Friction Stir Welded Aluminum Matrix Research Articles

Corrosion behavior and analysis on friction stir welded aluminium matrix composites

Friction stir welded (FSW) AA6061 aluminium matrix composites (AMCs) joints with 10% SiC particles were taken under investigation to reduce the corrosion rate. This study integrates the response surface methodology to optimize process parameters of FSW to achieve defect-free AMCs joints. The joint strength of 252 MPa was estimated as maximum tensile strength under rotational speed of 900.38 rpm and thrust force of 20.48 MPa. Furthermore, the turbulence flow of plasticized materials contributes to the restructuring of grains in the weld zone, and it is mainly influenced by the tool rotation. The cyclic potentiodynamic polarization test has been carried out in the different zones of friction stir welded AMCs joints using a 3.5% sodium chloride (NaCl) solution that is aerated naturally at 25 °C. It was seen that the corrosion polarization value of the Heat affected zone (HAZ) is 400 μA cm2, the un-welded aluminium matrix composite is 345 μA cm2, and the stir zone is 751 μA cm2 at the optimized conditions. The corrosion study reveals that the SiC reinforcement was a suspicious agent that propagated the pits in larger and deeper sizes when the various zones of the welded joint were exposed to electrochemical studies.

Experimental investigation of joint properties of friction stir welded aluminium matrix composite

The present study is focused on welding of particulate aluminium matrix composites using friction stir welding process and investigating the influence of various process variables on the joint properties. The microstructural study and mechanical behaviors such as tensile strength and hardness of the weld zone were measured. Microstructural studies showed that process variables play pivotal role in refinement of grains. Compared to the top of the weld region, smaller grains were formed at the bottom due to variation in the heating effect. Measurement of the tensile strength and hardness of the weld zone, indicated that process variables plays important role in controlling the joint properties. Beyond the optimum range of process variables, the joint strength of welded part deteriorates due to the insufficient stirring and lack of plasticization leads to defect formation. Joint welded with traverse speed of 100 mm/min and revolution speed of 1200 rpm exhibited better mechanical properties.

Influence of process variables on joint attributes of friction stir welded aluminium matrix composite

ABSTRACT The microstructure and mechanical attributes of the friction stir welded aluminium metal matrix composites (AMCs) are reported in this paper. Impacts of friction stir welding (FSW) process variables on the mechanical properties are evaluated. Metallographic studies showed that variation in welding process variables’ plays a vital role in obtaining recrystallised equiaxed fine-grain structures. The formed joint region indicates a gradual reduction in grain size as it moves from top to bottom of the weld region due to variation in the heat generation. Process variables like tool movement along the joint direction and tool revolution speed govern the joint strength of AMCs. Beyond the optimum values of process variables, the weld quality and joint strength of the welded part deteriorate due to the inappropriate stirring of the material at the weld region. The highest joint strength obtained for tool movement along the direction was 80 mm/min, and the revolution of the tool was 1000 rpm.

On the Role of Tool Tilt Angle on Friction Stir Welding of Aluminum Matrix Composites

The current study investigates the influence of tool tilt angle (TTA) on the mechanical strength of friction stir welded aluminum matrix composite (AMC). Aerospace-grade AA6092/ 17.5 SiCp- T6 plates of 6 mm thickness have been welded at different TTA of 1, 2 and 3 with fixed tool rotational speed of 1000 rpm and tool traverse speed of 1 mm/s. A conical pin-shaped tool of H13 tool steel having a hardness of 56 HRC has been used with a tool dimension of 16 mm shoulder dia., 6 mm pin root dia., and 4 mm tool tip dia. In order to study the microhardness, tensile strength, fracture toughness and fracture behavior of the joint the weld bead appearance, macrostructure and microstructure have been investigated. Results show that with an increase in TTA, the excessive flashing has been occurred in the weld bead and also affects the ratio of shoulder influenced region and pin influenced region in the macrostructure. The presence of detrimental Al2O3 has been found inside the weld at TTA of 3. It has found that the mechanical property of the joint increases as TTA increases from 1 to 2 and thereafter it decreases. The fractographic analysis shows a mixed-mode of failure for all the samples except for the TTA of 3 where it shows brittle failure. Overall the study suggests the implication of 1 to 2 TTA to get a sound weld of this particular type of AMC.

Study on Mechanical and microstructural characteristics of Friction Stir Welded Aluminium Matrix composite

Aluminium matrix composites (AMCs) are part of advanced materials, possesses capabilities to serve the present industrial needs due to its superior properties. Potential use of these AMCs in a particular application is limited if it is unable to join properly. In the present study AMCs are prepared by stir casting technique and welded by friction stir welding (FSW) process. FSW is performed using combined threaded and square profiled pin (CTSP). Further the welded joints were examined for microstructure and joint strength. Tensile test indicates that joint efficiency of 97 % is obtained, normal to the weld direction. Compare to the base material the nugget zone of weld region shows higher hardness. The microstructural study reveals that uniform distribution of finer grains are visible at nugget zone.

Friction-stir welding of AA6061-T6: The effects of Al2O3 nano-particles addition

In the present work, attempts were made to fabricate Al-based nanocomposites by Friction Stir Welding (FSW) process. Al2O3 nanoparticles were added into the aluminum matrix for refining the microstructure of the nugget zone (NZ) and to restrict the growth of granularly in the heat-affected zone (HAZ). The effects of Al2O3 nanoparticles addition on the grains structure evolution and various mechanical behavior of friction stir welded aluminum matrix was studied and elaborated in detail. The findings revealed that the addition of Al2O3 nanoparticles resulted in remarkable refining of grains in the nugget zone due to pinning effect produced by nano-sized Al2O3 particles which prevent the grain growth followed by recrystallization during FSW, leading to a remarkable reduction in grain size. A significant increment in tensile strength, micro-hardness and wear properties compared to sample without nanoparticles under the same operating conditions is attributed to nano-sized Al2O3 particles addition in the nugget zone. Also, the samples joined with rotating and transverse velocities of 2000 rpm and 70/80 mm/min showed higher tensile properties. However, the employment of single FSW pass resulted in an unusual Al2O3 nanoparticles distribution and void initiation at the interface between Al-matrix and Al2O3 nanoparticles in the heat-affected zone resulted in the sudden premature fracture of the specimen during tensile loading.

Experimental Investigations on Microstructural and Mechanical Behavior of Friction Stir Welded Aluminum Matrix Composite

The welding of materials by applying Friction Stir Welding technique is a new solid-state joining technique. The main advantage of this method compared to the traditional joining process is that it minimizes problem-related to metal resolidification as the method incorporates no melting phase. In this experimental work, the effect of friction stir welding (FSW) technique on the microstructure and mechanical properties of the cast composite matrix AA6063 reinforced with 7wt % SiC particles is studied. Friction stir welding, owing to the simultaneous effect of intense plastic deformation and frictional heat generated throughout welding, had impacts each on the reinforcement agents and the matrix alloy. FSW produced a notable reduction in the size of reinforcement agents and their homogeneous distribution in the weld region. It also induced the grain refinement due to dynamic recrystallization of the aluminum matrix alloy in the weld area. The frictional heat generated during friction stir welding had impacts on the growth, dissolution and reprecipitation of the hardening precipitates. The microstructural changes resulted in improved mechanical properties such as UTS, elongation, and hardness of the joint. A joint efficiency of 98.84% was observed for the welded joint. The XRD and EDX analysis of the welded area confirmed that there was no formation of any other compound due to the frictional heat produced during welding. The SEM fracture morphology of the welded joint revealed that the fracture behavior was changed from ductile to brittle following to FSW.

Microstructure, Hardness and Tensile Properties of Friction Stir Welded Aluminum Matrix Composite Reinforced with SiC and Fly Ash

In the present work, aluminum alloy 6061/SiC/fly ash aluminum matrix composites were welded successfully using friction stir welding process. Microstructure of weld joints was examined using optical microscope and scanning electron microscope. Mechanical properties namely, microhardness and ultimate tensile strength of the joints were studied. The results were correlated to microstructural changes caused by friction stir welding process. Microstructure in the stirred zone exhibits the uniform distribution of SiC and fly ash particles. Especially fine grains were formed on the advancing side than on the retreating side, due to the different variation between tool direction and welding direction. Higher hardness value is observed on the advancing side (132 Hv) than on the retreating side (124 Hv). Transverse tensile test of weld sample exhibits higher joint efficiency of 85.06% with respect to ultimate tensile strength. Fracture study reveals ductile mode of failure. Weld joints got fractured in heat affected zone on the retreating side, which indicates the weakest part of the weld joint. Based on thermodynamic analysis, the optimum heat input was found to be 756 J mm−1, resulting in higher strength of weld joints due to uniform distribution of reinforcement particles in the nugget zone.

Influence of Welding Process Parameters on Microstructure and Mechanical Properties of Friction Stir Welded Aluminium Matrix Composite

In this study, the effect of process parameters on microstructure and mechanical properties of friction stir welded aluminium matrix composites (AMC) have been explored. The results indicated that the recrystallized grain size at the bottom of the weld region is smaller than that at the top region due to difference in the heat transfer at the weld region. The joint strength of AMCs depends on proper selection of process parameters like tool rotational speed and welding speed. If process parameter values are beyond the optimal value, the joint strength decreases due to formation of defects. Maximum tensile strength is obtained for rotational speed of 1000 rpm and welding speed of 80mm/min.

Effect of Pin Profile on Friction Stir Welded Aluminum Matrix Composites

To clarify the role of pin profile geometry on some properties of friction stir welded of the considered aluminum matrix composites (Al-4 wt% Mg, reinforced with 1 wt% SiC and 1 wt% graphite particles) plates of 8 mm thickness were fabricated by compocasting method then annealed at 400°C for 2 h. Tools with different pin profiles (square, hexagonal, and octagonal) were manufactured to be used for friction stir welding (FSW) of aluminum matrix composites plates at four different levels of welding (transverse) and rotational speeds. The effects of these pin profiles on microstructure and some mechanical properties of the friction stir welded joints were studied. The results show that the plates welded by square head pin have better properties compared to the other pin profiles. This pin seems to cause better grain refinement and redistribution of SiC and graphite particles in the welded nugget zone (NZ) than the other two types. This has led to better improvements in the considered mechanical properties. Also, these properties were improved by increasing welding speed, while increasing the rotational speed has a diverse effect on them.

Statistical analysis of some mechanical properties of friction stir welded aluminium matrix composite

In this study, the effect of friction stir welding (FSW) parameters such as rotational speed, welding (transverse) speed, and the type of pin profile tool on some mechanical properties was statistically investigated. Plates of aluminium matrix composites fabricated by stir casting method were joined by friction stir welding process. The statistical analysis has shown that the most important factor affecting hardness and tensile strength is the welding (transverse) speed, while the rotational speed has a second ranking and pin profile tool geometry is the least. The rotational speed has no statistical significant influence on the wear rate. However, the nugget zone, which was welded by square pin profile tool, seemed to exhibit better mechanical properties compared to those obtained by other pin profile tools.

Prediction of tensile strength of friction stir welded aluminium matrix TiC p particulate reinforced composite

The usage of particulate reinforced metal matrix composite (MMC) is steadily increasing due to its properties such as high specific strength, high specific modulus and good wear resistance. Aluminium matrix composite (AMC) plays an important role to meet the above requirements. Effective utilization of AMC is based on not only its production but also on fabrication methods. Among AMCs, those based on particulate reinforcements are particularly attractive, due to their lower production costs. Aluminium matrix titanium carbide reinforced composite (Al–TiC p) was produced in an inert atmosphere by indigenously developed Modified Stir Casting Process with bottom pouring arrangement (3–7% TiC by weight). Friction stir welding process (FSW) is employed to make weld joints. The welding parameters such as axial force, welding speed, tool rotational speed, percentage TiC addition etc., and profile of the tool were considered for analysis. In this study, an attempt is made to predict ultimate tensile strength (UTS) of the welded joints using a mathematical model. The FSW specimens without any post-weld heat treatment belonging to a different set of parameters tested, exhibited a high joint efficiency (most of them ranging from 90% to 98%) with respect to the ultimate tensile strength of the base material AA6061. It was found from the analysis of the model that the tool pin profile and the welding speed have more significant effect on tensile strength.

Microstructural Evolution and Performance of Friction Stir Welded Aluminum Matrix Composites Reinforced by SiC Particles

The effect of friction stir welding (FSW) parameters on microstructure and properties of 15vol.%SiCp/2009Al composite welds was investigated at tool rotation rates of 400-1000 rpm for a constant welding speed of 50 mm/min. 8mm thick defect-free welds were produced at higher tool rotation rates of 600-1000 rpm, whereas an unwelded seam was distinctly visible at the root of plates at a lower tool rotation rate of 400 rpm. FSW resulted in generation of fine and equiaxed recrystallized grains of ~6 μm and significant improvement of SiC particle distribution in the weld nugget. Under as-FSW condition, the hardness of the weld nugget was significantly higher than that of as-extruded parent material. Furthermore, tensile and yield strengths of as-FSW composite welds in both the longitudinal and transverse directions were superior to those of as-extruded parent material. Post-weld T4 temper resulted in limited grain growth due to the pinning of SiC particles. Under the T4 condition, the tensile strength of the welds along the longitudinal and transverse directions reached 82 and 95% of the parent material, respectively.