Why is cementite a compound Fe3C in the compound database (SGSLbase) and a solution Fe-Cr-C in the solution database (SGSLSoln)?
Some of the compounds in the SGTE database such as Fe3C cementite are actually end members (phase constituents) of higher order solution phases. Thus in Fe-Cr-C (and higher order systems) the cementite phase is found in the list of solution phases. For Fe-Cr-C the constituents of cementite are Fe3C1 and Cr3C1. Both of these are metastable in the respective binary subsystems and the cementite phase is only found as a stable phase when both Cr and Fe are present in the system.
Some of the compounds in the SGTE database such as Fe3C cementite are actually end members (phase constituents) of higher order solution phases. Thus in Fe-Cr-C (and higher order systems) the cementite phase is found in the list of solution phases. For Fe-Cr-C the constituents of cementite are Fe3C1 and Cr3C1. Both of these are metastable in the respective binary subsystems and the cementite phase is only found as a stable phase when both Cr and Fe are present in the system. However, the degree of metastability of Fe3C1 with respect to Fe and C is much less than that of Cr3C1 with respect to Cr and C. Thus it is possible to find under certain conditions cementite in the Fe-C system but not in the Cr-C system. In order to facilitate appropriate equilibrium and phase diagram calculations for the respective binary subsystems, Fe3C (and other compounds) have been included separately as stoichiometric compounds in SGSLbase while Cr3C is only contained in the cementite solution phase that is
Related Questions
- Why is cementite a compound Fe3C in the compound database (SGSLbase) and a solution Fe-Cr-C in the solution database (SGSLSoln)?
- Is a compound whose water solution conducts electricity and turns phenolphtalein pink is HCL or NaOH?
- What is the purpose of the phase B2_BCC!BCC_A2 in the SGTE (SGSLsoln) solution database?
