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)

Solid-liquid interfacial energy in the Al-Ti system

WOS: 000223446900027The equilibrated grain boundary groove shapes for the Al-Ti peritectic system were directly observed. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient for solid Al in Al-Ti solution has been determined to be (1.281 +/- 0.06) x 10(-7) K in with a numerical method. The solid-liquid interface energy for solid Al in Al-Ti solution has been obtained to be (170.72 +/- 16.22) x 10(-3) J m(-2) from the Gibbs-Thomson equation. The grain boundary energy for the same material has been calculated to be (332.01 +/- 35.19) x 10(-3) J m(-2) from the observed grain boundary groove shapes. (C) 2004 Elsevier B.V. All rights reserved

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

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

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

WOS: 000258680500051The equilibrated grain boundary groove shapes of solid In(2)Bi solution in equilibrium with the In-Bi-Sn eutectic liquid were observed from a quenched sample at 59 degrees C. The Gibbs-Thomson coefficient, solid-liquid interfacial energy and grain boundary energy of the solid In2Bi solution have been determined to be (1.42 +/- 0.07) x 10(-7) Km, (49.6 +/- 5.0) x 10(-3) Jm(-2) and (97.1 +/- 10.7) x 10(-3) Jm(-2), respectively, from the observed grain boundary groove shapes. The thermal conductivities of the solid phases for In-21.23 at% Bi-19.04 at% Sn and In-30.5 at% Bi-3 at% Sn alloys and the thermal conductivity ratio of the liquid phase to the solid phase for In-21.23 at% Bi-19.04 at% Sn have also been measured with a radial heat flow apparatus and a Bridgman type growth apparatus, respectively, at their melting temperature.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 financial support

MEASUREMENTS OF SOLID-LIQUID INTERFACIAL ENERGIES IN THE ORGANIC MONOTECTIC ALLOYS

The commercial purity dibromobenzene (DBB) and succinonitrile (SCN) were purified using a columnar distillation system. Thin walled rectangular specimen cells (60-80 mu m thick) were fabricated and filled with the purified materials under the vacuum. The specimen cell was placed in a horizontal temperature gradient stage. A thin liquid layer was melted and the specimen was annealed in a constant temperature gradient for an enough time to observe the equilibrated grain boundary groove shapes. The thermal conductivities of solid and liquid phases for the purified DBB and DBB-5.7mol% SCN alloy were determined with the radial heat flow and the Bridgman-type growth apparatuses. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficients, solid-liquid interfacial energies, and the grain boundary energies for solid DBB in equilibrium with its melts and solid DBB in equilibrium with DBB-SCN monotectic liquid have been determined. The temperature coefficients of the purified DBB and DBB-5.7mol% SCN alloy were also determined from thermal conductivity curve vs temperature

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

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

Effect of solidification processing parameters on the cellular spacings in the Al-0.1 wt% Ti and Al-0.5 wt% Ti alloys

WOS: 000247383300020The aim of this work is to investigate the relationship between solidification processing parameters (temperature gradient, G, growth rate, V, and cooling rate T), and cellular spacing, lambda, in the Al-0.1 wt% Ti and Al-0.5 wt% Ti alloys grown at high growth rates. In order to achieve this aim, the specimens were solidified under argon atmosphere and steady-state conditions upward with different temperature gradients, G at a constant growth rate, V and with different V at a constant G for the Al-Ti alloys in the Bridgman type directional solidification apparatus. The cellular spacing,. was measured and expressed as functions of solidification processing parameters, G, V and T by using a linear regression analysis. The results were compared with similar previous experimental work and current theoretical models suggested for cellular growth. (c) 2006 Elsevier B.V. All rights reserved

Thermal conductivity and interfacial energies of solid Sn in the Sn-Cu alloy

WOS: 000273051800027The equilibrated grain boundary groove shapes of solid Sn in equilibrium with the Sn-Cu eutectic liquid were observed from a quenched sample. The Gibbs-Thomson coefficient, solid-liquid interfacial energy and grain boundary energy of solid Sn have been determined to be (8.7 +/- 0.6) x 10(-8) Km, (113.1 +/- 13.6) x 10(-3) J m(-2) and (222.4 +/- 28.9) x 10(-3) J m(-2), respectively. The thermal conductivity of solid phase and the thermal conductivity ratio of liquid phase to solid phase for Sn-1.3 at.%Cu alloy have also been measured with radial heat flow apparatus and Bridgman type growth apparatus, respectively. (C) 2009 Elsevier B. V. All rights reserved.Scientific and Technical Research Council of Turkey (TUBITAK) [107T095]This research was financially supported by the Scientific and Technical Research Council of Turkey (TUBITAK under Contract No: 107T095). Authors are grateful to the Scientific and Technical Research Council of Turkey (TUBITAK) for their financial supports