Showing papers on "Friction stir processing published in 2008"
TL;DR: Friction stir welding (FSW) is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components.
Abstract: Friction stir processing (FSP), developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys, is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.
955 citations
TL;DR: In this article, the applicability of hot working of metals and alloys is reviewed in the context of their applicability to friction stir welding (FSW) and friction stir processing (FSP) and two of these models are used to interpret microstructure and microtexture data for two aluminum alloys subjected to FSP.
470 citations
TL;DR: In this paper, the effect of tool pin profile and tool shoulder diameter on FSP zone formation in AA6061 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the FSP zones formation.
404 citations
TL;DR: In this article, the effect of welding speed and tool pin profile on FSP zone formation in AA2219 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the formation.
318 citations
TL;DR: In this article, the effect of axial force and tool pin profiles on FSP zone formation in AA6061 aluminium alloy has been analyzed macroscopically and the tensile properties of the joints have been evaluated and correlated with the formation.
Abstract: AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to the fusion welding processes that are routinely used for joining structural aluminium alloys, the 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. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force etc., and the tool pin profile plays a major role in deciding the weld quality. In this investigation an attempt has been made to understand the effect of axial force and tool pin profiles on FSP zone formation in AA6061 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 axial force levels. 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.
238 citations
TL;DR: Friction stir processing (FSP) is a novel metal-working technique that provides microstructural modification and control in the near-surface layer of metal components as discussed by the authors, which resulted in the break-up of coarse dendrites and secondary phases, refinement of matrix grains, dissolution of precipitates and elimination of porosity, thereby improving the mechanical properties of the castings significantly.
234 citations
TL;DR: In this article, the development of grain structure was found to be a complex process driven mainly by grain subdivision, but also involving the geometrical effect of strain and local grain-boundary migration.
152 citations
TL;DR: In this article, the mean hardness of the nanograined region reaches ∼1.5 GPa (or 150 Hv), about three times that of the matrix, and the evolution of the structure is also investigated.
145 citations
TL;DR: Friction stir processing (FSP) was applied to produce aluminum based nanocomposites from powder mixtures of Al-10-at%Fe Billet of powder mixture were prepared by the use of conventional press and sinter route The sintered billet was then subjected to multiple passages of FSP.
125 citations
TL;DR: In this article, a feasibility investigation was carried out of the formation of surface composite by uniformly distributing SiC particles 1˙25 µm in size into a surface layer of an A 1050-H24 Al plate through friction stir processing.
Abstract: A feasibility investigation has been carried out of the formation of surface composite by uniformly distributing SiC particles 1˙25 µm in size into a surface layer of an A 1050-H24 Al plate through friction stir processing (FSP). The SiC particle was filled into a groove cut on the Al plate, covered by an Al sheet 2 mm thick, and a rotating tool was penetrated from the cover sheet so that the probe tip reached a depth beyond the groove bottom. The effects of process parameters (rotation speed and travelling speed) and applying multiple passes on the distribution of SiC particle in the nugget zone were investigated. The effects of groove size and its position relative to the tool probe were also investigated. Applying multiple passes had a great effect on the homogeneity of the SiC particle distribution. At rotation speeds of 2000–3000 rev min−1, the SiC particles tended to cluster in some places in the nugget zone. By decreasing the rotation speed to 1000–1500 rev min−1, the SiC particle was distr...
107 citations
TL;DR: In this paper, a multipass friction stir processing of AA 2219-T87 aluminium alloy to a depth of 2 mm in a 5 mm plate resulted in fine α-Al grains, reduction and dissolution of both eutectic phase (CuAl2) and the strengthening precipitates (cuAl2).
Abstract: Multipass friction stir processing of AA 2219-T87 aluminium alloy to a depth of 2 mm in a 5 mm plate resulted in fine α-Al grains, reduction and dissolution of both eutectic phase (CuAl2) and the strengthening precipitates (CuAl2). Anodic polarization and electrochemical impedance tests in 3.5% NaCl showed an improved corrosion resistance of the processed alloy, which increased with the number of passes. Salt spray and immersion tests also showed improved resistance to corrosion. The increased resistance to corrosion is attributed to the dissolution of CuAl2 particles, which was established by XRD and DSC studies. © 2008 Elsevier B.V. All rights reserved.
TL;DR: Friction stir processing (FSP) was applied to extruded Al-Mg-Sc alloy to produce fine-grained microstructure with 2.6μm grains as mentioned in this paper.
TL;DR: In this paper, a set of equations are proposed to describe the horizontal onion ring patterns that are believed to result from a geometric effect, which indicates that the spacing of adjacent rings is equal to the advance per revolution.
TL;DR: In this paper, friction stir processing was used to produce ultra-fine-grained Al-Zn-Mg-Cu alloy and a low-temperature superplasticity of 350-540% was achieved at 200-350 degrees C.
TL;DR: In this article, the authors used a dual-beam focused ion beam device to evaluate the performance of investment-cast Ti-6Al-4V on four-point bend specimens and found that the fine-grained equiaxed structure has about a 12 pct higher compressive yield stress.
Abstract: Investment-cast titanium components are becoming increasingly common in the aerospace industry due to the ability to produce large, complex, one-piece components that were previously fabricated by mechanically fastening multiple pieces together. The fabricated components are labor-intensive and the fastener holes are stress concentrators and prime sites for fatigue crack initiation. The castings are typically hot-isostatically-pressed (HIP) to close internal porosity, but have a coarse, fully lamellar structure that has low resistance to fatigue crack initiation. The as-cast + HIP material exhibited 1- to 1.5-mm prior β grains containing a fully lamellar α + β microstructure consistent with slow cooling from above the β transus. Friction stir processing (FSP) was used to locally modify the microstructure on the surface of an investment-cast Ti-6Al-4V plate. Friction stir processing converted the as-cast microstructure to fine (1- to 2-μm) equiaxed α grains. Using micropillars created with a dual-beam focused ion beam device, it was found that the fine-grained equiaxed structure has about a 12 pct higher compressive yield stress. In wrought products, higher strength conditions are more resistant to fatigue crack initiation, while the coarse lamellar microstructure in the base material has better fatigue crack growth resistance. In combination, these two microstructures can increase the fatigue life of titanium alloy castings by increasing the number of cycles prior to crack initiation while retaining the same low-crack growth rates of the colony microstructure in the remainder of the component. In the current study, high-cycle fatigue testing of investment-cast Ti-6Al-4V was performed on four-point bend specimens. Early results show that FSP can increase fatigue strength dramatically.
01 Jul 2008
TL;DR: In this paper, the effect of friction stir processing (FSP) on electrical conductivity and corrosion resistance of AA6063-T6 Al alloy was studied, and the microstructural and mechanical properties of the alloy were investigated.
Abstract: The aim of this paper is to study the effect of friction stir processing (FSP) on electrical conductivity and corrosion resistance of AA6063-T6 Al alloy. Also, the microstructural and mechanical ch...
TL;DR: In this article, the residual stresses generated during the stir processing of AA7075-T6 aluminium blanks are examined through numerical simulation and experiments to highlight and distinguish the effects of thermal and mechanical loadings.
TL;DR: In order to obtain fine-microstructure magnesium alloys with superior mechanical properties, AZ61 alloy was processed by friction stir processing (FSP) combined with rapid heat sink as discussed by the authors.
TL;DR: In this paper, the effect of friction stir processing (FSP) on fatigue crack growth (FCG) behavior of a cast aluminum alloy was examined, and the crack path and interaction of the crack-tip with the microstructure was characterized.
TL;DR: In this paper, the flow behavior in friction stir processing of metals is investigated by tracking the motion of discrete particles and grid deformation in a plasticine workpiece, where the forward motion of the tool is stopped nearly instantaneously to freeze the flow of material around the tool.
TL;DR: In this article, the extruded Mg-Zn-Y-Zr plate was subjected to friction stir processing (FSP), which resulted in significant breakup and dispersion of bulky W-phase particles and remarkable grain refinement, thereby substantially enhancing superplasticity.
Abstract: The extruded Mg–Zn–Y–Zr plate was subjected to friction stir processing (FSP). FSP resulted in significant breakup and dispersion of bulky W-phase particles and remarkable grain refinement, thereby substantially enhancing superplasticity. Maximum superplasticity of 635% was achieved at 450 °C and a relatively high strain rate of 3 × 10−3 s−1. By comparison, the as-extruded sample did not exhibit superplasticity. Grain boundary sliding was identified to be the primary deformation mechanism in the FSP Mg–Zn–Y–Zr by superplastic data analyses and surfacial morphology observations. Furthermore, the superplastic deformation kinetics of the FSP Mg–Zn–Y–Zr is significantly faster than that of equal channel angular pressed (ECAP) magnesium alloys under both as-ECAP and annealing conditions.
Patent•
30 May 2008TL;DR: In this article, a detection system is provided for obtaining information related to a lateral alignment of the rotating member of a spindle actuator coupled to a rotary tool comprising a rotating member for contacting and processing the first workpiece.
Abstract: A friction stir system for processing at least a first workpiece includes a spindle actuator coupled to a rotary tool comprising a rotating member for contacting and processing the first workpiece. A detection system is provided for obtaining information related to a lateral alignment of the rotating member. The detection system comprises at least one sensor for measuring a force experienced by the rotary tool or a parameter related to the force experienced by the rotary tool during processing, wherein the sensor provides sensor signals. A signal processing system is coupled to receive and analyze the sensor signals and determine a lateral alignment of the rotating member relative to a selected lateral position, a selected path, or a direction to decrease a lateral distance relative to the selected lateral position or selected path. In one embodiment, the friction stir system can be embodied as a closed loop tracking system, such as a robot-based tracked friction stir welding (FSW) or friction stir processing (FSP) system.
TL;DR: In this article, the possibility of using FSP with and without SiC particles to modify the microstructure and hardness of commercial AZ31 is examined, and the mean grain size of the stir zone with the SiC particle was obviously smaller than the same zone without the particle.
Abstract: Friction stir processing (FSP) is a novel technique to produce ultrafine grained materials. Most of the researches conducted on FSP focus on aluminum alloys. Despite the potential weight reduction that can be achieved by using magnesium alloys, a few researches have been reported on FSP of magnesium alloys. In this work, the possibility of using FSP with and without SiC particles to modify the microstructure and hardness of commercial AZ31 is examined. SiC particles were uniformly dispersed into an AZ31 matrix by FSP. The mean grain size of the stir zone with the SiC particles was obviously smaller than the same zone without the SiC particles. SiC reinforced magnesium matrix composites created by FSP with cooling rapidly the plate that exhibit ultrafine grain size approximately 1μm and nearly doubled the hardness of the base material.
TL;DR: In this article, an analytical model is presented that can predict the strain rate distribution and the deformation zone in the friction stir processed zone as a function of process parameters, including the effects of both the shoulder and the pin of the tool on the material flow.
Abstract: Friction Stir Processing (FSP) is becoming an acceptable technique for modifying the grain structure of sheet metals. One of the most important issues that hinder the widespread use of FSP is the lack of accurate models that can predict the resulting microstructure in terms of process parameters. Most of the work that has been done in the FSP field is experimental, and limited modeling activities have been conducted. In this work, an analytical model is presented that can predict the strain rate distribution and the deformation zone in the friction stir processed zone as a function of process parameters. In the model, the velocity fields within the processed zone are determined by incorporating the effects of both the shoulder and the pin of the tool on the material flow. This is achieved by introducing state variables and weight functions. The model also accounts for different interfacial conditions between the tool and the material. The effects of different process parameters and conditions on the velocity fields and strain rate distributions are discussed. The results clearly show that the model can successfully predict the shape of the deformation zone and that the predicted strain rate values are in good agreement with results reported in the literature.
Patent•
18 Aug 2008
TL;DR: In this paper, an apparatus for forming a workpiece to a desired, non-planar configuration is provided, where at least one friction stir forming tool, having a shoulder and a pin, is used to urge the workpiece against a contour surface of a die or a shoulder that is opposite the structural member from the tool.
Abstract: An apparatus for forming a workpiece to a desired, non-planar configuration are provided. At least one friction stir forming tool, having a shoulder and a pin, is used to urge the workpiece to the desired configuration and friction stir form the workpiece. The forming tool can urge the workpiece against a contour surface of a die or a shoulder that is opposite the structural member from the tool. Thus, the forming tool plasticizes a portion of the workpiece and urges the workpiece to the desired configuration. In addition, the material properties of the workpiece can be improved by the friction stir processing.
TL;DR: A new surface hardening technology for cast irons was developed by applying the Friction Stir Processing (FSP) in which the matrix can be controlled in the solid state as discussed by the authors.
Abstract: A new surface hardening technology for cast irons was developed by applying the Friction Stir Processing (FSP) in which the matrix can be controlled in the solid state. Flake graphite cast iron (FC300) and spheroidal graphite cast iron (FCD700) were used to investigate the validity of this new method. As a result, it has been clarified that a Vickers hardness of about 700 HV is obtained for both the flake graphite cast iron and the spheroidal graphite cast iron, and that the hardness depends on the size and the density of the martensite phase. Moreover, the hardness can be controlled down to about 500 HV by changing the stirring degree. For previous hardening methods, post surface-processing was required because a large distortion was generated. However, with this new method, many advantages, such as a higher surface hardness and unnecessary post surface-processing, could be obtained.
TL;DR: Friction stir processing of cast and mill annealed Ti-6Al-4V was studied to determine whether this thermomechanical processing technique is feasible for local microstructural modification to improve fatigue properties for aerospace engine applications as discussed by the authors.
Abstract: Friction stir processing (FSP) of cast and mill annealed Ti-6Al-4V was studied to determine whether this thermomechanical processing technique is feasible for local microstructural modification to improve fatigue properties for aerospace engine applications. The ability to produce a friction stir processed surface layer is thought to provide a microstructure that is more resistant to fatigue crack initiation than the as-cast microstructure of the bulk. FSP resulted in a microstructure of either very fine equiaxed α or a colony microstructure with refined prior β grains when processing occurred below the β transus or above the β transus, respectively. The final microstructure observed in the stir zone was related to the processing conditions and was independent of the initial cast or wrought microstructures. Electron backscatter diffraction was used to assess the presence of microtexture in the stir zone. There was very little microtexture observed in sub-transus processed material. A moderate strength α phase texture was observed in the cast and wrought materials processed above the β transus. Fatigue tests performed on 4-point bend samples revealed a dramatic increase in fatigue life after FSP in both mill annealed (presented here) and cast + hot isostatic pressed materials (previously presented) although only a limited number of samples were available. Substantial tool wear is an issue and tungsten contamination is readily observed when FSP temperatures were below the β transus. This could be a concern in high temperature applications or for applications requiring postprocessing heat treatment.
Patent•
30 Sep 2008
TL;DR: In this article, a high strength aluminum alloy hollow extrusion formed member was used to prevent the breakage of a bumper reinforcement member during vehicle collision while achieving weight reduction by using a high-strength aluminum alloy.
Abstract: PROBLEM TO BE SOLVED: To prevent breakage of a bumper reinforcement member when occurrence of vehicle collision while achieving weight reduction by using a high strength aluminum alloy hollow extrusion formed member. SOLUTION: The bumper system 7 includes: a bumper reinforcement member 5 made of a hollow extrusion formed member of an aging-treated 7000-based high strength aluminum alloy; and bumper stays 6 mounted on the back sides of both ends of the reinforcement member 5 in the vehicle width direction. The bumper reinforcement member 5 has an upper and lower walls 5c and 5d coupling the collision surface side and the back surface side, and in front of the bumper stay 6s, friction stir processing (friction stir processed parts 4) is applied to the upper and lower walls 5c and 5d. The processing depth of the friction stir processing is 30% or more of the member thickness where the processing is applied. COPYRIGHT: (C)2010,JPO&INPIT
01 Jul 2008
TL;DR: In this article, the results of residual stress analysis in case of FSP of AA6061-T4 plates, 10 mm thickness, demonstrating the process ability to locally modify the base metal properties.
Abstract: Currently, after appropriate heat treatments, the 6xxx aluminium alloys are used in a variety of applications including aircraft fuselage skins and automobile body panels and bumpers, instead of more expensive 2xxx or 7xxx alloys. The paper presents the results of the residual stress analysis in case of Friction Stir Processing - FSP of AA6061-T4 plates, 10 mm thickness, demonstrating the process ability to locally modify the base metal properties. The residual stresses, DRX depicted, are correlated with the microstructure and hardness results.