The Influence of the effect of solute on the thermodynamic driving force on grain refinement of Al alloys

Grain refinement is known to be strongly affected by the solute in cast alloys. Addition of some solute can reduce grain size considerably while others have a limited effect. This is usually attributed to the constitutional supercooling which is quantified by the growth restriction factor, Q. However, one factor that has not been considered is whether different solutes have differing effects on the thermodynamic driving force for solidification. This paper reveals that addition of solute reduces the driving force for solidification for a given undercooling, and that for a particular Q value, it is reduced more substantially when adding eutectic-forming solutes than peritectic-forming elements. Therefore, compared with the eutectic-forming solutes, addition of peritectic-forming solutes into Al alloys not only possesses a higher initial nucleation rate resulted from the larger thermodynamic driving force for solidification, but also promotes nucleation within the constitutionally supercooled zone during growth. As subsequent nucleation can occur at smaller constitutional supercoolings for peritectic-forming elements, a smaller grain size is thus produced. The very small constitutional supercooling required to trigger subsequent nucleation in alloys containing Ti is considered as a major contributor to its extraordinary grain refining efficiency in cast Al alloys even without the deliberate addition of inoculants.The Australian Research Council (ARC DP10955737)

The measurement of solid-liquid surface energy

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Dependency of the microstructure parameters on the solidification parameters for camphene

WOS: 000089379800018Camphene (>95% purity) was unidirectionally solidified in a temperature gradient stage. The microstructure parameters, viz., the primary dendrite arm spacing lambda(1), secondary dendrite arm spacing lambda(2), dendrite tip radius R, and mushy zone depth d, were measured for five different growth rates in a constant temperature gradient G and for five different temperature gradients in a constant growth rate V. The dependency of the microstructure parameters on the solidification parameters (V, G, and GV) for camphene were determined by linear regression analysis. Our results are in good agreement with previous works. (C) 2000 Elsevier Science Ltd. All rights reserved

Directional solidification of Al-Cu-Ag alloy

WOS: 000264809500045Al-Cu-Ag alloy was prepared in a graphite crucible under a vacuum atmosphere. The samples were directionally solidified upwards under an argon atmosphere with different temperature gradients (G=3.99-8.79 K/mm), at a constant growth rate (V=8.30 mu m/s), and with different growth rates (V=1.83-498.25 mu m/s), at a constant gradient (G=8.79 K/mm) by using the Bridgman type directional solidification apparatus. The microstructure of Al-12.80-at.%-Cu-18.10-at.%-Ag alloy seems to be two fibrous and one lamellar structure. The interlamellar spacings (lambda) were measured from transverse sections of the samples. The dependence of interlamellar spacings (lambda) on the temperature gradient (G) and the growth rate (V) were determined by using linear regression analysis. According to these results it has been found that the value of lambda decreases with the increase of values of G and V. The values of lambda (2) V were also determined by using the measured values of lambda and V. The experimental results were compared with two-phase growth from binary and ternary eutectic liquid.Scientific and Technical Research Council of Turkey (TUBITAK) [105T481]This research was supported financially by the Scientific and Technical Research Council of Turkey (TUBITAK) under contract No. 105T481. The authors are grateful to the Scientific and Technical Research Council of Turkey (TUBITAK) for their financial supports

Effects of growth rate and temperature gradient on the microstructure parameters in the directionally solidified succinonitrile-7.5 wt.% carbon tetrabromide alloy

WOS: 000257095200019Succinonitrile (SCN)-7.5 wt.% carbon tetrabromide (CTB) alloy was unidirectionally solidified with a constant growth rate (V = 33 mu m/s) at five different temperature gradients (G = 4.1-7.6 K/mm) and with a constant temperature gradient (G = 7.6 K/mm) at five different growth rates (V = 7.2-116.7 mu m/s). The primary dendrite arm spacings, secondary dendrite arm spacings, dendrite tip radius and mushy zone depths were measured. Theoretical models for the microstructure parameters have been compared with the experimental observations, and a comparison of our results with the current theoretical models and previous experimental results have also been made. (C) 2007 Elsevier B.V. All rights reserved

Measurements of Microhardness and Thermal and Electrical Properties of the Binary Zn-0.7wt.%Cu Hypoperitectic Alloy

WOS: 000274947700006Zn-0.7wt.%Cu hypoperitectic alloys were directionally solidified upwards with different temperature gradients (3.85 K/mm to 9.95 K/mm) at a constant growth rate (0.042 mm/s), and with different growth rates (0.0083 mm/s to 0.436 mm/s) at a constant temperature gradient (3.85 K/mm), using a Bridgman-type growth apparatus. Measurements of microhardness of the directionally solidified samples were carried out. The dependence of micro- hardness (HV) on growth rate (V) and temperature gradient (G) was analyzed. According to these results, it has been found that, for increasing values of G and V, the value of HV increases. Variations of electrical resistivity (rho) and electrical conductivity (sigma) for cast samples with temperature from 300 K to 670 K were also measured by using a standard direct-current (DC) four-point probe technique. The variation of the Lorenz coefficient with temperature for the Zn-0.7wt.%Cu hypoperitectic alloy was determined using the measured values of electrical conductivity and thermal conductivity. The enthalpy of fusion for the same alloy was determined by means of differential scanning calorimetry (DSC) from the heating trace during the transformation from liquid to solid.Scientific and Technical Research Council of Turkey (TUBITAK) [107T095]; Scientific and Technical Research Council of Turkey (TUBITAK)This research was supported financially by the Scientific and Technical Research Council of Turkey (TUBITAK) under Contract No. 107T095. The authors are grateful to the Scientific and Technical Research Council of Turkey (TUBITAK) for their financial support

Determination of interfacial energies of solid Sn solution in the In-Bi-Sn ternary alloy

WOS: 000264252800004The equilibrated grain boundary groove shapes of solid Sn solution (Sn-40.14 at.% In-16.11 at.% Bi) in equilibrium with the In-Bi-Sn liquid (In-21.23 at.% Bi-19.04 at.% Sn) were observed from the quenched sample at 59 degrees C. Gibbs-Thomson coefficient, solid-liquid interfacial energy and grain boundary energy of the solid Sn solution have been determined from the observed grain boundary groove shapes. The thermal conductivity of solid phase for In-21.23 at.% Bi-19.04 at.% Sn alloy and the thermal conductivity ratio of liquid phase to solid phase at the melting temperature have also been measured with radial heat flow apparatus and Bridgman type growth apparatus, respectively. (C) 2008 Elsevier Inc. All rights reserved.Scientific and Technical Research Council of Turkey (TUBITAK) [105T481]This research was financially supported by the Scientific and Technical Research Council of Turkey (TUBITAK under Contract No: 105T481). Authors are grateful to the Scientific and Technical Research Council of Turkey (TUBITAK) for their financial supports

Determination of Interfacial Energies for Solid Al Solution in Equilibrium with Al-Cu-Ag Liquid

WOS: 000277712900008The equilibrated grain boundary groove shapes of a solid Al solution in equilibrium with Al-Cu-Ag liquid were observed from a quenched sample using a radial heat flow apparatus. The Gibbs-Thomson coefficient, solid-liquid interfacial energy, and grain boundary energy of the solid Al solution were determined from the observed grain boundary groove shapes. The thermal conductivity of the solid phase for Al-16.42 at.% Ag-4.97 at.% Cu and Al-16.57 at.% Ag-11.87 at.% Cu alloys and the thermal conductivity ratio of the liquid phase to the solid phase for Al-16.57 at.% Ag-11.87 at.% Cu alloy at the melting temperature were also measured with a radial heat flow apparatus and a Bridgman-type growth apparatus, respectively.Scientific and Technical Research Council of Turkey (TUBITAK) [105T481]This research was financially supported by the Scientific and Technical Research Council of Turkey (TUBITAK under Contract No: 105T481). The authors are grateful to the Scientific and Technical Research Council of Turkey (TUBITAK) for their generous financial support