Friction stir processing of dual phase steel: Microstructural evolution and mechanical properties

Kucukomeroglu, Tevfik/0000-0002-4392-9966; Davut, Kemal/0000-0002-9860-881X; Aktarer, Semih Mahmut/0000-0001-5650-7431WOS: 000483411900009The influence of friction stir processing (FSP) on the microstructure and mechanical properties of a DP 600 steel has been studied. the microstructure evolution during the FSP has been characterized using electron back scatter diffraction (EBSD) technique and scanning and transmission electron microscopes. Standard tension and hardness tests were used to characterize the mechanical properties. the results show that the FSP produced a refined microstructure composed of ferrite, bainite, martensite, and tempered martensite which in turn increased the hardness and strength magnitudes by a factor of 1.5. the initially 2.83 mu m average grain size of ferrite has decreased to 0.79 mu m in the pin effected zone of (PE-SZ-I) of the processed region. Both EBSD and TEM observations showed regions with high dislocation density and sub-structures region in the processed zone. the grain size became coarser, the density of both dislocations and low-angle grain boundaries decrease, away from the processed zone. Moreover, phase fractions and hardness values were predicted using CALPHAD thermodynamic based software based on commercial material properties. Although the prediction does not take into consideration the influence of severe plastic deformation, the results were within 10% uncertainties of the experimental findings. the present study demonstrates that an ultra-fine grained structure can be obtained through the thickness of a 1.5 mm thick D P600 steel sheet via FSP. FSP can produce a range of different hardness and strength values; which can also be predicted successfully by inputting the composition and local temperatures reached during the FSP.Scientific Research Projects of Karadeniz Technical University [FBA-2016-5509]This study was supported by Scientific Research Projects of Karadeniz Technical University, under Grant No: FBA-2016-5509. Authors would like to thank Dr. Cemil Giinhan ERHUY and Ermetal Automotive and Goods (ERMETAL) Inc., Bursa, Turkey for supplying the DP600 steel sheets

Investigation of mechanical and microstructural properties of friction stir welded dual phase (DP) steel

2nd International Conference on Material Strength and Applied Mechanics (MSAM) -- MAY 27-30, 2019 -- Kiev, UKRAINEWOS: 000562383900010The application of dual phase (DP) steels has been increasing significantly in the automotive industry because of their high strength as well as good ductility, thus, cold formability. These steels are generally joined using conventional welding methods such as resistance spot welding and laser welding in the production of automotive parts. in recent years, several studies have been conducted to investigate the possibility of joining the advanced high-strength steels such as DP steels using the solid-state friction stir welding (FSW) method due to its advantages over conventional fusion joining methods such as metallurgical benefits, energy efficiency, and environmental friendliness. the aim of this study is to investigate the microstructure, hardness and tensile properties of friction stir welded DP 600 steel plates. Thus, 1.5 mm thick DP 600 steel plates were friction stir butt-welded by a tungsten carbide stirring tool consisting of a concave shoulder having a diameter of 14 mm and a conical pin (angle=30 degrees) with a diameter and length of 5 mm and 1.25 mm, respectively. in the weld trials conducted, the tool was tilted 2 degrees and the down-force of the tool was kept constant at 6 kN. the tool rotation and traverse speeds used in FSW trials were 1600 rpm and 170 mm.min-1, respectively. the microstructure of friction stir welded zone comprised of main martensite, bainite, and refined ferrite. the average hardness of the stir zone has increased to about 400 HV. the tensile specimens failed in the base plate away from the weld zone and tensile strength as high as that of the base plate was obtained from the welded specimens, i.e., about 640 MPa. However, the elongation of the welded plates was significantly reduced, i.e. about 55% of that of the base.Natl Acad Sci Ukraine, Pisarenko Inst Problems StrengthScientific Research Projects Council of Karadeniz Technical University [FBA-2016-5509]This study was financed by the Scientific Research Projects Council of Karadeniz Technical University, under Grant No: FBA-2016-5509. Authors would like to thank Dr. Cemil Gunhan ERHUY and Ermetal Automotive and Goods (ERMETAL) Inc., Bursa, Turkey for their support in supplying the initial material

Friction Stir Welding of Low-Carbon Shipbuilding Steel Plates: Microstructure, Mechanical Properties, and Corrosion Behavior

Aktarer, Semih Mahmut/0000-0001-5650-7431WOS: 000477997600019In this study, low-carbon steel plates (ASTM 131A) used generally in shipbuilding applications were joined by friction stir welding (FSW) using optimum processing parameters. the microstructure, mechanical properties, formability, and corrosion behavior of the joint were investigated. From the results of the investigation, it was discovered that two distinct regions, stir zone (SZ) and heat-affected zone (HAZ), were formed in the welded region during FSW of the plates. FSW decreased the ferritic grain size of the SZ from 25 mu m to about 4 mu m. Refined grains were separated mostly by a high angle of misorientation with the low amount of dislocations. the hardness of the SZ increased from 140 Hv0.3 to about 230 Hv0.3. the yield and tensile strength values of the SZ increased from 256 and 435 MPa to about 457 and 585 MPa, respectively, by the effect of FSW without a considerable decrease in ductility. FSW did not cause a significant change in the formability of the joint. Displacement at the maximum bending force decreased slightly after FSW from 6.31 mm to about 5.69 mm. Also, corrosion resistance after FSW slightly increased as a result of grain refinement. Current density values were obtained as 3.36 x 10(-6) A/cm(2) (base material 4.44 x 10(-6) A/cm(2)).The World Academy of Sciences (TWAS) under the Visiting Researchers Program of TWAS-UNESCO Associateship Scheme [3240260896]Dr. G. Purcek was supported by "The World Academy of Sciences (TWAS) under the Visiting Researchers Program of TWAS-UNESCO Associateship Scheme (Ref. 3240260896)." the authors would like to thank Dr. T. Kucukomeroglu for his help in conducting the FSW

Impact toughness of friction stir processed low carbon steel used in shipbuilding

Xue, Peng/0000-0003-3981-117X; Aktarer, Semih Mahmut/0000-0001-5650-7431WOS: 000381952300006Effect of single-pass friction stir processing (FSP) on the impact toughness of a low carbon steel mainly used in shipbuilding was investigated via Charpy impact test at different temperatures, and the results were correlated with the radical microstructural alterations during processing. A fine-grained (FG) microstructure was achieved in the processed zone by both large deformation and simultaneous dynamic recrystallization of coarse-grained (CG) structure during FSP. the grain size of ferritic phase decreased from 25 mu m down to about 3.0 mu m after processing. This microstructural changes brought about a considerable increase in strength values of the steel with a slight decrease in its ductility values. More importantly, significant refinement in the FSPed steel increased the impact energies in the upper shelf and partially lower shelf energy regions, and it considerably decreased the ductile-to-brittle transition temperature (OBIT) from -40 degrees C for the CG steel to about -65 degrees C for the FG steel. the improvement in the impact toughness of the steel was attributed mainly to the substantial microstructural refinement with grains separated mostly by high-angle grain boundaries. (C) 2016 Elsevier B.V. All rights reserved."The World Academy of Sciences, Italy (TWAS)" under the Visiting Researchers Program of TWAS-UNESCO Associateship Scheme [3240260896]Dr. G. Purcek was supported by "The World Academy of Sciences, Italy (TWAS)" under the Visiting Researchers Program of TWAS-UNESCO Associateship Scheme (Ref. 3240260896)

Effect of two-pass friction stir processing on the microstructure and mechanical properties of as-cast binary Al-12Si alloy

Kucukomeroglu, Tevfik/0000-0002-4392-9966; Aktarer, Semih Mahmut/0000-0001-5650-7431WOS: 000355886100038The effect of two-pass friction stir processing (FSP) on the microstructural evolution, mechanical properties and impact toughness of as-cast Al-12Si alloy was investigated systematically. Severe plastic deformation imposed by FSP resulted in a considerable fragmentation of the needle-shaped eutectic silicon particles into the smaller ones. the length of eutectic Si particles decreased from 27 +/- 23 mu m to about 2.6 +/- 2.4 mu m. the average aspect ratio of 6.1 +/- 5.1 for eutectic Si particles in the as-cast state decreased to about 2.6 +/- 1.0 after FSP with a corresponding increase in their roundness. the hardness, strength, ductility and impact toughness of the alloy increased simultaneously after two-pass FSP. the increase in the yield and tensile sirength values after FSP was about 20% and 29%, respectively. the FSPed alloy exhibited 25% elongation to failure and 15% uniform elongation which were almost seven times and five times higher, respectively, than those of the as-cast alloy. the hardness of the alloy increased from 58 Hv0.5 for the as-cast state to about 67 Hv0.5 after FSP. the absorbed energy during impact test increased to about 8.3 J/cm(2) after FSP, which is about seven times higher than that of the as-cast alloy. Improvements in all mechanical properties were mainly attributed to the radical changes of the shape, size arid distribution of the eutectic silicon particles along with the breakage and refined of the large alpha-Al grains during two-pass FSP. (C) 2015 Elsevier B.V. All rights reserved

Friction Stir Processing for Architectured Materials

Friction Stir Processing (FSP) is a solid-state process derived from Friction Stir Welding (FSW). FSP may be applied for the efficient manufacturing of metallic alloys based architectured materials. Indeed, the FSP tools allow locally modifying the microstructure of alloys or assembling dissimilar materials. The architectured materials that were or may be manufactured by friction stir processing will be discussed in this chapter. FSP may improve the mechanical performances of cast alloys, process metal matrix composites (MMC), make sandwiches, foams or additively manufactured structures. The aim is to process materials with improved lightweight performances, static or fatigue properties, crack resistance, toughness or wear resistance