Determination of heat treatment parameters by experiments and CALPHAD for precipitate hardening of Cr-Alloys with Si, Ge and Mo

• Published in: Intermetallics 2020-01, Vol.116, p.106636, Article 106636
• Main Authors: Pfizenmaier, Petra, Ulrich, Anke S., Galetz, Mathias C., Glatzel, Uwe
• Format: Article
• Language: English
• Subjects: Alloy systems; Binary alloys; Chromium base alloys; Computer simulation; Cr alloys; Cr–Si phase diagram; Germanium; Heat treating; High temperature materials; Image analysis; Intermetallic phase Cr3Si; Microstructure; Molybdenum; Phase diagrams; Phase volume fraction; Solid solutions; Solubility; Solution heat treatment; Thermo-Calc
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2019.106636

Binary Cr–Si alloys as well as ternary Cr–Si-Ge and Cr–Si–Mo-systems on the Cr rich side of the phase diagram are examined at 1050 °C and 1350 °C regarding the maximum solubility in the bcc solid solution matrix and the A15-phase volume fraction. SEM, EDS and image analysis measurements showed, that the addition of 2 at.% Ge has the same effect on the A15-phase formation as Si but leads to a coarser microstructure. The addition of 2 at.% Mo leads to a decreased A15-phase volume fraction but a small-sized precipitate distribution. The maximum solubility of Si in the binary Cr–Si system is still not clear and has to be verified in further examinations. Thermo-Calc calculations showed, that a reduction of Si content and the addition of Ge and Mo is beneficial for an increase in the process window for solution heat treatment and a decrease of the solvus temperature. •Microstructural characterization and thermodynamic calculations of Cr–Si alloys with additions of Ge and Mo.•The addition of Ge leads to higher A15 vol fractions whereas Mo additions lead to a fine microstructure.•Substitution of Si by Ge and Mo leads to a decrease in Tsolvus A15 and an increased solution heat treatment process window.