Reordering a deformation disordered intermetallic compound by antiphase boundary movement

• Published in: Journal of alloys and compounds Vol. 713; pp. 148 - 155
• Main Authors: Gammer, C., Karnthaler, H.P., Rentenberger, C.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.08.2017; Elsevier BV
• Subjects: Antiphase boundaries; Differential scanning calorimetry; Differential scanning calorimetry (DSC); Diffusion; Enthalpy; Ferrous alloys; Heat measurement; Intermetallic compounds; Intermetallic FeAl; Iron aluminides; Iron compounds; Migration; Parameter estimation; Plastic deformation; S parameters; Severe plastic deformation (SPD); Vacancies; Vacancy migration; Differential scanning calorimetry (DSC); Vacancy migration; Severe plastic deformation (SPD); Intermetallic FeAl
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.04.045

Long-range ordered intermetallic compounds can be disordered by severe plastic deformation and upon heating up the order is restored. A model for reordering is presented that considers recent TEM results showing that reordering is connected with the growth of antiphase boundary (APB) domains. The model is applied to the case of B2 ordered FeAl disordered by high-pressure torsion. The model makes use of the reordering peak observed by differential scanning calorimetry. The agreement between the vacancy migration enthalpy (HVM) determined using a Kissinger plot and using the model, indicates that reordering occurs by the diffusion of vacancies along the APB. Also, the calculated size of the ordered domains during reordering agrees well with the experimental value. Furthermore, the model allows an estimation of material's parameters that are hard to access experimentally, e.g. the density of the vacancies at the APB (210−2) involved in reordering. By applying the model to FeAl reordered under high pressure, the model yields HVM values effective for different pressures. The resulting low value of the vacancy migration volume supports the concept that reordering occurs by diffusion of vacancies along APB. Finally, the model demonstrates that by unloading a specimen deformed under high pressure, the density of vacancies active during reordering is significantly reduced (by about a factor of 2). [Display omitted] •The long-range order in FeAl is destroyed by high pressure torsion deformation.•Reordering during heating is connected with the growth of antiphase boundary domains.•A model for the heat flow during reordering is presented and validated.•For reordering under pressure the model reveals a low vacancy migration volume.•Releasing the pressure after deformation reduces the vacancy density by a factor of 2.