A constitutional diagram of the system TiC?HfC?“MoC” |
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Authors: | Dr Peter Rogl Subhash K Naik Erwin Rudy |
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Institution: | (1) Materials Science Department, Oregon Graduate Center for Study and Research, Beaverton, Oregon, USA;(2) Institute of Physical Chemistry, University of Vienna, Währinger Straße 42, A-1090 Wien, Austria |
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Abstract: | The system TiC–HfC– MoC was investigated by means of melting point, differentiothermoanalytical, X-ray diffraction and metallographic techniques on hotpressed as well as melted alloy specimens. A constitutional diagram from 1500°C through the melting range was established.Investigation of the (Hf, Mo)C system (isopleth: HfC0.98– MoC1.0 ) showed a small miscibility gap within the cubic monocarbide solution ( ) Tc=1630°C, (HfC)0.45(MoC)0.55]. The miscibility gap interacts with the solvus curve with a monotectoid-like decomposition reaction at 1575°C, (HfC) 0.35(MoC) 0.65.At temperatures below 1630°C, phase equilibria within TiC–HfC– MoC are characterized by a large miscibility gap connecting the TiC–HfC and HfC–MoC boundary systems. Additions of MoC to TiC–HfC alloys decrease the critical temperature (1780°C); additions of TiC to HfC– MoC alloys raise the critical temperature (1630°C). No maximum type ternary critical point or saddle point was found to occur.Isothermal sections were prepared at 1500°C and 1650°C. At temperatures above 1960°C ( -MoC+C![rlarr](/content/w1013177g8qh6013/xxlarge8644.gif) -MoC) a complete solid solution ( -B 1) is formed within TiC–HfC– MoC . The melting behaviour (liquidus projection of TiC–HfC– MoC ) shows flat melting temperatures in the MoC corner but extremely heterogeneous melting near the TiC–HfC boundary.Isothermal sections have been calculated assuming regular solutions.With 5 Figures |
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