Papers by Keyword: Friction Stir Processing (FSP)

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Authors: Wen Liang Chen, Chun Ping Huang, Li Ming Ke
Abstract: Carbon nanotubes(CNTs) reinforced copper matrix composites were successfully produced by Friction Stir Processing (FSP). The effect of applying multiple FSP passes on the forming of composites was studied, the microstructure, microhardness and conductivity of the good forming composite were analyzed. The experimental results showed that CNTs uniformly distributed and good forming composite can be obtained by three FSP passes. Compared to the parent material, the grain size of the composite has significantly refined, and the microhardness of the composite has also greatly improved, but the conductivity of the composite has a small decrease.
524
Authors: Ali H. Ammouri, Ali H. Kheireddine, Ramsey F. Hamade
Abstract: Grain size determines to a large degree the mechanical properties of the friction stir processed (FSP) material. Developed in this work is a numerical (FEM) based-model for predicting values of the Zener-Hollomon parameter (Z-parameter) as function of input process parameters during friction stir processing of AZ31B. Prediction of Z values is desirable given that direct relations exist between the Z-parameter and the average grain size in the dynamically recrystallized zone (DRX). For this purpose, utilized in this work is a robust finite element model with a suitable constitutive equation and boundary conditions the results of which have been previously validated against published experimental data. A virtual test matrix constituting of 16 cases (4 spindle speed, N, x 4 feed, f) was run. Based on resulting state variables of strain rates and temperatures at a representative point within the stir zone, a statistically-validated power equation model was developed that relates Z-parameter values to input parameters of speed and feed. The results of the numerically developed power equation were validated against experimental results. This model can be readily used in future control frameworks to FSP produce AZ31B sheets of a predefined target grain size.
93
Authors: Marek Stanislaw Węglowski
Abstract: The effect of rotational and travelling speeds and down force on the torque in Friction Stir Processing (FSP) process are presented. To find a dependence combining the spindle torque acting on the tool with the rotational speed, travelling speed and the down force, the artificial neural networks have been applied. Studies have shown that the increase in the rotational speed causes decrease in the torque while the increase in the travelling speed and down force causes the increase in the torque at the same time. The relationship between parameters of the process and the temperature of the tool, based on measurement head TermSTIR, were presented. Tests were conducted on casting aluminium alloy AlSi9Mg. Application of FSP process resulted in a decrease in the porosity in the modified material and microstructure refining
1787
Authors: Chun Y. Chan, Philip B. Prangnell, Simon J. Barnes
Abstract: Friction Stir Processing (FSP) has potential for locally enhancing the properties of Al-Si alloy castings, for demanding applications within the automotive industry, by greatly refining the second phase particle size. In the present study, the homogeneity of particle refinement and second phase spatial distribution within the process zone, as well as the relationship to the processing parameters, were investigated in a gravity die cast Al-Si LM24/A380 alloy, subjected to a range of FSP conditions. Detailed image analysis and the dirichlet tessellation method were used to quantify particle clustering. ‘Stop-action’ experiments were also used to study the process of particle break up, by following the behaviour through the deformation zone surrounding the tool.
85
Authors: Telmo G. Santos, João Faria, Pedro Vilaça, R.M. Miranda
Abstract: Eddy currents are based on electromagnetic induction and analysis of electrical currents on conductive materials. This method is used for thickness measurements, corrosion and defects detection, electrical conductivity and magnetic permeability measurements. Recently, it has been exploited as a materials characterization technique, namely in solid state welding, since, compared to hardness, it is based in distinct physical phenomena. Electrical conductivity is controlled by electronic mobility, while hardness depends on crystal defects and thus a scale factor exists. This paper presents results of this characterization technique applied to multipass solid state friction stir processing (FSP) of AA1100 alloy. These results were compared to microstructural analysis and hardness measurements and show that eddy current is a feasibly, reliable and expedite technique to characterize processed materials. The electrical conductivity measured by eddy currents, maps more precisely structural features, while hardness does not. Measurement of electrical conductivity field suggests having potential to constitute an alternative and/or complement to hardness evaluation with the further advantage of being a non-destructive method.
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Authors: B. Ratna Sunil, T.S. Sampath Kumar, Chakkingal Uday
Abstract: Magnesium and its alloys are promising candidates for temporary implant applications due to their combination of mechanical properties, biocompatibility and biodegradation. But higher degradation rate restricts their wider applications. Recently friction stir processing (FSP) has emerged as a promising tool to attain near surface fine grain structure in materials. In the present work commercial purity magnesium was processed by FSP to obtain fine grain structure and the effect of the grain refinement on the bioactivity was investigated. The microstructural observations were carried out at different locations of the processed regions, from an original grain size of 1500μm, grain refinement was achieved to a level of 6.2μm at the nugget zone. Microhardness was measured across the processed regions and improvement was observed at the nugget zone. Contact angle measurements were carried out to estimate the wettability of the material and the measurements indicate increased wettability due to the increased surface energy induced by grain refinement. For studying the bioactivity the FSPed samples were immersed in simulated body fluids (SBF 5X) for different intervals of time. The phases formed on the samples were investigated by X-ray diffraction (XRD) method, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The phases on the samples after 72hr of immersion were confirmed as magnesium hydroxide, hydroxyapatite and magnesium phosphate by XRD. Controlled degradation due to formation of these phases was observed. FSPed samples have more deposition of Ca/P than non FSP samples which implies better control over the degradation. Hence grain refinement by FSP can be a simple technique to control the degradation of magnesium for temporary implant applications.
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Authors: Anne Mertens, Aude Simar, Francis Delannay
Abstract: Mg-Al-Zn alloys have been reinforced with carbon fibres using either the liquid state process of squeeze casting (SC), or friction stir processing (FSP), a solid state process developed more recently and that appears as a promising alternative for the large-scale production of C-Mg composites. Both processes have shown their ability to produce sound composites with enhanced strength compared to the non-reinforced alloys. In SC composites, the unsized woven C fabric remains intact while in the FSP composites the sized C fabric is fragmented in short fibres, with an aspect ratio typically equal to 4, homogenously distributed in the Mg alloy matrix.
1221
Authors: Ali H. Ammouri, Ramsey F. Hamade
Abstract: Utilizing a proper material model for describing the mechanical behavior of any material is key for a successful simulation of friction stir processing (FSP) where temperature, strain, and strain rate gradients vary abruptly within, and when moving away, from the stirring zone. This work presents a comparison of how faithfully do three different constitutive equations reproduce the state variables of strain, strain rate, and temperature in an FEM simulation of a test-case FSP (1000 rpm spindle speed, and 90 mm/min feed). The three material models considered in this comparison are namely: Johnson-Cook (JC), Sellars-Tegart (ST), and Zerilli-Armstrong (ZA). Constants for these constitutive equations are obtained by fitting these equations to experimental mechanical behavior data collected under a range of strain rates and temperatures of twin-rolled cast wrought AZ31B sheets.It is widely recognized that JC-based models over predicts stress values in the stir zone whereas ST-based models are incapable of capturing work hardening outside of the stir zone. Therefore, a ZA model, being a physical based-HCP specific model, is hereby investigated for its suitability as a material model that would overcome such drawbacks of JC-and ST-based models. The equations from the constitutive models under consideration are fed into an FEM model built using DEFORM 3D to simulate the traverse phases of a friction stir process. Amongst these three material models, comparison results suggest that the HCP-specific ZA model yield better predictions of the state variables: strain, strain rate, and temperature, and, consequently, the estimated values for flow stresses.
2239
Authors: Ali H. Ammouri, Ramsey F. Hamade
Abstract: Utilizing a proper material model for describing the mechanical behavior of any material is key for a successful simulation of friction stir processing (FSP) where temperature, strain, and strain rate gradients vary abruptly within, and when moving away, from the stirring zone. This work presents a comparison of how faithfully do three different constitutive equations reproduce the state variables of strain, strain rate, and temperature in an FEM simulation of a test-case FSP (1000 rpm spindle speed, and 90 mm/min feed). The three material models considered in this comparison are namely: Johnson-Cook (JC), Sellars-Tegart (ST), and Zerilli-Armstrong (ZA). Constants for these constitutive equations are obtained by fitting these equations to experimental mechanical behavior data collected under a range of strain rates and temperatures of twin-rolled cast wrought AZ31B sheets.It is widely recognized that JC-based models over predicts stress values in the stir zone whereas ST-based models are incapable of capturing work hardening outside of the stir zone. Therefore, a ZA model, being a physical based-HCP specific model, is hereby investigated for its suitability as a material model that would overcome such drawbacks of JC-and ST-based models. The equations from the constitutive models under consideration are fed into an FEM model built using DEFORM 3D to simulate the traverse phases of a friction stir process. Amongst these three material models, comparison results suggest that the HCP-specific ZA model yield better predictions of the state variables: strain, strain rate, and temperature, and, consequently, the estimated values for flow stresses.
18
Authors: Ning Sun, Diran Apelian
Abstract: Friction stir processing (FSP) is a post-processing method that locally manipulates the microstructure by imparting a high level of energy in the solid state giving rise to improved mechanical properties. Additionally, FSP has emerged as an advanced tool to produce surface composites and synthesize the second phase into the matrix. In the current study, FSP was investigated for the manufacture of localized zones of composite materials made by the emplacement of a second phase into cast A206 Al alloy matrix. Both the discontinuously reinforced aluminum (DRA) and some encapsulated powders (nano-sized SiC or Ta) were used for the second phase emplacement. Through SEM and EDS mapping, the morphology and distribution of second phase particles have been studied. The work shows that friction stir processing is a viable means of producing localized composite zones in Al components.
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