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The friction stir welding computational fluid dynamics (CFD) model in three dimensions (FSW) for quantitatively study to effect heat generation on the work piece material at different tool pin profile are revealed in this study. The simulated thermal parameter are studies and compare with experimental results. The FSW process is modeled the laminar flow and transient condition for various welding condition. The rotating tool geometry such as cylindrical, tapered, triangular and square are used for FSW. Analysis of the thermomechanical behavior of various pin profiles at spindle speeds of 1000 rpm and feed rates of 16–63 mm/min. The tapered tool pin profile is effective as compared to other tool pin because it generates maximum temperature and strain rate. The tapered pin profile has lower surface area and therefore gives better performance due to maximum heat generation of 695 K and high strain rate of 0.9 S−1 as compared to other. On the other hand, modelling results for the tapered pin profile reveal an increase in temperature of around 80% of the base materials' melting point. [ABSTRACT FROM AUTHOR]

The joints of aluminum alloy frames are usually welded by manual TIG welding. In order to study the distribution law of welding stress level and welding temperature field of intersecting joints of 6061-T6 aluminum alloy bicycle frames, a intersecting joints model of welding parts was established by Finite Element Model (FEM), Software. Based on ABAQUS software, the welding temperature field and welding stress field were studied and analyzed by using direct thermal coupling method. The accuracy of welding simulation is fully verified, which can meet the simulation requirements required for the subsequent optimization process design, and achieve the purpose of shortening the time required for the accumulation of practical inspection.

This work mainly focuses on designing a novel aluminum alloy 6061-T6 pressure vessel liner intended for use in launch vehicles. Fabrication of custom-made welding fixtures for the assembly of liner parts, namely two hemispherical domes and end boss, is illustrated. The parts of the liner are joined using the cold metal transfer welding process, and the welding trials are performed to arrive at an optimized parametric range. The metallurgical characterization of weld joint reveals the existence of dendritic structures (equiaxed and columnar). Microhardness of base and weld metal was 70 and 65 HV, respectively. The tensile strength of base and weld metal was 290 and 197 MPa, respectively, yielding a joint efficiency of 68%. Finite-element analysis of a uniaxial tensile test was performed to predict the tensile strength and location of the fracture in base and weld metal. The experimental and predicted tensile test results were found to be in good agreement. [ABSTRACT FROM AUTHOR]

In machining, heat concentration is generated at the surface contact between the tool and workpiece. This is the effect of hard frictions at the shear cutting plane to remove hard and brittle materials. The highly adhesive behavior of aluminum alloy 6061-T6 is more severe in higher cutting temperature, which may affect tool failures such as flank wear, tool chip and built-up edge, particularly on the edge of cutting inserts during the process. As a result, this may lead to the rough surface and low-dimensional accuracy of the machined parts. Realizing that metal-cutting industry players are demanding high-quality products with better surface finish and dimensional accuracy led to this study. Aluminum alloy 6061-T6 is a standard alloy used in automotive, aerospace and food packaging due to good hardness, high strength-to-weight ratio, resistance to corrosion and weldability. In order to address this problem, a newly developed metal working fluid which is SiO2-Al2O3-ZrO2 tri-hybrid nanofluid is applied in the cutting zone to achieve a good surface finish of the machined parts and lowering the cutting temperature. This study is the first attempt to enhance machining performance, particularly at high-speed machining, by employing a combination of tri-hybrid nanofluids and a minimum quantity lubricant technique. Industrial standards include uncoated tungsten carbide and CVD TiCN-Al2O3 carbide used during machining of aluminum alloy 6061-T6. The minimum quantity lubricant method is an alternative in supplying the lubricant into the machining zone due to flood machining and conventional fluid possess safety, health, economic and environmental effects. In this study, the experimental data were analyzed statistically using analysis of variance and response surface methodology. The responses studied were reduced significantly when tri-hybrid nanoparticles present at the cutting interface with higher MQL flow rate and concentration. There are two-factor interactions which are significant to the responses studied. Therefore, the combinations of MQL and excellent tri-hybrid nanofluids characteristics have enhanced between 16 and 76% of surface roughness and the cutting temperature, respectively, which is very promising in the future. [ABSTRACT FROM AUTHOR]

Obtaining high-quality AA6061-T6 weldment is difficult because of the dissolution of its strengthening precipitates at temperatures beyond 250°C. In this work, the surface quality, mechanical and wear properties of AA6061-T6 friction stir welded joints at varying SiC addition (0.56-1.72 g) and number of weld passes (1-6) were investigated and discussed. SiC content was varied by changing the center groove width (CGW). Also, microstructure analysis of the entire welded joints was performed. For the first time, a process map predicting the surface characteristics of SiC reinforced AA6061-T6 friction stir welded joint at varying combinations of CGW and number of weld passes was developed. Increasing the number of passes resulted in better matrix refinement, particles fragmentation and improved particles distribution while increase in SiC content produced particles clustering and lower particles fragmentation. All the reinforced joints showed higher hardness but lower ductility than the unreinforced joint. Only joints reinforced with 0.56 g SiC showed improved tensile strength than the unreinforced joint (156 MPa) with the highest value of ~196 MPa (67% of the base metal) obtained at 4 weld passes. Increased hardness and tensile strength obtained as the weld passes increased from 2 to 4 was traced to better grain refinement, improved particles distribution and fragmentation. However, slight reduction in these properties at 6 passes was observed. Ductile fracture mode was found in all the joints except for joints reinforced with 1.01-1.72 g of SiC that showed evidence of brittle fracture. The specific wear rates of the entire reinforced joints are lower than that of the unreinforced joint. The weldment formed with 0.56 g SiC addition at 4 weld passes exhibited the best combination of properties among the entire weldments. [ABSTRACT FROM AUTHOR]

Aluminum alloys 6061-T6 are widely utilized in the automotive, aerospace, and marine industries due to high corrosion resistance, high strength, and good workability and machinability. The machining performance of these alloys depends on several factors including tool's material, coating, and geometry. Cutting tool edge radius is one of the most effective factors in cutting forces, energy requirement, and chip formation during metal cutting. The present article aims to study the interactions between the cutting edge radius and cutting speed, feed rate, and rake angle and examine the impacts of the aforementioned tool geometry and cutting conditions on machining forces, cutting temperature, and chip thickness in cutting an aluminum alloy 6061-T6. Special attention is devoted to examining the influence of the cutting edge radius on machining variables and comparing the results of conventional machining (CM) and high speed machining (HSM). A finite element model was developed to simulate the above interactions and was experimentally validated for different machining parameters. The results demonstrate that although increasing the cutting edge radius clearly raises the machining forces, it has a slight influence on the chip thickness. It is also found that the maximum cutting temperatures remain nearly constant with changes in the tool edge radius, while the average temperatures of the tool tip increase especially in HSM. Furthermore, it was found that the location at which the maximum cutting temperature occurs depends more on cutting conditions and tool geometry than workpiece and tool materials. [ABSTRACT FROM AUTHOR]

This study proposes a methodology to predict the capacity of aluminum welded connections. In order to evaluate the material characteristics within the heat-affected zone, an inverse analysis methodology, using full-field measurements of the strain field using digital image correlation, was developed during uniaxial tensile tests on specimens extracted from gas metal arc welded 6061-T6 aluminum alloy plates. The identification of the constitutive law problem was formulated within the Virtual Fields Method. The inverse analysis methodology was compared with an identification process of the material in the vicinity of the weld using a fully coupled multiphysics simulation considering thermal, metallurgical, and mechanical mechanisms during heating and cooling. The simulation accounts for the nonhomogeneous hardening properties within the heat-affected zone to extract the constitutive material laws of a welded join. The proposed simulation methodology was used to analyze the structural response of a plate–square hollow structural section (SHSS) joint subjected to tensile loading. The predicted capacity of the specimens was compared with the experimental findings as well as analyses using Canadian code recommendations. It is shown that it is possible to improve the prediction of the capacity of welded aluminum connection using the Canadian recommendations if the width of the heat-affected zone is reduced to 15 mm instead of the original 25 mm. [ABSTRACT FROM AUTHOR]

The Refill Friction Stir Spot Welding (RFSSW) process—an alternative solid-state joining technology—has gained momentum in the last decade for the welding of aluminum and magnesium alloys. Previous studies have addressed the influence of the RFSSW process on the microstructural and mechanical properties of the AA6061-T6 alloy. However, there is a lack of knowledge on how the tool wear influences the welding mechanical behavior for this alloy. The present work intended to evaluate and understand the influence of RFSSW tool wear on the mechanical performance of AA6061-T6 welds. Firstly, the welding parameters were optimized through the Designing of Experiments (DoE), to maximize the obtained ultimate lap shear force (ULSF) response. Following the statistical analysis, an optimized condition was found that reached a ULSF of 8.45 ± 0.08 kN. Secondly, the optimized set of welding parameters were applied to evaluate the wear undergone by the tool. The loss of worn-out material was systematically investigated by digital microscopy and the assessment of tool weight loss. Tool-wear-related microstructural and local mechanical property changes were assessed and compared with the yielded ULSF, and showed a correlation. Further investigations demonstrated the influence of tool wear on the height of the hook, which was located at the interface between the welded plates and, consequently, its effects on the observed fracture mechanisms and ULSF. These results support the understanding of tool wear mechanisms and helped to evaluate the tool lifespan for the selected commercial RFSSW tool which is used for aluminum alloys.

The present research work aimed to study the effects of cutting environments and conditions on tool wear and residual stresses induced by orthogonal cutting of AA6061-T6. Cutting environments included dry- and flood-coolant modes and cutting conditions consisted of cutting speed and feed rate. A 2D finite element (FE) model was developed to predict tool wear and residual stresses and was validated by experimental measurements including machining forces, tool wear, and residual stresses. This was obtained by exploring various magnitudes of the shear friction factor and heat transfer coefficient and choosing proper coefficients using the calibration of the predicted results with the measured ones. The experimental results showed that the effect of cutting environment including dry and flood-coolant modes was negligible on machining forces. The experimental investigation also demonstrated that increasing feed rate raised machining forces, tool wear and residual stresses in both cutting environments. Low Speed Cutting (LSC) led to the highest value of tool wear and High Speed Cutting (HSC) provided the lowest values of resultant machining forces and residual stresses in both modes. Flood-coolant mode reduced tool wear and slightly decreased tensile residual stresses in comparison with dry mode. As a result, low feed rate and high-speed cutting under flood-coolant mode were proposed in order to improve tool wear and residual stress in orthogonal cutting of AA6061-T6.

At present, it is difficult to join the non-polar thermoplastic vulcanization based on Polypropylene (PP)/Ethylene-Propylene-Diene (EPDM) to aluminium alloy 6061-T6 (A6061) directly because of the great difference in physical and chemical properties between them. In this paper, zinc sorbate (ZDS) was introduced into the dynamic vulcanization process of PP/EPDM TPV to achieve high performance TPV interface modification. The results show that the polymerization of ZDS can enhance the interface compatibility, melt strength and surface energy of PP/EPDM/ZDS TPV while reducing the linear expansion coefficient of TPV. On this basis, the plate curing machine is used to simulate friction stir welding, and the heat input (temperature:180 °C, pressure:20 MPa, welding time:60 s) was optimized. PP/EPDM/ZDS TPV was directly connected to A6061, and the influencing factors of the joint strength were analyzed. The results show that the tensile shear strength of composite joints decreases with the static time and then keeps stable, reaching 3.53 MPa. The chemical bond (Al-C) is formed at the interface between A6061 and PP/EPDM/ZDS TPV, which plays a key role in improving the strength of the joint. The results of this work can expand the application range of PP/EPDM TPV, and provide basic data and theoretical support for the connection between TPV and metal. • The interface modification of PP/EPDM TPV was realized by in-situ zinc sorbate generation. • PP/EPDM/ZDS TPV was directly connected with aluminum alloy by simulating welding. • Zinc sorbate can form the "Al-C" bond, which plays a key role in improving joint strength. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 m s−1) were studied, contrasting then with stationary (no flow) conditions. Monitoring of open-circuit potential and current fluctuations, both considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, in which dynamic is controlled by oxygen diffusion and its renewal at the metal interface. The changes in the morphology and elemental composition of the formed layers revealed that the localized attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes.

Self-reacting friction stir welding (SR-FSW), also called bobbin-tool friction stir welding (BT-FSW), is a solid state welding process similar to friction stir welding (FSW) except that the tool has two opposing shoulders instead of the shoulder and a backing plate found in FSW. The tool configuration results in greater heat input and a symmetrical weld macrostructure. A significant amount of information has been published in the literature concerning traditional FSW while little has been published about SR-FSW. An optimization experiment was performed using a factorial design to evaluate the effect of process parameters on the weld temperature, surface and internal quality, and mechanical properties of self-reacting friction stir welded aluminum alloy 6061-T6 butt joints. The parameters evaluated were tool rotational speed, traverse speed, and tool plunge force. A correlation between weld temperature, defect formation (specifically galling and void formation), and mechanical properties was found. Optimum parameters were determined for the welding of 8-mm-thick 6061-T6 plate. [ABSTRACT FROM AUTHOR]

Ultra-low cycle fatigue (ULCF) life of ductile metal is closely correlated with monotonic tension coupon test results. This paper aims to propose a novel approach to evaluate crack initiation of aluminum alloy under ULCF loading only with monotonic tension coupon test results. ULCF tests on 15 specimens made of aluminum alloy 6061-T6 were conducted, and numerical analyses using a previously proposed cyclic void growth model indicated that the ULCF life of aluminum can be greatly underestimated by the model. A new fracture model based on the concept of different dislocation structures is thus proposed, which classifies damage into kinematic hardening correlated and isotropic hardening correlated. A material constant is employed to consider the relatively low damage induced by the kinematic hardening compared with the isotropic hardening one. The newly proposed fracture model can well simulate the instants of crack initiation for the specimens. A process to evaluate the ULCF life of aluminum alloy based on both monotonic coupon test results and simple numerical analysis is presented. [ABSTRACT FROM AUTHOR]

In this study, we characterize the Bauschinger effect by quantifying the isotropic and kinematic hardening in extruded 6061 aluminum alloy. Reverse loading experiments were performed up to a prestrain of 5% in both tension-followed-bycompression and compression-followed-by-tension. The development of isotropic and kinematic hardening and subsequent anisotropy was indicated by the observation of the Bauschinger effect phenomenon. Experimental results show that 6061 aluminum alloy exhibited an increase in the kinematic hardening versus applied prestrain. However, the ratio of kinematic-toisotropic hardening remained near unity. An internal state variable (ISV) plasticity and damage model was used to capture the evolution of the anisotropy for the as-received T6 and partially annealed conditions. [ABSTRACT FROM AUTHOR]

A novel external axial magnetic field (EMF) hybrid CMT welding-brazing process was adopted to join pure titanium TA2 and aluminum alloy 6061-T6. The effects of the magnetic intensity and frequency on microstructure and mechanical properties of the resultant joints were revealed. The experimental results indicated that the magnetic field can affect the flowability and surface spreadability of the molten filler metal on TA2 plate, thus forming the reliable Al/Ti joint. Grain refinement, decreased Al-Ti intermetallic compounds, and increased microhardness in both the heat-affected zone and the weld were observed with the applied of the EMF. The microstructure of the interfacial IMC layer was identified as TiAl 3 , and its thickness was decreased from 10 μm to 5 μm. In addition, the tensile shear strength of the Al/Ti joint reached a maximum value of 4.105 KN and fractured at the Ti base metal with the coil current and magnetic frequency set at 1.0 A and 10 Hz respectively, increasing by 93.4% compared to the normal welding process. However, the additional magnetic field could be an inverse effect on the process of Al/Ti dissimilar metal joining because of the unstable welding process. [ABSTRACT FROM AUTHOR]

Six unique tool shoulder designs were produced with the objective of improved metal constraint and flow to the pin. The six tools were made of Ti–6Al–4V by metallic additive manufacturing. Each tool was used to produce butt welds using aluminum 6061-T6 plates. The welds were subjected to nondestructive evaluation and tensile testing to determine weld soundness and strength. A FSW tool shoulder having a raised spiral design produced the weld with the best combination of surface quality and mechanical properties. The additive-manufactured Ti–6Al–4V tooling had good wear characteristics and appears to be a suitable route to rapidly produce unique FSW tool designs. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of coated carbide cutting tool performance on the surface roughness of aluminum alloy 6061-T6 machining through end mill processes using the minimum quantity lubrication technique. Process parameters including the cutting speed, depth of cut and feed rate are selected. The central composite design method is used for design of experiments. Two types of coated carbide tool are used in this experiment - an uncoated tungsten carbide insert and TiAlN+TiN-coated carbide insert. The analysis of variance method is utilized to validate the experimental data and to check for adequacy. The response surface method was used to develop the mathematical models and to optimize the machining parameters. Second-order regression models are developed based on the surface roughness results. It is observed that the surface roughness depends significantly on depth of cut and feed rate, followed by spindle speed for both the coated carbide inserts. The performance of the dual-layered coating of TiAlN+TiN is competent as compared to the surface quality obtained with TIAlN-coated inserts. The results can be used as an example of MQL applied to the machining of aluminum alloys, providing economic advantages in terms of reduced lubricant costs and better machinability. [ABSTRACT FROM AUTHOR]

In this paper, the use of a microstructure-sensitive fatigue model is put forth for the analysis of discontinuously reinforced aluminum alloy metal matrix composite. The fatigue model was used for a ceramic particle-reinforced aluminum alloy deformed under conditions of fully reversed strain control. Experimental results revealed the aluminum alloy to be strongly influenced by volume fraction of the particulate reinforcement phase under conditions of strain-controlled fatigue. The model safely characterizes the evolution of fatigue damage in this aluminum alloy composite into the distinct stages of crack initiation and crack growth culminating in failure. The model is able to capture the specific influence of particle volume fraction, particle size, and nearest neighbor distance in quantifying fatigue life. The model yields good results for correlation of the predicted results with the experimental test results on the fatigue behavior of the chosen aluminum alloy for two different percentages of the ceramic particle reinforcement. Further, the model illustrates that both particle size and volume fraction are key factors that govern fatigue lifetime. This conclusion is well supported by fractographic observations of the cyclically deformed and failed specimens. [ABSTRACT FROM AUTHOR]

Failure loads of a friction stir spot welding (FSSW) joint of two aluminum alloy 6061-T6 sheets under specific loading cases were predicted using the finite-element method. The detailed modelling technique of a FSSW joint using available experimental data is presented in this paper. The characteristics and dimensions of different zones of the FSSW joint including the stir zone (SZ), heat-affected zone (HAZ), thermal-mechanically affected zone (TMAZ), and base metal (BM) were obtained from literature. The mechanical properties calculated from a relation between the measured hardness values and the corresponding strengths for each zone were then applied to the failure prediction model. In this model the ESI–Wilkins–Kamoulakos (EWK) rupture model of the PAM-CRASH commercial software was employed to verify the case of the lap-shear tension test. The failure load obtained in this model showed a good agreement with the experimental value in the reference. The failure prediction for the other loading cases (peel-tension test and cross-tension test) was then conducted following the same analysis procedure. [ABSTRACT FROM AUTHOR]

The Refill Friction Stir Spot Welding (RFSSW) process—an alternative solid-state joining technology—has gained momentum in the last decade for the welding of aluminum and magnesium alloys. Previous studies have addressed the influence of the RFSSW process on the microstructural and mechanical properties of the AA6061-T6 alloy. However, there is a lack of knowledge on how the tool wear influences the welding mechanical behavior for this alloy. The present work intended to evaluate and understand the influence of RFSSW tool wear on the mechanical performance of AA6061-T6 welds. Firstly, the welding parameters were optimized through the Designing of Experiments (DoE), to maximize the obtained ultimate lap shear force (ULSF) response. Following the statistical analysis, an optimized condition was found that reached a ULSF of 8.45 ± 0.08 kN. Secondly, the optimized set of welding parameters were applied to evaluate the wear undergone by the tool. The loss of worn-out material was systematically investigated by digital microscopy and the assessment of tool weight loss. Tool-wear-related microstructural and local mechanical property changes were assessed and compared with the yielded ULSF, and showed a correlation. Further investigations demonstrated the influence of tool wear on the height of the hook, which was located at the interface between the welded plates and, consequently, its effects on the observed fracture mechanisms and ULSF. These results support the understanding of tool wear mechanisms and helped to evaluate the tool lifespan for the selected commercial RFSSW tool which is used for aluminum alloys. [ABSTRACT FROM AUTHOR]

The present research work aimed to study the effects of cutting environments and conditions on tool wear and residual stresses induced by orthogonal cutting of AA6061-T6. Cutting environments included dry- and flood-coolant modes and cutting conditions consisted of cutting speed and feed rate. A 2D finite element (FE) model was developed to predict tool wear and residual stresses and was validated by experimental measurements including machining forces, tool wear, and residual stresses. This was obtained by exploring various magnitudes of the shear friction factor and heat transfer coefficient and choosing proper coefficients using the calibration of the predicted results with the measured ones. The experimental results showed that the effect of cutting environment including dry and flood-coolant modes was negligible on machining forces. The experimental investigation also demonstrated that increasing feed rate raised machining forces, tool wear and residual stresses in both cutting environments. Low Speed Cutting (LSC) led to the highest value of tool wear and High Speed Cutting (HSC) provided the lowest values of resultant machining forces and residual stresses in both modes. Flood-coolant mode reduced tool wear and slightly decreased tensile residual stresses in comparison with dry mode. As a result, low feed rate and high-speed cutting under flood-coolant mode were proposed in order to improve tool wear and residual stress in orthogonal cutting of AA6061-T6. [ABSTRACT FROM AUTHOR]

Air Slip direct chill cast 6061 small diameter ingots (Direct Forge) were compared with 6061 extruded bar stock. The T6 mechanical properties were compared for both the Direct Forge ingot and the extruded bar stock, as well as cold impact extruded cylinders produced from Direct Forge small diameter ingot and extruded stock. It was found that the tensile and fatigue properties of Direct Forge ingot and cylinders from this ingot were significantly superior to those of extruded stock and cylinder produced from this stock. The improved properties are a result of higher solidification rates leading to smaller alloy-constituent dispersed particles and, thus, the production of smaller and more stable grain sizes. Direct Forge has the additional advantages of (a) not requiring hot or cold work prior to forming impacted extruded or forged parts, (b) being utilized in the T6 temper without any prior deformation, (c) having isotropic and consistent properties, (d) not requiring machining to remove surface segregation or defects, and (e) having more consistent and refined grain sizes. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour and surface changes on AA6061-T6 alloy exposed to Caribbean seawater from the Cozumel Channel for 30 days under laminar flow (0.1 m s−1) were studied, contrasting then with stationary (no flow) conditions. Monitoring of open-circuit potential and current fluctuations, both considered as electrochemical noise (EN), were employed as two nondestructive methods. The calculated corrosion current, based on Rn, was one order higher in laminar flow. The fluctuations of current were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning the dynamic of the spontaneous release of energy during the corrosion process. The value of the exponent β in PSD graphs suggested that the localised corrosion on AA6061-T6 surface occurs as a persistent stationary process, in which dynamic is controlled by oxygen diffusion and its renewal at the metal interface. The changes in the morphology and elemental composition of the formed layers revealed that the localized attacks occurred in the vicinity of intermetallic particles rich in Fe and Cu, which act as cathodes. [ABSTRACT FROM AUTHOR]