Microstructural study and numerical simulation of phase decomposition of heat treated Co–Cu alloys

Abstract

The influence of heat treatment on the phase decomposition and the grain size of Co-10 at% Cu alloy were studied. Few samples were aged in a furnace for either 3 or 5 h and then quenched in iced water. The materials and phase compositions were investigated using energy dispersive spectrometry and X-ray diffraction techniques. X-ray diffraction analysis showed that the samples contained Co, Cu, CuO, CoCu 2 O 3 , CoCuO 2 phases in different proportions depending on the heat treatment regimes. The formation of dendrite Co phase rendered the spinodal decomposition while the oxidations prevent the initiation of the spinodal decomposition even for a deep long aging inside the miscibility gap. Since the Bragg reflections from different phases of Co-Cu alloy significantly overlap, the crystal structural parameters were refined with FULLPROF program. The shifts in the refined lattice constants (a, b and c), the space group and the grain size were found to be phase-and heat treatment-dependant. Two-dimensional computer simulations were conducted to study the phase decomposition of Co-Cu binary alloy systems. The excess free energy as well as the strain energy, without a priori knowledge of the shape or the position of the new phase, was precisely evaluated. The results indicate that the morphology and the shape of the microstructure agree with SEM observation.

Re-Examination of the Microstructural Evolution in Undercooled Co-18.5at.%B Eutectic Alloy

“…Most solidification behaviors take place outside of the equilibrium state because of the rapid cooling rate or the large undercooling (∆T), which result in various microstructures and properties [2,3]. So far, the microstructural evolution and phase selection behaviors of undercooled melts have been investigated in many systems, such as the Mn-Si [4] and Cu-Sn [5] systems, using cyclic overheating combined with glass fluxing [6], directional solidification [5], and laser melting [7], with in situ observations [8] or numerical simulations [9], to manipulate and control the microstructures and properties. For instance, the uniform nature and refinement of the grains can be obtained as the ∆T increases, which can effectively improve the yield strength [10] and the physical properties [11].…”

Theoretical and Experimental Parameters of the Structure and Crystallization Kinetics of Melt-Quenched As30Te64Ga6 Glassy Alloy

“…In contrast, the constant heating rate experiments do not have the mentioned drawback [23]. Generally, the differential thermal analysis (DTA) and DSC are the common techniques used for investigating the phase transitions and the crystallization kinetics of the chalcogenide glasses and polymers among other techniques [22,[24][25][26][27].…”