Browsing by Author "Bala Narasimha, G."

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    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.
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    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.
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    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)
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    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.
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    Role of alloying additions on phase transformations, mechanical and pseudoelastic behavior of Cu-Al-Be shape memory alloys
    (Elsevier Ltd, 2022) Kalinga, T.; Bala Narasimha, G.; Murigendrappa, S.M.; Kattimani, S.
    In this study, the influence of alloying additions on phase transformations, microstructure, transformation temperatures, mechanical properties, and pseudoelastic behavior of polycrystalline Cu-Al-Be shape memory alloy has been investigated. Four different SMAs were prepared in the range of 11.0–11.8 wt.% of aluminum and 0.5–0.6 wt.% of beryllium. Results reveal that the alloying of Al ≥ 11.5 wt.% and Be ≥ 0.57 wt.% forms austenite β1(DO3) at room temperature. An increase in both aluminum and beryllium decreases the transformation temperatures, and Cu-11.5Al-0.57Be SMA exhibits smaller energy differences (ΔH) between austenite and martensite. Alloying aluminum and beryllium didn't exhibit significant improvement in mechanical properties due to the existence of coarse grains. Maximum pseudoelasticity of 4% was achieved in Cu-11.5Al-0.57Be SMA with a retained strain of 0.192%. © 2021