H. Kaya

Effect of growth rates and temperature gradients on the lamellar spacing and the undercooling in the directionally solidified Pb-Cd eutectic alloy

Lead-cadmium of high (99.99%) purity eutectic alloy was melted in a graphite crucible under vacuum atmosphere. These regular eutectic alloys were directionally solidified upward with a constant growth rate of 8.3 {mu}m/s, and different temperature gradients G ({approx}1.6-6.4 K/mm range), and also with a constant temperature gradient ({approx}6.4 K/mm) and different growth rates V (8.3-165.5 {mu}m/s range) in the Bridgman-type directional solidification furnace. The lamellar spacings {lambda} were measured from both transverse section and longitudinal section of the specimen. The variations of {lambda} with respect to G and V were determined by using linear regression analysis. The dependence of {lambda} on {delta}T{sub e} (the extremum undercooling) was also analysed. The variation of {delta}T{sub e} with V at constant G and with G at constant V were investigated. According to these results, it has been found that {lambda} decreases with the increasing values of G and V. Also {delta}T{sub e} increases with increasing V for a constant G and with the increasing G for a given V, respectively. The results obtained in this work have been compared with the Jackson-Hunt eutectic theory and the previous experimental results.

Effect of the Temperature Gradient, Growth Rate, and the Interflake Spacing on the Microhardness in the Directionally Solidified Al-Si Eutectic Alloy

An alloy of composition Al-12.6 wt.% Si was prepared using metals of 99.99% purity. Weighed amounts of aluminium and silicon were melted in the vacuum-melting furnace. This irregular eutectic alloys were directionally solidified upward with a constant growth rate V (8.3×10−3 mm/s) and different temperature gradients G (2.0–7.8 K/mm) and also with a constant temperature gradient G (7.8 K/mm) and different growth rates V (8.3–498.7×10 −3mm/s) in the directional solidification furnace. The interflake spacings λ and microhardness HV were measured from both transverse section and longitudinal section of the specimen. The variations of HV with respect to G, V, and λ have been determined by using the linear regression analysis method. It has been shown that HV increases with the increasing values of G and V. On the other hand HV values decreases with the increasing λ values. The Hall-Petch type relationships obtained in this work have been compared with the previous works.

Effect of growth rate and composition on the primary spacing, the dendrite tip radius and mushy zone depth in the directionally solidified succinonitrile–Salol alloys

The succinonitrile (SCN)–Salol alloys for four different concentrations Salol were unidirectionally solidified for five different growth rates in a constant temperature gradient. The microstructure parameters, viz., the primary dendrite arm spacing, λ1, dendrite tip radius, R and mushy zone depth, d, were measured. The dependence of the microstructure parameters on the solidification parameters for SCN–Salol alloys were determined by linear regression analysis. The results are compared with theoretical models and published data.

Effect of growth rates and temperature gradients on the spacing and undercooling in the broken-lamellar eutectic growth (Sn-Zn eutectic system)

The Sn-Zn system has a eutectic structure of a broken lamellar type. Dependence of the broken-lamellar spacing λ and the undercooling ΔT on V and G were investigated, and the relationship between them was examined. A Sn-Zn (99.99%) high-purity eutectic alloy was melted in a graphite crucible under vacuum atmosphere. This eutectic alloy was directionally solidified upward with a constant growth rate V (8.30 µm/s) and different temperature gradients G (1.86–6.52 K/mm), and also with a constant temperature gradient (6.52 K/mm) and different growth rates (8.30–165.13 µm/s) in a Bridgman-type directional solidification furnace. The lamellar spacings λ were measured from both transverse and longitudinal sections of the specimen. The λ values from the transverse section were used for calculations and comparisons with the previous works. The undercooling values ΔT were obtained using growth rate and system parameters K1 and K2. It was found that the values of λ decreased while V and G increased. The relationships between lamellar spacing λ and solidification parameters V and G were obtained by linear regression analysis method. The λ2V, ΔTλ, ΔTV−5, and λ3G values were determined using λ, ΔT, V, and G values. The experimentally obtained values for the broken-lamellar growth (Sn-Zn eutectic system) were in good agreement with the theoretical and other experimental values.

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.

Dependence of electrical resistivity on temperature and composition of Al–Cu alloys

Abstract Different compositions of Al–Cu alloys were directionally solidified upward with constant growth rate (V≅18·6 μm s−1) and constant temperature gradient (G≅4·7 K mm−1) using a Bridgman type growth apparatus. The variations in electrical resistivity ρ with temperature for directionally solidified Al–Cu alloys were measured in the range of 373−773 K using a standard four-point probe technique. According to the present experimental results, the resistivity of directionally solidified Al–Cu alloys linearly increases with increasing temperature and composition of Cu in the Al–Cu alloys. The variations in Lorenz number with the temperature and composition of Cu in the Al–Cu alloys were also determined from the Wiedemann–Franz law using the measured values of thermal and electrical conductivities for the same alloys.

Experimental determination of interfacial energies for Ag2Al solid solution in the CuAl2?Ag2Al system

The equilibrated grain boundary groove shapes of solid solution Ag2Al in equilibrium with an Al—Cu—Ag liquid were observed from a quenched sample with a radial heat flow apparatus. The Gibbs–Thomson coefficient, solid—liquid interfacial energy and grain boundary energy of the solid solution Ag2Al have been determined from the observed grain boundary groove shapes. The thermal conductivity of the solid phase and the thermal conductivity ratio of the liquid phase to solid phase for Ag2Al — 28.3 at the % CuAl2 alloy at the melting temperature have also been measured with a radial heat flow apparatus and Bridgman type growth apparatus, separately.

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.

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

The equilibrated grain boundary groove shapes of solid In2Bi solution in equilibrium with the In–Bi–Sn eutectic liquid were observed from a quenched sample at 59 °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) × 10−7 K m, (49.6 ± 5.0) × 10−3 J m−2 and (97.1 ± 10.7) × 10−3 J m−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.

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.