Observing the D0 3 phase in Fe–Mn–Al alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 337; no. 1; pp. 281 - 286
• Main Authors: Cheng, Wei-Chun, Liu, Chia-Fu, Lai, Yi-Fan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2002
• Subjects: Aging; D0 3 phase; Fe–Mn–Al alloy; Quenching; TEM; Fe–Mn–Al alloy; Aging; D0 3 phase; TEM; Quenching
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(02)00047-3

Two Fe–Mn–Al alloys with compositions of Fe–23.0 wt.% Mn–7.4 wt.% Al–0.03 wt.% C (alloy A) and Fe–28.5 wt.% Mn–8.8 wt.% Al–0.09 wt.% C (alloy B) were studied throughout the quenching and aging process. After the specimens were heated at 1050 °C for 1 h, and then quenched in room temperature water, both alloys have a small amount of austenite distributed randomly along the ferrite grain boundary. In the TEM study, alloy B shows D0 3 precipitates exist within the ferrite grains while alloy A does not. Samples in alloy B were heated at 1050 °C for 1 h, and then quenched directly into a salt bath at lower temperatures. The upper-limit temperature for the existence of the D0 3 phase in the ferrite matrix for alloy B is between 500 and 510 °C. After quenching alloy A from 1050 °C and aging at temperatures below 430 °C, we observed that the D0 3 phase precipitated homogeneously inside the ferrite grains. This result is consistent with the classical nucleation and growth mechanism of D0 3 precipitates growing within the ferrite matrix. The upper limit temperature for the existence of the D0 3 phase in the ferrite grains of alloy A is between 430 and 440 °C. Measuring the Al contents in the ferrite grains of these alloys, we found that the 14.5 at.% Al in the ferrite grains of alloy A is, so far, the lowest Al content yielding the possible existence of a D0 3 phase in both binary Fe–Al and ternary Fe–Mn–Al alloys.