In this work, commercial pure aluminum was subjected to FRICTION STIR PROCESSING (FSP) up to six passes, then, mechanical properties, electrical conductivity, and microstructure analysis of the processed samples were compared with the initial condition. Better yield strength, ultimate tensile strength, and hardness are achieved after imposing the process. Also, strengthening rate is reduced at the subsequent passes. It was found that hardness magnitude is decreased mildly by getting away from the center. Although material formability is reduced after the first pass, it is grown a little by adding the pass number. The microstructure analysis indicated that application of one pass FSP changes considerably grain size of the annealed aluminum and leads to extreme decrease of the high-angle grain boundaries density which plays the main role in the reduction of electrical conductivity. Addition of FSP pass number leads to increment of dislocations density, transformation of low-angle to high-angle grain boundaries, and the further intersection of shear micro bands, causing improvement of sample formability and electrical conductivity compared to the first pass. Therefore, this process has the capability for fabrication of pure aluminum with improved mechanical properties and acceptable electrical conductivity.

The wear behavior AISI 304 stainless steel was investigated after FRICTION STIR PROCESSING (FSP). FSP was carried out using a WC pin less tool at tool rotation of 560 rpm and tool feed of 50 mm/min. Microstructure analysis was conducted by using optical and scanning electron microscopy evaluations. Wear resistance of the FS processed and base metal specimens were compared using pin-on-disk tests. The results demonstrated that FSP homogenized and refined the grain size of 304 stainless steel. A reduction in grain size throughout the STIR zone (26±3) compared to that of the base metal (93±3) was achieved through FSP. These results were confirmed by microhardness evaluations. According to the wear results, wear resistance of 304 base material improved significantly (two orders of magnitude) after FSP. This behavior was attributed to the grain refinement obtained by FSP. According to SEM observations, the abrasive wear was the main mechanism of wear after FSP.

FRICTION STIR PROCESSING is a solid state process to modify microstructure and mechanical properties of sheet metals and as-cast materials. In this process STIRring action of the tool causes the material to intense plastic deformation that yields a dynamical recrystallization. In this study the effect of FSP and process parameters on hardness, and microstructure of Al5083 has been investigated. Also by using of FSP, composite layer of TiO2/Al5083 has been produced. Results show that, FSP leads to finer and homogenized grain structure, as well as increased hardness, strength, toughness, and elongation of material. The composites produced by FSP have uniformly distribution of TiO2 particles between the grains of base metal.

One of the main problems in oil and gas pipelines is abrasion corrosion on the edges of the flow channel in the plug and ball valves. Under normal conditions, the gas is moving at a pressure of about 145 bar and an approximate speed of 70 feet per second,the suspended particles in the gas collide with the edges of the flow channel and cause severe erosion on them. The abrasion resistance of steels depends mainly on their surface properties and can be increased by increasing the surface hardness by FRICTION STIR PROCESSING (FSP). In this study, A216-WCB steel, which is used in the manufacturing of casting parts for valves, flanges, and fittings, was processed using an FSP for one and three passes. The microstructure, hardness, and wear properties of the processed area were investigated. The results showed that two distinct zones, the STIR zone (SZ) and the thermo-mechanical affected zone (TMAZ), are formed in the processed zone. Due to the FSP, the grain size in the STIRring region decreased from 25 microns to about 3 microns. The hardness of the SZ increased from 165 Vickers to about 784 HV. Tensile strength increased by 24%, and elongation was reduced by 25% for the processed sample compared to the raw metal. This may be due to phase transformation to martensite and grain size refinement. Also, the abrasion resistance of the STIRring area increased up to 2. 5 times.

In the present study, Al5083- Al2O3 nanocomposite was successfully prepared by FRICTION STIR PROCESSING (FSP) with the rotational speed of 710 rpm and travel speed of 14 mm/min. In order to improve the distribution of Al2O3 particles, a net of holes was designed on the surface of Al5083 sheet. The samples were characterized by optical (OM) and scanning electron microscopy (SEM), and microhardness, tensile, and wear tests. The results showed that FSP is an effective process to fabricate Al5083- Al2O3 surface nanocomposite. Microstructural observation demonstrated fine and equiaxed grains and homogenous distribution of Al2O3 nanoparticles in the STIR zone (SZ). The presence of Al2O3 nanoparticles leads to a decrease in the grain size from 45 to 7 mm and an increase in microhardness from 80 to 140 Hv and tensile strength from 280 to 335 MPa. Wear test results showed an improvement in wear resistance due to its higher hardness. Also, the wear mechanism in all samples was abrasive.

FRICTION STIR PROCESSING (FSP) was used to fabricate AZ31/Al2O3 nanocomposites for surface applications. The effects of probe profile, rotational speed and the number of FSP passes on nanoparticle distribution and matrix microstructure were studied. Three tool designs, non-threaded, threaded and three flutes were used. The grain refinement of matrix and improved distribution of nanoparticles were obtained after each FSP pass. By increasing the rotational speed, as a result of greater heat input, grain size of the base alloy increased and simultaneously more shattering effect of rotation, cause a better nanoparticle distribution. In the non-threaded and three flutes FSP tool due to absence of threads some voids was observed. XRD results show that the reinforcement volume is low. Also, the texture of FSPed samples changes significantly. Some fluctuations were measured in the hardness values which are due to banded structure of the STIR zone. With increase of rotational speed a smoother hardness results was produced.

FRICTION STIR PROCESSING (FSP) was conducted on a SAF 2205 duplex stainless steel at advancing speed of 50 mm/min and rotational speed of 400 rpm. Characterization of evolved material was studied using electron microscopy equipped with electron back scattered diffraction (EBSD) system. The results indicated that the severe plastic deformation and the heat generated during the FSP developed a very fine microstructure in the STIR zone (SZ). It was found that the finest grains with average grain size less than 1 μ m were formed in the bottom of the SZ where the material was more likely to receive the lowest temperature in both constituent phases of ferrite and austenite. Therefore, it can be inferred that the material in the bottom of the SZ was less affected from the heat generated by the shoulder. The presence of such severe deformation along with the elevated temperature during the welding procedure inside the SZ activates the occurrence of continuous dynamic recrystallization mechanism throughout the material which seems to be responsible for grain refinement. Moreover, 111 and 110 pole figures of both constituent phases demonstrated that the rotating tool broke the initial microstructure, modified the pre-existence rolling texture of the starting material, and introduced simple shear texture components into the SZ.

This review paper deals with the FRICTION STIR PROCESSING (FSP) for manufacturing of metal-matrix composites (MMCs) based on the Mg-8Al-0.5Zn (AZ80) magnesium alloy. Accordingly, the reported investigations on the AZ80 surface composites with various reinforcements, including the carbon nanotubes (CNTs), high-entropy alloys (HEAs), hybrid reinforcements, and composite plates, were summarized. Accordingly, the effects of introducing the second-phase particles, tool rotation rate, tool traverse speed, tool design, and vibration were considered. In this regard, the grain refinement by dynamic recrystallization (DRX) and Zener pinning effect, the uniformity of the particle distribution and avoiding agglomeration, and improvement of mechanical properties and wear behavior were critically discussed. Moreover, useful suggestions for future works were proposed, including focusing on the common reinforcing phases and PROCESSING parameters, tensile testing to evaluate the strength-ductility balance, metal additive manufacturing processes, and the correlation of DRX grain size with the Zener–Hollomon parameter similar to hot deformation studies.

FRICTION STIR PROCESSING as a relatively new and effective solid-state process is used for surface modification of metals and alloys in order to modify their microstructure and properties. In this study، the effect of FRICTION STIR PROCESSING on the microstructure and mechanical properties of an Al-0.9Ni-Fe alloy was investigated. The process was performed under the rotational speeds of 600-2000 rpm and the traverse speed of 25 mm/min. According to the results، the severe surface plastic deformation refined the intermetallic compounds present in the microstructure، improved their distribution within the matrix، and substantially reduced the amount of casting defects. As a result of these microstructural variations، the tensile strength and percent elongation of the base alloy are increased by almost 40 and 205%، respectively. The fracture toughness is also improved by 205%. It was also found that the hardness of processed alloy is about 24% higher as compared to the base alloy.