Pinning effect of second-phase particles on grain growth in polycrystalline films studied by 3-D phase field simulations

Three-dimensional simulations of grain growth in thin films containing finely dispersed second-phase particles were performed using a phase field model. The simulations show that although the growth behavior of the columnar grain structures in thin films is essentially two-dimensional, the interaction between the particles and the grain boundaries is three-dimensional. Grain boundaries can therefore more easily break free from the particles than in purely two-dimensional systems, resulting in fewer grain boundary–particle intersections and a larger final grain size. For a given volume fraction f_V and size of the particles r, the final grain size ${\overline{R}}_{\text{lim}}$ increases with film thickness. Moreover, it was found that particles located in the middle of the film are most efficient in pinning grain boundaries. A classical Zener type relation ${\overline{R}}_{\text{lim}}/r=K(1/f_{\text{V}}^b)$ cannot describe these effects.     

Nucleation potency prediction of LaB6 with E2EM model and its influence on microstructure and tensile properties of Al-7Si-0.3Mg alloy

The edge-to-edge matching (E2EM) crystallographic model was used to predict the orientation relationships (ORs) between LaB₆ and Al. Three different possible ORs can be predicted between LaB₆ and Al, which are ${\left(100\right)}_{\text{Al}}6{\left(100\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[001\right]}_{\text{Al}}6{\left[001\right]}_{{\text{LaB}}_{\text{6}}}$; ${\left(110\right)}_{\text{Al}}6{\left(110\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[001\right]}_{\text{Al}}6{\left[001\right]}_{{\text{LaB}}_{\text{6}}}$; and ${\left(111\right)}_{\text{Al}}6{\left(111\right)}_{{\text{LaB}}_{\text{6}}}$, ${\left[01\overline{1}\right]}_{\text{Al}}6{\left[01\overline{1}\right]}_{{\text{LaB}}_{\text{6}}}$. The prediction results are perfectly confirmed through TEM analysis and prove the nucleation potency of LaB₆. The refining efficacy of Al-2La-1B refiner and its influence on the tensile properties were investigated in the as-cast Al-7Si-0.3Mg alloy. According to the results, LaB₆ has higher nucleation potency than TiB₂, leading to better grain refining efficacy of Al-2La-1B refiner in the as-cast Al-7Si-0.3Mg alloy. Regarding the mechanical performances, tensile properties of the as-cast Al-7Si-0.3Mg casting alloy are prominently improved after addition of Al-2La-1B refiner, due to the refined microstructures.     

Thermochemistry of the nickel–phosphorus system

In the first part, an extensive overview is given over the thermodynamic information for the nickel–phosphorus system which is available in the literature. In the second part, phosphorus vapor pressure measurements over nickel–phosphorus alloys are described for which an isopiestic method was employed. Data points were obtained between 33.82 and 44.40 at% P in the temperature interval from 977 to 1325 K. Based on these measurements partial thermodynamic properties and integral Gibbs energy values were determined. The standard molar Gibbs energy of formation of Ni₅P₄ for the temperature range 977–1042 K was obtained as:${\mathrm{\Delta }}_{\text{f}}{G}_{\text{m}}^{\text{o}}\left({\text{Ni}}_5{\text{P}}_4\right)\left(\text{s}\right)\pm 9.8/\left(\text{kJ}{\text{mol}}^{?1}\right)=?632.1+0.2136T/\text{K}$