Mechanical Properties Of Friction Stir Research Articles

Microstructure and mechanical properties of friction stir welded Haynes 282

Advanced ultra-supercritical (A-USC) steam plants are designed to operate at high temperatures and pressures due to the necessity for higher operational efficiency. The extreme operating conditions of A-USC requires the deployment of precipitation strengthened Ni-base alloys that exhibit elevated temperature strength and good fabricability. Fusion welding of precipitation strengthened nickel alloys lead to solidification cracking in fusion zone and/or liquation cracking in heat affected zone. Therefore, an alternative non-melting welding technique is a necessity to efficiently join nickel alloys. In the current study, friction stir welding, a solid-state joining technique was implemented on a precipitation strengthened nickel-based superalloy, Haynes 282. Detailed microstructural and mechanical properties characterization was carried out. The processed region exhibited wrought, fine-grained microstructure, absence of weld defects such as voids and cracks and absence of elemental segregation. Both hardness and cross-weld tensile tests demonstrated that the weld region was stronger than the base material. And the cross-weld tensile samples failed in the base material. Based on joint efficiency analysis, friction stir welded Haynes 282 outperformed fusion welds.

Effects of tool wear on the microstructure evolution and mechanical properties of friction stir welded TA5 alloy

Effects of tool wear on the microstructure evolution and mechanical properties of friction stir welded TA5 alloy

Effects of different cooling conditions on friction stir processing of A356 alloy: Numerical modeling and experiment

In the present work, the effects of in-process cooling are investigated on the material flow, temperature distribution, axial force, wear resistance, and microstructural and mechanical properties of friction stir processed (FSPed) Al-Si aluminum alloy. The finite element method (FEM) was developed for modeling the process, based on the eulerian-lagrangian technique, and then verified by the experimental force and temperature histories. Next, the material flow and temperature distribution during the friction stir process (FSP) with in-process cooling under different conditions were considered. After that, the experimental investigations, including the optical microscopy, hardness, and wear tests, were conducted. Finally, the stir zone (SZ) shape obtained by experiments and simulation model were compared for the FSPed samples without cooling and with air cooling. The material flow achievements reveal that using a coolant affects the material flow in the pin-driven zone more significantly than in the shoulder-driven zone, leading the SZ to change from the basin shape into the V shape. The SZ shapes obtained from the experiments and the simulation model show a good agreement between the shapes of the samples FSPed without cooling and with air cooling. Moreover, experimental results showed that using in-process cooling reduces Si particles' size and thus significantly increases the hardness and wear resistance. The Si particles size is reduced from 10 μm in the base metal to 2.6 μm and 2 μm in the air-cooled and water-cooled samples. Consequently, the wear mass loss reduced almost 28% and 40%, and hardness increased almost 35% and 80% for the air-cooled and water-cooled samples compared to the processed samples without coolant.

Microstructure and Mechanical Properties of Friction Stir Welded 2205 Duplex Stainless Steel Butt Joints.

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.

Modification of mechanical properties of friction stir welded AM60 magnesium alloy with changing rotational speed and addition of nano alumina particles

Modification of mechanical properties of friction stir welded AM60 magnesium alloy with changing rotational speed and addition of nano alumina particles

Investigations on the Effect of Cyclic Heat Treatment on the Mechanical Properties of Friction Stir Welded Aluminum Alloys (AA5052 & AA6061)

Investigations on the Effect of Cyclic Heat Treatment on the Mechanical Properties of Friction Stir Welded Aluminum Alloys (AA5052 & AA6061)

Effect of Laser Shock Peening on micro-structure and mechanical properties of Friction Stir Welded CuCrZr sheets

Friction stir welding (FSW) of CuCrZr sheets was performed and Laser Shock Peening (LSP) was carried out as a post-weld surface treatment. Effect of LSP on hardness, tensile and fatigue strength was investigated. Depth of compressive residual stress in base material increased from 550 μm to 700 μm when the number of LSP shots was increased from one to five. However, noticeable change in surface residual stress could not be observed which is attributed to the saturation of dislocation density or plastic deformation at the surface. An increase in yield strength up to ∼35% as well as an improvement in the fatigue life up to ∼70% after LSP could be achieved for base and FSW specimens. Increase in low angle grain boundaries after LSP indicates the increase in substructure induced by plastic deformation. A quantitative analysis using grain boundary misorientation and kernel average misorientation was used to understand microstructural changes due to the LSP and correlate it with the mechanical properties.

Study of Material Flow and Mechanical Properties of Friction Stir Welded AA2024 with AA7075 Dissimilar Alloys using Top-Half-Threaded Pin Tool

This research work was aimed at evaluating the material flow behavior and mechanical properties of dissimilar aluminum alloys (2024 and 7075) joints prepared by friction stir welding using a tool with top-half-threaded pin. Macro and microstructural study for material flow investigation was carried out. Whereas mechanical properties of welded joints are examined using tensile and micro-Vicker's hardness tests. Zeiss EVO 18 SEM was used for the fractographic study. Average grain sizes were determined at various weld regions. The effect of grain size with the hardness and strength has been discussed. The results demonstrate that the thread's location on the pin significantly affects the flow of the material. The area where the material has been severely plasticized and moved was located at the weld root. Hence welding root defects like void, pinhole, insufficient filling, etc. are avoided. The tensile strength of friction stir welded joint was 312.7 MPa, equivalent to the joint efficiency of 66.5 %. HIGHLIGHTS The threaded pin tool pushed the soft material downwards hence avoiding root defects. The onion ring structure formation has been observed The tool pin is responsible for creating two separate regions at weld line: Low flow region at the top and high flow region at central areas The maximum tensile strength obtain is 312.7 MPa and 66.5 % joint efficiency GRAPHICAL ABSTRACT

Tribological behavior and mechanical properties of friction stir processed HDPE/Fe-Fe3O4 composites

In the current work, high density polyethylene (HDPE) composites were fabricated via Friction Stir Processing (FSP). A two-phase Fe-Fe3O4 powder was used as the reinforcing agents. The extremely low cost powder was obtained from shot-blasting of as-forged low carbon steel components. X-ray diffraction (XRD) was used to phase analysis and evaluation of the purity of the as-received powder. The size distribution of the powder was determined by Laser Particle Size Analysis (LPSA). Also, Scanning Electron Microscopy (SEM) was employed to investigate the particles morphology. The processing used a cylindrical tool to impose the severe plastic deformation and material stirring in order to improve the mechanical properties and particles distribution. The tribological and mechanical properties of the fabricated samples were examined. According to the results, both the friction coefficient and specific wear rate of FSPed samples reduced remarkably. The hardness and tensile strength of the FSPed composites were higher than the FSPed HDPE samples; however, their elongations were lower.

Effect of microstructure heterogeneity on the mechanical properties of friction stir welded reduced activation ferritic/martensitic steel

The microhardness distribution in the different zones of a friction stir welded reduced activation ferritic/martensitic steel has been investigated and correlated to the hierarchical martensitic microstructure in the respective zones, characterized by electron backscatter diffraction orientation analysis. It is found that the variation of prior austenite grain size, packet size, and block width in different subzones is influenced by the peak temperature and effective strain rate during the friction stir welding process. The distribution of the microhardness correlates directly with the geometrically necessary dislocation density observed in the different zones.

Effect of Heat Input on Microstructure and Mechanical Properties of Friction Stir Welded AA6092/17.5 SiCp-T6

Effect of Heat Input on Microstructure and Mechanical Properties of Friction Stir Welded AA6092/17.5 SiCp-T6

Effect of Welding Parameters and Artificial Aging on Mechanical Properties of Friction Stir Welded AA 7004 Alloys: Experimental and Artificial Neural Network Simulation

Effect of Welding Parameters and Artificial Aging on Mechanical Properties of Friction Stir Welded AA 7004 Alloys: Experimental and Artificial Neural Network Simulation

Influence of aluminium-rich intermetallics on microstructure evolution and mechanical properties of friction stir alloyed Al Fe alloy system

In the present investigation, the AlFe alloy system is developed by using the solid-state friction stir alloying (FSA) technique. The objective is realized by using multiple passes (1–4) of FSA with 100% overlap at constant process parameters. The TEM analysis confirms the interfacial reaction between the Al and Fe particles leading to the formation of nano-sized hard and brittle Al13Fe4 intermetallic (IMC) phase. The SEM, EDS, and XRD analysis also indicates the existence of a very small amount of Al5Fe2 IMC layer at the AlFe interface. The microstructural analysis from EBSD confirms that the grain size is reduced from ~27 μm in the base material to ~2 μm in the 4 pass FSAed AlFe alloy through dynamic recrystallization mechanism. The microhardness in the SZ is increased by ~14% in the 4 pass FSAed AlFe alloy as compared to that with 1 pass. The increased hardness of AlFe alloys as compared to the 4 passes processed Al alloy (without Fe) suggest that the AlFe alloys system presented here can be an alternative solution for underwater friction stir welding (UFSW) to compensate for the stir zone softening occurred by the high heat input process parameters or precipitate dissolution in the heat treatable Al alloys. The ultimate tensile strength and percentage elongation are increased by ~30% and ~48% in the 4 pass FSAed AlFe alloy as compared to the alloy fabricated at 1 pass, respectively. The increased strength and hardness of the 4 passes FSAed alloy is attributed to the increased reaction rate between Al and Fe particles owing to the higher heat input which results in the precipitation of a more number of Al13Fe4 IMC phases during 4 passes. Also, the uniform dispersion of nano-sized IMC phases in 4 passes FSAed alloy as compared to the alloy fabricated with 1 pass, contribute significantly to the dislocation blockade and dispersion strengthening mechanism. The shreds of evidence provided in the present investigation suggest that the precipitation hardening is the dominant strengthening mechanism in the AlFe alloy system as compared to the Hall-petch strengthening mechanism.

Investigation on the microstructures and mechanical properties of friction stir processed 2A14 aluminum alloy fabricated by different initial precipitation states

Six-millimeter-thick 2A14 Al alloy plates were friction stir processed (FSP) with different initial precipitation states of as-cast, homogenization, rolling, and T6. The results indicated that FSP can dramatically reduce the grain and particle size and promote the formation of fine recrystallized grains with random orientation in the stirred zone (SZ). No significant influences of the initial precipitation states of base metal (BM) on the grain size, grain boundary characteristic, texture component, and texture intensity of SZ were perceived. Rather, the initial precipitation states can evidently affect the morphology and distribution of precipitates and dislocations. The dominant C and A1* texture components developed in the SZ are correlated with the shear deformation and dynamic recrystallization. And the weakened texture intensity created in the SZ after FSP also signifies that discontinuous dynamic recrystallization might be involved. Compared with the corresponding BM, the SZ fabricated by the BM under as-cast and homogenized states was strengthened arising from the obvious refined grains, uniform dispersed particles, and elimination of casting defects caused by FSP, while the softening of SZ was observed for the BM under rolled and T6 states, which are mainly dependent on the reduction of dislocation density and dissolution/coarsening of fine precipitates during FSP.

Enhancing corrosion resistance and mechanical properties of dissimilar friction stir welded 5083-6061 aluminium alloys using external cooling environment

Dissimilar friction stir welding of AA5083-AA6061 alloys in different cooling environments (air, liquid nitrogen, and water) was successfully employed as an alternative method to enhance corrosion resistance and mechanical properties. The evolution of microstructure, corrosion behavior, and mechanical properties of friction stir welded joints were studied using optical microscopy (OM), electron backscattered diffraction, scanning electron microscope, electrochemical workstation, and universal testing machine. The results indicated that the width of the stir zone and grain size of heat-affected zones were reduced by the use of external cooling media. Electron backscattered diffraction results showed that the grain size in air-cooled friction stir welding, nitrogen-cooled friction stir welding and water-cooled friction stir welding were 7.6 µm, 4.5 µm, and 3.2 µm, respectively, and water-cooled friction stir welding joint developed a larger fraction of high-angle grain boundaries at stir zone. The intermetallics formed in the joints using cooling media were finer compared to that of the air-cooled samples. The corrosion behavior of the stir zone was impacted by the cooling environment while potentiodynamic polarization results revealed that the water-cooled friction stir welding joint showed excellent corrosion resistance due to the finer size of intermetallics. The minimum hardness values shifted to the stir zone in the case of nitrogen-cooled friction stir welding and water-cooled friction stir welding from the heat-affected zone location as in the air-cooled friction stir welding joint. For the joint made with water-cooled friction stir welding, maximum yield strength was obtained with a joint efficiency of 96% relative to AA5083 base material.

Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel

In the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min/min). A defect free weld was witnessed for both of the welding conditions. The mutual effect of severe plastic deformation and frictional heat generation by pin rotation during the FSW process resulted in grain refinement due to dynamic recrystallization in the stir zone (SZ) and thermo-mechanically affected zone (TMAZ). Lower tensile elongation and higher yield and ultimate tensile strengths were recorded for welded-samples as compared to the base material (BM) DP780 steel. The joints were subsequently annealed at various temperatures at 450–650 °C for 1 h. At higher annealing temperature, the work hardening rate of joints gradually decreased and subsequently failed in the softened heat-affected zone (HAZ) during the uniaxial tensile test. Reduction in yield strength and tensile strength was found in all PWHT conditions, though improvement in elongation was achieved by annealing at 550 °C. The digital image correlation analysis showed that an inhomogeneous strain distribution occurred in the FSWed samples, and the strain was particularly highly localized in the advancing side of interface zone. The nanoindentation measurements covering the FSWed joint were consistent with an increase of the annealing temperature. The various grains size in the BM, TMAZ, and SZ is the main factor monitoring the hardness distribution in these zones and the observed discrepancies in mechanical properties.

Effect of Heat Input on Microstructure and Mechanical Properties of Friction Stir Welded AA2024 and AA7075 Dissimilar Alloys

Effect of Heat Input on Microstructure and Mechanical Properties of Friction Stir Welded AA2024 and AA7075 Dissimilar Alloys

Effect of Axial Load-Dependent Deformation Rate on the Grain Size Distribution and Mechanical Properties of Friction Stir Processed Copper

Abstract During friction stir processing (FSP), the combination of rotation and movement of the tool leads to frictional heat generation and plastic deformation at the tool-material contact surface, leading to a microstructurally refined formation region. The deformation rate in the material can be altered by varying the axial load by increasing or decreasing the tool’s plunging depth. In the present study, FSP was carried out on a pure copper plate of 3-mm thickness by varying the plunge depth from 2.3 to 2.6 mm for a tool pin length of 2.4 mm. The microstructure of the processed samples was studied by optical microscopy, and the grain size was measured by the linear intercept method. Tensile testing was carried out perpendicular to the processing direction. The grain size distribution was narrower at low axial loads and wider at the higher axial loads, measured between 1 and 120 µm. At higher axial loads, microstructure consisted of bands indicative of the heterogeneity in the deformation. The formation of bands at higher axial loads leads to improved mechanical properties. The ductility of the processed materials at higher axial loads was 16%, which was four times the increase observed at lower axial loads (4%). The formation of a bi-modal microstructure (alternating layers of fine and coarse grains) at high axial load enhanced the processed materials’ strength and ductility.

Effect of traverse and rotational speeds on microstructure, texture, and mechanical properties of friction stir processed AZ91 alloy

In the current work, the influences of both traverse and rotational speeds of friction stir processing (FSP) on the microstructural evolution, crystallographic texture, and mechanical properties of AZ91 alloy were investigated. The tool traverse and rotational speeds used in the present study were 20, 40, 60 mm/min, and 400, 800, 1200 rpm, respectively. The average grain size significantly decreased from 61.6 μm in the as-cast condition to below 10 μm in the FSP-processed samples owing to the occurrence of dynamic recrystallization (DRX). By increasing the tool traverse speed and decreasing the rotational speed, the grain size reduced. The grain boundaries pinned by fine β-Mg17Al12 particles, retarding the grain growth. The fraction of the β-Mg17Al12 remarkably decreased after the FSP owing to fragmentation and dissolution. The high strain rate of the 800–40 and 1200–40 samples coupled with their higher peak temperatures increased the dissolution of β-Mg17Al12 during FSP. It was found that a texture transition from (10.1) pyramidal to (00.2) basal occurred by decreasing the traverse speed and increasing the rotational speed. The highest microhardness, which was equal to 104.4 HV, belongs to the 800–20 sample due to its very fine grains. When the rotational speed increased from 400 to 1200 rpm, the ultimate tensile strength (UTS) improved from 236.8 to 267.1 MPa, the total elongation (TE) decreased from 7.5% to 6.6%, and the energy absorption (EA) improved from 13.1 to 14.2 J/cm3. These results were due to the higher accumulated strain, the larger solid solution strengthening, the lower aspect ratio of β-Mg17Al12, stronger {0002} texture, and the lower content of β-Mg17Al12 of the 1200–400 sample. The UTS and TE of the 1200–40 sample showed an enhancement of 96.4% in UTS, 26.9% in TE, and 132.8% in EA as compared to the as-cast AZ91. Up to the true strain of 0.05, with increasing the rotational speed, the strain hardening rate increased owing to decreasing the fraction of grain boundaries. After the true strain of 0.05, the strain hardening rate reduced by increasing the rotational speed due to strengthening the {0002} texture. The fractured surface of the 800–20 sample had the largest number and smallest size of dimples as compared to the other FSP-processed samples owing to its lowest grain size. Finally, the strong {0002} basal texture in the 800–40, 1200–40, and 800–20 samples led to tear ridges aligning with the normal direction of fractured surfaces.

Fatigue and fracture behaviour of Friction Stir Welded AA-2024-T351 joints

The presented paper deals with the mechanical properties of Friction Stir Welded (FSW) AA2024-T351-joints. The material’s response to the static and fatigue strength (S–N curve) is summarised from previous work and referenced, while the testing methods and results for the fatigue and fracture mechanics’ parameters regarding to the fatigue crack growth and occurrence of final fracture are discussed in the greater details and represent the main contribution of this work. The evaluation of the obtained experimental results was performed for three different welding speeds (v = 73, 116 and 150 mm/min), which enabled the determination of the most appropriate welding speed in regard to the fatigue and fracture behaviour of the analysed FSW-joint. The highest value of the threshold stress intensity factor range, ΔKth, and, consequently, the highest resistance against crack extension, was obtained for the welding speed v = 116 mm/min. A similar conclusion was observed when determining the fracture toughness KJIc, where the highest value was obtained for the same welding speed. On the other hand, not significant differences in the slope m were obtained between the considered welding speeds when analysing the fatigue behaviour in the modified Paris diagram. In that respect, it can be concluded that the welding speed v = 116 mm/min is favourable in regard to the fatigue and fracture behaviour of the analysed FSW-joint.