U. Böyük

Influence of growth rate on microstructure, microhardness, and electrical resistivity of directionally solidified Al-7 wt% Ni hypo-eutectic alloy

Al-7 wt% Ni alloy was directionally solidified upwards with different growth rates, V (8.3–489.5 μm/s) at constant temperature gradient, G (4.2 K/mm) using a Bridgman-type growth apparatus. The dependence of the dendritic microstructures such as primary dendrite arm spacing (λ1) and secondary dendrite arm spacing (λ2) on the growth rate were determined using a linear regression analysis. The present experimental results were also compared with similar previous experimental results. Measurements of microhardness (HV) and electrical resistivity (ρ) of the directionally solidified samples were carried out. The dependence of the microhardness and electrical resistivity on the growth rate (V) was also analyzed. According to these results, it has been found that, for increasing values of V, the values of HV and ρ increase. However, the values of HV and ρ decrease with increasing values of λ1 and λ2.

Solid–liquid interfacial energy of dichlorobenzene

Commercial-purity dichlorobenzene was purified using a columnar distillation system. The equilibrated grain boundary groove shapes for purified dichlorobenzene (DCB) were directly observed by using a temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs–Thomson coefficient and solid–liquid interfacial energy of purified DCB were determined to be (6.2 ± 0.6) × 10−8 K m and (29.3 ± 4.4) × 10−3 J m−2 with the present numerical model and the Gibbs–Thomson equation, respectively. The grain boundary energy of the DCB phase was determined to be (54.1 ± 9.2) × 10−3 J m−2 from the observed grain boundary grooves. The thermal conductivity ratio of the liquid phase to the solid phase was measured to be 0.94.

Solid-liquid interfacial energy of pyrene

The equilibrated grain boundary groove shapes for commercial purity pyrene (PY) were directly observed by using a temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient and solid-liquid interfacial energy of PY have been determined to be (8.9±0.9)×10−8Km and (21.9±3.3)×10−3Jm−2 with the present numerical model and Gibbs-Thomson equation, respectively. The grain boundary energy of PY phase has been determined to be (42.8±7.3)×10−3Jm−2 from the observed grain boundary groove shapes. Thermal conductivity ratio of liquid phase to solid phase has also been measured to be 0.89.

Measurement of solid-liquid interfacial energy in the In-Bi eutectic alloy at low melting temperature

The Gibbs‐Thomson coefficient and solid‐liquid interfacial energy of the solid In solution in equilibrium with In Bi eutectic liquid have been determined to be (1.46 ± 0.07) × 10 −7 Kma nd(40.4 ± 4.0) × 10 −3 Jm −2 by observing the equilibrated grain boundary groove shapes. The grain boundary energy of the solid In solution phase has been calculated to be (79.0 ± 8.7) × 10 −3 Jm −2 by considering force balance at the grain boundary grooves. The thermal conductivities of the In‐12.4 at.% Bi eutectic liquid phase and the solid In solution phase and their ratio at the eutectic melting temperature (72 ◦ C) have also been measured with radial heat flow apparatus and Bridgman-type growth apparatus.

Effect of Solidification Parameters on the Microstructure of Directionally Solidified Sn-Bi-Zn Lead-Free Solder

Sn-Bi-Zn lead free solder alloy was directionally solidified upward at a constant temperature gradient (G=3.99 K/mm) with a wide range of growth rates (8.3–478.6 μm/s) and at a constant growth rate (V=8.3 μm/s) with a wide range of temperature gradients (1.78–3.99 K/mm) using a Bridgman type directional solidification furnace. Wavelength-Dispersive X-ray Fluorescence spectrometry and X-ray diffraction were used to identify the compositions and phases in the microstructure. Dependence of eutectic spacings (λ) on the growth rate (V), temperature gradient (G) and cooling rate (Ṫ) were determined using linear regression analysis. From the experimental results, it can be concluded that the values of λ decrease with the increasing the values of V, G and Ṫ. The value of λ2V was determined using the measured values of λ and V. The results obtained in the present work have been compared with previous results obtained for binary or ternary alloys.

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 μm 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–5.7 mol% 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–5.7 mol% SCN alloy were also determined from thermal conductivity curve vs temperature.

DETERMINATION OF ANISOTROPY OF CRYSTAL-MELT INTERFACIAL ENERGY FROM THE OBSERVED GRAIN BOUNDARY GROOVE SHAPES AT MULTIPLE ORIENTATIONS

A specialized high-precision thermal gradient furnace with a rotating stage was developed for in situ observation of the equilibrated grain boundary groove shapes at multiple crystallographic orientations in transparent materials. Anisotropies of solid–liquid interfacial free energy for the distillated succinonitrile (SCN) and pivalic acid (PVA) are determined experimentally through direct observation of the equilibrated grain boundary grooves at the multiple crystallographic orientations stabilized within a controlled thermal gradient. The average anisotropies of solid–liquid interfacial energy for distillated SCN and PVA are found to be 0.42 and 3.12% from observed grain boundary groove shapes at multiple crystallographic orientations. Details related to the experimental apparatus and experimental procedures are given.