Lattice parameter measurement in retained austenite by CBED

Abstract

The thin film (50-400 Å) retained austenite (ret-γ) (fig.1.a-b) has been identified at the lath boundaries of dislocated martensitic medium carbon (C) low alloy experimental steels, which were designed for structural applications. The existance of this parent γ-phase at the ambient temperatures has been attributed to several stabilization mechanisms in which the intersititial C has important effects, especially when it partitions into ret-γduring the course of the austenite to martensite transformation. Hence, the measurement of any C enrichment in γ has prime importence in understanding the exact nature of the stabilisation. However, any quantitative measurement on the amount of C in such restricted conditions requires a method with high chemical and spatial resolutions. In the present work convergent beam electron diffraction method, which has been shown to give highly accurate results, has been utilized succesfully.