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Effect of heat treatment on chemical and microstructural heterogeneity of magnesium alloy AZ61

Horynova M., Dolezal P., Janova D., Gejdos P.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2010

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z. 97

51-52

EN

The contribution is focussed on the assessment of the influence of a heat treatment of magnesium alloy AZ61 on its chemical and microstructural heterogeneity. The experimental material was manufactured by squeeze casting method using alternative two-stage casting. The microstructure of the alloy in as cast state composed of ä solid solution, Mg17Al12 intermetallic phase and minor phases based on Mn. The heat treatment applied on the alloy was the solution annealing at the temperature of 380 °C and with graded dwell from 1 to 8 hours. Chemical etching was employed in order to estimate the micro-segregation of the elements in the matrix qualitatively and to discern the phases in the microstructure. The differences in matrix heterogeneity between the as cast state and after annealing were documented by means of light microscopy. Differences in etching between the central part and periphery of the crystalline units are apparent in the metallographic images. Quantitative assessment of chemical heterogeneity was done by mapping and local chemical microanalyses. It was found by mapping that with increasing delay at annealing temperature the Mg17Al12 intermetallic phase gradually dissolves and the micro-heterogeneity of each element decreases. Chemical heterogeneity of particular elements was measured by local chemical analysis and the intensity of chemical micro-heterogeneity of each sample was further expressed using effective distributive coefficients. It follows from the results that the solution treatment of the AZ61 magnesium alloy leads to diminishment of the chemical and microstructural heterogeneity. It also follows from the results presented that the combination of metallographic analyses with X-ray spectral analysis of wave- or energy-dispersive type is advantageous for the quantitative assessment of micro-segregation of elements in the matrix of magnesium alloys.

2

Intermetallic phase AL12MG17

Ptáček L., Janova D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 72

81-83

3

Analýza vzniku lomu hřídele převodovky extrudéru

Pacal B., Janova D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 72

125-128

4

Complex approach to surface reconstruction of microscopic samples from bimodal image stereo data

Jan J., Janova D.

Machine Graphics and Vision

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2001

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Vol. 10, No. 3

261-288

EN

The paper describes a set of approaches and mathods enabling robust and relatively precise stereo-analysis-based surface reconstruction in scanning electron microscopy(SEM). The paper primarily deals with the disparity analysis problem, namely with selection of a suitable similarity criterion to be used for finding image correspondences. The search-and-match method (as opposed to feature-based analysis) is shown as probablyn the only practical solution in the given environment of SEM when no prior constraints on the surface type are allowed. Extensive comparison of some common and newly suggested similarity criteria lead to the conclusion that the designed angle criterion is the only one acceptable so far with respect to the error rate. Use of the criterion has been shown equivalent to applying a non-linear two-dimensional matched filter, which enables efficient frequency domain implementation in the form of a linear matched filter modification. An important improvement in reliability of the computed disparities has been achieved by using both available imaging modalities (back-scattered electrons - BEI and secondary electrons - SEI), thus providing vector image data. Expressing the criterion for the vector case in terms of both individual scalar cases cuts computational requirements by half, besodes allowing for an additional reliability criterion - comaprison of three different, though partly, dependent criteria. Secondly, the comprehensive approach includes also solution of problems which may seem marginal but are important for the practical success of the analysis. Recent improvements, solving some of such specific problems of SEM stereo analysis, are discussed as well. The paper summarises the present state of the method's development over the past few years partial descriptions of which can be found scattered in previous publication devoted to individual specific problems.