Ovservations of Aluminum Nitride in Steel by Electron Microscopy
Study on aluminum nitride in steel-I
1961 Volume 47 Issue 6 Pages 809-817
Details
1961 Volume 47 Issue 6 Pages 809-817
Aluminum nitride precipitates in low-manganese steels, an aluminum-killed low-carbon steer and a medium-carbon steel were directly observed by carbon extraction replica. The steels contained 0.005-0.02% N and 0.03-0.12% Al.
1) AIN precipitates extracted from a forged and normalized steel were hexagonal in structure, and rectangular and of thin sheets in shape.
2) AlN precipitates in the steel heated at the 1200°C or above for 6h after solution-treatment, were of a large rod shape. At 1000-1100°C the precipitates were lengthened, and some of them reached to be distributed into 5μ. or over. At 900°C many AIN precipitates shorter than 1μ were seen to be scattered. The less the content of N and Al in the steel, the smaller the AlN precipitate. They were 0.1μ long or shorter and scattered on large numbers.
3) AlN precipitates were arranged along the grain boundary of austenite.
4) Isothermally treated after solution-treatment AIlN precipitates were present on the subgrain boundaries of ferrite, but not in the austinite. The precipitates at the 700°C heating for 2h were 0.02-0.1mu; long.
5) Si3N4 precipitates were found mixed with the AlN precipitates in the ferrite. The former were granular and of different shape from the latter. By electron-diffraction pattern the former were determined to be Si3N4 precipitates.
6) Fe3C particles seemed to become the nuclei forming AlN and promoted the its precipi tation.
7) AlN precipitates extracted from an aluminum-killed low-carbon steel subject to anneal-ing at 700°C afteri cold rolling; were found in lavers parallel to the rolling direction.
8) Some of the AIN preciepitates extracted from the steel ingot as cast have been previousiy precipitated, at the grain boundaries of austenite, and some of them were later preci-pitatea in tne ferrrue Theitormer were lined at the central part of ferrite net. The shapes of them were variedeivith tide size of ingots and the content of N and Al.
