Mechanical Properties and Fracture of an Intermetallic Alloy Fe-28Al-4Cr-0.1Ce (at %)

Abstract

Structure, mechanical properties and fracture of a vacuum cast and hot deformed Fe-28Al-4Cr-0.1Ce (at %) alloy were studied. The material was extruded at 1 140 °C and the samples then annealed in the temperature range from 500 to 800 °C, in the D03 and B2 ordered regions. Mechanical properties were evaluated from Vickers hardness and tensile tests. Structure was examined by optical and electron metallography. Besides coarse Ce bearing particles in the matrix, a Cr-Fe precipitate has also been found, mainly on the grain boundaries. Annealing at 700 and 800 °C leads to recovery of the dislocation structure and to the corresponding decrease of the yield stress. The fracture mechanism depends on the thermal treatment of the alloy and on the test temperature. Micromorphology of fracture surfaces was characterized by different fractographic features, including transgranular cleavage, intergranular decohesion and ductile dimple fracture. Maximum room temperature ductility of 4.3 % was achieved after hot extrusion and annealing for 2 h at 700 °C.