Calorimetric Measurements of Ga-Li System by Direct Reaction Method

The direct reaction calorimetric method was used for the determination of the formation enthalpy of alloys which concentrations correspond to the: Ga7Li2, Ga9Li5, GaLi, Ga4Li5, Ga2Li3, and GaLi2intermetallic phases. The obtained experimental values of the formation enthalpy were: −18.1 ±0.8 kJ/mol at., −26.5 ±0.3 kJ/mol at., −34.7 ±0.3 kJ/mol at., −33.5 ±0.5 kJ/mol at., −32.8 ±0.3 kJ/mol at. and −24.6 ±1.4 kJ/mol at., respectively. After the calorimetric measurements, all the samples were checked by way of X-ray diffraction investigations to confirm the structure of the measured alloys. All the measured values of the formation enthalpy of the Ga-Li alloys were compared with literature data and the data calculated with use of the Miedema model.

Diffusion Kinetics in Explosive Cladding of Dissimilar Alloys as Described through the Miedema Model/ Kinetyka Procesu Dyfuzji W Układach Platerów Wytwarzanych Z Wykorzystaniem Energii Wybuchu, Na Bazie Stopów O Silnie Odmiennych Właściwościach, Opisanych Modelem Miedema

Explosive cladding of dissimilar plates is achieved by the intensive deformation occurring at high pressure and temperature generated from the detonating explosive at the collision interface. The interface morphology, with its characteristic undulations, is dictated by the extent of kinetic energy spent at the mating interface. Nevertheless, the inter-metallic compound formation at the mating interface weakens the joint. The prediction of the probability of inter-metallic formation at aluminum-SS 304, copper-SS 304 and titanium-SS 304 explosive cladding interfaces is attempted in this study by employing Miedema model. Granular explosives (detonation velocity: 4000 m/s) and parallel plate combination were employed with uni-loading ratio (standoff distance-5 mm). The influence of chemical energy in determining the bond strength of explosive clads is discussed as well.

Effect of Al2Ca Compound on Microstructure of As-Cast AZ31 and AZ61 Alloys

The inoculation effect of Al2Ca intermetallic compound on microstructure evolution was examined performed on as-cast AZ31 and AZ61 alloys. The refinement mechanism of Mg-Al alloys was discussed with the Miedema model and edge-to-edge matching model. Al2Ca compound has a good crystallographic matching relation with Mg matrix, which formed in the solidification process. It is considered that Al2Ca can act as a potential and effective heterogeneous nucleation center. The results reveal that the grain refinement effect of Al2Ca compound has more pronounced in AZ31 alloy compared with in AZ61 alloy.

Thermodynamic Parameters Analysis of MgS Superfine Inclusion in Grain Boundary

Activity coefficients and concentrations of dissolved magnesium and sulfur in grain boundary are two essential parts for the calculation of the Gibbs free energy of MgS superfine inclusion in grain boundary. Activity coefficients of dissolved magnesium and sulfur in grain boundary are gained first by the use of Miedema Model and Free Volume Theory. Concentrations of dissolved magnesium and sulfur in grain boundary of Fe-matrix are gained by Mclean’s equation. At last the Gibbs free energy of MgS in grain boundary is -14.048KJ/mol in E-class ship plate steel at T=1363K. By comparing the values of the Gibbs free energy of MgS in grain boundary and that in grain interior, a conclusion can be come to that MgS superfine inclusions may form in grain boundary instead of in grain interior.

Thermodynamic Evaluation and Assessment of the Ti-U Binary System

The thermodynamic description of the Ti-U binary system is obtained by the CALPHAD method using Thermo-Calc software and based on the estimated thermodynamic properties using ion-bonding model and Miedema model as well as the experimental phase diagram information. The liquid, αU, βU, δTi, and γ phases are assumed to be substitutional solutions with Redlich-Kister formula for the expressions of their excess Gibbs energy. The intermetallic compound TiU2 is treated as a stoichiometric compound. The calculated phase equlibria are in good agreement with the estimated and available experimental phase diagram data.