Effect of phosphorus on the structure and properties of iron hemiboride in Fe–B–P alloys

Abstract

UDC 669.017 The iron corner of the Fe-B-P phase diagram is plotted for room temperature based on metallographic and x-ray analyses. The structure and properties of phosphorus-doped iron hemiboride in Fe-3.8 wt.% B alloys containing 0 to 5 wt.% P are examined. varied from 0.5 to 5 wt.%. The content of carbon was no more than 0.018%. To make alloys, we used high-purity carbonyl iron, amorphous boron (to 99.5 wt.% B), and ferrophosphorus (FR-20). The melt cooling rate was 100°C/sec over the range of temperatures at which iron boride crystals grow. The chemical and phase compositions of the alloys are summarized in Table 1. The structure of the alloys was determined using chemical and thermal etching. A quantitative metallographic analysis of the Fe-B-P alloys was carried out with an Epiquant analyzer. The linear dimensions were determined with an accuracy of ±2% and the volume content of the phases with an accuracy of 3%. The phase composition of the alloys was examined in Fe-K α radiation using x-ray diffraction and a DRON-3M diffractometer. The microhardness, microbrittleness, and critical stress intensity factor (fracture toughness) K 1c were determined with a PMT-3 microhardness tester under a load of 0.5-2 N and calculated with the formulas given in (6, 7).