Mechanical Properties Of Friction Stir Research Articles

Tool rotational speed variant response on the evolution of microstructure and its significance on mechanical properties of friction stir welded 9Cr-1Mo steel

Abstract In this study, the effect of the tool rotational speed on the microstructure evolution and its significance on the mechanical properties of friction stir welded 9Cr-1Mo (P9) steel is investigated, and its properties are compared with A-TIG welding process. Friction stir welding (FSW) was carried out at two different rotational speeds viz., 200 rpm and 500 rpm with the constant traverse speed of 30 mm/min using the W-La2O3 tool. The consequence of this study showed that irrespective of tool rotational speed, the better tensile properties are achieved by the FSW process, and it is comparable to the A-TIG welded joint. This study proved that FSW is a potential welding technique for welding of P9 steel, and also, there is scope to avoid PWHT by lowering the tool rotational speed (

Microstructure gradient characteristics and mechanical properties of friction stir welded high strength QP980 steel

Friction stir welding (FSW) was carried out on 1.2 mm thick QP980 steel plate and W-Re stirring tool was used for FSW. This study focused on the microstructure gradient characteristics and mechanical properties of QP980 FSW joints. The FSW joints without defect could be obtained under welding parameter of 400 rev min−1–400 mm min−1. The martensite was the mainly microstructure in the stir zone (SZ) and the microhardness of the SZ was increased to about 480 HV. The martensite of the subcritical heat affected zone (SCHAZ) underwent tempering transformation and decomposition, small amount of carbides were precipitated from the martensite, so the microhardness of the SCHAZ was slightly decreased. The microstructure in the SZ had the highest dislocation density and the highest fraction of low angle boundaries. The tensile test results indicated that the joints were broken in the base metal (BM), which indicated that the FSW joints had excellent performance.

Effect of pin offset on the mechanical properties of friction stir welded AA 6013 aluminum alloy plates

AbstractIn this study, AA 6013 aluminum plates were butt‐welded with friction stir welding via pin offset technique. Macrostructural observations revealed that kissing bonds, originated from the broken oxide layers, were found to occur in the welded joints. The fracture location of welded joints after tensile tests was found to be outside the joint area, revealing that kissing bonds which were formed in the stir zone exhibited no detrimental effect on the mechanical properties of joints. Microstructural observations revealed that phases belonging to Mg2Si, Al4Cu2Mg8Si7 and Al(MnFe)Si were observed in the x‐ray diffraction pattern of friction stir welded joints. The highest tensile strength with a value of 206 MPa was achieved with the process parameters of 1.5 mm pin offset towards the advancing side and 500 min−1 tool rotational speed, leading the ratio of tensile strength of joint to ultimate tensile strength of base metal, also known as joint efficiency, to reach 74 %.

Effects of cooling condition on microstructural evolution and mechanical properties of friction stir processed 2A14 aluminum alloy

Detailed analysis on the microstructural evolution and mechanical properties of 2A14 aluminum alloy subjected to friction stir processing (FSP) under different cooling conditions has been conducted. SEM, EBSD and TEM were used to reveal the microstructure characteristic, while the microhardness and tensile tests were also performed. The results showed that microstructures formed by fine, equiaxed and highly misoriented grains with the average grain size in the range of 1.19∼3.1 μm were obtained in the stirred zone (SZ). Compared with FSP under air cooling, rapid cooling can significantly reduce grain size, second phase particles size and fraction of high angle grain boundaries in the SZ. Besides, recrystallized grains with random orientation are formed throughout SZ during FSP. The microtexture analysis also demonstrated the dominance of shear texture ({hkl}〈110〉 and {111}〈uvw〉 fibers), with C and A1* components are produced through the geometrically dynamic recrystallization mechanism. And the texture intensity in SZ of the samples is slightly increased with accelerated cooling method, indicating that another mechanism of grain refinement through discontinuous dynamic recrystallization might be involved. Additionally, the strength and microhardness of friction stir processed samples were improved with increasing the cooling rate due to grain refinement, the increase of dislocation density and fine and uniformly distributed second phase particles.

Effects of Cooling Conditions on Microstructure and Mechanical Properties of Friction Stir Welded Butt Joints of Different Aluminum Alloys

The aim of this work is to evaluate the difference between the properties of several aluminum alloy joints welded with the traditional air-cooled friction stir welding process and others obtained by the combination of the traditional friction stir welding setup with a water-cooling system. In particular, precipitation-hardening alloys AA2024-T3, AA6082-T6 and AA7075-T6, and a work-hardening alloy, AA5754-H111, were taken into account. From Rockwell and Vickers hardness maps, it was possible to observe a clear dependence of the hardness distribution on the cooling systems; joints obtained using a water-cooling system showed higher values of hardness, reached in the central zone and a narrow area interested by the hardness reduction for all the tested alloys. From tensile tests executed orthogonally to the welding direction, it was possible to observe that the alloys have responded differently in terms of ultimate tensile strength and final elongation when the water-cooling system was used. The microstructural analysis of the three precipitation-hardening alloys showed a larger average grain size in the nugget zones for the water-cooled condition. Moreover, in the thermo-mechanically altered zones of the water-cooled AA6082 and AA7075 joints, the grains were characterized by a smaller average size than the grains of the same air-cooled welds.

Microstructure and mechanical properties of friction stir welded duplex Mg–Li alloy LZ91

Superlight duplex Mg–Li alloy LZ91 with a thickness of 3 mm was successfully joined by friction stir welding utilizing a tungsten carbide tool. The microstructures in the stir zone showed refined grains consisting of an equiaxed Mg-rich α phase and a Li-rich β phase. The grains in the Mg-rich α phase showed randomized crystal orientations after dynamic recrystallization. Due to the grain refinement and the random orientation of the Mg-rich α phase, the mechanical properties of the stir zone were optimized, and the hardness of the stir zones were higher than that of the base metal. At the same time, the heat affected zone showed no decrease in its strength. Digital image correlation analyses revealed that the strain in the stir zone and base metal were respectively 0.05 and 0.6 before the samples fractured during the joint tensile tests. Therefore, the joints demonstrated 100% tensile efficiency compared with the base metal.

Mechanical Properties Evaluation of Friction Stir Welded AA6061-AA7075 Alloys for Different Tool pin Geometries

The friction stir welding is a solid state welding in which welding takes place at a temperature below the melting point. This welding is also known as green technology welding as no harmful gases are generated, as well as fluxes are not formed. In this process joining of two dissimilar materials can be achieved. Through this welding one can overcome defects like porosity, solidification, cracks etc by selecting suitable wilding parameters. Present work investigates the effect of different tool pin geometries on mechanical properties of friction stir welded AA6061 and AA7075 alloys keeping the process parameters constant. The welding is carried with process parameters 1000rpm, 50mm/min and 5KN as tool rotational speed, welding speed and axial load respectively, and for four different pin geometries: (a) cylindrical pin, (B) triangular pin, (c) square pin and (d) hexagonal pin. The welded samples are characterized by mechanical properties like tensile strength and micro Vickers hardness test. By considering the both properties the hexagonal pin shown better characteristics under optimum process parameters.

Microstructure and Mechanical Properties of Friction Stir Welded Joint of an Aluminum Alloy Sheet 6005A-T4

The 6005A-T6 alloy had been widely applied in rail transmit industry due to its combination properties of moderate strength, superior resistance to corrosion, and excellent extrusion plasticity. However, few reports were related to the 6005A-T4 alloy in spite of it also presenting considerable properties. In this work, we introduced the FSW method to investigate the weldability and mechanical properties of a thin plate aluminum 6005A-T4 to evaluate its potential application. Fully recrystallized microstructure was obtained in the nugget zone, characterized by equiaxed grain with a size of 2.2 μm under current welding parameters. The tensile strength can reach as high as 174 ± 2 MPa with the absence of β phase, which is equivalent to 83.8% of that of base metal. The dissolution of β phase will dramatically reduce the micro-indentation hardness down to as low as 58 HV0.2 and the fine grain, for example 2 μm in this work, will reversely raise this value up to 64 HV0.2. Our investigation provides some perspectives to understand weldability, mechanical properties of the 6005A-T4 alloy, and develop its further applications in the related field.

Microstructural Development and Mechanical Properties of Friction Stir Welded Ferritic Stainless Steel AISI 409

This work investigates the effect of friction stir welding process parameters (rotation rate and traverse speed) on the microstructural evolution of friction stir welded (FSWed) ferritic stainless steel (FSS) AISI 409. Optical microscope, scanning electron microscope and electron backscattering diffraction are used to quantitatively assess the development in grain structure and texture. The microstructural development suggested that thermo-mechanical deformation occurs in the stir zone within the austenite/ferrite phase region, ultimately transforming upon cooling into bainitic/ferritic microstructure. The fraction and size of the bainitic/ferritic grains are found to vary through the thickness of the joints. High fractions of coarse ferritic grains are found near the top of the stir zone, and low fraction of fine ferritic grains is found near the bottom of the stir zone. This bainitic/ferritic grain structure resulted in an increase in the hardness of the stir zone by about 74% relative to the base material. The tensile strength of the FSWed FSS joints is almost at the same level of the base material with reduction in the ductility as a result of the increased hardness of the weld zone.

Effect of Heat Treatment on the Microstructure and Mechanical Properties of the Friction Stir Processed AZ91D Magnesium Alloy

We study the microstructure and mechanical properties of friction stir processed AZ91D cast magnesium alloy under various conditions of heat treatment. It is shown that, in the initial as-cast state, the structure of the alloy contained a continuously networked β-phase with an average grain size of 150 μm. The friction stir processed (FSP) specimens had an average grain size of 12 μm and smooth grain boundaries. The subsequent heat treatment of the FSP specimens at various temperatures between 150°C and 250°C led to the appearance of numerous particles of the β-phase. The FSP specimens heat-treated at 200°C had finer grains, a larger number of fine particles of the β-phase, and better mechanical properties than any other specimens.

Evaluation of Microstructure, Hardness and Mechanical Properties of Friction Stir Welded Al–Ce–Si–Mg Aluminium Alloy

A vast majority of the research on friction stir welding(FSW) is mainly focused on welding of aluminium alloys. The research studies in this paper are based on one such alloy known as Al–Ce–Si–Mg aluminium alloy, of which, the microstructure and other mechanical properties of the friction stir welded joints are yet to be studied. The plates of Al–Ce–Si–Mg aluminium alloy were friction stir welded using a non consumable, rotating tool with triangular profile pin and circular shoulder, with different combinations of tool rotation speeds and weld speeds. The microstructure, hardness and mechanical properties of the weld were analyzed. The microstructure of the weld zones revealed that, the average grain size at the bottom of the Nugget Zone (NZ) is 5 ± 0.12 μm and gradually increases to 15 ± 0.23 μm at the top of the NZ. In the TMAZ the grain size is 20 ± 0.14 μm and is bigger compared to the NZ. In the HAZ, the grain size is around 37 ± 0.21 μm and is bigger than that in the TMAZ. The maximum Vickers hardness value at the NZ center is 231.9 ± 2 Hv, and uniformly reduces to 100 ± 2.4 Hv in the TMAZ and 65 ± 1.3 Hv in the HAZ and then increases to 98 ± 1 Hv in the base material (BM). The maximum ultimate tensile strength (UTS) of FSW joint was found to be around 102.55 ± 3 MPa with elongation at fracture of 2.5%. The BM UTS was 154 ± 4.5 MPa. For a tool rotation speed of 800RPM and a weld speed of 20 mm/min a maximum joint efficiency of 67%. was obtained. Hence these were chosen as the optimum process parameters to join the alloy Al–Ce–Si–Mg by FSW.

Effect of Process Parameters on Structure and Mechanical Properties of Friction Stir Welding Joint of 5052 Aluminum Alloy

2.5 mm thick sheets of AA5052 were welded using friction stir welding technology. The effects of welding speed, rotational speed of pin, length of pin, single-side and double-side welding process on the morphology, microstructure and mechanical properties of welded joints were studied and analyzed. The failure mode was studied. The results show that the joints with good mechanical properties and without welding defects can be welded when the rotational speed of pin is 500-1200r/min and the welding speed is 100-480mm/min. The microstructure of weld nugget is mainly composed of α phase solid solution and β phase particles. The process parameters of friction stir welding have great influence on the static strength of welded joints. The static strength increases with the increasing of rotational speed of pin, however decreases with the increasing of welding speed. The peak load of the double-side welding increases by 30% compared with the single-side welding. The length of pin has little effect on the tensile strength. The tensile fracture of the single-side welding is located in the weld nugget zone, whereas the fracture of double-side welding is located in the base material zone.

Study of microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

Study of microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

Evaluating the microstructure and mechanical properties of friction stir processed Al–Si alloy

ABSTRACTIn this study, mechanical behaviour and microstructural evolution in friction stir processing (FSP) of casting hypereutectic A390 aluminium alloy have been investigated. The mechanical behaviour of FSP samples was investigated by measuring the strain rate sensitivity using shear punch testing. The room-temperature shear punch tests were conducted at shear strain rates in the range of 10−4–10−1 s−1. The results indicate that the strain rate sensitivity index increases from about 0.015 to 0.120 for as-cast A390 after third FSP pass and then experiences a further growth in FSP passes. The increase in the grain size and CuAl2 intermetallic particle size result in a reduction in strain sensitivity index as well as shear strength after third FSP pass.

Investigation of residual stress distribution of dissimilar Al-7075-T6 and Al-6061-T6 in the friction stir welding process strengthened with SiO2 nanoparticles

In this study, residual stress distribution and mechanical properties of friction stir welded dissimilar 7075-T6 and 6061-T6 aluminum alloys were investigated. Welding and rotational speeds were defined using trial and error method in order to reach non-defect welding samples without any crack or cavity. With the selection of H13 steel as the material of the tool, shoulder diameter of 30 mm and Taper Cylindrical Threaded (TCT) pin with 6 mm diameter, non-defect welds achieved. Rotational speeds of 450, 560, 710, 900 RPM with welding speeds of 25, 31.5, 50, 80 mm/min were set together, respectively. In other conditions defects of cavity and low surface quality could be obtained. Contour method was used to determine residual stress distribution at the weld zone. With investigation of the residual stresses distribution, it was observed that they were tensile in the center of the cut sample, and compressive on the edges. Considering the lowest value of yield strength (YS) for the base metal in this research which was 292 MPa for Al-6061-T6 alloy and the highest value of residual stress which was 63.2 MPa, it can be concluded that the residual stress amount is 21.6% of the YS of the base Al-6061-T6 alloy. Also, to increase the metal’s yield strength and ultimate tensile strength, SiO2 ceramic nanoparticles used as a reinforcing phase. With adding the SiO2 nanoparticles, the ultimate tensile strength (UTS) increased but the YS and the residual stress decreased.

Effect of welding speed and post-weld aging on the microstructure and mechanical properties of friction stir welded B4Cp/6061Al-T6 composites

2.9 mm thick 20 wt% B4Cp/6061Al-T6 composite sheets were friction stir welded using a threaded cermet tool at welding speeds of 50–400 mm/min and a tool rotating rate of 1000 rpm and then subjected to post-weld artificial aging. Sound joints were achieved under all welding speeds. The threaded cermet pin only exhibited slight abrasion at the top thread of the screw after all of the welding operations with a total length of 1200 mm. The B4C particles were blunted and fragmented, and uniformly distributed in the nugget zone (NZ), due to the severe material deformation combined with the particle/pin interaction. The fine precipitates in the matrix alloy were mostly dissolved in the NZ but were significantly coarsened in the heat affected zone (HAZ). The joints exhibited significantly decreased tensile strength compared with the base material. The joint strength increased slightly with increasing welding speed, with maximum joint efficiency of ∼70% at 400 mm/min. Artificial aging resulted in significant improvement in the NZ hardness and joint strength due to the re-precipitation of the precipitates, with a larger increment for the joint under higher welding speed. The joint at 400 mm/min exhibited the highest joint efficiency of ∼85% after artificial aging. Artificial aging changed the hardness profiles of the NZ from flat to “M” shapes due to the change in quantities of solutes after FSW with increasing distance from the NZ centerline. The fracture of both as-welded and aged joints occurred in the HAZ.

Development and characterization of Al5083-CNTs/SiC composites via friction stir processing

Carbon nanotubes (CNTs) and or micron-sized silicon carbide (SiC) particles were reinforced with Al5083 matrix to develop mono and hybrid composites via friction stir processing (FSP). The effect of CNTs/SiC either individually or in aggregate form, on microstructural evolution, texture, and mechanical properties of friction stir processed (FSPed) Al5083 composites were studied. EBSD and TEM analyses revealed an equiaxed recrystallized microstructure and dislocations rearranged to form high angle grain boundaries (HAGBs) upon dynamic recrystallization (DRX), respectively. The overall weak texture intensity was observed across the stir zone of FSPed samples due to the multiple passes. Incorporation of CNTs/SiC particles in Al5083 matrix resulted in the activation of Zener-Holloman mechanism and particle-stimulated nucleation (PSN) mechanism by developing randomly oriented grains. In FSPed composites, SiC particles are dispersed homogeneously with good interfacial bonding and CNTs are partially reacted with an Al5083 matrix to form in-situ Al4C3 intermetallic compound. The maximum tensile strength of 361 MPa was obtained for Al5083-CNTs/SiC hybrid composite. The fracture surface of the SiC reinforced composite revealed that the voids initiation at the matrix-particle interface regions.

Microstructure evolution and mechanical properties of friction stir welded dissimilar joints of as-extruded AM60 and AZ31 alloys

Two types of material positions, with AZ31 or AM60 in retreating side, were used for dissimilar friction stir welding in this study. The appearance, microstructure evolution, mechanical properties and fracture mechanism of the joints were investigated. The results showed that significant microstructure evolution occurred in the joint under the intense stirring and thermal cycling. Furthermore, the material positions had little influence on the appearance, tensile properties and failure locations of the joints. It is interesting that all the tensile joints fractured at the boundary of thermo-mechanically affected zone (TMAZ)/nugget zone (NZ) near the AZ31 side. In order to explore the fracture mechanism of the joints, the relationship of failure locations, microstructure and texture evolution of joints were analyzed. The analysis on EBSD demonstrated that the texture evolution in both TMAZ and NZ, as well as a certain extent of dislocation density and strain existing adjacent to TMAZ/NZ interface, was the main factor leading to the fracture at the boundary of TMAZ/NZ. The tensile strength of AZ31 alloy was smaller than that of AM60, the grain gradient and the second phases size near the NZ/TMAZ interface of AZ31 side were larger than those of AM60, resulting in the fracture tending to AZ31 side.

Characterization of friction stir welded AL6063/nano fly ash composite

In this work Aluminum Matrix Composites (AMCs) reinforced with nano fly ash (NFA) particles in 1 wt%, 2 wt% and 3 wt% were fabricated through ultrasonic assisted stir casting process. These composites were subsequently welded through Friction Stir Welding (FSW). It is proposed to explore the effect of NFA on refinement of grain structure and to investigate the mechanical properties of friction stir welded AMC joints. Through Scanning Electron Microscope (SEM) images it is observed that homogeneous dispersion of NFA in the Aluminum matrix material was achieved. The increase in tensile strength and hardness was observed in the developed AMCs. It was concluded that the FSW process is the better option to join Al6063/NFA composites.

Effect of Tool Pin Eccentricity on the Microstructure and Mechanical Properties of Friction Stir Processed Al-6061 Alloy

Three different stir tools with the pin eccentricity of 0, 0.4 and 0.8 mm were applied to the friction stir processing (FSP) of Al-6061 alloy. Results show that the pin-affected zone (PAZ) enlarges and the grain size in the stir zone (SZ) decreases as the pin eccentricity increases. Moreover, the low peak FSP temperature induced by the pin eccentricity gives rise to the coarsening of strengthening precipitates in the SZ. Compared with the pin-eccentric FSP samples, the SZ produced without pin eccentricity exhibits the highest hardness and yield strength due to the high amount of fine precipitates. However, the application of pin eccentricity elevates the overall tensile properties of FSP samples through changing the failure location from heat-affected zone (HAZ) to SZ.