Effect of solidification parameters on microstructural characteristics and mechanical properties of directionally solidified binary TiAl alloy

Fan, Jiangkun; Liu, Jianxiu; Tian, Shuai; Wu, Shen; Gao, Hongxia; Guo, Jingjie; Wang, Xiao; Su, Yanqing; Fu, Hengzhi

doi:10.1016/j.jallcom.2015.05.160

Cited by 22 publications

(15 citation statements)

References 45 publications

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“…Directional solidification 5 is one of the most important solidification methods used for material processing. The mechanical properties of the alloys can be improved by obtaining finer microstructure result from higher solidification rates and higher cooling rates under several directional solidification conditions [6][7][8][9][10][11][12][13] . The directionally solidified alloy exhibited higher strength than the non-directionally solidified alloy under the same cooling rate 14,15 .…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification

2018

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Sn-36Bi-22Cu (wt.%) ternary eutectic alloy was prepared using vacuum melting furnace and casting furnace. The samples were directionally solidified upwards solidification rate varying from 8.3 to 166 µm/s and at a constant temperature gradient (4.2 K/mm) in a Bridgman-type directional solidification furnace. The composition analysis of the phases and the intermetallics (Cu 3 Sn and Cu 6 Sn 5 ) were determined from EDX and XRD analysis respectively. The variation of the lamellar spacing (Bi-rich phase) and the Cu 3 Sn phase spacing with the solidification rate were investigated. The dependence of microhardness, ultimate compressive strength and compressive yield strength on solidification rate were determined. The spacing and microhardness were measured from both longitudinal and transverse sections of the samples. The dependence of microhardness on the lamellar spacing and the Cu 3 Sn phase spacing were also determined. The relationships between phase spacings, solidification rate and mechanical properties were determined from linear regression analysis.

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Section: Introductionmentioning

confidence: 99%

Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification

2018

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“…The γ phase presents lower microhardness value than α 2 phase in TiAl alloys 29,30 . As current densities increase, the relative volume fraction of α 2 phase increases and the formation of γ phase is reduced to various extents accordingly 31 .…”

Section: Resultsmentioning

confidence: 92%

“…Microhardness ( HV ) presents the resistance behavior for localized plastic deformation, densification and cracking of materials and is well correlated to tensile strength 28 . The property of microhardness is strongly dependent on the alloying component, processing conditions and structural parameters 29 . Figure 7 shows the Vickers microhardness curve of Ti-48Al-2Cr- 2 Nb alloy with different direct current densities.…”

Section: Resultsmentioning

confidence: 99%

“…Based on the Hall-Petch relations, microhardness along with yield strength of conventional polycrystals are scaled by square roots of mean microstructural parameters of materials:where σ y is the microhardness or yield stress, σ 0 is material-dependent constant, k is Hall–Petch slope, and λ is microstructure length scale such as average grain size or interlamellar spacing 29,35,36 . According to Eq.…”

Section: Resultsmentioning

confidence: 99%

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An innovation for microstructural modification and mechanical improvement of TiAl alloy via electric current application

Chen

Ding

Chen

et al. 2019

Sci Rep

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In this article, microstructural evolution during the solidification of Ti-48Al-2Cr-2Nb with current density, as well as the formation mechanisms, are discussed, along with the impacts on microhardness and hot compression properties. The applied electric current promotes the solidification from the α primary phase to a largely β solidification in Ti-48Al-2Cr-2Nb. With an increase in supercooling, the solidification process have a tendency to change from an α-led primary phase to (α + β)-led primary phase. The primary dendrites, grain size, and lamellar spacing show a tendency to decrease first before increasing with increasing current density. Microhardness and high-temperature yield strength increase with a decrease in primary dendrite spacing, grain size, and lamellar spacing. Correlations between primary dendrite spacing, lamellar spacing, microhardness, yield strength, and current density are described by a fitting formula. An increase of α 2 phase, due to the application of electric current, results in improved microhardness. The yield strength of Ti-48Al-2Cr-2Nb alloy increases linearly with microhardness. Yield stress increases with a decrease in microstructure parameters, in accordance with the Hall–Petch equation. The predominant modification mechanism with electric current application for TiAl solidification is the variation of supercooling and temperature gradients ahead of the mush zone due to Joule heating.

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“…In most cases, due to the opaque nature of metal alloys, only a post mortem analysis is possible, whereby the samples are cut, polished, and etched after solidification and then observed by optical or electron microscopy techniques. These types of procedures allow for the direct observation of relevant details, like the final grain structure and size, or the dendritic arm spacing [7][8][9][10]. Nevertheless, the observation of some features may still be difficult, as in the case of alloys that experience solid-state phase transformations that may alter or completely remove the initial solidification microstructure [11].…”

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confidence: 99%

Numerical simulation of Bridgman solidification of binary alloys

Battaglioli

McFadden

Robinson

2017

International Journal of Heat and Mass Transfer

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A transient 2D axisymmetric numerical model for the Bridgman solidification process for a stationary furnace and moving sample is presented. The model is able to predict the evolution of temperature and solid fraction of binary alloys in cases where buoyancy induced convection is negligible, such as in microgravity conditions. A dimensionless form of the governing equations was derived in order to identify the dimensionless parameters that characterize the process, those being the Stefan, Péclet, and Biot numbers. The problem was solved using a finite volume method and an explicit time stepping scheme. To test the efficacy of the model, simulated results were compared with experimental data from the literature and acceptable agreement was obtained. Finally, a parametric analysis was performed for understanding the influence of the process parameters on solidification. One key feature of this study was the inclusion of a term describing the advection of latent heat due to the translation of the mushy zone with varying solid fraction. This thermal transport mechanism was shown to be significant, since its magnitude was comparable to the advection of sensible heat. It was also found that when small Biot numbers were due to low values of the heat transfer coefficients at the surface of the sample, rather than to small sample radii, advective mechanisms were enhanced resulting in more convex shapes of the liquidus isotherm. This highlighted the importance of considering both axial and radial heat fluxes when describing the process.

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Effect of solidification parameters on microstructural characteristics and mechanical properties of directionally solidified binary TiAl alloy

Cited by 22 publications

References 45 publications

Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification

Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification

An innovation for microstructural modification and mechanical improvement of TiAl alloy via electric current application

Numerical simulation of Bridgman solidification of binary alloys

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