CTi-tx

J.L.Murray
The condensed Ti-C system has been characterized from0to about70at.%C.In addition to the bcc(βTi)and cph(αTi) solutions,there is an equilibrium carbide,TiC,with the homogeneity range32to48.8at.%C.The carbide has another form,
designated Ti2C,in which vacancies are ordered on the carbon sublattice[67Gor].This ordered phase is not the same as that
mentioned by[Hansen].
The most important phase diagram investigations were conducted by[53Cad],[55Ogd],[56Wag],[59Bic],and[65Rud].At higher temperatures,the assessed diagram is based on[65Rud];at lower temperatures,it is based on[53Cad]and[56Wag].A thermodynamic assessment was presented by[85Uhr],in which agreement is good between calculated and experimental
diagrams;the assessed TiC liquidus is drawn from the calculations of[84Uhr].
[59Bic]estimated liquidus compositions by chemical analysis of the liquid held at temperature until the melt composition was changing only very slowly.These data imply a eutectic composition of about4.5at.%C.[65Rud]estimated the liquidus to be somewhat above the temperature at which the samples collapsed.[65Rud]placed the eutectic composition at slightly less than2 at.%C,based on metallographic examination of as-cast alloys.They noted that the low carbon content of the eutectic and
structural changes that occurred during quenching made the metallographic work difficult.
癈and The Ti-rich limit of the TiC phase field was determined metallographically by[53Cad](38at.%C at920)
癈Reported congruent melting points of TiC metallographically and from the melting point data by[65Rud](32at.%C at1650).
癈The value3067±15癈[65Rud]is chosen for the assessed diagram.The reaction L↔TiC+ range between1940and3250.
癈with the eutectic composition about63at.%C[65Rud].
C(graphite)is placed at2776,
No distinction has yet been made between equilibria involving TiC and those involving ordered Ti2C.[62Bit]found discontinuities in the magnetic susceptibility of TiC as a function of composition.[67Gor]performed neutron diffraction studies
癈Superlattice lines were found in the range32to36at.%C.At33at.%C,Ti2C of alloys annealed between1100and2000.
癈
was estimated to be stable up to about1900.
53Cad:I.Cadoff and J.P.Nielsen,Trans.AIME,197,248-252(1953).
55Ogd:H.R.Ogden,R.I.Jaffee,and F.C.Holden,Trans.AIME,203,73-80(1955).
56Wag:F.C.Wagner,E.J.Bucur,and M.A.Steinberg,Trans.ASM,48,742-761(1956).
59Bic:R.L.Bickerdike and G.Hughes,J.Less-Common Met.,1,42-49(1959).
62Bit:H.Bittner and H.Goretzki,Monatsh.Chem.,93,1000-1004(1962)in German.
65Rud:E.Rudy,D.P.Harmon,and C.E.Brukl,AFML-TR-65-2,Part I,Vol.II(1965).
67Gor:H.Goretzki,Phys.Status Solidi,20,K141-K143(1967).
84Uhr:B.Uhrenius,Calphad,8(2),101-119(1984).
Published in Phase Diagrams of Binary Titanium Alloys,plete evaluation contains4figures,4tables,and43 references.
Special Points of the Ti-C System
Temperature,
Reaction Composition,at.%C°C Reaction type
βTi↔αTi0882Allotropic
L↔βTi01670Melting
L↔(βTi)+Ti2C 1.80.6321648±5Eutectic
L↔TiC443067±15Congruent
TiC↔Ti2C?33.3∼1900Congruent
L↔TiC+C6348.8∼1002776±6Eutectic
(βTi)+TiC↔(αTi)0.638 1.6920±3Peritectoid
Copyright (C) 1996 ASM International
1。