Papers by Author: Ivona Černičková

Abstract: The work is aimed at searching for compositionally variant isostructural mutations of the cubic F-phase in both as-annealed (850°C/500 h) and DTA-cooled conditions of the Al₇₂Pd₉Co₁₉ alloy. Recently, the mutations were reported for the U-phase in the Al_69.8Pd_13.8Co_16.4 alloy annealed at 700°C for 2000 h. In the investigation, scanning electron microscopy including energy dispersive X-ray spectroscopy, powder X-ray diffraction, and differential thermal analysis (DTA) were used. Two isostructural mutations of the F-phase, F_L (the product of L-parent) and F_V (the product of V-parent), were identified (symbol L stands for liquid). On DTA-cooling, the bivariant heterogeneous transition (L_part→V), the monovariant heterogeneous transformation (L_rest→V+F_L), and the monovariant quasi-eutectoid transformation (V_rest→Al₅Co₂+F_V) were recorded.

Abstract: The recent findings related to binary and ternary structurally complex phases in selected complex metallic alloys coming under Al-Pd-Co, Al-Cu-Co, and Al-Mn-Fe systems are presented. The phases were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, high-angle annular dark-field imaging, X-ray diffraction, and differential thermal analysis. There are highlighted some unusual features of phases D, U, T, and ε-family from both structural and compositional points of view.

Abstract: The U-phase in the Al₇₂Pd_12.8Co_15.2 alloy was studied under non-equilibrium (casting, differential thermal analysis) and near-equilibrium (long-term annealing) conditions to consider its compositional homogeneity. In the investigation, scanning electron microscopy including energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and differential thermal analysis were used. Contrary to the finding reported for the Al_69.8Pd_13.8Co_16.4 alloy, the results obtained for the investigated Al₇₂Pd_12.8Co_15.2 alloy did not confirm the compositional heterogeneity of the near-equilibrium U-phase after annealing at 700°C for 2000 h and at 850°C for 500 h.

Abstract: The microstructure characterization of Al73Mn23Pd4 and Al73Mn21Pd6 alloys was done after annealing at 900°C for 312 h and subsequent water quenching, as well as after thermal cycling. DTA and EDX/WDX/SEM techniques were used in the investigation. It was found out that the alloys consist of the single ternary T-phase after annealing and water quenching. The DTA experiment confirmed the stability of this phase also at lower temperatures. After DTA, the alloys exhibited double-phase microstructure consisting of the ternary T-phase and probably the icosahedral I-phase. It was proved an incongruent transformation of the ternary T-phase into the liquid and vice versa.