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Showing papers on "Friction stir processing published in 2007"


Book
30 Mar 2007
TL;DR: Friction stir welding (FSW) is a relatively new solid-state joining process that is used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding as discussed by the authors.
Abstract: Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

4,750 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of FSP zone has been analyzed macroscopically and tensile properties of the joints have been evaluated and correlated with the friction stir processed (FSP) zone formation.
Abstract: AA2219 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio. Compared to the many fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. The welding parameters and tool pin profile play a major role in deciding the weld quality. In this investigation an attempt has been made to understand the influences of rotational speed and pin profile of the tool on friction stir processed (FSP) zone formation in AA2219 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different tool rotational speeds. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square tool pin profile produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles.

385 citations


Journal ArticleDOI
TL;DR: In this article, the mean hardness of the UFG region reaches ∼120Hv, which is more than twice as high as that of the AZ31 matrix, and the grain refinement kinetics are analyzed and the results are self-consistent.

268 citations


Journal ArticleDOI
TL;DR: In this paper, a Mg-Al-Zn casting was subjected to friction stir processing (FSP) and subsequent aging, which resulted in significant breakup and dissolution of the coarse, network-like eutectic β-Mg17Al12 phase distributed at the grain boundaries and remarkable grain refinement, thereby improving significantly the tensile properties of the casting.

257 citations


Journal ArticleDOI
TL;DR: In this article, the effect of various process parameters on thermal histories, resulting microstructure and properties of commercial AZ31B-H24 magnesium alloy sheets is investigated and it is shown that FSP leads to finer and more homogenized grain structure.

219 citations


Journal ArticleDOI
TL;DR: In this article, material flow during friction stir processing (FSP) was investigated with respect to the dispersion of the fullerene molecules and it was revealed that the formation mechanism of the ion ring was closely related to the convectional flow induced by the shoulder of the rotating tool.
Abstract: Fullerene was successfully dispersed into A5083 by friction stir processing (FSP). Dispersion of the fullerene enhanced the grain refinement by recrystallization during the FSP and the grain size reached 200 nm. The hardness was also remarkably increased by both the grain refinement and the dispersion of the fullerene molecules. In this study, material flow during the FSP was investigated with respect to the dispersion of the fullerene. It was revealed that the formation mechanism of the ‘‘onion ring’’ was closely related to the convectional flow induced by the shoulder of the rotating tool. This material flow by the shoulder is very important when fabricating the surface composites by the FSP in order to provide a uniform dispersion of the reinforcement. � 2007 Elsevier Ltd. All rights reserved.

148 citations


Journal ArticleDOI
TL;DR: In this paper, a staggered pass sample of friction stir processed (FSP) 7075 aluminum was created to make samples with one through four passes of FSP under identical conditions.
Abstract: A staggered pass sample of friction stir processed (FSP) 7075 aluminum was created to make samples with one through four passes of FSP under identical conditions. The tensile testing temperatures ranged from 673 to 763 K with initial strain rates ranging from 1 × 10−3 to 1 × 10−1 s−1. Materials processed by single as well as multiple passes exhibited superplasticity across various testing temperatures and strain rates while the as received materials exhibited elongations below 200%. This study demonstrated the effectiveness of four consecutive FSP passes in creating large areas of superplastic material. However, the largest elongations were observed for the single pass material.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the room temperature and hot tensile properties of AZ91 magnesium alloy produced by high pressure die cast after friction stir processing (FSP) were studied in the present paper.

112 citations


Journal ArticleDOI
TL;DR: In this article, friction stir-processing (FSP) was used to successfully disperse and embed nitinol particles in the Al 1100 matrix, and directional residual stresses were introduced in the prepared material that consequently showed improved mechanical properties.

105 citations


Journal ArticleDOI
TL;DR: In this article, friction stir processing is applied to produce intermetallic-reinforced aluminum matrix composites from elemental powder mixtures of Al-Cu and Al-Ti.

99 citations


Journal ArticleDOI
TL;DR: In this article, the mechanical and microstructural properties of AM60B magnesium alloy resulting from the friction stir processing (FSP) were analyzed in the nugget zone parallel to the processing direction.
Abstract: The mechanical and microstructural properties of AM60B magnesium alloy resulting from the friction stir processing (FSP) were analysed in the present study. The sheets were produced by high-pressure die casting (HPDC) into the form of trial sheets 2.5 mm thickness and then friction-stir processed. The tensile mechanical properties were evaluated at room temperature in the longitudinal direction respect to the processing one. Tensile tests were also performed at higher temperatures and different strain rates in the nugget zone parallel to the processing direction, in order to analyse the superplastic properties of the recrystallized material and to observe the differences with the parent material as a function of the strong grain refinement due to the friction stir process. The dynamic recrystallized structure of the material was observed by employing optical and electron microscopy. The high temperature behaviour of the material was studied in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 150–300 °C and 10 −2 to 10 −4 s −1 , respectively. The deformation behaviour in the high temperature regime (275–300 °C) is related to the grain boundary sliding (GBS) acting in the material parallel to the tensile direction, differing strongly from the lower temperature one in which the deformation is strongly linked to grain triple junctions fracture.

Journal ArticleDOI
TL;DR: In this paper, a plate of as-cast NiAl bronze (NAB) material was sectioned from a large casting and a six-pass fusion weld overlay was placed in a machined groove; a portion of the weld reinforcement was removed by milling and a single friction stir processing (FSP) pass was conducted in a direction transverse to the axis of and over the weld overlay.
Abstract: A plate of as-cast NiAl bronze (NAB) material was sectioned from a large casting. A six-pass fusion weld overlay was placed in a machined groove; a portion of the weld reinforcement was removed by milling and a single friction stir processing (FSP) pass was conducted in a direction transverse to the axis of and over the weld overlay. A procedure was developed for machining of miniature tensile samples and the distributions of strength and ductility were evaluated for the fusion weld metal; for the stir zone (SZ) produced by the friction stir processing; and for a region wherein friction stir processing had taken place over the fusion weld. A region of low ductility in the heat affected zone (HAZ) of the fusion weld and in the thermomechanically affected zone (TMAZ) of friction stir processed material was attributed to partial reversion of an equilibrium lamellar eutectoid constituent upon local heating above ∼800 °C and formation of non-equilibrium transformation products upon subsequent cooling. The adverse effect on ductility is worse in the heat affected zone of the fusion weld than in the thermomechanically affected zone of friction stir processing due to the lower heat input of the latter process. The implications of this work to engineering applications of friction stir processing are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed terminology to standardize the descriptions of the microstructures created during FSP and FSW of titanium alloys, and also described the microstructure changes that occur in the stir zone (SZ), transition zone (TZ), and heat-affected zone (HAZ) during friction stir welding of Ti-6Al-4V.
Abstract: Friction stir processing (FSP) was used to modify the coarse fully lamellar microstructure on the surface of investment-cast and hot isostatically pressed (HIP) Ti-6Al-4V plate. The α colony and platelet structure in the base material (BM) was refined such that the effective slip length was reduced from the α colony size of the BM, several hundred microns, to that of fine equiaxed primary α grains that are on the order of 1 μm. This change in the microstructure resulting from FSP is expected to increase fatigue crack initiation resistance making it beneficial for titanium components for aerospace applications. The as-cast coarse lamellar microstructure has superior fatigue crack growth resistance compared to other microstructures that can be obtained by thermomechanical processing. Thus, it is likely that an increase in fatigue life is obtainable by FSP. Given the growing interest in friction stir welding (FSW) and FSP of titanium alloys, we believe some consistent microstructural descriptors will help avoid confusion. Accordingly, we propose terminology to standardize the descriptions of the microstructures created during FSP and FSW of titanium alloys. We also describe the microstructure changes that occur in the stir zone (SZ), transition zone (TZ), and heat-affected zone (HAZ) during FSP of Ti-6Al-4V.

Journal ArticleDOI
TL;DR: In this paper, the authors developed equations to model the rate of heat input from different geometries of friction stir processing (FSP) tools and compared with actual heat input obtained from embedded thermocouples within the stirred region.
Abstract: In this research, equations are developed to model the rate of heat input from different geometries of friction stir processing (FSP) tools. The model is then compared with actual heat input obtained from embedded thermocouples within the stirred region. The cooling curves obtained from the thermocouple data are then applied to the Derby–Ashby model for high angle grain boundary migration to predict the final grain size of a bulk sample produced by the friction stirring method. Submerged friction stir processing (SFSP) is introduced as a way of increasing the cooling rate of the bulk samples in an attempt to decrease the grain size. Microstructures obtained from both FSP and SFSP are characterized using transmission electron microscopy.

Journal ArticleDOI
TL;DR: In this paper, a continuously cast AA5083 aluminum sheet was friction stir processed and cold rolled in order to compare the properties with the as-cast and rolled material, and it was found that the inclusion of the FSP step refined the recrystallized grain size, increased the elongations, and lowered the flow stresses.
Abstract: AA5083 aluminum is a material of choice for superplastic automotive and aerospace aluminum panels. The cost of superplastic grade aluminum sheet, despite some reductions in recent years, remains relatively high. Continuous strip casting holds promise for low cost superplastic sheet. A continuously cast AA5083 aluminum sheet was friction stir processed and cold rolled in order to compare the properties with the as-cast and rolled material. It was found that the inclusion of the FSP step refined the recrystallized grain size, increased the elongations, and lowered the flow stresses.

Journal ArticleDOI
TL;DR: In this paper, the authors applied FSP to fabricate 10~20 vol% nano-sized ZrO2 and 5~10 vol% SiO2 particles into an Mg-AZ31 alloy to form bulk composites under the FSP parameters of advancing speed of 800 rpm and pin rotation of 45 min/min.
Abstract: Friction stir processing (FSP) has been applied to fabricate 10~20 vol% nano-sized ZrO2 and 5~10 vol% nano-sized SiO2 particles into an Mg-AZ31 alloy to form bulk composites under the FSP parameters of advancing speed of 800 rpm and pin rotation of 45 min/min. The microstructures and mechanical properties of the resulting composites were investigated. The clustering size of nano-ZrO2 and nano-SiO2 particles, measuring average ~200 nm was relatively uniformly dispersed, and the average grain size of the both Mg alloy of the composites varied within 1.0~2.0 μm after four FSP passes. No evident interfacial product between ZrO2 particles and Mg matrix was found during the FSP mixing in AZ31-Mg/ZrO2. However, significant chemical reactions at the AZ31-Mg/SiO2 interface occurred to form the Mg2Si phase. The mechanical responses of the nano-composites in terms of hardness and tensile properties are examined and compared.

Journal ArticleDOI
TL;DR: In this paper, a post-FSP compressive strain of ∼6% could raise the yielding stress of the AZ61 alloy from 140 to 260 MPa by inducing deformation twins.

Journal ArticleDOI
TL;DR: In this article, a dual-band thermography approach is used to measure the temperature distributions of AA5052 sheet during FSP, and the variation of temperature with process parameters and their correlation to the resulting microstructure are discussed.
Abstract: Despite the large number of studies that are being conducted to advance the friction stir processing (FSP) technology, the effects of FSP on various mechanical and microstructural properties are still in need for further investigations. In addition, correlations between FSP parameters, mechanical properties and microstructural characteristics are not yet well understood. Accurate correlations are needed for successful modeling and process optimization. It is established that the temperature generated during FSP plays an important role in determining the microstructure and properties of the processed sheet and defining the tool life. Process parameters must be carefully chosen to allow the generation of enough heat to soften the material while limiting significant grain growth. Accurate measurement of the temperature distributions during processing are essential to understand the complicated deformation and associated mechanisms and to allow for effective process optimization. In this work, a dual-band thermography approach is used to measure the temperature distributions of AA5052 sheet during FSP. The setup utilizes two infrared detectors, to neutralize the emissivity and the facial effects, with 30 Hz acquisition rate. The variation of temperature with process parameters and their correlation to the resulting microstructure are discussed.

Journal ArticleDOI
TL;DR: In this article, a finite element simulation of superplastic forming of a bowl shape component with inhomogeneous properties has been conducted and the pressure schedule, the overall forming time and the final thickness distribution in the formed component were calculated.
Abstract: For many superplastically formed components, only some regions undergo superplastic deformation. In these cases, instead of choosing expensive starting sheet material with superplastic properties, a low-cost, conventional material can be chosen and friction stir processing (FSP) can be performed in the selected regions to impart superplastic properties locally. This is called “selective superplastic forming” [R.S. Mishra, M.W. Mahoney, US Patent 6,712,916, 2002]. In this study, finite element simulation of superplastic forming of a bowl shape component with inhomogeneous properties has been conducted. We chose commercial 7075 Al alloy as the starting material and FSP was used to generate fine grains in some regions. The pressure schedule, the overall forming time and the final thickness distribution in the formed component were calculated. This simulation demonstrates the design possibilities with this new concept.

Patent
13 Jun 2007
TL;DR: In this article, a friction stir tool is provided to perform friction stir riveting using a partially consumable pin, wherein the pin includes a cutting edge on a bottom surface thereof, and the tool is rotated at a first speed to enable cutting by the pin into a first material that is overlapping a second material.
Abstract: A friction stir tool is provided to perform friction stir riveting using a partially consumable pin, wherein the pin includes a cutting edge on a bottom surface thereof, wherein the tool is rotated at a first speed to enable cutting by the pin into a first material that is overlapping a second material, wherein after the pin has cut to a sufficient depth, the rotational speed of the tool is increased to thereby enable plasticization of the consumable pin, the first material, and the second material, wherein the tool is then rapidly decelerated until stopped, enabling diffusion bonding between the pin, the first material and the second material.

Journal ArticleDOI
TL;DR: In this paper, the mechanical and microstructural properties of a Zr-modified 2014 aluminium alloy resulting from friction stir processing were analyzed, and the high temperature and high temperature tensile properties of the material were studied, in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 400-500°C and 10 −2 to 10 −4 ǫs −1, respectively.
Abstract: The mechanical and microstructural properties of a Zr-modified 2014 aluminium alloy resulting from friction stir processing were analysed. The sheets were processed parallel to the extrusion direction, the tensile mechanical properties were evaluated at room temperature in transverse and longitudinal direction respect to the processing one. Tensile tests were also performed at higher temperatures and different strain rates in the nugget zone, in order to analyse the superplastic properties of the recrystallized material and to observe the differences with the parent materials as a function of the strong grain refinement due to the friction stir process. The high temperature behaviour of the material was studied, in the parallel direction, by means of tensile tests in the temperature and strain rate ranges of 400–500 °C and 10 −2 to 10 −4 s −1 , respectively. Scanning electron microscopy (field-emission gun) examinations were also carried out to investigate more closely the fracture surfaces of the specimens tested at different temperatures and strain rates. The dynamic recrystallized structure of the material was observed by employing optical and electron microscopy. The room temperature and high temperature tensile properties of the heavily refined structure resulted optimal for superplastic deformation thanks to very high levels of strain to fracture and strain-rate sensitivity exhibited at high strain rate levels (10 −2 s −1 ).

Journal ArticleDOI
TL;DR: In this paper, the effect of friction stir processing (FSP) without the stirring pin on the formability and microstructure of Al5052-H32 sheets was investigated.

Journal ArticleDOI
TL;DR: In this paper, the deformation mechanism at room temperature was the same in both alloys, but at a high strain rate the elongation-to-failure of the friction stir processed material was significantly larger than that of the base material.

Journal ArticleDOI
TL;DR: In this paper, the effects of FSP parameters including forge force and traverse speed on the microstructure of an AZ31B-H24 magnesium alloy after friction stir processing (FSP) were examined.

Journal ArticleDOI
TL;DR: In this paper, a tool was manufactured from a tungsten alloy, which stabilizes the β phase and can locally suppress the β transus, and a post-processing α/β heat treatment was performed to demonstrate the microstructure effects of Tungsten dissolution.
Abstract: Significant tool wear manifested as submicron tungsten-rich particles was observed in the workpiece after friction stir processing (FSP) of investment cast Ti-6Al-4V on both the surface and in the bulk of the stir zone. The tool was manufactured from a tungsten alloy, which stabilizes the β phase and can locally suppress the β transus. A postprocessing α/β heat treatment was performed to demonstrate the microstructure effects of tungsten dissolution.

Patent
02 Feb 2007
TL;DR: Friction stir processing is applied to an aluminum-scandium alloy workpiece in either a wrought or cast state including scandium-containing precipitates as mentioned in this paper, which selectively modifies the microstructure of the workpiece by reducing grain size and recrystallization of the substrate.
Abstract: Friction stir processing is applied to an aluminum-scandium alloy workpiece in either a wrought or cast state including scandium-containing precipitates The process selectively modifies the microstructure of the aluminum-scandium workpiece, for example, by reducing grain size and recrystallization of the substrate Benefits include increased physical properties of the aluminum-scandium alloys as well as the ability to form unique alloy structures

Journal ArticleDOI
TL;DR: In this paper, the impact of crystallographic texture on tensile properties of AA5182-O and AA6111-T4 alloys was investigated using electron backscatter diffraction.
Abstract: The present article is the first part in a two-part series in which crystallographic texture developed during friction stir processing of AA5182-O and AA6111-T4 is characterized and its impact on tensile properties explored. For the texture measurements, coupons were cut from the friction stir processed zone at selected orientations relative to the direction of tool translation. Texture was characterized with electron backscatter diffraction (EBSD) in a scanning electron microscope. Measurements were made at key positions along the coupon surfaces and texture differences between the two friction stir processed Al alloys are discussed in detail. Grain size variations were also measured in both the base and friction stir processed materials and subsequently compared. In part 2, a state-of-art digital image correlation technique is used to investigate tensile properties of both friction stir processed Al alloys. The impact of crystallographic texture on mechanical properties is also explored in this latter part.


Journal ArticleDOI
TL;DR: In this article, the microstructure in the friction zone (FZ) exhibited an amorphous band-like structure with widths of 10-45nm and a small number of nanoscale crystalline particles were observed along the "band-like" structure.

Journal ArticleDOI
TL;DR: In this paper, Controlled Plasticity Burnishing (CPB) was applied to FSP Ni-Al Bronze to produce a depth of compression of 2.5 mm and a maximum subsurface magnitude of -150 ksi.
Abstract: Friction stir welding (FSW) allows the joining of aluminum alloys in ways previously unattainable offering new manufacturing technology. Friction stir processing (FSP) of cast alloys such as Ni-Al bronze eliminates casting voids and improves the properties to that of wrought material. However, the local heating produced by both FSW and FSP can leave a fusion zone with reduced mechanical properties and a heat-affected zone with tensile residual stresses that can be deleterious to fatigue performance. Controlled plasticity burnishing (CPB) is an established surface treatment technology that has been investigated and described extensively for the improvement of damage tolerance, corrosion fatigue, and stress corrosion cracking performance in a variety of alloys. Mechanical CPB processing in conventional CNC machine tools or with robotic tool positioning is readily adapted to industrial FSW and FSP fabrication of components, either simultaneously or as a post process. CPB was applied to FSP Ni-Al Bronze to produce a depth of compression of 2.5 mm and a maximum subsurface magnitude of –150 ksi. The effect of FSP on the fatigue performance in a saltwater marine environment and in the presence of foreign object damage (FOD) was documented with and without CPB processing. FSP was found to increase the fatigue strength of the Ni-Al Bronze by 70% without affecting the corrosion behavior of neutral salt solution. FSW actually produced a more noble material in the acidic salt solution. CPB after FSP mitigated damage 1 mm deep.