Taguchi Optimisation of Friction Stir Processing Parameters to Achieve Maximum Tensile Strength of Mg AZ31B Alloy

In this investigation, the effect of friction stir processing process variables such as rotational speed, traverse speed and tool tilt angle on the tensile strength of magnesium alloy AZ31B was studied. The experiments were carried out according to the Taguchi parametric design L9 at various combinations of process parameters and statistical optimization technique ANOVA was used to determine the optimum levels and to find the percentage of contribution of the process parameters. The results indicate that the rotational speed is the most significant factor followed by the traverse speed and tool tilt angle for maximising the tensile strength of the friction stir processed magnesium alloy.     

镁合金搅拌摩擦焊接技术

对5mm厚镁合金AZ31B板材的摩擦焊接技术进行了试验研究，结果表明：适合其板材的搅拌摩擦焊接的搅拌头，材料为W6MoSCr4V2高速钢，结构为凹面圆台形，根部直径5．5mm，端部直径为2．5mm，轴肩尺寸为12mm，长度为4．7mm。镁合金搅拌摩擦焊接头的抗拉强度可达母材的90％，延伸率可达母材的50％。搅拌摩擦焊接头焊合区为动态再结晶组织，在接头前进边焊合区与母材有明显的分界线，返回边过渡区有金属微熔的迹象。     

Effect of Nano Particle Deposition on Mechanical Properties of Friction Stir Welded Dissimilar Aluminium Alloys by Taguchi Technique

Improving the mechanical properties while joining of dissimilar alloys by FSW has been a choice of research during the past decade. Hence, an attempt has been made in the present research to join dissimilar Al alloys (AA5052 and AA6063) by addition of Copper nanoparticles in the weld joint. A 5T NC FSW machine has been employed to perform the desired task. To achieve optimum values of the process parameters, an optimization study has been carried out using Taguchi technique. The results obtained from the optimization studies and experimental investigations match very well proving the efficacy of the study. The results from the investigation show an improvement in mechanical properties when Cu nanoparticles are deposited which are further supported by microstructure and EDX analysis.     

Microstructure and Mechanical Properties of Al Tube Processed by Friction Stir Tube Back Extrusion (FSTBE)

Friction stir tube back extrusion is presented as a method to produce fine-grained tubes based on friction stir back extrusion process. In this method, a tubular aluminium alloy specimen whose inner diameter is less than the diameter of the rotating tool, is placed on a cylindrical die and penetrated by a rotating tool. Mechanical properties and microstructural evaluation of the processed tube have been investigated. The optical micrographs of the microstructure demonstrate strain gradient along the tube wall. Reduction in grain size and grain refinement occurs across the inner wall of the formed tube as well. Hence, the grain size with an initial value of ~100 µm is decreased to ~39 µm in the inner side of the formed tube wall. The obtained results from tensile tests illustrate that the ultimate strength and elongation at failure increases from the initial value of 183–225 MPa and 19–22 %, respectively. Microhardness assessments represent an increase in initial value from 74 to 86 Hv. Moreover, the microhardness values of the inner surface of the formed tube are more than the outer surface. The results show that this method is suitable for fabricating a kind of ultrafine-grained tube which possess an acceptable combination of strength and ductility.     

挤压工艺参数优化

挤压速度及温度极限与挤压机能力，合金的高温屈服强度，变形程度，表面质量和组织性能有关，本文主要阐述利用计算机确定挤压极限图，优化挤压工艺参数的方法。     

Production of Wire From AA7277 Aluminum Chips via Friction-Stir Extrusion (FSE)

In this research, fully consolidated wires from aluminum alloy AA7277 machining chips were produced by the friction-stir extrusion (FSE) process. The components used in the friction-stir extrusion process consist of a stationary cartridge and a rotating plunger with a scroll-faced head. The rotating plunger was rotated at three different speeds. Optical microscopy was used to probe the microstructures formed in the wires. The hardness profile of each sample is characterized using a Vickers microhardness tester. In this work, surface quality is sufficient by using a rotation speed of 160 rpm. Cold crack and hot crack defects were shown on wires fabricated using either too low or too high plunger rotation speeds. The microstructure of extruded wire is composed of fully equiaxed, recrystallized fine grains in the center of samples. The microhardness tests show an uneven distribution, and the hardness of the center was lower than that of the parent metal. The tensile tests revealed that the mechanical properties of the extruded wires were comparable with parent material.     

Influence of Friction Stir Processing Parameters on the Microstructure of Aluminum Foams

In the present study, friction stir processing (FSP) has been used to fabricate aluminium foams. The effects of the number of FSP passes, FSP tool rotational speed, foaming time and temperature on the porosity have been investigated. Aluminium foam with porosity up to 40% was successfully fabricated. In the samples foamed at 923 K (650 °C), a few irregular pores were produced as a result of high aluminium matrix stiffness in this temperature. In general with increase in foaming temperature the porosity increased. However, in the samples foamed for 30 or 60 min, lower porosity was detected at higher foaming temperature. Also, in the samples which were produced with more FSP passes, the foaming time decreased and more uniform pore structure was obtained.     

Friction Stir Welding (FSW) of Aged CuCrZr Alloy Plates

Friction Stir Welding (FSW) of Cu-0.80Cr-0.10Zr (in wt pct) alloy under aged condition was performed to study the effects of process parameters on microstructure and properties of the joint. FSW was performed over a wide range of process parameters, like tool-rotation speed (from 800 to 1200 rpm) and tool-travel speed (from 40 to 100 mm/min), and the resulting thermal cycles were recorded on both sides (advancing and retreating) of the joint. The joints were characterized for their microstructure and tensile properties. The welding process resulted in a sound and defect-free weld joint, over the entire range of the process parameters used in this study. Microstructure of the stir zone showed fine and equiaxed grains, the scale of which varied with FSW process parameters. Grain size in the stir zone showed direct correlation with tool rotation and inverse correlation with tool-travel speed. Tensile strength of the weld joints was ranging from 225 to 260 MPa, which is substantially lower than that of the parent metal under aged condition (~ 400 MPa), but superior to that of the parent material under annealed condition (~ 220 MPa). Lower strength of the FSW joint than that of the parent material under aged condition can be attributed to dissolution of the precipitates in the stir zone and TMAZ. These results are presented and discussed in this paper.

     

Application of Taguchi Method on Biaxial Stretch Forming of Friction Stir Processed Mg AZ31B Alloy

The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.     

Effect of Process Parameters on Microstructure and Mechanical Properties in Friction Stir Welding of Aluminum Alloy

Friction stir welding process is a promising solid state joining process with the potential to join low melting point materials, particularly aluminum alloys. The most attractive reason for this is the avoidance of solidification defects formed during conventional fusion welding processes. Tool rotational speed and the welding speed play a major role in deciding the weld quality. In the present work an effort has been made to study the effect of the tool rotational speed and welding speed on mechanical and metallurgical properties of friction stir welded joints of aluminum alloy AA6082-T651. The micro hardness profiles obtained on welded zone indicate uniform distribution of grains in the stir zone. The maximum tensile strength obtained is 263 MPa which is about 85% of that of base metal. Scanning electron microscope was used to show the fractured surfaces of tensile tested specimens.     

Producing of AA5083/ZrO2 Nanocomposite by Friction Stir Processing (FSP)

In this study, friction stir processing (FSP) was used to produce AA5083/ZrO₂ nanocomposite layer. Optical microscopy and SEM were used to probe the microstructures formed in the composite layer. In addition, the mechanical properties of each sample are characterized using both tensile and hardness tests. Results showed that FSP is an effective process to fabricate AA5083/ZrO₂ nanocomposite layer with uniform distribution of ZrO₂ particles, good interfacial integrity, and significant grain refinement. On processing, in the proper combination of process parameters, the metal matrix composite layer was observed to have increased tensile and hardness properties.     

Sub-zero Temperature Dependence of Tensile Response of Friction Stir Welded Al-Cu-Li (AA2198) Alloy

Mechanical properties at ambient and cryogenic temperatures of Al-Cu-Li alloy are required for design and fabrication of liquid hydrogen and liquid oxygen tanks of satellite launch vehicles. In the present work, bead-on-sheet, friction stir welding was carried out with three different rotation speeds. The yield and strain hardening behaviors of the welds were evaluated in temperature range of 20 K to 298 K. Both yield stress and strain hardening ability in the specimen increased with decrease in testing temperature. The dependence of yield stress on temperature was modeled on the basis of thermally activated dislocation mobility, while that of strain hardening was modeled on the temperature dependence of dynamic recovery rate parameter. The recovery parameter followed an Arrhenius-type relationship with temperature. The model parameters determined from the experimental data were further used to simulate the stress–strain curves at different sub-zero temperatures for the friction stir welds.

     

Optimization of Stirring Parameters Using CFD Simulations for HAMCs Synthesis by Stir Casting Process

Hybrid aluminum matrix composites (HAMCs) are capable to meet recent demands of advanced engineering applications due to its tunable mechanical properties and lower cost. Stir casting is one of the prominent and economical method for processing of continuous reinforced HAMCs. In this method, flow pattern is the key factor for distribution of particles in the molten metal. Effective flow pattern can be achieved by optimizing stirring parameters i.e. blade angle, impeller size and stirring speed. However, complete study and optimization of flow is a challenge for research community. Finite element method simulation along with optimization technique is one of the effective combination to guide experimental research. In this paper, computational fluid dynamics has been used to simulate fluid flow during stir casting, whereas optimization of stirring parameters is done by Grey Taguchi method. Optimized parameters have been used for experimental synthesis of HAMCs. Furthermore, optical micrograph and hardness confirms about the uniform dispersion of reinforcements. These results may guide the researchers for the preparation of HAMCs with uniform particle distribution by stir casting route for industrial applications.     

Control of Reaction Kinetics During Friction Stir Processing

Friction stir processing (FSP) was used to successfully embed galfenol particles into aluminum (AA 1100 Al) matrix uniformly. However, intermetallic layer of Al₃Fe was formed around the galfenol particles. Activation energy for Al₃Fe formation during FSP was estimated, and attempts were made to minimize the Al₃Fe layer thickness. By changing the processing conditions, FSP successfully eliminated the intermetallic layer. Hence, FSP, in addition to microstructural control, can successfully fabricate intermetallic-free embedded regions by controlling the reaction kinetics.     

Effects of Friction Stir Processing Parameters and In Situ Passes on Microstructure and Tensile Properties of Al-Si-Mg Casting

Friction stir processing (FSP) was applied to modify the microstructure of an as-cast A356 alloy. The effects of rotation rate, travel speed, in situ FSP pass, FSP direction, and artificial aging on microstructures and tensile properties were investigated. FSP broke up the coarse eutectic Si phase into 2.5 to 3.5 μm particles and distributed them homogeneously, and resulted in the dissolution of the coarse Mg₂Si particles and the elimination of porosity, thereby improving both the strength and the ductility of the casting. Increasing the rotation rate was beneficial to breaking up and dissolving the particles, but it contributed little to eliminating the porosity. The travel speed did not affect the size of the particles apparently, but lower speed was beneficial to eliminating the porosity. 2-pass FSP showed an obvious advantage in the microstructure modification and tensile properties compared with the single-pass. However, a further increase of FSP passes only resulted in slight improvement. The FSP direction of the following pass did not show distinct effect on the microstructure and tensile properties. After post-FSP artificial aging, the strengthening phase (β″-Mg₂Si) precipitated, which increased the strength and decreased the ductility of the FSP samples.