Adrienn Hlavacs

The volume fraction of austenite (γ), ε martensite and α′ martensite is of key importance in the research of TWIP/TRIP steels. When mechanical loading is involved, the crystallographic texture also develops, which complicates X-ray diffraction-based phase ratio determination. The problem is more pronounced when only a couple, or only one Bragg-reflection can be measured. A solution for such cases is to determine the ratio of the phases based on the pole distribution function of a selected Bragg-reflection of the present phases. In this manuscript, this method is reconsidered for and applied to non-transmittable bulk specimens for the first time in the reflection mode of XRD pole figure measurements. First, the method was applied to a series of γ–α′ powder mixtures. The results were compared to those obtained by the Rietveld method. Afterwards, the technique was applied to strongly textured, bulk TWIP/TRIP steel specimens which were tensile tested at different temperatures. It was shown that the results of the presented method were close to those of the Rietveld technique in the case of powder mixtures. The results of the tensile-tested steels revealed that the α′ content increases with decreasing test temperatures, and the variation of the α′ ratio correlates very well with the ultimate tensile strength versus the temperature, confirming the contribution of the α′ content to the strength of TWIP/TRIP steels.

The formation of uneven cup heights during deep drawing is called earing. This phenomenon is caused by the planar anisotropy of formability in sheets, which is the result of crystallographic texture. In addition to analytical and finite element methods, a simple and quick method was developed recently to predict the earing profile of Al sheets solely from the data of {200} pole figures. So far, the method was applied on final state sheets cold rolled to 0.3–3 mm thickness and subsequently annealed. Within this manuscript, the earing prediction method is applied on 3003 type Al sheets with the thickness of ~6 mm, being in the hot-rolled state. Texture examinations were performed at different depths, from which earing profiles were calculated. For comparison, earing profiles were calculated from Lankford values that were determined by tensile tests. It is shown that in the case of hot-rolled Al sheets, if the grain structure is uniform across the thickness of the sheet, the earing profile can be appropriately calculated from the full {200} pole figure obtained from surface X-ray Diffraction (XRD) texture measurements.

Earing of deep drawn cups is an effective measure of plastic anisotropy. It is the result of crystallographic anisotropy, i.e. texture. There are several methods to predict earing, but all of these methods are rather complex. Furthermore, above a certain sheet thickness, deep drawing cannot be performed, and prediction methods fail since they are usually valid within a certain sheet thickness range. A new, simple method has been proposed to predict earing. Besides simplicity, another major benefit of the method is that it can be applied to a wide range of sheet thicknesses. The method has been previously applied for unidirectionally rolled and recrystallized and cross-rolled Al sheets. In the present manuscript, the proposed method is applied on the AW-5056 type, unidirectionally and cross-rolled, then annealed Al sheets having very weak (close to random) structure. It is shown that for such samples, the method predicts negligible earing. It is also revealed that for the 5056 type Al alloy, the differences in texture and earing between unidirectionally and cross-rolled samples become so small after annealing, that the benefit of cross rolling is negligible.

The plastic anisotropy of rolled Al sheets is the result of a crystallographic texture. It leads to the formation of uneven cup heights during deep-drawing, which is called earing. A new, simple and rapid method had been previously developed by the authors to predict earing directly from {h00} pole figures. In the present manuscript, this method is applied to cross-rolling for the first time. 5056 type aluminum sheets were unidirectionally- (conventionally) and cross-rolled from 4 to ~1 mm thickness in 6 or 12 passes. Earing was predicted from recalculated {200} pole figures obtained after X-ray diffraction texture measurements. The results were validated by deep-drawing tests. It is shown that the proposed method predicts the type (locations of ears) and magnitude of earing with satisfactory results. However, a different scaling factor must be used to calculate the magnitude of earing for cross-rolling than for unidirectional rolling even if all other parameters (including cold rolling, texture measurements, and deep-drawing) are the same. This is because the cross-rolled sheets exhibit a similar type but weaker earing compared to the unidirectionally rolled samples.