CRESCIMENTO ANORMAL DO GRÃO AUSTENÍTICO E SUA INFLUÊNCIA NA FRAÇÃO VOLUMÉTRICA DE AUSTENITA RETIDA APÓS A TÊMPERA DE UM AÇO ABNT 5135

Grain size in the steels is a relevant aspect in quenching and tempering heat treatments. It is known that high\udaustenitizing temperature and long time provide an increase in austenitic grain sizes. Likewise, after hardening of low\udalloy steel, the microstructure consists of martensite and a volume fraction of retained austenite. This paper evaluates\udthe influence of austenite grain size on the volume fraction of retained austenite measured by metallographic analyses and\udX-ray diffraction. The Mi\ud and Mf\ud temperatures were calculated using an empirical equation and experimentally determined\udby differential thermal analysis. The mechanical behavior of the steel was evaluated by Vickers microhardness testing.\udDifferently from other results published in the literature that steel hardenability increases with the austenite grain size,\udit was observed that the increase in austenite grain promotes greater volume fraction of retained austenite after water\udquenching