جستجوی مقالات مرتبط با کلیدواژه « Friction stir processing » در نشریات گروه « مواد و متالورژی »

In recent years, a wide range of studies have focused on the surface modification of titanium, especially in terms of its biomedical applications. However, comparatively less researches have been conducted on the fabrication of titanium surface composites in bulk form. The primary objective of this investigation is to successfully produce hydroxyapatite (HA)-Ti surface composites with a homogenous dispersion of nano hydroxyapatite particles through friction stir processing (FSP). The secondary aim is to investigate the effect of FSP parameters, specifically filler mixture, on the microstructure and mechanical properties of the composites. Two different mixtures of HA and FSP parameters, traverse speeds of 30 and 45 mm min-1, rotational speed of 1200 rpm, and a conical tool shape, were used. It was found that the samples obtained by a filler mixture of HA-polyvinyl alcohol (PVA) showed better dispersion of HA in the Ti base, as well as higher tensile strength. Also, a 30 mm min-1 traverse speed led to higher strength in both filler mixtures. Therefore, the sample produced by a traverse speed of 30 mm min-1 and HA/PVA filler mixture was selected as the optimum sample.

Novelty: Most of the open literature research has focused on the microstructural evolution and mechanical properties of AA2050 alloy. Also, a significant study discusses the corrosion behavior of AA2050 alloy based on immersion and electrochemical characteristics. The influence of heat treatment on the microstructure and mechanical properties of friction stir processed AA2050 alloy is scarcely discussed in the open literature. The hot salt corrosion characteristics of friction stir processed AA2050 seldom exists in the available literature. This study concentrates on microhardness, tensile strength, and corrosion properties of friction stir processed AA2050. Also, the work focuses on the influence of artificial aging on the microhardness, and tensile strength of the friction stir processed AA2050.Highlights1.    Friction stir processing of AA2050 (Al-Cu-Li) alloy refined grains and distribution of intermetallic phases2.    Heat treatment increased the ductility of friction stir processed AA2050 alloy 3.    Hot salt corrosion test of friction stir processed AA2050 alloy indicated a less mass loss per unit area than the base material. Abstract - In this work, AA2050 alloy was friction stir processed at various tool rotation speeds and feed rates. The material was subjected to artificial aging to investigate its influence on macrostructure, microstructure, microhardness, and tensile strength of friction stir processed AA2050. Besides, a hot salt corrosion test was done on the test specimens at 130 °C for 168 hours. The results indicate that grain refinement and dispersion of secondary phase particles improved the microhardness and strength of friction stir processed specimens. The artificial aging of the friction stir processed specimens improved the ductility by 81.5%. However, the tensile strength of the specimens decreased by 2.8%. The corrosion (mass loss per unit area) of the specimen processed with a single pass at a speed of 600 rpm and feed rate of 60 mm/min decreased by 90% compared to the base material.

Friction stir processing (FSP) and friction stir welding (FSW) methods are two types of severe plastic deformation (SPD) processes. SPD methods are useful in producing nanoparticle or ultrafine-grained materials (UFG) microstructure. In FSP and FSW, a rotating cylinder tool (pin), which could take the form of various geometries, pierces into the workpiece with a particular angle and depth. Furthermore, it refines grains by moving in the direction of interest along with the tool's movements. The uniform distribution of nanoparticles in the stir zone is one of the main challenges of using nanoparticles. Controlling variables such as tool rotational speed, tool travel speed, number of passes, etc., the distribution of nanoparticles and the grain size can be changed in the stir zone. Microstructure, texture, and grain size directly affect the hardness of the stir zone. Recent studies have shown that using nanoparticles enhances the mechanical properties of the stir zone. The main aim of this review article is to collect the results of previous articles focused on analyzing the operation of FSW and FSP, the microstructure of the stir zone in FSW and FSP, the impact of effective parameters on the microstructure after adding nanoparticles to the stir zone, and the applications of FSW and FSP in various industries. Moreover, the fundamental mechanisms of grain refinement throughout FSW and FSP, including morphology and grain boundaries forming, were discussed.

Tungsten Inert Gas Welding (TIG) is the most preferred joining process for aluminum alloys, but it produces weld joint having inferior mechanical property in comparison with base metal because of inherent limitations of the process. To improve the mechanical properties, the weld is post processed by friction stir processing (FSP) upto depth of 2mm. This paper presents the effect of performing FSP on autogenous TIG welded butt joint of Al-5083, 6mm thick plate. Mechanical and metallurgical properties of both processed and unprocessed autogenous TIG weld are compared. Characterisation techniques adopted to evaluate weld joint are tensile test, microhardness measurement, microstructural examinations and SEM analysis. Tensile strength of autogenous TIG weld joint is lowered by 6.5% compared to base metal because of presence of micro porosities in the weld metal. Friction stir processing produces the fine grain refined structure, marginally improves the tensile strength of the autogenous TIG weld joint by 2.7%. Microhardness of the autogenous TIG weld metal of the surface is raised from 163.6 HV to 298 HV after performing FSP. However, SEM images of fractured surface of friction stir processed specimen reveals fine dimpled structure which indicates that ductility of the weld joint remain unaffected after performing FSP on autogenous TIG weld joint.

Friction-Stir Processing (FSP) was applied on AA1050 Aluminum Alloy (AA) to find the highest mechanical properties among 28 combinations of the rotational and traverse speed (800-2000 rpm and 50-200 mm.min-1) and four different tool probe shapes (threaded, columnar, square and triangle). To this aim, the AA standard sheet went through a single pass of FSP. The 1600 rpm and 100 mm.min-1 with threaded tool probe was chosen as the best combination of rotational and traverse speed. Grain size at the Stirred Zone (SZ) was studied using Optical Microscopy (OM). The results showed that the SZ’s grain size was refined from 30 μm down to about 12 μm due to dynamic recrystallization during FSP. The processed sample exhibited improved hardness, yield stress, ultimate tensile strength, elongation up to 65, 80, 66, and 14%, respectively, compared to the annealed AA sample. Studying fractographic features by OM and field emission scanning electron microscope (FESEM) revealed a dominantly ductile fracture behavior.

For more than a decade, there has been considerable interest in the fabrication of metal matrix composites by employing Friction Stir Processing (FSP). In this study a new model based on Zener-Hollomon (Z) parameter has been developed, which is believed to be the first of its kind, to accurately predict microstructural characteristics of Al-based composites Additionally, the processing window of composite fabrication determined and revealed that sound samples achieve within the range of 2.42 to 24.61 rev/mm for the ratio of rotation speed to travel speed (ω/ν). Recording the peak temperatures during processing beside the optical and Scanning Electron Microscopic (SEM) studies showed that increasing the number of FSP passes and the ratio of ω/ν have a remarkable influence on bolstering the role of nanoparticles in grain refinement. Results also indicated that the mean grain size of FSPed samples and matrix of nanocomposites decreases with an increase in the Z parameter. Finally, particular equations for various numbers of passes developed, which make a correlation between the grain size of Al-based composites and the FSP parameters via Z parameter.

In order to improve the properties of aluminum and its alloys, some various approaches (e.g. reduction of grain size, addition of alloying elements and composite manufacturing) have been considered. Among all these processes, the use of solid-state processes such as the friction stir processing (FSP) is highly convenient to create surface composites at temperatures below the melting point. Therefore, in this research, considering the FSP’s ability as a thermo-mechanical process and its advantages in the production of surface composites, the Al7075 surface composites were produced using reinforcing particles (Al2O3) and based on the FSP process in accordance with the design of experiments (DOE) approach. So, the response surface methodology (RSM) was selected as the experiment design method and variable factors such as: tool rotational speed, tool feed rate, diameter of tool shoulder and size of reinforcing particles were determined as the input variables. Statistical analysis and optimization of those parameters which affect the mechanical properties (yield strength and hardness) of surface composite Al7075/Al2O3 were performed. The results of the ANOVA and regression analysis of the experimental data approved the accuracy of regression equations and showed that the linear, interactional and quadratic terms of the input variables affect the yield strength and hardness of the composite specimens. Also, the optimal condition of the input variables was determined using the desirability method. In addition to the high values of desirability function (0.835, 0.822, 0.764), it could be found that the procedure of optimization has well fulfilled the pre-determined targets. In addition, the optimal condition has been confirmed by implementing the verification test.

Friction stir processing (FSP) was used as a cladding method for the fabrication of a AA2024 clad layer on a AA1050 sheet. Crossover multi pass FSP with 50% overlap was considered as the cladding method. Effects of the number of FSP passes and post heat treatment on the microstructure and properties of clad layers were evaluated. Microstructural evolutions during the FSP and heat treatment were investigated by field emission scanning electron microscopy (FESEM). The results showed that a defect free clad layer and a uniform metallurgical interface between the clad layer and base material can be achieved by the FSP. Moreover, clad layers exhibited higher hardness values in comparison to the base material. T4 Heat treatment of the FSPed samples resulted in comparatively high hardness values after natural aging. The highest hardness value of about 160 HV was achieved after heat treatment of the sample obtained from 3 intersecting FSP passes. Tensile strength of clad layers increased to 317 MPa after three intersecting FSP passes, compared to about 70 MPa of Al substrate.