Φ8 mm 00Cr19Ni10不锈钢(％:0．025C、18．75Cr、10．96Ni)经700℃、挤压速度9 mm／s、8道次等通道挤压后获得150-350 nm超细晶组织。通过光学显微镜,扫描和透射电镜,X-射线衍射,分析了在等通道挤压变形过程钢的微观组织演变,提出晶粒细化的位错、孪晶和动态再结晶机制,研究发现在1-4道次以孪晶细化机制为主,5-8道次以动态再结晶细化机制为主。
Using thermomechanical simulation experiment,the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation.The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism,wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation,whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs,wherein,the nucleation rate of ferrite in the initial stage of transformation is low,and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete.Using carbon extraction replica TEM,niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite.The mechanism of the effect of niobium on the isothermal transformation was discussed.
