Faculty Publications
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Item A Bottom-Up Optimization Approach for Friction Stir Welding Parameters of Dissimilar AA2024-T351 and AA7075-T651 Alloys(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Anil Kumar, K.S.; Murigendrappa, S.M.; Kumar, H.In the present study, optimum friction stir weld parameters such as plunge depth, tool rotation speed and traverse speed for butt weld of dissimilar aluminum alloy plates, typically 2024-T351 and 7075-T651, are investigated using a bottom-up approach. In the approach, optimum FSW parameters are achieved by varying any one parameter for every trial while remaining parameters are kept constant. The specimens are extracted from the friction stir-welded plates for studying the tensile, hardness and microstructure properties. Optimum friction stir weld individual parameters are selected based on the highest ultimate tensile strength of the friction stir-welded butt joint specimens produced by varying in each case one parameter and keeping the other two constant. The microstructure samples were investigated for presence of defects, grain refinement at the weld nugget (WN), bonding between the two materials and interface of WN, TMAZ (thermomechanically affected zone) of both advancing and retreating sides of the dissimilar joints using optical microscopy and scanning electron microscopy analyses. In the experimental investigations, the optimum FSW parameters such as plunge depth, 6.2 mm, rotation speed, 650 rpm and traverse speed of 150 mm/min result in ultimate tensile strength, 435 MPa, yield strength, 290 MPa, weld joint efficiency, 92% and maximum elongation, 13%. The microstructure of optimized sample in the WN region revealed alternate lamellae material flow pattern with better metallurgical properties, defect free and very fine equiaxed grain size of about 3-5 µm. © 2017, ASM International.Item Influence of Gd on the microstructure, mechanical and shape memory properties of Cu-Al-Be polycrystalline shape memory alloy(Elsevier Ltd, 2018) Bala Narasimha, B.N.; Murigendrappa, S.M.In the present study, the influence of rare earth element gadolinium (Gd) on Cu-Al-Be polycrystalline shape memory alloy has been investigated. Cu 88.13 Al 11.42 Be 0.45 ternary alloy with addition of Gd from 0.05 to 0.15 wt% has been used for investigation. The tests have been carried out for microstructure, morphology, ductility, phases, crystal structure, phase transformation temperatures and shape recovery ratio. Refinement of the grain size resulted as gadolinium increased from 0 to 0.08 wt%, the grain size decreases from 463.45 to 81.80 µm with reduction of 82.34%. The tensile strength has increased from 398.93 to 581.42 MPa with improvement in the ductility from 10.05% to 23.72% at 0.08 wt% gadolinium. The phase transformation temperatures increases as gadolinium increases and reduction in shape recovery ratio from 97% to 65%. © 2018 Elsevier B.V.Item Experimental investigation on effects of varying volume fractions of SiC nanoparticle reinforcement on microstructure and mechanical properties in friction-stir-welded dissimilar joints of AA2024-T351 and AA7075-T651(Cambridge University Press, 2019) Anil Kumar, K.S.; Murigendrappa, S.M.; Kumar, H.Effects of varying volume fractions of SiC nanoparticle (SiC NP ) reinforcement on microstructure and mechanical properties of dissimilar AA2024-T351 and AA7075-T651 joints by friction stir welding (FSW) have been investigated experimentally. A rectangular section edge groove was prepared at the adjoining surfaces of the two plates with the butt configuration before FSW. Initially, four fractional volumes with 0, 5, 8, and 13% of SiC NP are reinforced into the grooves of width, 0, 0.2, 0.3, and 0.5 mm and the FSW was performed with the first and second pass to obtain metal matrix nanocomposite (MMNC) at the weld nugget zone (WNZ). The characterization of microstructure specimens was investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction technique (XRD). The FSW joint specimen produced with 5 vol% fraction of SiC NP for second pass processing observes a defect-free, homogeneous distribution of SiC NP with a mean grain size of about 2-3 ?m at the WNZ and weld joints higher in tensile strength, 411 MPa, yield strength, 252 MPa, and percentage elongation, 14.3. The result shows that varying volume fractions (5, 8, 13%) of the SiC NP after the FSW second pass led to significant grain refinement at the WNZ and higher mechanical properties compared with FSW specimens prepared without SiC NP . Higher hardness of 150 Hv was observed in the WNZ for specimen produced with 13 vol% fraction SiC NP . © Materials Research Society 2019.Item Effect of zirconium on the properties of polycrystalline Cu-Al-Be shape memory alloy(Elsevier Ltd, 2019) Bala Narasimha, G.; Murigendrappa, S.M.This paper presents an investigation of the effect of zirconium on the properties of polycrystalline Cu-Al-Be shape memory alloy. Mechanical and shape memory properties have been evaluated by varying the compositions of Zr to Cu88.13-Al11.42-Be0.45 alloy ranging from 0.05 to 0.4 wt% with step 0.1 wt%. The results unveil reduction in the grain size of 89.18% with the improved tensile strength of 667 ± 30 MPa and ductility of 23.95 ± 0.86% and excellent shape recovery ratio of 100% with the addition of Zr up to 0.3 wt%. Increase in transformation temperatures is observed with the addition of Zr. © 2019 Elsevier B.V.Item An investigation on the properties of boron modified Cu–Al–Be polycrystalline shape memory alloys(Elsevier Ltd, 2020) Bala Narasimha, G.; Murigendrappa, S.M.Effect of microalloying of boron (B) i.e., 0.02–0.15 wt% and the variation of composition of Al and Be from 11.3 to 11.9 wt% and 0.41–0.44 wt% respectively, has been investigated on the grain refinement and shape memory properties of polycrystalline Cu–Al–Be shape memory alloy. The tests have been carried out for microstructure, morphology, phases, crystal structure, phase transformation temperatures and shape recovery ratio. The investigation results in boron has strong impact on grain refinement with minimal addition, followed by Al and Be. AlB2 acts as heterogeneous nucleation site in grain refinement and it increases with increase in B and Al. Transformation temperatures increases with boron up to 0.08 wt% and then decreases, whereas increase in Al and Be decreases the temperatures. Doping and increasing of boron up to 0.15 wt% exhibits complete shape recovery, whereas Be < 0.42 wt% and Al < 11.8 wt% exhibits poor recovery ratio. © 2020 Elsevier B.V.Item Investigation on Properties of Shape Memory Alloy Wire of Cu-Al-Be Doped with Zirconium(Springer, 2020) Singh, R.K.; Murigendrappa, S.M.; Kattimani, S.Abstract: In this paper, the effect of wire drawing on the microstructures, mechanical properties, and shape memory effect of compositions Cu87.85-Al11.70-Be0.45 (CAB) and Cu87.73-Al11.70-Be0.45-Zr0.12 (CABZ) has been experimentally investigated. The wires with a diameter of 1.33 mm are manufactured from the casted round bars through the rolling and drawing (secondary) process. Investigations are performed on microstructure and phase for both as-cast and wire-drawn SMAs. Further, wire-drawn SMAs are investigated for phase transformation temperatures, hardness, ductility, and shape memory effect. The results show that the average grain size decreased with 73.06% by adding Zr to the CAB alloy. Further, the grain size of CABZ alloy wire decreased with 67.38% in the longitudinal direction and 67.07% in the transverse direction as compared to CAB alloy wire after the secondary process. Improvement of the grain structure in CABZ alloy wire resulted in an enhancement in the hardness of 13.86% in longitudinal and 12.43% in the transverse direction, and tensile strength of 134.58% and ductility of 177.06%. The phase transformation temperatures reduced by the addition of Zr, and better shape recovery is observed in CABZ alloy wire. Graphic Abstract: [Figure not available: see fulltext.] © 2020, ASM International.Item Effect of manganese and homogenization on the phase stability and properties of Cu–Al–Be shape memory alloys(Elsevier Editora Ltda, 2021) Bala Narasimha, G.; Murigendrappa, S.M.In this study, the effect of addition of manganese to the ternary Cu–Al–Be shape memory alloys on phase stability, phase transformation temperatures, microstructure, morphology and grain size has been investigated. Secondly, the effect of betatization temperatures and time period has been investigated on the phases and properties of Cu–Al–Be–Mn SMAs. Results reveal that the addition of manganese in the alloys with Al ? 11.8 wt.% forms coexistence of ?1? and ?1? martensites, and manganese ?1 wt.% forms austenite ?1 (DO3). DSC studies exhibit two stage reverse transformation attributes to coexistence of martensites. Increase in manganese decreases the transformation temperatures and increase in betatization temperature and time increases transformation temperatures. Alloying manganese didn't exhibit significant grain refinement and results reduced shape recovery due to the coexistence of martensites. © 2021 The Author(s)Item Effect of Cerium and Aluminium on the phase stability and properties of polycrystalline Cu-Al-Be shape memory alloys(Elsevier Inc., 2022) Bala Narasimha, G.; Murigendrappa, S.M.This study presents the outcomes of an investigation of the effect of wt% of cerium and Aluminium on the phases, crystal structure, microstructure, morphology, phase transformation temperatures, shape recovery ratio and mechanical properties of the polycrystalline Cu-Al-Be shape memory alloys (SMAs). SMAs exhibit martensite phase at room temperature up to 0.49 wt% of Be and ≥ 0.52 wt% of Be transforms to austenite phase. An increase in cerium by 0, 0.05, 0.1, 0.15 and 0.2 wt% decreases the grain size by 0, 70.87%, 82.73%, 83.8% and 94.6%, respectively. An increase in cerium increases the transformation temperatures owing to the Al-rich secondary precipitates, and the shape recovery ratio reduces. Alloying cerium of 0.1 wt% exhibits a maximum tensile strength of 474 ± 23 MPa with the ductility of 24.11 ± 1.42%. © 2021 Elsevier Inc.Item Experimental investigation of the pseudoelastic behavior on zirconium modified Cu-Al-Be shape memory alloys for seismic applications(IOP Publishing Ltd, 2022) Kalinga, T.; Murigendrappa, S.M.; Kattimani, S.This paper examines the effect of 0.05-0.3 wt.% of zirconium-doping on microstructure, transformation temperatures, tensile properties, and pseudoelastic behavior of the parent β1 -phase Cu87.93-Al11.5-Be0.57 shape memory alloys (SMAs). Results reveal that alloying zirconium in the evaluated SMA samples exhibits an excellent grain refinement up to 0.15 wt.%. Further, higher additions of Zr ≥ 0.2 wt.% lowers the grain refinement efficiency due to precipitates agglomeration. Larger the size and volume fraction of Al3Zr precipitates led to higher transformation temperatures. Tensile properties were improved with Zr-doping, resulting enhancements in the maximum tensile strength and ductility with the addition of 0.15 wt.% Zr. The alloy with 0.05 wt.% of Zr-dope showed a good pseudoelastic strain recovery of deformation strain and then lowered by retaining large residual strain, indicating deterioration in the pseudoelasticity of SMAs. © 2022 IOP Publishing Ltd.