Effect of carbon addition on the strength and creep resistance of FeAl alloys

Abstract

We investigated the effect of carbon content (0.05, 0.12, and 0.2 wt pct C) and heat-treatment temperature (1100°C and 1300°C for 2 hours and air cooled) on the tensile and the creep properties of Fe-24 wt pct Al alloy. The increase of carbon content increased the yield strength without affecting the tensile ductility of the alloys. Carbon content appears to be beneficial in suppressing the hydrogen embrittlement at the grain boundary, because the fracture mode changes from predominantly intergranular failure in a low carbon (0.05 wt pct C) alloy to a predominantly transgranular cleavage failure in a high carbon (0.2 wt pct C) alloy. With the increase of carbon content, the anomalous yield strength peak shifted to a higher temperature possibly due to the interaction between carbon and vacancies. Significant improvements were noted in the tensile and the creep properties of medium (0.12 wt pct C) and high carbon (0.2 wt pct C) alloys after heat treating at 1300°C. The improvements in the tensile and the creep properties were attributed to the synergetic effect of retained vacancies and fine carbide precipitates present in the alloys after 1300°C heat treatment. However, the improved strength and creep properties associated with 1300°C heat treatment were lost when the heat-treated alloys were further subjected to a vacancy removal annealing. Our results suggest that the retained vacancies present in the FeAl alloys after high-temperature heat treatment and air cooling are effective in improving the creep resistance at 700°C, and yield strength up to 800°C. The creep resistance of the present high carbon FeAl alloy is comparable to or better than several grades commercial heat-resistant Fe-based and Ni-based alloys.

The effect of carbon and silicon additions on the creep properties of Fe-40 at. % Al type alloys at elevated temperatures

“…% C. The composition is similar to that of recently studied FeAl-based alloys with different additions of carbon [3e5]. The creep properties were reported by Sundar and Deevi [5]. They showed that increasing the carbon content from 0.2 to 0.75 at.…”

Improvement of the creep resistance of FeAl-based alloys

“…The effect of heat treatment on the creep resistance of these alloys was reported elsewhere [7]. Note that the 787 alloy exhibits a typical creep rate vs. stress curve of ODS alloys with the stress exponent n changing from 3 to 5 at high stresses to , 20 at low stresses [8].…”

Microstructure and wear behaviour of FeAl-based composites containing in-situ carbides

“…Recently, different studies showed that the carbon addition may improve the strength, creep resistance, machinability, wear resistance and resistance to environment embrittlement [3][4][5]. Among the FeAl alloys, FeAl with ordered B2 structure shows better wear resistance as compared with Fe 3 Al and α-Fe [6].…”