Coarsening of second phase in a two-phase Zr-2.5Nb: On the role of phase boundaries

Deformed two-phase Zr-2.5Nb was subjected to 700 degrees C annealing and associated coarsening. After primary recrystallization, the second-phase body-centered cubic beta was well dispersed on the grain boundaries of hexagonal alpha matrix. Prolonged annealing led to the presence of the beta, mainly at the alpha tri-junctions. The two-phase coarsening was associated with clear trends of widening in the second-phase size distribution and changes in phase boundary nature. The former is contrary to what is expected. Changes in phase boundary nature were through increased concentration of 45 degrees[0 0 1] phase boundaries-good-fit interfaces, present in larger beta particles, which were estimated to have higher three-dimensional lattice coincidence and hence lower energy. Simple analytical modeling, assuming dissolution-controlled particle coarsening and a lower interfacial energy of the phase interface with the 45 degrees[0 0 1], was shown to explain these experimental observations. (C) 2009 Acta Materialia Inc

Annealing related microstructural developments in a two-phase ZR-2.5 NB alloy

Deformed/pilgered two-phase, 10-15% cubic second phase - rest being primary hexagonal phase, Zr-2.5 Nb alloy was subjected to various annealing treatments treatments ranging from recovery to recrystallization and grain growth. Associated microstructural developments were monitored through combinations of characterization techniques - bulk crystallographic texture & microtexture measurements and estimations of lattice strain and residual stress. Significant texture changes were associated only with grain growth of the primary phase - a process facilitated by second phase coarsening. From nearly continuous presence at the primary phase grain boundaries, latter stages of grain growth had shown coarsened second phase present only at the tri-junctions. This process was associated with significant changes in phase-boundary nature. An effort was made to explain such changes from an 'extended', i. e. extended to phase boundaries, CSL (coincident site lattice) theory

Defining recrystallization in pilgered Zircaloy-4: From preferred nucleation to growth inhibition

Pilgered Zircaloy-4 was subjected to recrystallization annealing at 650 degrees C: temperature sufficient for primary recrystallization but inadequate for noticeable competitive grain coarsening. Associated microstructural developments were monitored through bulk and microtexture measurements. The deformed microstructure had two, generalized, types of grains: fragmenting/deforming and non-fragmenting/non-deforming. The former had higher stored energy of cold work and defined the early recrystallization stages through preferred nucleation. Non-fragmenting grains, on the other hand, did not contribute directly to recrystallization: but provided significant growth inhibition or pinning to the recrystallized grains. A combination of these two mechanisms defined the recrystallization behavior of pilgered Zircaloy-4. (C) 2011 Elsevier B.V. All rights reserved

Microstructural and textural developments during Zircaloy-4 fuel tube fabrication

Developments in crystallographic texture and in microstructure were characterized during the fabrication steps of Zircaloy-4 fuel tube. Textural developments were generalized in terms of (10 (1) over bar0) and (0001) fibers. These two fibers were observed to get enhanced by the processes of deformation and annealing respectively. Microstructural evolution, on the other hand, ranged from bimodal grain size and shape distribution of the hot extruded stage, to visible heterogeneous deformation associated with pilgering and to fully or partially recrystallized structures after annealing. Textural evolution, associated with individual processing steps during both deformation as well as annealing, had a stronger contribution from relatively larger grains. (C) 2008 Published by Elsevier B.V

Application of Total Cardiovascular Risk Estimation in The Management of A Patient with Cardiovascular Risk

Medical intervention based on the concept of total coronary risk in the asymptomatic population without cardiovascular disease (CVD) is widely advocated throughout the world.All adults above 40 years, without history of CVD or diabetes, and who are not on treatment for blood pressure (BP) or lipids, should be considered for a comprehensive risk assessment in primary care once every five years. Our patient is an asymptomatic obese, hypertensive, dyslipidaemic individual who is also a smoker. He has a family history of premature atherosclerotic disease. His co-morbidities include mild asthma and hepatic impairment. His estimated total cardiovascular risk according to Joint British Society risk score1 for 10 year cardiovascular event is 40% which qualifies him in the high risk category.His estimated score according to HEART score based on the SCORE project2 is 7% which refers to a 10-year risk mortality. According to HEARTSCORE, a score of more than 5 is considered to be at high risk. The following discussion aims to cut down his cardiovascular risk by having life-style changes and use of cardioprotective medication where appropriate. DOI: http://dx.doi.org/10.3329/uhj.v7i1.10207 UHJ 2011; 7(1): 28-34</jats:p