Faculty Publications
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Item Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy(American Institute of Physics Inc. subs@aip.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; Bhat, K.U.The current investigation is focused on evaluating the mechanical properties and the microstructure of cast Al-10Zn-2Mg alloy processed through equal channel angular pressing (ECAP). The ECAP processing was attempted at minimum possible processing temperature. Microstructural characterization was carried out in optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Hardness measurement and tensile tests were employed to estimate the mechanical properties. Experimental results showed that, ECAP processing leads to noticeable grain refinement in the alloy. Reasonable amount of dislocations were observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was detected in the XRD analysis. ECAP leads to considerable enhancement in the mechanical properties of the material. After ECAP processing, microhardness of the material is increased from 144 Hv to 216 Hv. Also, after ECAP processing the UTS of the material is increased from 140 MPa to 302 MPa. The increase in the mechanical properties of the alloy after ECAP processing is due to the dislocation strengthening and grain refinement strengthening. Finally, fracture surface morphology of the tensile test samples also studied. © 2018 Author(s).Item Severe plastic deformation of Al-15Zn-2Mg alloy: Effect on wear properties(Trans Tech Publications Ltd ttp@transtec.ch, 2019) Manjunath, G.K.; Bhat, K.U.; Preetham Kumar, G.V.In the present work, Al-Zn-Mg alloy having highest zinc content was deformed by one of the severe plastic deformation (SPD) technique, equal channel angular pressing (ECAP) and effect of ECAP on the microstructure evolution and the wear properties were studied. ECAP was performed in a split die and the channels of the die are intersecting at an angle of 120°. ECAP was attempted at least possible temperature and the alloy was successfully ECAPed at 423 K. Below this temperature samples were failed in the first pass itself. After ECAP, significant drop in the grain size was reported. Also, ECAP leads to significant raise in the microhardness of the alloy. Predominantly, after ECAP, upsurge in the wear resistance of the alloy was noticed. To figure out the response of ECAP on the wear properties of the alloy; worn surfaces of the wear test samples were analyzed in SEM. © 2019 Trans Tech Publications Ltd, Switzerland.Item Optimization of Annealing Parameters for Ferritic Hot-Rolled IF Grade Steel(Springer, 2022) Kumar, D.S.; Sambandam, S.; Bhat, K.U.Ferritic hot rolling of low carbon steel is now widely adopted by steelmakers for reducing energy costs and increasing the yield. These ferritic hot-rolled coils carry forward different grain morphology and texture which result in variation in properties after cold rolling and annealing compared to austenitic hot-rolled coils. These ferritic hot-rolled coils require different annealing treatments based on the hot rolling temperature for better results. In the present work, a Nb–Ti stabilized interstitial free (IF) grade steel was hot rolled at two different temperatures in the ferritic regime in an industrial hot strip mill and was subsequently cold rolled. These cold-rolled sheets were subjected to different continuous annealing cycles with soaking temperatures varying from 740 to 820 °C on a thermo-mechanical simulator for optimization of temperatures and study its effect on microstructure and properties. These coils were compared with simulated conventional austenitic hot-rolled coils. Ferritic rolled coils show better elongation and a higher percentage of equiaxed grains indicating better formability. The optimum continuous annealing temperature was found to be a function of hot rolling temperature in the ferritic regime. Elongation and grain size increased with an increase in temperature in all the samples, but the ferritic rolled coils show faster change due to higher stored energy. Comparison of elongation and microstructure indicates that temperatures above 780 °C should be sufficient for achieving complete recrystallization in ferritic rolled samples, compared to 810 °C required in the conventional austenitic rolled sheets which is an industrial advantage. Based on simulation studies, full-scale plant continuous annealing was carried out under the optimized temperature conditions where microstructure and properties matched closely with the simulation results and electron backscatter diffraction (EBSD) analysis confirmed improved texture. © 2022, ASM International.Item SiC particulate reinforced A356 Al metal matrix composites were laser treated using pulsed Nd-YAG laser beam. The processing was carried out in air atmosphere at varying pulse energy (5 to 20 J) and scan rates (30 to 150 mm/sec). The samples were cut perpendicular to the track and they were characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. Microstructure of laser treated region consists of regular succession of coarse and fine microstructure signifying the presence of low velocity bands. Transition from cellular/columnar dendritic to equiaxed dendritic structure has been observed. Microstructure of samples laser treated with specific energy greater than 13 kJ/cm2 show presence of Al 4C3 platelets. © 2004 Kluwer Academic Publishers.(Microstructural studies in low specific energy laser surface treated Al(A356)-SiCp composites) Bhat, K.U.; Surappa, M.K.2004Item Metastable microstructures at the interface between AISI 321 steel and molten aluminum during hot-dip aluminizing(Elsevier B.V., 2018) Huilgol, P.; Udupa, K.R.; Bhat, K.U.The microstructure at the interface between AISI 321 stainless steel and molten aluminum was investigated which occurs during the process of hot-dip aluminizing. Microstructural characterization was carried out by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The study revealed the formation of metastable FeAlm and multiple twinned Al13Fe4 phases at the interface between steel and aluminum. Multiple twinned Al13Fe4 phase exhibits pseudo tenfold electron diffraction pattern. Another metastable phase Al3(NiFe) with an orthorhombic structure was formed as one of the eutectic phase mixture in the solidified aluminum topcoat. The Al3(NiFe) phase in the eutectic shares crystallographic orientation relationship with the Al matrix. Metastable intermetallic phases are being reported for the first time during hot-dip aluminizing. © 2018 Elsevier B.V.Item Microstructural investigations on the hot-dip aluminized AISI 321 stainless steel after diffusion treatment(Elsevier B.V., 2019) Huilgol, P.; Udupa, K.R.; Bhat, K.U.The microstructure of the hot-dip aluminized AISI 321 stainless steel was studied after diffusion treatment at 900 °C for 3 h. The microstructural characterization was carried out by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The microstructure of the as aluminized steel consisted of two regions, viz.; aluminum topcoat and aluminide layer. During the diffusion treatment, the coating transformed into a layered structure consisting of four layers. The Fe2Al5 phase was formed in the outermost layer and the presence of Al13Fe4 quasicrystalline approximant phase was observed. The innermost layer adjacent to the base metal transformed to ferrite phase with NiAl precipitates. Next, to this layer, a disordered FeAl phase was observed. The lattice parameter of the disordered FeAl phase was found to be larger than that of the ordered B2 FeAl phase. The layer between outer Fe2Al5 phase and disordered FeAl phase consists of a mixture of three phases, namely Fe2Al5, disordered FeAl and a new phase with the simple cubic structure. The phase with simple cubic structure shares cube on cube crystallographic orientation relationship with the disordered FeAl phase. © 2019 Elsevier B.V.