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Krishna Kishore Mugada,Kumar Adepu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8
Understanding the flow of plasticized material during friction stir welding was critical for producing quality welds. The toolgeometry such as shoulder and pin designs play a significant role in altering the material flow characteristics. In the presentinvestigation, scroll shoulder design with varying pins were addressed in the aspects of tool axial force, material flow andmechanical properties. Marker insert method was used to study the flow of plasticized material with copper as inserts. Theresults show that the pin geometry variation has showed a significant change in the axial force plot in the welding phase. The taper cylindrical pin tool (TS) facilitated a constant force, hexagonal pin (TS)H and pentagonal pin (TS)P tools facilitateda decreasing force behavior, and triangular pin designed tool (TS)T facilitated an increasing behavior of force in the weldingphase. The material flow experiments showed that the scroll shoulder with triangular pin shaped tool (TS)T completely shearedthe marker inserts in both parallel and perpendicular to weld conditions compared to other pin shapes. The sheared copperfragments were uniformly distributed on both advancing and retreating sides of the weld for (TS)T tool. Superior mechanicalproperties were noticed for (TS)T tool with a tensile strength of 184 MPa and Microhardness of 78 HV at stir zone.
Marukurti V. N. V. Satyanarayana,Kumar Adepu,Karan Chauhan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
The present work studies the influence of five-pass overlapping friction stir processing (FSP) on microstructure, mechanicalproperties and corrosion behavior of AA6061 alloy. The fine equiaxed grains were produced in large-area stir region ofoverlapping FSP and it was identified that the grain size of each overlapping pass is uniform in large area stir region (averagegrain size = 3.9 ± 3.5 μm). The five-pass overlapping FSP resulted in ductility enhancement while the strength remainedinferior to that of parent metal due to thermal softening during FSP. On the other hand, corrosion resistance greatly improvedafter FSP due to the formation of a homogenous fine-grained structure and discontinuous precipitates.