Showing papers on "Friction stir processing published in 2005"

Microstructure evolution during FSW/FSP of high strength aluminum alloys

Abstract: Microstructural characteristics of friction stir processed (FSP) 7075 Al samples in different regions behind the pin tool were investigated. Furthermore, the microstructure evolutions during friction stir welding (FSW)/FSP has been revealed. Multi-mechanisms, including dDRX, grain growth, dislocation introduction, dynamic recovery (DRV) and cDRX, were found to be inherent in the process at different stages. Because inhomogeneous plastic deformation was introduced by the process, individual grains in the final microstructure have undergone different evolution mechanisms. These are either from growth of initially recrystallized grains or are the result of cDRX of subgrains formed during DRV. Grains within the processed region exhibit different densities of dislocations and are in various degrees of recovery.

Submerged friction stir processing (SFSP): An improved method for creating ultra-fine-grained bulk materials

Abstract: This research demonstrates the use of submerged friction stir processing (SFSP) as an alternative and improved method for creating ultra-fine-grained bulk materials through severe plastic deformation. SFSP is compared with friction stir processing (FSP) done in air, through the use of thermocouples and transmission electron microscopy. Samples of Al-6061–T6 were created by SFSP that exhibit grain sizes less than 200 nm, while still obtaining a suitably stirred region.

Novel production for highly formable Mg alloy plate

Abstract: The principle and advantages of multi-pass friction stir processing (FSP) for the production of a highly formable Mg alloy, and some convincing experimental results are reported in this paper. FSP is a solid state processing technique which involves plunging and traversing a cylindrical rotating FSP tool through the material. FSP achieved grain refinement and homogenization of the as-cast microstructure in Mg alloy AZ91D. Multi-pass FSP produced a fine homogeneous microstructure having a grain size of 2.7 μm throughout the plate. The plate containing this FSPed microstructure exhibited fracture limit major strains six times larger than the diecast plate in the fracture limit diagram (FLD). The present study shows that multi-pass FSP is an efficient production method for a large-scale plate of a highly formable Mg alloy.

Mechanical properties of Friction Stir Processed 2618/Al2O3/20p metal matrix composite

Abstract: The effect of Friction Stir Processing (FSP) on the mechanical properties of 2618 aluminium alloy reinforced with 20% of alumina particles aluminium alloy has been studied in the present paper. The material was processed into the form of sheets of 7 mm thickness after T6 treatment and was tested in tension and fatigue at room temperature. 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 longitudinal direction, by means of tensile tests in the temperature and strain rate ranges of 400–500 °C and 10 −3 –10 −1 s −1 , respectively. Fracture surfaces of the deformed fatigue test specimens were comprehensively examined in a scanning electron microscope equipped with field emission gun to determine the macroscopic fracture mode and characterize the fine-scale topography and microscopic mechanisms governing fatigue fracture. The mechanisms governing fatigue life, cyclic deformation and fracture characteristics are analysed in function of magnitude of applied stress, intrinsic micro structural evolution and material deformation behaviour.

The influence of friction stir processing parameters on microstructure of as-cast NiAl bronze

Abstract: The influence of friction stir processing (FSP) parameters on the evolution of microstructure in an equilibrium-cooled, as-cast NiAl bronze (NAB) material was evaluated by optical microscopy (OM) and transmission electron microscopy (TEM) methods. A threaded pin tool was employed and tool rotation and traversing rates were varied in order to examine the spatial variation of stir zone microstructures in relation to FSP parameters. For processing at low rotation and traversing rates, the microstructure throughout the stir zone consists of elongated and banded grains of the primary α and transformation products of the β phase. Such microstructures reflect severe deformation at temperatures up to ∼900 °C in the α+β two-phase region for this NAB material. Increasing rotation and traversing rates, coarse Widmanstatten α near the surface in contact with the tool became apparent. The appearance of this constituent reflects nearly complete transformation to β during FSP with peak temperatures of ∼1000 °C. Also, complex stir zone flow patterns, often referred to as onion ring structures, become distinct in the mid regions of the stir zones as rotation and traversing rates increase. Schematic representations illustrating the effect of FSP parameters on thermal cycles at various locations in stir zones were prepared based on microstructure observations. Thus, processing at higher rotation and traversing rates results in higher peak temperatures near the surface in contact with the tool but also in steeper temperature gradients when compared to lower rotation and traversing rates.

Effect of Friction Stir Processing on the Kinetics of Superplastic Deformation in an Al-Mg-Zr Alloy

Abstract: The effect of friction stir processing on the superplastic behavior of extruded Al-4Mg-1Zr was examined at 350 °C to 600 °C and at initial strain rates of 1×10−3 to 1 s−1. A combination of a fine grain size of 1.5 μm and high-angle grain boundaries in the friction stir-processed (FSP) alloy led to considerably enhanced superplastic ductility, much-reduced flow stress, and a shift to a higher optimum strain rate and lower optimum temperature. The as-extruded alloy exhibited the highest superplastic ductility of 1015 pct at 580 °C and an initial strain rate of 1×10−2s−1, whereas a maximum elongation of 1280 pct was obtained at 525 °C and an initial strain rate of 1×10−1s−1 for the FSP alloy. The FSP alloy exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. A possible origin for enhanced superplastic deformation kinetics in the FSP condition is proposed.

Friction stirring and its application to drill bits, oil field and mining tools, and components in other industrial applications

Abstract: Solid state processing is performed on a workpiece that operates alone or is a component of equipment used in various demanding, harsh and wearing environments in which failure of a product could compromise safety or the environment or otherwise result in significant cost for repair or replacement, wherein the solid state processing performed by using a tool capable of friction stir processing, friction stir mixing, or friction stir welding results in a workpiece that offers a longer life-cycle and/or improved performance and/or improved reliability as a result of the solid state processing.

Solid state processing of materials through friction stir processing and friction stir mixing

Abstract: Solid state processing is performed on a workpiece (16) by using a tool (10) capable of friction stir processing, friction stir mixing, or friction stir welding, wherein solid state processing modifies characteristics of a workpiece while substantially maintaining a solid phase in some embodiments, allowing some elements to pass through a liquid phase in other embodiments, and wherein modified characteristics of the material include, but are not limited to, microstructure, macrostructure, toughness, hardness, grain boundaries, grain size, the distribution of phases, ductility, superplasticity, change in nucleation site densities, compressibility, expandability, coefficient of friction, abrasion resistance, corrosion resistance, fatigue resistance, magnetic properties, strength, radiation absorption, and thermal conductivity

Deconvoluting the influences of heat and plastic deformation on internal strains generated by friction stir processing

Abstract: Internal-strain profiles in friction-stir processed aluminum-alloy plates were investigated using neutron diffraction. Three different specimens were prepared with a purpose of separating the effects of frictional heating and severe plastic deformation on the internal-strain distribution: (Case 1) a plate processed with both stirring pin and tool shoulder, (Case 2) a plate processed only with the tool shoulder, and (Case 3) a plate processed only with the pin. The comparison between Cases 1 and 2 shows distinctly different strain profiles revealing deconvoluted effects of the different sources (i.e., heat, deformation, or the combination) on the internal strains generated during the friction-stir processing.

Deep cup forming by superplastic punch stretching of friction stir processed 7075 Al alloy

Abstract: Multiple overlapping passes of friction stir processing (FSP) were used to cover 80 mm wide region for punch stretching of 7075 Al alloy plate. The forming experiments were performed at 723 K. While a maximum depth of 52 mm (depth/punch diameter ∼ 2.7) could be achieved by punch stretching at a slow strain rate of 10 −3 s −1 , the maximum depth obtained at a higher strain rate of 10 −2 s −1 was 40.4 mm. However, tolerable variations in thickness can be maintained up to a depth of 18.5 mm which is nearly equal to the punch diameter. FEM simulation closely predicts the load and thickness variation till the point of initiation of cavities and instabilities.

The Effect of Friction Stir Processing on the Microstructure and Mechanical Properties of AF/C458 Aluminum Lithium Alloy

Abstract: : Aluminum-lithium alloys have been under development for lightweight-high strength aerospace structures but implementation has been slowed significantly because of poor short transverse fracture toughness and brittle intergranular delamination cracking. The alloy AF/C458 (now designated AA 2099) has been designed to exhibit decreased mechanical anisotropy and improved fracture toughness while maintaining ductility and strength levels. This thesis examines the application of Friction Stir Processing (FSP) of AF/C458 as an approach to refine and homogenize the grain structure and enhance mechanical properties. FSP of peak-aged material results in refined, equiaxed grains but with reduced hardness due to the heat input of the process. The effect of post-FSP heat treatment has been established and the influence of FSP on tensile and fatigue properties has been determined.

Friction stir welding of copper and copper alloys

Abstract: Copper, through having good thermal conductivity and a relatively high melting point, generally requires preheating treatment to maintain satisfactory penetration during arc welding, ranking as a hard-to-weld material. Like aluminium and magnesium, however, copper is basically a soft metal and can therefore be relatively easily joined by friction stir welding. Available FSW research has focused on fabrication of copper (oxygen-free copper) containment canisters for nuclear waste,1–6 fabrication of copper backing plates for sputtering devices by FSW seal welding,7, 8 and some other applications,9 whereas FSW research on copper alloys has thus far been little documented.10, 11 Related research topics include studies of Al alloy to Cu alloy dissimilar joints12, 13 as well as – although not quite the same as friction stir welding – friction stir processing of Ni–Al bronze for casting structure modification14–16 and friction stir processing of a Cu–Mn alloy for surface modification purposes.17

High-Strengthening of Mg-5.5 mass%Y-4.3 mass%Zn Cast Alloy by Friction Stir Processing

Abstract: High-strength Mg–Y–Zn alloy plate was obtained by friction stir processing (FSP) after casting. In this study, the Mg–Y–Zn alloy by FSP showed sufficiently high performance with low cost. As-cast material was held at 723 K for 95 h. It then showed a lamellar structure, which might have resulted from long-range periodic structure. However, this lamellar structure showed very low hardness, as did the as-cast material. Plates cut from heat-treated ingot were processed as single, overlapped double, and multiple pass FSP. After FSP, each processed materials was cut for microscopic measurement and hardness testing. Ultra-fine-grained microstructures are obtainable using the FSP. Micro-Vickers hardness tests for each pass result in the occurrence of strengthening for FSP of Mg–Y–Zn alloy. There was little change in grain size and hardness of prestirred zone by the next pass of stirring.

Pre-treated effect of friction stir processing of Al alloy 5052 on vibration fracture behavior under resonant vibration

Abstract: In this study, 5052 Al–Mg alloy was pre-treated and friction stir processing (FSP) was then performed on the specimens to explore the deformation resistance. The experimental results indicate that the FSP specimens not only had better tensile properties but also better vibration fracture resistance. It is significant that the tensile elongation and deformation resistance tended to increase as the grain was refined by friction stir processing. Results show that the use of FSP yielded uniform hardness distribution and slightly larger n values which improved the vibration fracture resistance of the specimens. However, even without FSP, more uniform elongation and larger n values could still improve the vibration fracture resistance of the specimens. Consequently, the uniform elongation and larger n values play an important role in increasing vibration fracture resistance. As for crack propagation, the FSP specimens revealed only a few slip bands in the vicinity of the main crack, and the 5052H34 specimen displayed a few slip bands in the vicinity of the main crack. However, more slip bands were observed in the vicinity of the main crack on the 5052-O specimens, and there were deformation traces and advancing cracks rising at the front of the main crack. Consequently, vibration fracture resistance can also be better improved if the crack initiation and propagation through the stir zone of FSP specimens are controlled. This is correlated with the formation of fine grains through dynamic recrystallization in the vicinity of stir zone.

Correlation Between the Microstructure and Forces Generated During Friction Stir Processing of AA5052

Abstract: The microstructure of friction stir processed AA5052 sheets is investigated using Scanning Electron Microscopy (SEM) and Orientation Imaging Microscopy. The correlation between the generated forces during processing and the microstructure is evaluated. Observations indicate that the finest microstructure are achieved when the plunging forces are at minimum.

Statistical Investigation of Friction Stir Processing Parameter Relationships

Abstract: STATISTICAL INVESTIGATION OF FRICTION STIR PROCESSING PARAMETER RELATIONSHIPS Jonathan H. Record Department of Mechanical Engineering Master of Science Friction Stir Welding (FSW) is an emerging joining technology in which basic process understanding is still inadequate. Knowledge of FSW parameter relationships is needed to better understand the process and implement proper machine control. This study utilized a 3-factor, 3-level factorial design of experiments to investigate relationships between key process inputs and measured output parameters. All experiments utilized 7075-T7 aluminum and a threaded pin tool with a 25.4 mm shoulder diameter, 4.76 mm pin length, and 7.9 mm pin diameter. Spindle speed, feed rate, and tool depth were varied throughout 54 welds while X, Y, and Z forces, X torque, three tool temperatures, and motor power were measured. Empirical models were developed to relate outputs to inputs. The relationships between inputs and outputs are nonlinear and require, at a minimum, a quadratic equation to reasonably model them. These models were further analyzed to explore possible control schemes. Tool depth was found to be the most fundamental means of controlling weld forces and tool temperatures. This research describes the input/output relationships enumerated above for FSW as well as a discussion of possible control schemes.

Experimental and analytical study of friction stir processing

Abstract: OF THESIS EXPERIMENTAL AND ANALYTICAL STUDY OF FRICTION STIR PROCESSING Friction stir processing (FSP) has recently become an effective microstructural modifications technique. Reported results showed that for different alloys, FSP produces very fine equiaxed and homogeneous grain structure. FSP is considered to be a new processing technique and more experimental and analytical investigations are needed to advance the industrial utilization of FSP. Most of the work that has been done in the friction stir processing field is experimental and limited modeling activities have been conducted. Attempts to develop a predictive model to correlate the resulting microstructure with process parameters are scarce. In this work, commercial 5052 Aluminum alloy sheets are friction stir processed at different rotational and translational speeds. The effects of process parameters on the resulting microstructure and mechanical properties are investigated. The results show that FSP produces very fine and homogenous grain structure, and it is observed that smaller grain size structure is obtained at lower rotational speeds. It is also observed that the hardness of the processed sheet depends strongly on the rotational and translational speeds and varies widely within the processed region. The results suggest that the temperature achieved during processing plays an important role in determining the microstructure and properties of the processed sheet. In addition, a new modeling approach based on experiments and theory is proposed to predict the grain size of the friction stir processed material as a function of process parameters. The proposed approach involves determination of the strain rate distribution in the processed (deformation) zone based on the velocity fields of the material and correlating the strain rate distribution with the average grain size of the resulting microstructure using Zener-Holloman parameter.

Solid state processing of industrial blades, edges and cutting elements

Abstract: A system and method for friction stir processing of an industrial blade, wherein friction stir processing techniques are used to modify the properties of the industrial blade to thereby obtain superior edge retention and superior resistance to chipping.

Effect of Mg Content on Vibration Fracture Resistance of Friction Stirred Al-Mg Alloys

Abstract: In this study, the effect of Mg content on friction stirred Al–Mg alloy is discussed, and the experimental results indicate that grains of parent plate which are refined through FSP (friction stir processing) are effective in enhancing tensile properties of materials through FSP and improving the vibration fracture resistance of friction stirred specimens. It should be noted that the deterioration of vibration fracture resistance can be recognized as Mg content increases, the grain size actually has been refined by FSP. From crack propagation result, an intergranular crack propagation feature can be recognized in the specimen with higher Mg content, and it is reasonable to suggest that the precipitation of β phase plays an important role in the deterioration of vibration fracture resistance. However, all cross-sectioned microstructures at stir zone show that distinct finer grains which can be acquired by dynamic recrystallization during FSP. That meaningful improvement of uniform elongation on friction stirred specimens can be recognized is not only resulted from controlling the grain size factor, but also microstructural characteristics factor which are resulted from high temperature shear deformation.

Solid state processing of hand-held knife blades to improve blade performance

Abstract: A system and method for friction stir processing of a hand-held cutting edge, wherein friction stir processing techniques are used to modify the properties of the hand-held cutting edge to obtain superior edge retention and superior resistance to chipping of the hand-held cutting edge.

Effects of friction stir processing on mechanical properties of the cast aluminum alloy A356

Abstract: Surfaces of A356 castings were treated by friction stir processing to reduce porosity and to create more uniform distributions of second-phase particles. Dendritic microstructures were eliminated in stir zones. The ultimate tensile strength, ductility, and fatigue life of the cast A356 was increased by friction stir processing. Tensile specimens of cast and friction stir processed metal were also given a T7 heat treatment. Higher tensile strengths and ductilities were also measured for these friction stir processed specimens.

Microstructure Refinement and Void Evolution via Friction Stir Processing of AA 5052

Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005