Solvus Composition Paths in Multicomponent Alloys—Experimental Approach and Correlation with Calphad Calculations for the Example Al–Mg–Si

Abstract

An experimental approach employing temperature and concentration gradients is presented that is suitable for determining a sequence of solvus concentrations in a single experimental cycle. The Al-Mg-Si system is used as an example. Al solid solutions (''(Al)'') with different compositions and Mg 2 Si precipitates were equilibrated in the temperature range between 350 and 550 8C. The equilibrium compositions of (Al) were measured by energy dispersive X-ray spectroscopy in the transmission electron microscope. The coupled temperature-concentration values represent a path on the ternary solvus surface. Calphad calculations using different thermodynamic data sets were carried out to relate the experimental results to phase diagram evaluations. The measured solvus path agrees well with solvus data calculated with most recent thermodynamic parameter sets. The experimental approach can be applied to multicomponent alloys irrespective of their number of components with the same experimental effort. The efficiently generated solubility data are suitable to support phase diagram evaluations of multicomponent systems by the Calphad method.

Growth of an oriented Bi40−xInxTe60 (x = 3, 7) thermoelectric material by seeding zone melting for the enhancement of chemical homogeneity

“…A schematic illustration of the experimental set-up is shown in Fig. [22][23][24][25][26][27] After complete resolidification of the mushy zone, a longitudinal section of the rod was ground and polished, and the microstructure and composition distribution along the axis direction were determined using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). One end of the sample was heated to a temperature above the liquidus temperature and the other end was kept below the solidus temperature, leading to the formation of a mushy zone between the non-melted as-cast zone and the completely melted liquid zone, as illustrated in Fig.…”

“…Due to thermodynamic equilibration in the temperature gradient and the accompanying formation of concentration gradients, upward solute diffusion and further processes such as temperature gradient zone melting (TGZM) occur, and the mushy zone transforms to a completely solid zone with a solute concentration that follows the local solidus concentration. [22][23][24][25][26][27] After complete resolidification of the mushy zone, a longitudinal This journal is © The Royal Society of Chemistry 2015 section of the rod was ground and polished, and the microstructure and composition distribution along the axis direction were determined using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS).…”

“…Hence, the liquidus and solidus lines in the Bi 2 Te 3 -rich part of the pseudo-binary phase diagram of the Bi 2 Te 3 -In 2 Te 3 system were first experimentally reassessed using the temperature and concentration distribution in a former mushy zone that resolidified in a temperature gradient. [22][23][24][25][26][27]…”

Diffusion in a temperature gradient – A single cycle method to determine frequency factor and activation energy of solid diffusion coefficients in alloys

“…Temperature and concentration gradients were utilized in an earlier work to determine ternary solid/solid phase equilibria [13]. Now this approach is extended to generate diffusion profiles with the aid of temperature and concentration gradients that contain information on the diffusivities over a chosen temperature range.…”

Resolidification of a mushy-zone and directional solidification: a method for efficient alloy development demonstrated using the example of Cu–Ga–Sn

“…In this work, mushy-zone resolidification in a temperature gradient is used for preparing sample rods with longitudinal concentration gradients of the alloying elements. This technique has already been utilized to determine solid/liquid equilibria 18 , solvus composition paths in multicomponent alloys 19 as well as frequency factor and activation energy of diffusion coefficients in solids 20 , efficiently reducing the experimental effort compared to conventional strategies.…”