Influence of the Microstructure on Flow Stress and Deformability of Iron-Aluminium Alloys

Abstract

Due to their higher weight-specific and high-temperature strength, iron-aluminium alloys have a high potential to replace steel in various applications. The good availability of the two materials, the excellent recyclability, lower density with increasing aluminium content and the high corrosion resistance in sulphide- and sulphur-rich environments are further advantages. However, with increasing aluminium content, ductility of FeAl alloys decreases due to hydrogen embrittlement at room temperature. As a result, iron-aluminium alloys have been excluded from potential applications, particularly structural ones. Investigations on powder metallurgical produced iron-aluminium alloys show that fine-grained microstructures can lead to significant improvement in ductility. Assuming equal grain diameters, higher toughness is expected in case of metallurgical ingot production followed by hot forming. The present work deals with the mechanical properties of fine-grained microstructure in iron-rich iron-aluminium alloys, pre-processed through Equal Channel Angular Pressing. In order to characterize the mechanical properties, compression tests with the alloys Fe9AI, Fe28AI and Fe38AI are carried out at different temperatures. The flow curves determined are then compared with those from as-cast state. In addition, deformation capacity is examined optically on slopes of external cracks. In conclusion, the results are discussed based on the microstructure.