Multi-pass Friction Stir Processing Research Articles

The influence of multi-pass friction stir processing on microstructure and sliding wear behavior of Cu/ZrO2 surface composite

Abstract In this study, copper/ZrO2 surface composites were produced using nano-particles via friction stir processing in order to enhance surface tribological properties. The present research aimed to generate copper matrix composites and analyze the effect of processing parameters on the evolving microstructure, microhardness, and wear-resistance behavior. It is worth noting that the processed composite layer had more homogeneity in the four-pass process. In comparison to the base metal and non-powder samples, it had higher mechanical characteristics. Based on the results, the highest recorded hardness, approximately 288 HV, was found in a four-pass state with powder. Remarkably, it showed a double peak compared to 80 HV in the base metal. The lowest friction coefficient of four-passes with the powder sample was about 0.47, which showed a significant efficiency in comparison to the friction coefficient of base metal that was about 0.81.

The influence of multi-pass friction stir processing on microstructure and sliding wear behavior of Cu/ZrO2 surface composite

Abstract In this study, copper/ZrO2 surface composites were produced using nano-particles via friction stir processing in order to enhance surface tribological properties. The present research aimed to generate copper matrix composites and analyze the effect of processing parameters on the evolving microstructure, microhardness, and wear-resistance behavior. It is worth noting that the processed composite layer had more homogeneity in the four-pass process. In comparison to the base metal and non-powder samples, it had higher mechanical characteristics. Based on the results, the highest recorded hardness, approximately 288 HV, was found in a four-pass state with powder. Remarkably, it showed a double peak compared to 80 HV in the base metal. The lowest friction coefficient of four-passes with the powder sample was about 0.47, which showed a significant efficiency in comparison to the friction coefficient of base metal that was about 0.81.

Experimental investigations of A359/Si3N4 surface composite produced by multi-pass friction stir processing

Lightweight and high strength materials are the primary requirements in the field of defense like in aircraft structures and aerospace applications. In this context, aluminum-based composites are one of the suitable choices because of its improved characteristics. In the present work, an attempt is made to develop aluminum (A359) based surface composites by incorporating the Si3N4 particles through friction stir processing (FSP). The numbers of FSP tool passes (single, two and three) are considered as variable parameters to evaluate its effect on various characteristics. The microstructural examination has been carried out by optical microscope and surface morphological analysis was done by scanning electron microscopy images. EDS with mapping images are used to observe the phase distribution and to identify the elements of the alloying and reinforcement materials. The elemental presences are also validated by X-ray diffraction and Raman spectroscopy. Further, mechanical properties like tensile test supported by fracture analysis and Rockwell hardness profile of the FSP zone are also discussed. In addition to it, the present work also an emphasis on the effect of the number of FSP tool passes on its wear resistance and thermal expansion. The results revealed that the value of maximum tensile strength and hardness were found to be 576 MPa and 125 HRB respectively in single pass FSPed composite. However, if the number of passes is increased then the maximum wear loss (11.7 × 10−3 g), maximum expansion due to heat (9 mm3) is observed at three-pass of FSP tool.

Mechanical properties enhancement of cast Al-8.5Fe-1.3V-1.7Si (FVS0812) alloy by friction stir processing

This study was conducted to investigate the capability of multi-pass friction stir processing (FSP) on microstructure modification and mechanical properties improvement of FVS0812 alloy. FSP was performed at different rotation speeds (1250, 1600, 2000, and 2500 rpm) and traverse speeds (8, 12, and 25 mm/min) for one, two, and four passes. According to the results, applying single-pass FSP at optimized conditions (i.e. 1600 rpm and 12 mm/min) enhanced the tensile strength, fracture strain, and microhardness of the alloy by about 1020, 1050, and 60%, respectively. This improvement can be mainly attributed to the intense breakage and uniform distribution of θ-Al13Fe4 and α-Al12(Fe,V)3Si intermetallics within the matrix, formation of ultrafine recrystallized grains, and elimination of casting defects. Increasing the number of FSP passes up to four slightly decreased the average size of intermetallic particles, but significantly improved their distribution within the matrix which led to 18 and 200% improvement of tensile strength and fracture strain of one-pass FSPed sample, respectively. The fractography results also revealed that multi-pass FSP has changed the fracture mode of Al-8.5Fe-1.3V-1.7Si alloy from low-energy brittle to a more ductile-dimple fracture.

On the High-Temperature Flow Response of Friction Stir Processed Magnesium Metal Matrix Composites

AbstractIn the current work, multi-pass friction stir processing (FSP) was utilized to fabricate samples of fine-grained aluminum–zinc (AZ) magnesium alloy and its metal matrix composite (MMC). The microstructure and high-temperature tensile behavior of friction stir processed (FSPed) AZ31 and AZ31/SiC MMC at various strain rates in the range of 10−2 to 10−4 s−1 were investigated, and the fracture mechanisms of each condition were analyzed. The results verified that MMC samples exhibited a remarkable enhancement in microhardness. The evolution of inclined basal texture was observed after processing for both FSPed and MMC samples. The ambient temperature stress–strain response revealed that the formability of AZ31 has improved after friction stir processing, whereas high-temperature flow curves were discernibly sensitive to strain rate. Equiaxed deep dimples were detected on the fracture surfaces of FSPed samples, but decreased strain rate led to an increase in the number of dimples as attributed to the recrystallization of new grains.

Fatigue behaviour of the multi-pass friction stir processed AA8011-H14 and AA6082-T651 dissimilar joints

The AA8011-H14 and AA6082-T651 were used to produce dissimilar joint through the use of friction stir welding (FSW) technique. The produced dissimilar joint was processed using multi-pass friction stir processing (FSP). The microstructural analysis revealed that the grain sizes reduced with an increase in the number of FSP passes irrespective of material positioning. However, the multi-pass AA6082-AA8011 joints had finer grain structure compared to the multi-pass AA8011-AA6082 one. The ultimate tensile strength of the multi-pass FSP had an increase of 11.6% compared to that of the single-pass one, but only for the AA8011-AA6082 joints, while the AA6082-AA8011 had an increase of 9% on the two-pass FSP. The number of FSP passes was found to have a marginal effect on the microhardness of the joints. The two-pass FSP joints were found to be more ductile compared to the other passes. The fatigue results revealed that the AA6082-AA8011 joints had longer fatigue life compared to that of the AA8011-AA6082 joints. The increase in the number of FSP passes increased the fatigue life of the AA8011-AA6082 joints, while AA6082-AA8011 joints experienced extended fatigue life cycle on the single-pass FSP.

Microstructure and mechanical properties of CuZn-Al2O3 nanocomposites produced by friction stir processing

For the first time, ceramic nano particles were incorporated into the brass alloy to produce surface nano composites by friction stir processing. For this aim, Al2O3 particles with an average diameter of 30 nm were inserted into a Cu-37Zn alloy at different tool rotational speeds of 450, 710, and 1120 rpm, multi passes, and a constant traverse speed of 100 mm/min. The microstructures of the processed materials were analyzed using optical and scanning electron microscopes equipped with an energy dispersive spectroscopy. In addition, tensile test was employed to evaluate the mechanical properties. The results showed that the optimum rotational speed was 710 rpm. At lower rotational speeds, Al2O3 particles were agglomerated. On the other hand, at higher rotational speeds, tool was damaged by severe wear. The effect of multi passes showed that one and two passes could not distribute the Al2O3 particles, uniformly. However, three passes resulted in a uniform distribution of the Al2O3 particles inside a bimodal grain structure composed of both 3–5 μm grains and ultra-fine grains (< 1 μm). By using multi-pass friction stir processing, a synergic increase in ultimate tensile strength and elongation was obtained. Moreover, three passes caused superior mechanical properties i.e. ultimate tensile strength of 430 MPa and elongation of 39%. The fracture behavior and strengthening mechanisms are also discussed in details.

Multipass Friction Stir Processing of Steel/SiC Nanocomposite: Assessment of Microstructure and Tribological Properties

A surface layer of steel/SiC nanocomposite was fabricated by multiple passes of friction stir processing (FSP) on a low-carbon steel. The characterization methods such as optical microscopy, field emission scanning electron microscopy, microhardness, and wear test were performed to obtain the microstructure and mechanical properties of the produced layers. The results revealed that the dispersion of nano-SiC particles is directly related to the FSP passes and that the superior scattering of the nanosized SiC particles is achieved at higher FSP passes. Nano-composite surface layers demonstrated an average microhardness value of ~ 424 HV, which is ~ 3.4 times higher than that of the as-received substrate. Moreover, ultra-fine submicron grains were formed by FSP due to the role of SiC particles as obstacles to grain growth. The produced surface-layer nanocomposite exhibited an outstanding enhancement in wear resistance in comparison with the FSPed sample without reinforcing particles.

Friction stir processing of high-entropy alloy reinforced aluminum matrix composites for mechanical properties enhancement

Metal matrix composites have been developed to overcome the urgent demand of light-weight design. High entropy alloys (HEAs) are newly emerged as a new kind of potential reinforcement for metals due to their outstanding physical and mechanical properties. Here, a kind of novel Al matrix composite reinforced by Al0.8CoCrFeNi HEA particles was fabricated by multi-pass friction stir processing (FSP). The incorporated HEA particles were homogeneously distributed into the composites and maintained the structural integrity. The average grain size of the FSPed composites decreased from 4.6 μm of Al matrix to 2.8 μm due to the particle-stimulated nucleation mechanism. The hardness, yield strength and ultimate tensile strength of the FSPed composites increased by 56%, 42% and 22% than that of the FSPed Al matrix with no obvious decrease of elongation. Interfacial diffusion occurred and the interfacial region is confirmed to be the Al3CoCrFeNi rather than the intermetallic phases. HEA particles have great potentials in mechanical properties enhancement for conventional light-weight alloys.

Development of multi-pass processed AA6082/SiCp surface composite using friction stir processing and its mechanical and tribology characterization

The uncontrollable wear at the surface of AA6082 against the EN-31 steel has restricted its use in the tribology application. Also, the mechanical properties of AA6082 play a crucial role on the surface wear. So, it is important to improve the mechanical properties to enhance the wear resistance of AA6082. Though, there are several research contributions available for the fabrication of Al/SiCp composite using Friction Stir Processing (FSP), no work pertaining to the AA6082/SiCp composite with multi-pass (one, two and three pass) condition was done earlier. Hence, the present work aims to improve the microstructure, mechanical and wear behavior of AA6082 through surface composite (AA6082/SiCp) fabricated using multi-pass FSP. The influence of multi passes on the microstructure, hardness, surface roughness, phase composition, tensile strength and wear rate are carried out. A significant improvement in the microstructure is achieved for the three pass condition due to the homogeneous distribution of SiCp with reduced particle size evidenced in Transmission Electron Microscope (TEM) analysis. The microhardness of AA6082/SiCp composite increased 2.5 times than the parent AA6082. The strong interfacial bonding between the SiC particle and Al matrix has been achieved for three pass FSPed composite, which is significantly improved the Ultimate Tensile Strength (UTS). The transformation of severe adhesive wear to mild abrasive is observed in a three pass FSPed AA6082/SiCp composite. Wear track characterization is employed using Scanning electron microscope (SEM) to examine the wear mechanism of AA6082 and AA6082/SiCp composites against the EN-31 steel under the dry sliding condition.

Enhancing the mechanical and tribological properties of Mg2Si-rich aluminum alloys by multi-pass friction stir processing

Particle strengthening of in-situ Al-Mg2Si composites hinges on effective geometrical parameters (size, distribution, morphology, and volume fraction) of the inherent primary Mg2Si particles. The use of solid-state friction stir processing (FSP) in a multi-pass mode is recognized as a secondary processing route capable of achieving desirable geometrical parameters of Mg2Si particles in Al-Mg2Si composites as compared to other routes. This paper thus studies the microstructure, mechanical properties, and tribological behavior of the multi-pass FSPed in-situ Al-25Mg2Si composite with a threaded triangular pin tool. The FSP was conducted at constant tool rotational and traverse speeds of 1000 rpm and 80 mm/min for 1–6 passes. The results showed a decline in the average Mg2Si size (115–3.25 μm), porosity content (5.8–0.14%), and primary Mg2Si particle-depleted region as the FSP passes are increased (0–6). Improved geometrical parameters of the primary Mg2Si particles enhance microhardness (178–272 HV), tensile strength (102–233 MPa) and wear resistance of the Al-25%Mg2Si composite via particle dispersion and dislocation strengthening effects, grain refinement, and microstructural densification. Multi-pass FSP can be adopted as a better substitute to element addition, casting modification, heat treatment and electromagnetic stirring in effectively controlling the geometrical parameters of the primary Mg2Si in in-situ Al-Mg2Si composites for improved mechanical and tribological properties.

Microstructure and Tensile Properties of SiC Particles Reinforced AZ31 Magnesium Alloys Prepared by Multi-pass Friction Stir Processing

Two different sized SiC particles (~ 60 nm and ~ 1 μm) were mixed into AZ31 alloy by multi-pass friction stir processing (FSP). The microstructure and mechanical properties of the processed material were investigated by optical microscope, scanning electron microscope, and uniaxial tensile tests. After FSP without SiC addition, the grains were refined to several microns. The elongation was improved significantly after processing, at an expense of significant sacrifice in yield strength. 60 nm SiC particles were composited homogeneously in the matrix by four passes of FSP to enhance the yield strength. The yield strength exhibited a 68% improvement which could well compensate the decreased yield strength in FSP without SiC addition. In addition, the 1 μm SiC particles were inhomogeneous in the stir zone which also induced an increase in yield strength. However, the elongation decreased sharply because cracks nucleated and propagated quickly at the SiC–matrix interface.

Effects of Multi-Pass Friction Stir Processing on Microstructures and Mechanical Properties of the 1060Al/Q235 Composite Plate

Steel cuttings, holes and cracks always exist at the interfaces in the composite plate. Multi-pass friction stir processing (M-FSP) is proposed in this research to optimize the interface microstructure and the interface connection for the 1060Al/Q235 composite plate. Results show that the microstructures of 1060Al after M-FSP are fine and uniform owing to the strong stirring effect and recrystallization. Micro-defects formed by the welding can be repaired by the M-FSP. However, tunnel defects can also be formed in the matrix of aluminum by M-FSP, especially when the passes are one and two. The melting block and the melting lump in the composite plates are easy to become the source of crack. The shear strengths and the bending properties for the 1060Al/Q235 composite plate after M-FSP are the best when the passes are three, with the tool rotation speed of 1200 rpm and the forward speed of 60 mm/min. The optimized interfaces for the composite plate after M-FSP are mainly by the metallurgical bondings, with a certain thickness and discontinuous mechanical connections. Therefore, the crack extension stress is the largest and the mechanical properties are the best.

Microstructural and mechanical characteristics of AA1050/mischmetal oxide in-situ hybrid surface nanocomposite by multi-pass friction stir processing

Surface hybrid in-situ aluminum matrix nanocomposite (AMNC) was fabricated by multi-pass friction stir processing (FSP) and a tool traversing speed of 100 mm/min and rotating speed of 1600 rpm with an objective to enhance mechanical properties. Mischmetal oxide (MMO) powder with an initial size of 50 nm, at a concentration of 8.5 vol% was used as the reinforcing particles. EDS particle analyses revealed in-situ solid-state chemical reactions between the Al matrix and the MMO particles. The reaction products, MM3Al and MM3Al11, were distributed uniformly in the discontinuously dynamic recrystallized nano and UFG microstructure. Increasing pass number improved the particle distribution and decreased agglomerated particle size while promoting the in-situ solid-state reaction. The nanocomposite produced by 6 FSP passes enhanced yield stress, 180% (YS = 70 MPa) and strength, 120% (UTS = 132 MPa) while reduced the tensile ductility from 35% to 23%. Fractographic studies showed that dimple-shape ductile fracture mode changed to ductile-brittle mode.

Tribology of Si-rich TIG-deposited coatings on Zn–40Al–2Cu alloy

ABSTRACTThe effect of Zn–40Al–2Cu–xSi (x = 4 and 8 wt-%) tungsten inert gas (TIG) surfaced coatings and multi-pass friction stir processing (FSP) on the tribological properties of Zn–40Al–2Cu alloy was studied. The coatings had a well-modified microstructure comprising of finely dispersed primary Si particles (SiP). These particles act as in-situ reinforcements, improving coating resistance against the friction-induced strains applied during sliding wear. The results of dry sliding wear showed that, at the applied pressures of 0.25, 0.5, and 0.75 MPa, the wear resistance of 4-pass FSPed coatings containing 4 wt-% Si is higher than that of the base alloy by 27, 47, and 57%, respectively. This can be attributed to the substrate strengthening and formation of compacted tribolayers on the surface of FSPed samples.

Foaming of friction stir processed Al/MgCO3 precursor via flame heating

In the recent years, metal foams have become promising candidate materials in the engineering sector owing to their light weight and excellent energy absorption properties. Friction stir processing (FSP) has emerged as a cost-effective route to fabricate metal foam precursors from bulk substrates. Although the short processing time in FSP is able to provide high productivity, the cost of the foaming agent, TiH2 in the case of aluminum foams is still high. This paper introduces flame heating to achieve localized foaming of aluminum alloy AA5754 to explore the possibility of using magnesium carbonate as a foaming agent stirred using multi-pass FSP. A specially designed slot based strategy using two plates arranged in lap configuration is devised to stir the foaming agent and understand the material movement after each subsequent pass. Microscopy techniques were carried out to evaluate the distribution of the foaming agent after each pass and the resulting microstructure of the processed plates as well as the morphology of the foamed sample. EDX results showed higher Mg and O content around the pore walls.

Development of Al1070-Quasicrystal (Al65Cu23Fe12) composites using friction stir processing and its mechanical characterization

This study aims at analysing the microstructure and mechanical behaviour of quasicrystalline (Al65Cu23Fe12) strengthened Al1070 composites by Friction Stir Processing (FSP). The composites with various volume fractions of quasicrystal are fabricated by a multipass (3 passes) Friction Stir Processing with 1200 rpm speed, 30 mm min−1 feed rate and tilt angle of 2.5°. The hardness measurement and tensile test performed in the fabricated composites divulged an increasing trend in the hardness values and Ultimate tensile strength up to a volume fraction of 8% of quasicrystals. The microstructural studies disclosed the increase in the hardness values are ascribed to the reduction in grain size due to the dynamic recrystallization and the strengthening of Al matrix by quasicrystals. Though the composites with higher volume fraction exhibited improved Ultimate tensile strength, the fractographic studies depicted there is transformation from ductile to brittle failure in those composites.

Effect of Scandium on Homogenization Treatment and Friction Stir Processing on Mechanical Properties of 7075 Aluminium Alloy Prepared by Foundry Route

The aluminium alloy (7075 series) with minor scandium (Sc) addition prepared by foundry route, was subjected to homogenization treatment at different temperatures from 300 to 500°C for 8h and also multi-pass friction stir processing (MP-FSP) was performed to improve surface properties of cast aluminium alloy. The effect of minor scandium (0.33wt.%) on the microstructure and mechanical properties of prepared alloy was investigated using optical microscopy, SEM, FESEM, XRD, TEM, Vickers’s hardness and tensile test. The homogenized microstructure was obtained showing fine grains because homogenization of cast structure and dispersion of second-phase particles also occur. The Al-Zn-Mg alloy with high strength, good corrosion resistance and good welding property is used widely in various industrial applications. In addition of scandium to increase the strength mainly comes from fine grain strengthening, substructure strengthening and precipitation strengthening caused by Al3 (Sc) and MgZn2 particles. These particles are formed during homogenization treatment of cast aluminium alloy and it has great influence on precipitation behaviour of Al3 (Sc) particles

Effect of multi-pass friction stir processing on thermal distribution and mechanical properties of AZ91

In this paper, the effect of multi-pass friction stir processing on mechanical properties of AZ91 alloy has been studied. For this purpose, the microhardness, tensile, and creep tests were conducted at several temperatures. Optical microscopy and scanning electron micrograph were used to study the microstructure of the processed samples. The experimental results indicated that at room temperature, the microhardness, tensile, and creep strength of the processed samples as compared to the unprocessed ones increased by 23%, 29%, and 38%, respectively. Also, after friction stir processing, the tensile and creep strength of the samples at 210 °C increased by 31% and 47%. In addition, a three-dimensional model was developed to simulate two-pass friction stir processing using ABAQUS/Explicit software. This model involved the Johnson-Cook models for defining material behavior during the process and identifying the fracture criterion. To control the mesh distortion during consecutive passes, the Arbitrary Lagrangian-Eulerian technique was used. Using the developed model, the peak temperature, thermal distribution, and residual stress field during multi-pass friction stir processing on AZ91 have been studied. The empirical results indicated the beneficial influence of the multi-pass friction stir processing on the microstructure and high-temperature mechanical properties of AZ91 alloy.

An investigation of microstructure, wear and corrosion resistance of AZ31B–SiO2–graphite hybrid surface composite produced by friction stir processing

Magnesium-based hybrid composites are light and have better mechanical and tribological properties than magnesium. In this research, AZ31B–SiO2–graphite hybrid surface composite was produced by multipass friction stir processing (FSP). The effect of FSP passes on microstructure, microhardness, wear resistance, and corrosion resistance of the composite was investigated and compared with friction stir processed (FSPed) AZ31B and as-received AZ31B. The results indicated that after 4 passes, SiO2 and graphite particles properly dispersed in the microstructure and grain growth was restricted due to the pinning effect of these particles; therefore, the mean grain size of the composite decreased by 80% compared with as-received AZ31B. The microhardness of the composite increased about 18% compared with as-received AZ31B and microhardness variation decreased in the stir zone, which indicates more homogeneity in grain size and particle distribution by increasing FSP passes. Furthermore, the investigation of strengthening mechanisms showed that grain size decrease, due to recrystallization and pinning effect of particles, had more influence on increasing composite hardness than dispersion hardening. The wear resistance of the composite which underwent 4 passes was 33% more than as-received AZ31B. It also had the highest corrosion resistance due to more stability of the passive film as a result of fine grain size.