EFFECT OF PROCESSING PARAMETERS ON THE STRUCTURE AND PROPERTIES OF POWDER Fe-Al INTERMETALLIC COMPOUNDS OBTAINED BY SINTERING AND IMPULSE HOT PRESSING

Abstract

The paper examines the effect of high-energy grinding and post-treatment conditions on the structure and physical and mechanical properties of iron aluminide Fe–15 wt.% Al obtained by sintering and impulse hot pressing. It was shown that the grinding of a mixture of iron and aluminum powders in a planetary mill results in the formation of lamellar particles whose morphology is preserved in the alloy structure after sintering and hot pressing. After grinding, sintered intermetallic compounds obtained from powder mixtures demonstrate low physical and mechanical properties due to the low quality of grain boundaries. The use of impulse hot pressing for compaction of samples from milled powders at temperatures of 850–1150 °C significantly increases the density of intermetallic compounds compared to sintered materials of a similar composition — from 5 to 6,5 g/cm³. The increase in the temperature of impulse hot pressing contributes to an increase in mechanical characteristics, where the maximum values of bending strength and fracture toughness are 880 MPa and 21 MPa · m^0.5, respectively. Subsequent high-temperature annealing (1350–1450 ºC) leads to an improvement of the quality of grain boundaries with the formation of a predominantly discontinuous grid, coagulation of impurity segregation, and, as a result, to a sharp increase in bending strength and fracture toughness, which are 1400 MPa and 27 MPa · m^0.5, respectively. It was shown that the interparticle destruction observed in the samples after impulse hot pressing at relatively low temperatures changes to transcrystalline after high-temperature annealing.