PARTICLE BONDING DURING HEAT-TREATMENT OF GREEN COMPACTS INTENDED FORAC SOFT-MAGNETIC APPLICATIONS

Previous studies have shown that heating at 175 degrees C for 1h in ai r increases significantly the mechanical strength of green iron powder compacts. This study examines the effect of temperature, duration and atmosphere on the transverse rupture strength and electrical resistiv ity of iron powder compacts. Scanning electron microscopy observations , x-ray photoelectron spectroscopy and ultrasonic speed measurements w ere performed to elucidate the mechanisms responsible for the interpar ticle bonding enhancement. The results obtained suggest that oxygen pl ays an important role in interparticulate bonding; the oxide layer gro wing between the iron particles can form cohesive bonds which are resp onsible for the mechanical strength increase while maintaining a level of electrical resistivity significantly higher than that in sintered compacts.