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Author: search.filters.author.Majumdar P.Subject: search.filters.subject.Microstructure

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    Effects of heat treatment on evolution of microstructure of boron free and boron containing biomedical Ti-13Zr-13Nb alloys
    (2012) Majumdar P.
    In the present study, the effects of heat treatment on the microstructure of Ti-13Zr-13Nb (TZN) and Ti-13Zr-13Nb-0.5B (TZNB) alloys have been investigated. Depending on the heat treatment conditions, the microstructure of the heat treated TZN alloy consisted mainly of elongated and/or equiaxed ?, ? or martensite. Slow cooling (furnace or air cooling) from the solution treatment temperature produced ? and ? phases in the microstructure. Rapid cooling (water quenching) resulted in martensite and retained ? when the solution treatment temperature was above or close to ? transus. However, martensite was not formed after water quenching from a solution treatment temperature which was below ? transus due to partitioning effect of the alloying elements. Increasing the cooling rate from the furnace cooling to the air cooling led to finer microstructure. Aging of water quenched samples transformed the martensite, if present, into ? and ?, and the morphology of ? phase changed from elongated to equiaxed and enhanced the growth of ?. The microstructure of all the TZNB samples consisted of dispersed precipitated particles of TiB in the matrix. The majority of the boride particles showed an acicular (needle like) morphology. The other phases present in the TZNB alloy were similar to those in the similarly heat treated TZN alloy. Moreover, a growth of ? phase was observed in the microstructure of TZNB alloy when compared with that of TZN alloy. � 2012 Elsevier Ltd.
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    Effect of heat treatment and boron addition on corrosion behavior of Ti-35Nb-7.2Zr-5.7Ta (wt%) ?-titanium alloy in simulated body fluid
    (2011) Majumdar P.; Singh S.B.; Chatterjee U.K.; Chakraborty M.
    The corrosion behavior of Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys subjected to different heat treatment conditions was investigated in Hank's solution. Depending on the heat treatment conditions, the microstructure of the water-quenched, single-stage aged or duplex aged samples consists of very small amounts of ? or a precipitates in equiaxed � grains. Addition of boron to the TNZT alloy results in the formation of dispersed precipitates of titanium boride (TiB) in the � matrix. The other features present in the TNZTB alloy are similar to those in the TNZT alloy. Compared with single aging, duplex aging decreases the corrosion potential (Ecorr) and substantially decreases corrosion current density (icorr) and passive current density (ipass) values. Addition of boron to the TNZT alloy shifts the Ecorr value toward a more active direction and increases the icorr as well as ipass values significantly, and therefore deteriorates the corrosion resistance of the titanium alloys. In general, duplex aged TNZT samples show better corrosion resistance than other heattreated TNZT or TNZTB samples. � 2011, NACE International.
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    The role of heat treatment on microstructure and mechanical properties of Ti-13Zr-13Nb alloy for biomedical load bearing applications
    (2011) Majumdar P.; Singh S.B.; Chakraborty M.
    The suitability of heat treated Ti-13Zr-13Nb (TZN) alloy for biomedical load bearing applications has been investigated. Depending upon the heat treatment conditions, the microstructure of TZN alloy mainly consists of ?, ? or ?" martensite phases. In general, for all the deformation and solution treatment temperatures the variation of the hardness and tensile strength with cooling rate is similar. The elastic modulus of TZN alloy decreases with an increase in cooling rate from the solution treatment temperature. Relatively fine ?+? microstructure increases the hardness and tensile strength. The presence of martensite and/or retained ? in the microstructure decreases the hardness and elastic modulus and increases the ductility substantially whereas higher amount of ? phase in the matrix increases the elastic modulus. Decomposition of martensite and retained ? into ? phase during aging increases the hardness, elastic modulus and tensile strength and decreases the ductility. Among the samples studied, the aged TZN sample, which was deformed and solution treated at 800 �C followed by water quenching, is a promising candidate for the application as implant material. � 2011 Elsevier Ltd.