Editorial

5 pages, 163 KiB

Open AccessEditorial

Challenges to Be Tackled in the Computational Modeling and Numerical Simulation of FSW Processes

by Carlos Agelet De Saracibar

Metals 2019, 9(5), 573; https://doi.org/10.3390/met9050573 - 17 May 2019

Cited by 7 | Viewed by 2201

The computational modeling and numerical simulation of Friction Stir Welding (FSW) processes is an extremely challenging task due to the highly nonlinear and coupled nature of the physical problem and the complex computational issues that need to be properly tackled in the numerical [...] Read more.

The computational modeling and numerical simulation of Friction Stir Welding (FSW) processes is an extremely challenging task due to the highly nonlinear and coupled nature of the physical problem and the complex computational issues that need to be properly tackled in the numerical model [...] Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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10 pages, 4144 KiB

Open AccessArticle

Performance of Plunge Depth Control Methods During Friction Stir Welding

by Jinyoung Yoon, Cheolhee Kim and Sehun Rhee

Metals 2019, 9(3), 283; https://doi.org/10.3390/met9030283 - 02 Mar 2019

Cited by 6 | Viewed by 4008

Abstract

Friction stir welding is a preferred solid state welding process for Al/Fe joints, and in friction stir lap welding, the plunge depth is the most critical parameter for joint strength. We compared three plunge depth control methods, namely conventional position control, offset position [...] Read more.

Friction stir welding is a preferred solid state welding process for Al/Fe joints, and in friction stir lap welding, the plunge depth is the most critical parameter for joint strength. We compared three plunge depth control methods, namely conventional position control, offset position control, and deflection compensation control in the friction stir lap welding of 3 mm-thick Al 5083-O alloy over 1.2 mm-thick DP 590 steel. The desired plunge depth was 0.2 mm into the steel sheet. However, the pin did not reach the steel surface under conventional position control due to deflection of the vertical axis of the welding system. In offset position control, an additional offset of 0.35 mm could achieve the desired plunge depth with considerable accuracy. Nevertheless, a gradual increase of the plunge depth along the longitudinal direction was unavoidable, due to an in-situ decrease of the material yield strengths. In deflection compensation control, the deflection is estimated by the coaxially measured plunging force and the force-deflection relationship, and then corrected by feedback control. Thus, the plunge depth is stabilized along the longitudinal direction and is precisely controlled with a 3.3-μm standard deviation of error during the tool traverse phase. There is also a consistent bias of 32 μm caused by the resolution of the measuring system, and it can be easily calibrated in the feedback control system. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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17 pages, 9705 KiB

Open AccessFeature PaperArticle

Effect of the Tool Tilt Angle on the Heat Generation and the Material Flow in Friction Stir Welding

by Narges Dialami, Miguel Cervera and Michele Chiumenti

Metals 2019, 9(1), 28; https://doi.org/10.3390/met9010028 - 29 Dec 2018

Cited by 60 | Viewed by 6802

Abstract

This work studies the effect of the tool tilt angle on the generated heat and the material flow in the work pieces joint by Friction Stir Welding (FSW). An apropos kinematic framework together with a two-stage speed-up strategy is adopted to simulate the [...] Read more.

This work studies the effect of the tool tilt angle on the generated heat and the material flow in the work pieces joint by Friction Stir Welding (FSW). An apropos kinematic framework together with a two-stage speed-up strategy is adopted to simulate the FSW problem. The effect of tilt angle on the FSWelds is modeled through the contact condition by modifying an enhanced friction model. A rotated friction shear stress is proposed, the angle of rotation depending on the process parameters and the tilt angle. The proposed rotation angle is calibrated by the experimental data provided for a tilt angle 2.5°. The differences of generated heat and material flow for the cases of tool with tilt angle of 0° and 2.5° are discussed. It is concluded that due to the higher temperature, softer material and greater frictional force in the trailing side of the tool, the material flow in the rear side of the FSW tool with the title angle is considerably enhanced, which assists to prevent the generation of defect. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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10 pages, 3712 KiB

Open AccessArticle

Compensation of Vertical Position Error Using a Force–Deflection Model in Friction Stir Spot Welding

by Jinyoung Yoon, Cheolhee Kim and Sehun Rhee

Metals 2018, 8(12), 1049; https://doi.org/10.3390/met8121049 - 11 Dec 2018

Cited by 9 | Viewed by 2721

Abstract

Despite increasing need for friction stir spot welding (FSSW) for high-temperature softening materials, system deflection due to relatively high plunging force remains an obstacle. System deflection results in the vertical position error of a welding tool and insufficient plunge depth. In this study, [...] Read more.

Despite increasing need for friction stir spot welding (FSSW) for high-temperature softening materials, system deflection due to relatively high plunging force remains an obstacle. System deflection results in the vertical position error of a welding tool and insufficient plunge depth. In this study, we used adaptive control to maintain plunge depth, the plunging force was coaxially measured, and the position error was estimated using a force–deflection model. A linear relationship was confirmed between the force and deflection; this relationship is dependent on the stiffness of the welding system while independent of process parameters and base materials. The proposed model was evaluated during the FSSW of an Al 6061-T6 alloy sheet and a dissimilar metal combination of Al 6061-T6 alloy/dual phase (DP) 590 steel. Under varying process parameters, the adaptive control maintained a plunge depth with an error of less than 50 μm. Conventional position control has a maximum error of nearly 300 μm. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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13 pages, 6490 KiB

Open AccessArticle

Influences of Pin Shape on a High Rotation Speed Friction Stir Welding Joint of a 6061-T6 Aluminum Alloy Sheet

by Yang Zhou, Shujin Chen, Jiayou Wang, Penghao Wang and Jingyu Xia

Metals 2018, 8(12), 987; https://doi.org/10.3390/met8120987 - 24 Nov 2018

Cited by 15 | Viewed by 2894

Abstract

In order to explore the influences of different pins on the weld based on the specialty of the aluminium alloy sheet welding, three kinds of pins were chosen to perform high rotation speed friction stir welding on a 1 mm thick 6061-T6 aluminium [...] Read more.

In order to explore the influences of different pins on the weld based on the specialty of the aluminium alloy sheet welding, three kinds of pins were chosen to perform high rotation speed friction stir welding on a 1 mm thick 6061-T6 aluminium alloy in this study. The microstructure and mechanical properties of the joints were analysed at the same time. When the rotation speed was 11,000 rpm and the welding speed was 300 mm/min, more sufficient stirring and a better joint (the tensile strength reaches 87.2% of the base metal) can be obtained with the pin design of a quadrangular frustum pyramid. The pattern of the weld cross section was a “flat T” and no obvious “S curve” was found in nugget zone (NZ). Heat affected zone (HAZ) and thermo-mechanically affected zone (TMAZ) were also narrow. The results demonstrate that the proportion of low angle boundaries in each area of the weld is lower than that of traditional Friction Stir Welding (FSW). The grain size of NZ is significantly refined and the proportion of low angle boundaries is only 20.1%, which have improved the welding quality. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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14 pages, 15592 KiB

Open AccessArticle

Another Approach to Characterize Particle Distribution during Surface Composite Fabrication Using Friction Stir Processing

by Namrata Gangil, Sachin Maheshwari, Emad Abouel Nasr, Abdulaziz M. El-Tamimi, Mohammed A. El-Meligy and Arshad Noor Siddiquee

Metals 2018, 8(8), 568; https://doi.org/10.3390/met8080568 - 24 Jul 2018

Cited by 21 | Viewed by 3777

Abstract

Surface composite fabrication through Friction Stir Processing (FSP) is evolving as a useful clean process to enhance surface properties of substrate. Better particle distribution is key to the success of surface composite fabrication which is achieved through multiple passes. Multiple passes significantly increase [...] Read more.

Surface composite fabrication through Friction Stir Processing (FSP) is evolving as a useful clean process to enhance surface properties of substrate. Better particle distribution is key to the success of surface composite fabrication which is achieved through multiple passes. Multiple passes significantly increase net energy input and undermine the essence of this clean process. This study proposes a novel approach and indices to relate the particle distribution with the FSP parameters. It also proposes methodology for predicting responses and relate the response with the input parameter. Unit stirring as derived parameter consisting of tool rotation speed in revolutions per minute (rpm), traverse speed and shoulder diameter was proposed. The particle distribution was identified to be achieved in three stages and all three stages bear close relationship with unit stirring. Three discrete stages of particle distribution were identified: degree of spreading, mixing and dispersion. Surface composite on an aerospace grade aluminum alloy AA7050 was fabricated successfully using TiB₂ as reinforcement particles. FSP was performed with varied shoulder diameter, rotational speed and traversing speed and constant tool tilt and plunge depth using single pass processing technique to understand the stages of distribution. Significant relationships between processing parameters and stages of particle distribution were identified and discussed. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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9 pages, 5463 KiB

Open AccessFeature PaperArticle

Characterization of Microstructural Refinement and Hardness Profile Resulting from Friction Stir Processing of 6061-T6 Aluminum Alloy Extrusions

by Nelson Netto, Murat Tiryakioğlu and Paul D. Eason

Metals 2018, 8(7), 552; https://doi.org/10.3390/met8070552 - 19 Jul 2018

Cited by 7 | Viewed by 3717

Abstract

In this study, the change in microstructure and microhardness adjacent to the tool during the friction stir processing (FSP) of 6061-T6 extrusions was investigated. Results showed that the as-received extrusions contained Fe-rich constituent particles with two distinct size distributions: coarse particles in bands [...] Read more.

In this study, the change in microstructure and microhardness adjacent to the tool during the friction stir processing (FSP) of 6061-T6 extrusions was investigated. Results showed that the as-received extrusions contained Fe-rich constituent particles with two distinct size distributions: coarse particles in bands and finer particles in the matrix. After FSP, Fe-containing particles exhibited single-size distribution and the coarse particles appeared to be completely eliminated through refinement. Microhardness tests showed the presence of four distinct zones and that hardness increased progressively from the dynamically recrystallized closest to the tool, outward through two distinct zones to the base material. The similarities and differences between the results of this study and others in the literature are discussed in detail. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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16 pages, 14749 KiB

Open AccessArticle

Effect of Tool Rotational Speeds on the Microstructure and Mechanical Properties of a Dissimilar Friction-Stir-Welded CuCrZr/CuNiCrSi Butt Joint

by Youqing Sun, Diqiu He, Fei Xue and Ruilin Lai

Metals 2018, 8(7), 526; https://doi.org/10.3390/met8070526 - 06 Jul 2018

Cited by 12 | Viewed by 3317

Abstract

In this study, dissimilar CuNiCrSi and CuCrZr butt joints were friction stir welded at a constant welding speed of 150 mm/min, but at different rotational speeds of 800, 1100, 1400, 1700, and 2100 rpm. Sound joints were achieved at the rotational speeds of [...] Read more.

In this study, dissimilar CuNiCrSi and CuCrZr butt joints were friction stir welded at a constant welding speed of 150 mm/min, but at different rotational speeds of 800, 1100, 1400, 1700, and 2100 rpm. Sound joints were achieved at the rotational speeds of 1400 and 1700 rpm. It was found that the area of retreating material and grain size in the nugget zone increased with the increase of tool rotational speeds. The base metal on the CuNiCrSi side (CuNiCrSi-BM) contains a large density of Cr and δ-Ni₂Si precipitates, and a great deal of Cr precipitates can be observed in the base metal on the CuCrZr side (CuCrZr-BM). All these precipitates are completely dissolved into the matrix in both the nugget zone on the CuCrZr side (CuCrZr-NZ) and the nugget zone on the CuNiCrSi side (CuNiCrSi-NZ). The precipitation strengthening plays a dominant role in the base metals, but the grain boundary strengthening is more effective in improving the mechanical properties in the nugget zone. Both the hardness and tensile strength decrease sharply from the base metal to the nugget zone due to the dissolution of precipitates. Mechanical properties such as microhardness and tensile strength in the nugget zone decrease with the increase of rotational speeds because the grain size is larger at a higher rotational speed. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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9 pages, 28716 KiB

Open AccessArticle

Abnormal Grain Growth in the Heat Affected Zone of Friction Stir Welded Joint of 32Mn-7Cr-1Mo-0.3N Steel during Post-Weld Heat Treatment

by Yijun Li, Ruidong Fu, Yan Li, Yan Peng and Huijie Liu

Metals 2018, 8(4), 254; https://doi.org/10.3390/met8040254 - 09 Apr 2018

Cited by 6 | Viewed by 4720

Abstract

The abnormal grain growth in the heat affected zone of the friction stir welded joint of 32Mn-7Cr-1Mo-0.3N steel after post-weld heat treatment was confirmed by physical simulation experiments. The microstructural stability of the heat affected zone can be weakened by the welding thermal [...] Read more.

The abnormal grain growth in the heat affected zone of the friction stir welded joint of 32Mn-7Cr-1Mo-0.3N steel after post-weld heat treatment was confirmed by physical simulation experiments. The microstructural stability of the heat affected zone can be weakened by the welding thermal cycle. It was speculated to be due to the variation of the non-equilibrium segregation state of solute atoms at the grain boundaries. In addition, the pressure stress in the welding process can promote abnormal grain growth in the post-weld heat treatment. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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17 pages, 8188 KiB

Open AccessArticle

Influence of Alloys Position, Rolling and Welding Directions on Properties of AA2024/AA7050 Dissimilar Butt Weld Obtained by Friction Stir Welding

by Alessandro Barbini, Jan Carstensen and Jorge F. Dos Santos

Metals 2018, 8(4), 202; https://doi.org/10.3390/met8040202 - 22 Mar 2018

Cited by 16 | Viewed by 4686

Abstract

Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed [...] Read more.

Friction stir welding (FSW) was carried out for the butt joining of dissimilar AA2024-T3 and AA7050-T7651 aluminium alloys with 2-mm thicknesses. A comparison between the position and orientation of different materials was performed by varying the welding speed while keeping the rotational speed constant. Through an analysis of the force and torque produced during welding and a simple analytical model, the results indicate that the heat input was reduced when the AA7050 alloy was located in the advancing side (AS) of the joint. The different material positions influenced the material transportation and the interface in the centre of the stir zone (SZ). The microhardness of both materials was lower when they were in the AS of the joint. The differences in the hardness values were reduced at higher welding speeds when the heat input was decreased. The mechanical performance increased when the lower strength alloy was located in the AS. The material orientation exhibited a small influence when the AA7050 alloy was in the AS and in general on the resulting microhardness for all the cases analysed. The tensile strength values were very similar for both orientations, but an increase in the yield strength could be measured when the materials were oriented in the transverse direction. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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11 pages, 16765 KiB

Open AccessArticle

A Correlation between the Ultimate Shear Stress and the Thickness Affected by Intermetallic Compounds in Friction Stir Welding of Dissimilar Aluminum Alloy–Stainless Steel Joints

by Florent Picot, Antoine Gueydan, Mayerling Martinez, Florent Moisy and Eric Hug

Metals 2018, 8(3), 179; https://doi.org/10.3390/met8030179 - 13 Mar 2018

Cited by 23 | Viewed by 5681

Abstract

In this work, Friction Stir Welding (FSW) was applied to join a stainless steel 316L and an aluminum alloy 5083. Ranges of rotation and translation speeds of the tool were used to obtain welding samples with different heat input coefficients. Depending on the [...] Read more.

In this work, Friction Stir Welding (FSW) was applied to join a stainless steel 316L and an aluminum alloy 5083. Ranges of rotation and translation speeds of the tool were used to obtain welding samples with different heat input coefficients. Depending on the process parameters, the heat generated by FSW creates thin layers of Al-rich InterMetallic Compound (IMC) mainly composed of FeAl₃, identified by energy dispersive spectrometry. Traces of Fe₂Al₅ were also depicted in some samples by X-ray diffraction analysis and transmission electron microscopy. Monotonous tensile tests performed on the weld joint show the existence of a maximum mechanical resistance for a judicious choice of rotation and translation speeds. It can be linked to an affected zone of average thickness of 15 µm which encompass the presence of IMC and the chaotic mixing caused by plastic deformation in this area. A thickness of less than 15 µm is not sufficient to ensure a good mechanical resistance of the joint. For a thickness higher than 15 µm, IMC layers become more brittle and less adhesive due to high residual stresses which induces numerous cracks after cooling. This leads to a progressive decrease of the ultimate shear stress supported by the bond. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing in Alloy Manufacturing)

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