Gamma-phase homogenization and texture in U–7.5Nb–2.5Zr (Mulberry) alloy

Lopes, Denise Adorno; Restivo, Thomaz Augusto Guisard; Lima, Nelson Batista de; Padilha, Angelo Fernando

doi:10.1016/j.jnucmat.2014.02.030

Cited by 8 publications

(9 citation statements)

References 16 publications

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“…Based on this knowledge, a hypothesis for the behavior shown in Figure 3 is that for lower degree of deformation (20 pct), the sample stores energy introduced by rolling and, in posterior annealing, uses that energy as a driving force to aid the formation of a¢¢, with Table I. Chemical Composition (Weight Percent) of the Induction Melted Alloy [24] Element (Wt Pct) a consequent increase in hardness. For a higher degree of deformation, the sample stored enough energy to promote both a'' precipitation and recovery.…”

Section: Resultsmentioning

confidence: 99%

“…As the heat treatments were performed separately and in random order, the c o phase was unlikely to have occurred due to experimental error, especially if we take into account the c s stabilization in the homogenized state. [24] It is reasonable to assume that recrystallization created some preferential orientation, and this orientation favored the formation of c o instead c s in the quench process.…”

Section: Resultsmentioning

confidence: 99%

“…8-XRD patterns of the alloy U-7.5Nb-2.5Zr cold rolled (degree of deformation 20 and 80 pct) subjected to isothermal annealing at 973 K (700°C) for 1 and 4 h compared to the homogenized (1273 K/5 h Ref. [24]) and deformed states (20 and 80 pct). The normal probability plot of residuals is provided in Figure 13.…”

Section: Resultsmentioning

confidence: 99%

“…[26] Two samples, taken from different positions in the longitudinal direction of the casting piece (top and center), were analyzed to check their homogeneity, as shown in Table I. [24] After melting, the alloy was heat treated at 1273 K (1000°C) for 5 hours in an argon atmosphere followed by water quenching to obtain a homogeneous microstructure of c-phase at room temperature. Retention of c-phase was verified by measurements of Vickers hardness (loaded with 500 gf for 10 seconds), optical microscopy, and Xray diffraction.…”

Section: A Alloy Preparationmentioning

confidence: 99%

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Hardness Response Surface for U-7.5Nb-2.5Zr Alloy: A Study of Recovery/Recrystallization and Phase Transformation Interactions

Lopes

Zimmermann

Restivo

et al. 2015

Metallurgical and Materials Transactions E

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Uranium alloys in monolithic form are an option for creating advanced nuclear fuels with very high uranium density, low isotopic enrichment, and high thermal conductivity. One aspect of the metallic fuel development is to demonstrate the retention of similar c-phase microstructure (c s) in the fuel alloy after fabrication and during the irradiation process. Unfortunately, there are few recent systematic studies in uranium alloys. Additionally, none of them are addressing the theme of recovery/recrystallization and phase transformations interactions that compose the basic metallurgical knowledge to manufacture nuclear fuel plates. This paper discusses this theme for U-7.5Nb-2.5Zr alloy employing a multivariate statistical technique, namely response surface methodology, to analyze the effect of the following process variables: degree of deformation, temperature, and time. Based on the results, in the range studied, the authors demonstrated that at low temperatures, the interaction between the recovery phenomenon and precipitation of metastable a¢¢ phase (isothermal martensitic shear transformation) shows a dependence with the degree of deformation, with prevalence of recovery for higher levels of this parameter. Interaction between a + c 3 phase nucleation and recrystallization is limited to a narrow temperature range [~848 K to 923 K (575°C to 650°C)] and during the first hour of annealing. Additionally, the series of phase transformations, c fi c s fi c o fi a¢¢, produced by shear was observed to be strongly dependent on crystallographic orientations and this fact could be used to enhance the retention of the metastable c s phase.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: A Alloy Preparationmentioning

confidence: 99%

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Hardness Response Surface for U-7.5Nb-2.5Zr Alloy: A Study of Recovery/Recrystallization and Phase Transformation Interactions

Lopes

Zimmermann

Restivo

et al. 2015

Metallurgical and Materials Transactions E

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“…Prior work involving the modeling of the homogenization kinetics in the as-cast U-10Mo does not exist; however preliminary work involving U-Nb alloy work was performed by Snyder in 1978 [10,11]and more recently by Lopez et. al on U-7.5Nb-2.5Zr [12] alloys. These models used scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) line scans and microhardness measurements to determine the degree of inhomogeneity.…”

Section: Introductionmentioning

confidence: 98%

Modeling the homogenization kinetics of as-cast U-10wt% Mo alloys

Joshi

et al. 2016

Journal of Nuclear Materials

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Low-enriched U-22at% Mo (U-10Mo) alloy has been considered as an alternative material to replace the highly enriched fuels in research reactors. For the U-10Mo to work effectively and replace the existing fuel material, a thorough understanding of the microstructure development from as-cast to the final formed structure is required. The as-cast microstructure typically resembles an inhomogeneous microstructure with regions containing molybdenum-rich and-lean regions, whichmay affect the processing and possibly the in-reactor performance. This as-cast structure must be homogenized by thermal treatment to produce a uniform Mo distribution. The development of a modeling capability will improve the understanding of the effect of initial microstructures on the Mo homogenization kinetics. In the current work, we investigated the effect of as-cast microstructure on the homogenization kinetics.

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