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EBSD mapping was used for phase analysis of multi-phase steels. Some products of austenite decomposition could be discriminated using a range of grain-average functions and properties derived from the map data. In DP steels, martensite could be extracted from the ferrite matrix using the average band contrast or a set of geographic information. Bainite in TRIP steel was identified with the local variations of band contrast and orientation inside a grain. As the proposed method reproduced a phase map, a visual confirmation of the result and additional analyses were possible.KEY WORDS: EBSD; phase analysis; steel; grain average function; DP steel; TRIP steel.separated unambiguously with a discrete threshold value. The result would be unreliable when there is considerable peak overlap. In addition, the result can indicate that both phases coexist in a single grain if a grain consists of pixels with PQ values similar to the threshold value, which is unreasonable in a metallurgical sense. Wu et al. dissociated the IQ profiles using several Gaussian peaks, each of which represented different phases. Subsequently, the volume fraction of each phase could be estimated from the peak area.13) This method can deal with the profiles of arbitrary shapes. However, the profile data is actually dissociated from the map data after the operation. Consequently, it is impossible to know the locations and orientations of the pixels that contribute to each Gaussian peak. Additional analyses, such as grain size measurements and texture evaluations for each phase, are not possible. The great potential of EBSD is underutilized in this case.In this study, an image-based method was developed for the phase analysis of steels that can fully exploit the EBSD mapping data. The applications to dual phase (DP) steel and transformation-induced plasticity (TRIP) steel are presented. Specimens and Experimental ConditionThe test materials were DP and TRIP steels with the composition of 0.06C-2.2Mn-1.0Si-0.02Mo-0.01Cr and 0.2C-1.8Mn-0.5Si, respectively. Cold rolled and intercritical-annealed samples were electro-polished with Struers Lectropol-5 at the final step of metallographic sample preparation. The electrolyte was 5% perchloric acid in ethanol. The electropolish was performed for 25 s at Ϫ20°C with the condition of 25V-20 flow rate.EBSD mapping was performed using a field emission scanning electron microscope (JSM-6500F) equipped with a HKL Nordlys II camera. Therefore, the quality of the pattern is represented by BC in this paper. The accelerating voltage, probe current and working distance was 20 kV, 4 nA and 15 mm, respectively, with the sample stage tilted by 70°. The camera resolution was 168ϫ128 pixels in operation of 8ϫ8 binning. The mapping grid was a regular square in 0.1 mm steps. FCC (austenite) and BCC iron (ferrite) were chosen as the input phases. Description of the MethodThe key feature of the methodology is to use various grain-average functions and properties for phase discrimination on a grain-by-grain basis. Although not clea...

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