PROCESSING, FABRICATION, AND MECHANICAL-PROPERTIES OF FE3AL BASED PM ALLOYS

Iron aluminides based on Fe3Al were produced by extrusion of gas atomi sed powders. The influence of alloying additions such as Cr, Mo, Nb, Z r, Ti, Si, Mn, and B was studied in order to improve the ductility at room temperature and mechanical strength at elevated temperatures with other properties retained or improved. Examinations were made on extr uded material in the as extruded as well as the heat treated condition . Heat treatments were performed in the temperature range 500-850 degr ees C. Microstructural studies show a strong extrusion texture and tha t most of the alloys recrystallise below 750 degrees C. Alloying addit ions affect the ordering transformation (D0(3) to B2) temperature, whi ch has been studied by differential scanning calorimetry. Transformati on temperatures from approximately 550 degrees C to 650 degrees C have been obtained. Hot hardness was investigated up to 700 degrees C. At room temperature the hardness values for the different alloys are in t he range 280-420 HV0.5. At 300 degrees C the hardness values are in th e range 210-330 HV0.5; at 500 degrees C they are 170-250 HV0.5; and at 700 degrees C they are 40-80 HV0.5. Tensile tests were performed in t he as extruded condition in air at room temperature and at 600 degrees C. At room temperature the elongation at fracture is in the range 5-1 0%; 0.2% proof strength R(p0.2) 470-840 MN m(-2): and tensile strength 880-1330 MN m(-2) At 600 degrees C R(p0.2) varies between 440 and 590 MN m(-2) with corresponding fracture elongations of 20-60%.