The Study For Defects Structure And Effects On The Properties Of Iron-Aluminides

Ten binary iron-aluminum alloy samples were prepared by arc melting with composition ranging from25to51at.%of aluminum. Then the samples were annealed at five desired temperatures from773K to1173K followed by water-quenching. The lattice constants were obtained by X-ray diffractometer. The mass density was measured by the Archimedes method. Vickers hardness measurements were carried out, and the relationship between vacancy defects and micro-hardness was analyzed. The lifetimes of positron in alloys were measured to confirm the defect configuration. According to the Grandcanonical Potential method, the point defects concentration was also obtained to confirm the defect type. The results were given as follows:(1) The changes of lattice constant indicated that the point defect of B2-FeAl alloy was triple defect type. Lattice constant decreased as the annealing temperature increased.(2) The vacancy concentration and Vickers hardness increased as the annealing temperature increased or the increment of Al content.(3) A good linear relationship between hardness and square root of vacancy concentration manifested vacancy hardening was one of the hardening mechanisms of FeAl alloys.(4) There existed vacancy-liked defects and defects with bigger open space in Fe-Al alloys. The mean positron lifetime increased with the increment of Al content or the annealing temperature increased.(5) The metallic bond and covalent bond coexisted in the Fe-Al alloys. There existed low electron density in the defect. The electron density in matrix decreases as the annealing temperature increases.(6) The point defect concentration and defect type strongly depend on the defect formation energies used with the Grandcanonical Potential method.