 8 FSP passes exhibit an interesting behavior with a slight increase in energy absorption and microhardness values after HCC. Microstructural analysis shows that FSP refines the microstructure, resulting in enhanced resistance to hydrogen-induced blistering effects. These findings contribute to the understanding of hydrogen embrittlement in FSPed aluminum alloys, providing insights for developing surface-modified materials suited for hydrogen-rich applications. Graphical Abstract

Enhanced strength ductility and wear resistance in a friction stir processing engineered AZ31B/TiC magnesium-based nanocomposites

ABSTRACTIn the present investigation, efforts have been made to fabricate a magnesium-based AZ31B nanocomposite by integrating nano-sized titanium carbide (TiC) particles via utilising the friction stir processing (FSP) process. The primary objective of the research was to enhance the metallurgical, mechanical, and tribological properties of the base material while investigating the influence of secondary phase particles and various FSP parameters. The findings were rigorously validated through a comprehensive analysis, which encompassed the use of various testing apparatus, such as optical microscopy, field emission scanning microscopy, microhardness testers, tensile and compressive testing machines, along with fractography analysis for wear morphology and tensile properties. The results indicate that the nanocomposite produced under the conditions of a tool rotation speed of 1600 rpm and a transverse speed of 40 mm/min along with three number of FSP passes exhibits superior mechanical and tribological properties compared to both other developed composites and the base alloy. A significant enhancement of nearly 2.68 times in microhardness values along with simultaneous refinement in grain size up to 14.85 times was obtained. Ultimate tensile and compressive strengths report an impressive increase in values up to 2.16 and 1.6 times respectively when compared to the base metal. Furthermore, the tensile fracture behaviour of the base magnesium alloy indicated brittleness, while the AZ31B/TiC composite displayed a combination of ductile and brittle features. In terms of wear morphology, the base magnesium alloy exhibited adhesive and abrasive wear, while the composite demonstrated particle pull-out, delamination, and localised plastic deformation, with enhanced resistance to wear. These findings underscore the significant improvements achieved in mechanical and tribological properties, thus emphasising the novel contributions of this research to the field.

Influence of pass number on microstructure, mechanical, and tribological properties of cold-rolled Al1050 during friction stir processing

In this investigation, cold-rolled Al1050 sheets underwent various passes of Friction Stir Processing (FSP), namely one, three, and five. Then, microstructural evolution was assessed by focusing on underlying restoration phenomena, including severe dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX), and their corresponding effects on mechanical and surface properties were evaluated. Findings illustrated that initial cold-rolling on Al1050 and its high stacking fault energy are the primary driving forces for accelerating DRV, contributing to the supremacy of the DRV-induced softening over sub-grain strengthening caused by CDRX. Increasing the FSP pass number resulted in a drop in yield stress (YS), ultimate tensile strength (UTS), and microhardness values of the FSP-treated samples such that the UTS of one, three, and five passes FSPed samples decreased by ∼18 %, 32 %, and 35 %, respectively, compared to the cold-rolled Al1050. Conversely, the %elongation of the FSP-treated samples dramatically increased with increasing FSP pass number, which is evident from stress-strain curves and the fracture surfaces. Furthermore, increasing the FSP pass number increased the mean coefficient of friction (MCOF) and weight loss during the pin-on-disk test. Also, conducting various passes of FSP improved corrosion resistance compared to the base metal. However, increasing the FSP pass number reduced the corrosion resistance due to grain growth such that the one-pass FSPed sample illustrated better corrosion resistance than the five passes FSPed sample. Repeating the FSP led to excessive frictional heat input to the matrix, contributing to grain growth after increasing FSP passes, thereby decreasing mechanical properties and corrosion resistance.

Assessment of microstructure, biocompatibility and in-vitro biodegradation of a biomedical Mg-Hydroxyapatite composite for bone tissue engineering

In the present study, an Mg-based biomedical composite is fabricated by addition of Hydroxyapatite bioactive nanoparticles into a substrate of bioabsorbable WE43 Mg alloy using multi pass friction stir processing (FSP). The findings indicate that applying 6 passes of FSP leads to a decrease of grain size by over 93%, crushing and redistribution of secondary phase particles within the Mg matrix, improved homogeneity of Hydroxyapatite bioactive particles and a reduction in their agglomeration. In vitro Biodegradation tests prove that as the number of FSP passes increases, the weight loss of fabricated bio-composites and biodegradation rate in simulated body fluid (SBF) decrease. Bioactivity of Mg-based bio-composites is assessed by in vitro immersion in SBF for 28 days. Biomineralization process shows that all fabricated Mg-Hydroxyapatite bio-composites exhibit bone-like apatite forming ability, and cauliflower-shaped Hydroxyapatite crystals form on their surface. Moreover, increasing the uniformity of Hydroxyapatite particles stimulates formation of cauliflower-shaped Hydroxyapatite denser crystals, which improves biocompatibility of bio-composites. Biocompatibility of fabricated bio-composites is also evaluated by MTT assay and DAPI staining. Mg-HA-6P demonstrates the highest number of healthy flattened spindle shaped L-929 fibroblast cells with 83.36% cell viability after 5 days of incubation compared to other samples. Increasing number of FSP passes causes high bioactivity, low biodegradation rate and homogeneous distribution of Hydroxyapatite particles, which in turn improve the viability of L-929 fibroblast cells. Furthermore, with the addition of Hydroxyapatite particles and an increase in the number of FSP passes, the yield strength values of the samples increase, reaching 212 MPa and 226 MPa for the Mg–6P and Mg–6P-HA samples, respectively.

An overview of friction stir processing of Cu–SiC composites: Microstructural, mechanical, tribological, and electrical properties

Copper matrix composite reinforced with SiC exhibits high electrical and thermal conductivity, as well as superior mechanical properties, making it a potential candidate for thermal management applications. There has been rapid progress in the understanding of Cu–SiC metal matrix composites during the past decade. To accomplish this, powder metallurgy, casting, selective laser melting, composite electroforming technology, and electrodeposition methods have been employed. The optimum cutting conditions for fabrication of Cu–SiC metal matrix composites are still being explored. In recent years, friction stir processing (FSP) has become increasingly popular in the fabrication of composites. FSP is capable of microstructural engineering in Cu–SiC systems. In light of the fact that the electrical/thermal conductivity and mechanical performance of Cu–SiC composites depend on microstructural characteristics such as SiC distribution, grain size, grain orientation, density of dislocations, and bulk density, it seems important to study the effect of manufacturing conditions on microstructure in detail. In this study, the influence of FSP parameters such as rotational and traversal speeds, the number of FSP passes, and the pin profile as well as the characteristics of SiC powder are discussed in detail with regard to macro- and microstructure, hardness, strength, tribological, and electrical properties of FSPed Cu–SiC composites.

Fabrication of osteogenesis induced WE43 Mg-Hydroxyapatite composites with low biodegradability and increased biocompatibility for orthopedic implant applications

Good biocompatibility, low biodegradation rate and excellent mechanical properties are essential for desirable performance of metallic biomaterials during osseointegration process. In the present study, bioabsorbable WE43 Mg alloy was used for fabrication of bio-composites with addition of nanosized hydroxyapatite (HA) particles by means of multi pass friction stir processing (FSP) for orthopedic implant applications. Microstructure, in vitro biodegradation and biocompatibility, wettability, and microhardness of resultant bio-composites were characterized. Results showed that applying severe plastic deformation through FSP caused significant grain refinement of Mg matrix and homogenous dispersion of fragmented secondary phase particles. Moreover, applying higher number of FSP passes increased uniformity of distribution of HA nanoparticles throughout Mg matrix. Compared to coarse grain samples, grain refined samples showed lower Mg2+ concentration and H2 evolution in simulated body fluid (SBF). Moreover, addition of HA into Mg matrix, reduced Mg2+ release and H2 evolution. The bio-composites illustrated uniformly and flatly corroded surface compared to samples without HA nanoparticles. During immersion of the bio-composites in SBF solution, a cauliflower structure of Ca–P compounds deposited on the surface of bio-composites which confirmed acceptable biomineralization. Contact angle measurement demonstrated that wettability of fabricated bio-composites increased by increasing number of FSP passes. Mouse osteoblast MC3T3 cell culture indicated that the fabricated bio-composites with uniform distribution of HA nanoparticles showed excellent in vitro biocompatibility, cell viability, and cell proliferation. Eventually, it was found that applying further FSP and presence of HA nanoparticles resulted in increased microhardness which is an indication of higher load-bearing capability of the fabricated bone implants.

Effect of multi-pass friction stir processing on mechanical, microstructural, bioactivity, and corrosion properties of novel magnesium-hopeite composite for biomedical applications

The mechanical properties of magnesium and its alloys are remarkably close to those of natural bone, and they are biodegradable, thus they have been studied for use in consumable bio-implant applications. However, their applicability is constrained by the unpredictable corrosion rate and the moderate bioactivity of Mg-based materials in a biological environment. Considering this, a Hopeite-reinforced magnesium composite was fabricated using friction stir processing (FSP). Along with the many other advantages of FSP, it significantly reduces grain size. The impact of reduced grain size and the presence of Hopeite particles on the control of magnesium degradation was studied. After FSP, there was a significant reduction in grain size owing to severe plastic deformation and dynamic recyclization. The effect of the number of passes was studied using samples with one pass, two passes, and three passes of Mg-Hopeite composite. There was a correlation between increasing the number of FSP passes and improvements in the material's mechanical characteristics, corrosion resistance, and bioactivity behavior. The samples were immersed in simulated body fluid for in vitro bioactivity studies, where it was determined that the 3 passes FSP Mg-Hopeite composite had the greatest Ca/P ratio and hence the best bioactivity, outperforming the 2 passes composite, the 1 pass composite, and pure Mg. Apatite layer formation in FSP Mg-Hopeite composite samples has also conformed to their bioactive behavior. Electrochemical and immersion studies designed to evaluate the corrosion behavior of the material in simulated bodily fluid revealed that grain refinement and an increase in biomineralization led to an improvement in the material's corrosion resistance. Considering the findings, which indicate that 3 passes of FSP Mg-Hopeite composite possess superior corrosion resistance, and bioactive and mechanical properties in comparison to either 1 pass and 2 passes of FSP Mg-Hopeite composite or pure Mg, this material is ideally suited for use as temporary implants for biomedical applications.

Macro- and Microstructure of In Situ Composites Prepared by Friction Stir Processing of AA5056 Admixed with Copper Powders.

This paper is devoted to using multi-pass friction stir processing (FSP) for admixing 1.5 to 30 vol.% copper powders into an AA5056 matrix for the in situ fabrication of a composite alloy reinforced by Al-Cu intermetallic compounds (IMC). Macrostructurally inhomogeneous stir zones have been obtained after the first FSP passes, the homogeneity of which was improved with the following FSP passes. As a result of stirring the plasticized AA5056, the initial copper particle agglomerates were compacted into large copper particles, which were then simultaneously saturated by aluminum. Microstructural investigations showed that various phases such as α-Al(Cu), α-Cu(Al) solid solutions, Cu3Al and CuAl IMCs, as well as both S and S'-Al2CuMg precipitates have been detected in the AA5056/Cu stir zone, depending upon the concentration of copper and the number of FSP passes. The number of IMCs increased with the number of FSP passes, enhancing microhardness by 50-55%. The effect of multipass FSP on tensile strength, yield stress and strain-to-fracture was analyzed.

The effect of multi-pass friction stir processing on microstructure, mechanical properties, and corrosion behavior of WE43-nHA bio-composite

The influence of multiple passes during friction stir processing (FSP) on the evolution of microstructure, hardness, compressive strength, and corrosion behavior of a Mg-based bio-composite has been investigated. WE43 Mg alloy was used as the matrix of the composite and nano-sized hydroxyapatite (nHA) was added as the second material to form the composite. After fabrication of the composite by one pass of FSP, the process was repeated six times. Significant grain refinement and fragmentation of secondary phase particles were observed during FSP. Increasing the number of passes of FSP was found to be associated with pronounced grain refinement coupled with the uniformity in distribution of nHAs. Corrosion resistance is enhanced with an increasing number of FSP passes, which is attributed to the fragmentation and redistribution of secondary phase particles in addition to a homogeneous distribution of nHA.

Parametric optimization of process parameters during friction stir processing of AA5083/(SiC-Gr) hybrid surface composite

Aluminum alloys are among the most widely used material in the manufacturing industries due to their high strength and lightweight properties. To enhance its surface properties, Friction Stir Processing (FSP) proved itself as an efficient method to enhance its microstructural, mechanical, and tribological properties. However, FSP has many process parameters that can affect the final properties of the material. Therefore, an optimized process parameter is required before the use of FSP to obtain the best results. In this paper, a mathematical model has been developed using Response Surface Methodology to predict the hardness of produced surface composite of AA5083 aluminum alloy by using SiC-Gr hybrid reinforcement. FSP was optimized for its hardness (HRB) property by optimizing the FSP process parameters like Tool rotating speed, Tool Traverse speed, number of FSP passes, and the ratio of hybrid reinforcement volume fraction. It was found that the Tool Rotating speed of 1000 rpm, traverse speed of 80 mm/min, 3 number of FSP passes, and Hybrid reinforcement ratio of 75:25 (SiC:Gr) produced the best result with the hardness of 32.6HRB.

Effect of tool pin profiles on the properties of foamable precursor developed by friction stir processing

The high-strength lightweight materials are commonly used in automotive industries. Foam is one such material that has a porous structure which makes it light but at the same time provides good absorbent of impact load. In recent years, friction stir processing (FSP) is commonly used for the development of foam. However, the quality of the foam developed mostly depends on the FSP parameters that control the distribution of foamable particles. Thus in this study, the impact of tool pin profiles and numbers of passes on the distribution of a foamable mixture of AA7075/TiH2 in the substrate has been investigated. The three different tool pin profiles, i.e. straight threaded cylindrical (STC), triangular (TR), and square (SQ) pins are used with 2, 4, and 6 number of FSP passes. It is observed that dispersion of TiH2/AA7075 particles in specimens produced with STC tool pin profiles is more uniform than that of TR and SQ pins, resulting in superior material stirring and flow. A significant reduction in particle clustering and improved mixture distribution has been observed in the STC pin profile. Vickers hardness test shows the SQ and TR pin profiles show higher hardness in the processed zone due to lower exposure of temperature. Microwave heating is used to heat the precursor for the development of foam. It is found that the foam developed by STC pin has superior compressive properties due to uniformly distributed small pores.

Properties Augmentation of Cast Hypereutectic Al–Si Alloy Through Friction Stir Processing

The present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium–silicon castings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainly two approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens were evaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, the specimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porosities and refined silicon particle uniform distribution throughout friction stir processed zone. This endeavour may be considered as a footstep towards more industrial readied material transformation.Graphical

Design of Functionally Graded Composites through Friction Stir Processing

An Investigation was conducted to produce Aluminium based Functionally graded material (FGM) composites by Friction stir processing (FSP). A reinforcement strategy featuring the use of Alumina and TiC reinforcements was investigated, where holes were drilled in an Aluminium plate, filled with reinforcements and stirred using FSP. A mathematical model was formulated for positioning of holes in such a manner that the composition of the reinforcements varies from maximum to minimum over a given length. Samples were subjected to various number of FSP passes from one to three with 100% overlap and its influence on particle distribution and homogeneity was studied using Scanning electron microscopy (SEM) at cross sections parallel to the tool traverse direction. A progressive gradient in hardness values was observed for the surface composites at all the passes.

Optimization of process parameters on the mechanical properties of AA6061/Al2O3 nanocomposites fabricated by multi-pass friction stir processing

In the present investigation, the empirical correlation was successfully developed to predict the input and output responses of the multi-pass friction stir processing (FSP)/Al2O3 nanoparticles at a 95% confidence interval (C.I). The base metal AA6061 was characterized by nanoparticles Al2O3 within the structure of the coarse dendrite. These coarse and dendrites clusters were successfully broken by multi-pass FSP (MPFSP), refined the matrix grains and produced a homogenous microstructure in the stir zone (SZ). The developed model reveals that the nanoparticles Al2O3 and FSP passes were the dominating parameters to enhance the mechanical properties of the MPFSP/Al2O3. The ultimate tensile strength (UTS) and hardness were increased with increases in nanoparticles Al2O3 and the FSP passes. The optimized value of UTS, % strain and microhardness was observed as 220.07 MPa, 13.36%, and 98.44 HV, respectively, while the optimized value of nanoparticles Al2O3 and number of FSP passes were 9.65% and 1.72, respectively.

Investigation of microstructure, crystallographic texture, and mechanical behavior of magnesium-based nanocomposite fabricated via multi-pass FSP for biomedical applications

In this work, the microstructure, crystallographic texture, hardness, and tensile behavior of AZ91/HA bio-nano composite manufactured by multi-pass friction stir processing (FSP) were investigated. With increasing the number of FSP passes, the average size of grains is reduced. The processed AZ91 and AZ91/HA nanocomposite after the third pass had the lowest grain size (4.5 and 2.6 μm, respectively). Also, the average grain size of composites was smaller than that of monolithic samples at the same pass number. The results showed that particle distribution in the AZ91/HA nanocomposite is significantly affected by the number of passes. The increment of the pass number led to a more uniform dispersion of HA nanoparticles in the matrix due to more plastic flow of materials. With increasing the pass number to three, the accumulated strain increased to 0.726 (monolithic) and 0.623 (composite) due to repeating mechanical stirring. There was a texture transition ({101‾1} to {0002}) via performing only one pass of FSP. Suppression of grain rotation by HA nanoparticles maintained the intensity of {101‾1} texture as a corrosion-resistant orientation after the third pass. With increasing the pass number of FSP, the hardness and strength of samples increased due to the grain size reduction and the more uniform dispersion of HA powder. The composite sample after the third pass exhibited the highest hardness of 117.0 HV and ultimate tensile strength of 306.6 MPa. The failure mode of processed samples was ductile. There were smaller dimples on the fracture surface of the composite samples due to their lower grain size and also the presence of HA nanoparticles. Considering the obtained results, the nanocomposite after the third pass can be a good load-bearing implant for biomedical applications.

A review on microstructures and properties of graphene-reinforced aluminum matrix composites fabricated by friction stir processing

Adding reinforcement is an effective way to improve the properties of aluminum alloy. Graphene is an ideal reinforcement for the fabrication of aluminum matrix composites (AMCs) due to its excellent comprehensive performances. Friction stir processing (FSP), as a novel processing technology, is an ideal candidate for fabricating graphene-reinforced AMCs with high performances under appropriate conditions. The present paper firstly summarizes the structure-property characteristics of graphene-reinforced AMCs fabricated by FSP. Then the influences of process conditions on the structure-property evolutions of the composites are discussed. It is found that the addition of graphene leads to grain refinement and texture variation of the stir zone during FSP. Besides, mechanical properties, electrical conductivity, thermal conductivity, tribological property and corrosion resistance of the AMCs are considerably affected by the content of graphene and various microstructure evolutions induced by the added graphene. Composite of reinforcement, adding method of graphene, FSP parameters, FSP pass number and FSP path pattern are critical process conditions that determine the microstructures and properties of the AMCs. The present paper not only concludes major findings of the previous researches but also suggests future recommendations for fabrication of graphene-reinforced AMCs through FSP.

The mechanical properties of AA6082/AA1050 dissimilar joints subjected to multi-pass friction stir processing

This paper reports ‘on the influence of multi-pass friction stir processing (MFSP) on AA6082/AA1050 dissimilar joints produced by friction stir welding (FSW) technique. The produced dissimilar joints were subjected to 1pass (1P), 2pass (2P), 3pass (3P), and 4pass (4P) friction stir processing (FSP) procedure. The microstructural analysis showed the decrease in grain size with an increase in number of FSP passes. However, the tensile properties showed inverse relations with the number of FSP passes and this was linked to the dissolution of strengthening precipitates. The fractographic analysis showed the presence of dimples on all the fractured surfaces and that is an indication ductile fracture. However, the fractured surface of the 4P specimen was characterized by the presence of dimples mixed with flat structures which indicates ductility mixed with brittleness. There was no major influence of the number’ of FSP passes on the microhardness of the AA6082/AA1050 joint.

Development and Parametric Optimisation of Pure Magnesium Matrix Surface Composite by Friction Stir Processing

Friction stir processing (FSP) is an emerging method for improving surface properties of materials by composite fabrication. This study aims at optimizing the major FSP parameters and analysis of their real-time influence on the mechanical performance of a surface composite fabricated with Magnesium (Mg) matrix and Titanium Carbide (TiC) as reinforcement. Effects of different process parameters, tool rotational speed, plunge depth, the linear speed of the tool, cooling condition, and number of FSP passes have been examined. Using L27 array, a total of 27 combinations of these process parameters were analyzed by taking microhardness as an output response to find influential parameters by Taguchi's technique. Maximum micro-hardness was achieved when tool rpm of 600, cooling temperature of -10o C, tool feed of 15 mm/min, plunge depth of 0.35 mm, and 3 passes of FSP tool were chosen with the help of Taguchi's method. Analysis of variance indicated that cooling temperature, the tool feed, and the number of passes of the FSP tool were the most significant parameters.

Effect of Zener-Hollomon Parameter on Microstructure of Aluminum Based Nanocomposite Layers Produced by Friction Stir Processing

For more than a decade, there has been considerable interest in the fabrication of metal matrix composites by employing Friction Stir Processing (FSP). In this study a new model based on Zener-Hollomon (Z) parameter has been developed, which is believed to be the first of its kind, to accurately predict microstructural characteristics of Al-based composites Additionally, the processing window of composite fabrication determined and revealed that sound samples achieve within the range of 2.42 to 24.61 rev/mm for the ratio of rotation speed to travel speed (ω/ν). Recording the peak temperatures during processing beside the optical and Scanning Electron Microscopic (SEM) studies showed that increasing the number of FSP passes and the ratio of ω/ν have a remarkable influence on bolstering the role of nanoparticles in grain refinement. Results also indicated that the mean grain size of FSPed samples and matrix of nanocomposites decreases with an increase in the Z parameter. Finally, particular equations for various numbers of passes developed, which make a correlation between the grain size of Al-based composites and the FSP parameters via Z parameter.

Synthesis of radar-absorbing NiFe2O4 nanoparticles and effects of pass number on mechanical properties of AA7075/NiFe2O4 surface nanocomposites fabricated by FSP

In this paper, first, the desired NiFe2O4 nanoparticles were produced using the hydrothermal method then the AA7075/NiFe2O4 surface nanocomposite was fabricated by the friction stir processing (FSP) method. The results show that the hydrothermal method is very suitable for making NiFe2O4 nanoparticles with a fine and uniform structure that the fabricated nanoparticles have a superparamagnetic property that can be used for radar-absorbing coatings. The nanoparticles were well distributed in the base AA7075 aluminum alloy sheet in addition to the fine-grained structure achieved using FSP. The microhardness of the FSPed and surface nanocomposites were significantly improved compared to the base metal and increased with the increasing pass number of FSP. Also, the tensile properties consist of the ultimate tensile strength (UTS), formability, and toughness decrease with increasing the number of FSP passes.