In elastically inhomogeneous solid materials, the presence of strains causes changes in both morphology and phase equilibria, thereby changing the mechanical and chemical properties. For any given initial phase-and grainstructure, it is difficult to determine experimentally or analytically these changes in properties. Phase-field models coupled with micro elasticity theory can be used to predict the morphological and chemical evolution of such strained systems, but their accuracy with respect to interfacial excess contributions has not been tested extensively. In this study, we analyse three existing phasefield schemes for coherent two-phase model systems and a Cu 6 Sn 5-Bct-Sn system. We compare the chemical composition and stress state obtained in the simulations with analytical values calculated from Johnson's (Johnson 1987 Metall. Trans. A 18 233-47) model. All schemes reproduce the shift in chemical composition, but not the strains. This deviation is due to excess interfacial energy, stresses, and strains not present in the analytical results, since all three schemes are based on assumptions different from the stress and strain relations at equilibrium. Based on this analysis, we introduce a new scheme which is consistent with the analytical calculations. We validate for the model system that this new scheme quantitatively predicts the morphological and chemical evolution, without any interfacial excess contributions and independent of the diffuse interface width.

Solid-state phase transformations are influenced by strains that are generated internally or applied externally. The stress state, composition, and microstructure evolution, which together determine the properties of solid materials can be studied using phase-field models coupled with micro-elasticity theory in the small strain limit. This coupling has been implemented using various schemes in literature. In a previous article (Durga et al., 2013 [1]), the authors evaluated three main existing schemes for a two-phase system and concluded that these schemes are not quantitative for inhomogeneous anisotropic elastic properties of the two phases. The stress states predicted by these models deviate from the expected values due to the generation of extra interfacial energy, which is an artefact of the models resulting from interfacial conditions different from local mechanical equilibrium conditions. In this work, we propose a new scheme with interfacial conditions consistent with those of the analytical results applicable to a general system where shear strains may be present. Using analytical solutions for composition and stress evolution, we validate this model for 2D and 3D systems with planar interface in the presence of misfit between phases and applied strains, and a 2D system with an elliptical second-phase particle. This extended scheme can now be applied to simulate quantitatively the microstructural evolution with coupled chemical and mechanical behaviour in any 2D or 3D two-phase system subject to internal or external strains irrespective of interface curva-

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In this article, we aim to study the problem of the growth of intermetallic phases in solder joints undergoing mechanical deformation, using a phase-field model for multi-phase systems that can treat diffusion, elastic and plastic deformation. A suitable model is formulated and applied to Sn-Cu/Cu lead-free solder joints. The growth of the intermetallic layers during solid-state annealing is simulated for different strain states. We assess the values of stiffness tensors available in literature and perform ab initio calculations to support the selection of reasonable values from literature. We also perform a parametric study with different eigenstrain values and applied strains. We find that there is a significant effect of the considered eigenstrains and applied strains on the growth kinetics of the system and parabolic growth kinetics is followed in cases where the intermetallic layers grow. We thereby establish the importance of strain in the growth of intermetallic layers and the need for more targeted experiments on the role of strain in the reliability of the solder joint.

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Thalassemia is a genetic blood disorder requiring life-long blood transfusions. This process often results in iron overload and can be treated by an ironchelating agent, like deferiprone (3-hydroxy-1,2-dimethylpyridin-4-one), C 7 H 9 NO 2 , in an oral formulation. The first crystal structure of deferiprone, (Ia), was reported in 1988 [Nelson et al. (1988). Can. J. Chem. 66, 123-131]. In the present study, two novel polymorphic forms, (Ib) and (Ic), of deferiprone were identified concomitantly with polymorph (Ia) during the crystallization experiments. Polymorph (Ia) was redetermined at low temperature for comparison of the structural features and lattice energy values with polymorphs (Ib) and (Ic). Polymorph (Ia) crystallized in the orthorhombic space group Pbca, whereas both polymorphs (Ib) and (Ic) crystallized in the monoclinic space group P2 1 /c. The asymmetric units of (Ia) and (Ib) contain one deferiprone molecule, while polymorph (Ic) has three crystallographically independent molecules (A, B and C). All three polymorphs have similar hydrogen-bonding features, such as an R 2 2 (10) dimer formed by O-HÁ Á ÁO hydrogen bonds, an R 4 3 (20) tetramer formed by C-HÁ Á ÁO hydrogen bonds andinteractions, but the polymorphs differ in their molecular arrangements in the solid state and are classified as packing polymorphs. O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds lead to the formation of two-dimensional hydrogen-bonded parallel sheets which are interlinked bystacking interactions. In the three-dimensional crystal packing, the deferiprone molecules were aggregated as corrugated sheets in polymorphs (Ia) and (Ic), whereas in polymorph (Ib), they were aggregated as a square-grid network. The characteristic crystalline peaks of polymorphs (Ia), (Ib) and (Ic) were established through powder X-ray diffraction analysis. The Rietveld analysis was also performed to estimate the contribution of the polymorphs to the bulk material.