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Joining and Fabrication of Metal Matrix Composites by Friction Stir Welding/Processing
Hrishikesh Das,Mounarik Mondal,홍성태,천두만,한흥남 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.5 No.1
Herein, friction stir welding (FSW) of metal matrix composites (MMCs) with different combinations of the reinforcement and the metal matrix is highlighted with a brief introduction into recent efforts that have been used to fabricate MMCs by FSW. As a solid state joining technique, FSW consumes significantly lower energy than conventional fusion welding processes. In addition to properly selecting the process parameters, the mechanical properties of the FSW joints of MMCs are closely related with the refinement and homogeneous distribution of reinforcements in the stir zone. The fatigue and fracture properties of MMCs may be enhanced or aggravated by FSW, depending on the combination of the reinforcement and the metal matrix. For FSW of MMCs, the selection of the tool material can also be a critical issue; the presence of hard reinforcements may increase the rate of tool wear. Macro- and microstructural phenomena for MMCs during FSW depend on the material flow due to plasticization and the behavior of the reinforcements. Even though FSW are generally expected to induce a homogeneous distribution of reinforcements in the stir zone (SZ), it can be difficult to obtain a homogeneous distribution of reinforcements in the SZ depending on the combination of the reinforcement and the metal matrix. The existence of reinforcements naturally affects the microstructure of the joint and can even induce the formation of intermetallics/complex phases in the joint. This review provides a general understanding of the joining or in-situ fabrication of MMCs using solid-state friction stirring.
Das, Hrishikesh,Mondal, Mounarik,Hong, Sung-Tae,Lim, Yeongseok,Lee, Kwang-Jin Elsevier 2018 Materials characterization Vol.139 No.-
<P><B>Abstract</B></P> <P>The microstructure and mechanical properties of friction stir spot welding of ultrahigh strength dual phase (DP) and complex phase (DP) steels are compared based on the experimental results. For both DP and CP steels, FSSW joints are successfully fabricated using the same process parameter set. While the microstructure of joints are characterized in detail using scanning electron microscopy, electron back scattered diffraction, and transmission electron microscopy, the mechanical property of joints are evaluated by shear tensile tests. The result of the microstructural analysis shows that the stir zone (SZ) of CP steel mainly consists of bainite and martensite, while no bainite is identified in the SZ of DP steel. The existence of bainite in the SZ of CP steel suggests that the cooling rate, which is nearly identical for both CP and DP steels, was not fast enough to suppress the effect of the alloying composition, particularly that of Mn, on the phase transformation. The result of the present study contributes to the development of solid state joining process of the ultrahigh strength steels.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The microstructure and mechanical properties of FSSW of ultra high strength DP and CP steels are compared. </LI> <LI> The stir zone (SZ) of CP steel mainly consists of bainite and martensite; no bainite is identified in the SZ of DP steel. </LI> <LI> The cooling was not fast enough for the CP steel to suppress the effect of chemical composition on phase transformation. </LI> </UL> </P>
Microstructure and mechanical properties evaluation of friction stir welded boron steel
Hrishikesh Das,Mounarik Mondal,Sung Tae Hong,이광진,Kinnor Chattopadhyay 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.5
The microstructure and mechanical properties of friction stir welded boron steel in butt joint configuration are experimentally studied. Two different friction stir welding (FSW) parameter combinations are used to successfully fabricate butt joints. Microstructural analysis exhibites that the stir zone (SZ) primarily consists of fine lath martensite, while the thermomechanically affected zone (TMAZ) comprises bainitic ferrite and granular bainite with a small amount of martensite. The presence of granular bainite in TMAZ suggests that alloying composition affects the phase transformation. The formation of recrystallized structures with lath martensites and high dislocation density in the SZ significantly enhance the hardness of the joints compared to that of the base metal. The results of the present study suggest that FSW can be used as a method for local hardening of structural components made of boron steels, without complicated heating and rapid cooling of a conventional hot stamping process.
안은영,Hrishikesh Das,홍성태,한경식,Michael Miles,이광진,박주원,한흥남 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
The effects of combinations of dissimilar aluminum alloys during Friction stir welding (FSW) on the process response and resultant joint properties are experimentally investigated using two dissimilar automotive structural aluminum alloys. Depending on the materials on the advancing and retreating sides of the tool travel direction during FSW, four different material combinations are considered. FSW joints without macroscopic defects are successfully fabricated for the four different material combinations. The optical microscopy results show that the macroscopic material mixing behaviors of the two dissimilar material combinations during FSW are somewhat different from each other, even though the process responses during joining are not much different. The results of the quasi-static tensile tests and EBSD analysis demonstrate that the mechanical behaviors and orientation changes of the joint during tensile deformation are affected by the material locations with respect to the tool travel direction during FSW.
김주리,안은영,Hrishikesh Das,정용하,홍성태,Michael Miles,이광진 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3
The effects of tool geometry and process parameters on the mechanical properties of friction stir spot welded (FSSW) dissimilar aluminum alloys are experimentally investigated. Two tools with different shoulder profiles, concave and convex, were considered. Two typical automotive aluminum alloys were selected for FSSW, thus resulting in two different material combinations for each shoulder profile. The experimental results showed that the two shoulder profiles caused significant differences in the axial force, the mixing of materials, and the mechanical properties of the joint. The sensitivity of joint strength to the variation of the tool rotation speed and the plunge speed was also quite dependent on the shoulder profile. The experimental result shows that the change of joint strength can be quite significant.
Mounarik Mondal,Hrishikesh Das,안은영,홍성태,김문조,한흥남,Tapan Kumar Pal 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5
Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferriticstainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultantdissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends onthe process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilarjoints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows moresevere dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking faultenergy.