Papers by Keyword: Liquidus Projection

Abstract: The present work addresses the microstructure evolution of refractory Me-Si-B (Me = Mo, V) alloys consisting of a refractory metal solid solution phase (Me_SS) and two intermetallic phases Me₅SiB₂ and Me₃Si. The aim of the present study is to find the ternary eutectic composition in such systems which are expected to combine a well-defined eutectic microstructure with properties such as high strength, an excellent creep resistance at high temperatures and acceptable oxidation behavior. Two refractory metal systems based on molybdenum and vanadium are investigated. Various alloy compositions located in different primary solidification areas were produced by arc-melting and analyzed via SEM. The obtained results are discussed in the light of published liquidus projections. By carrying out these experiments, a Me_SS-Me₅SiB₂-Me₃Si ternary eutectic could be determined in both Me-Si-B systems.

Abstract: The aim of the present study is to identify the ternary eutectic Mo-Si-B composition to produce directionally solidified materials, which are expected to have excellent high-temperature properties due to the well-defined microstructure. Different alloy compositions in the respective primary solidification areas of the phases were chosen to investigate the microstructural evolution. The results were compared to thermodynamic calculations of the liquidus projection and isopleth phase diagrams using the software FactSageTM. By carrying out these experiments the eutectic point was found to have a nominal composition of Mo-17.5Si-8B (at.%). In the next step, the eutectic alloy was directionally solidified by a zone melting (ZM) process. The evolution of a typical eutectic microstructure due to the growth of lamella-like structures is shown by microstructural investigations. Furthermore, we present a eutectic phase field model for the eutectic Mo-Si-B alloy. The equilibrium interface geometries and interface mobility were calculated using an isotropic model. The results are shown to be in an adequate conformity with the experimental observations.

Abstract: The ternary system Cu-Si-Ti was investigated using XRD, SEM-EDX, and DTA. The existence of two ternary phases τ1-CuSiTi and τ2-TiSi2-xCux as well as their crystal structures are confirmed. The isothermal section at 800°C is corroborated. From DTA data of equilibrated alloys a reaction scheme linking the isotherm at 700°C with the liquidus surface is derived. Using data on primary crystallisation of as cast alloys a projection of the liquidus surface is proposed.