The characterization for B2 structure and L21 structure in the silver-magnesium and silver-magnesium-indium system

The concentration of point defects and the long range order for ordered B2 AgMg alloys, quenched from 973K, was investigated by statistical thermodynamic modeling, powder X-Ray Diffractometery and diffraction simulation as a function of composition. Concentration of the equilibrium point defects at 973K was calculated from two thermodynamic models, where the Ag rich side was based on the constitutional and thermal anti-site defect formation and the Mg rich side was based on the hybrid defect formation, consisting of vacancy, Mg and Ag anti-site defects. The experimental long range order at 973K, determined from the integrated intensity ratio of (100) super-lattice reflection to (200) fundamental reflection, is in quite good agreement with the theoretical long range order at 973K based on the calculated integral intensities from the diffraction simulation, based on the equilibrium concentration of the point defect at both rich side. Furthermore, point defect hardening coefficients on both sides of stoichiometry were determined by the measurement of the Vickers hardness as a function of the equilibrium point defect concentration. The hardening coefficient is G/16 for the Ag rich side with respect to Ag anti-site defects and G/3.1 for the Mg rich side with respect to vacancy defects. It is indicated that the vacancy defect is more significant hardener than Ag anti- site defects for the ordered B2 AgMg intermetallic system.;The partial liquidus projection in the Ag-Mg-In ternary system was established by the primary phase and liquidus temperature. It is indicated that the AgMg 1--xInx phase of the Ag-Mg-In ternary system has a large primary solidification field up to In 90 at.%, so that most ternary invariant reactions of the In rich field must be formed beyond 90 at.% of In. Furthermore, the ordering phase transition of the Heusler AgMg1--xIn x alloys was investigated by powder X-Ray Diffractometery. This results show that the L21 structure ordering of the Heusler alloys was gradually decreased with increasing the annealing temperature, corresponding to decreasing the (111) super-lattice intensity and the long rang order parameters of the L21 structure. These behaviors suggest that the L2 1/B2 ordering transformation phenomena is a second order transformation with respect to temperature.