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Title: The use of X-ray diffraction, microscopy, and magnetic measurements for analysing microstructural features of a duplex stainless steel

Abstract

X-ray diffraction, light optical microscopy, and magnetization saturation measurements were employed to analyse the microstructural features of a UNS S31803 duplex stainless steel modified by high-temperature treatments. The samples were heated to 1300 deg. C and cooled by different ways to produce five different microstructures. Solution treatments at 1000 deg. C were also employed to produce another five conditions. Three methods were employed to determine the austenite/ferrite proportions. X-ray diffraction gave higher austenite values than the other methods, due to the influence of texture, but can be successfully used to determine the microstrain level in each phase. Magnetic saturation measurement is a very simple and precise method for quantification of austenite and ferrite volume fractions in samples that were fast-cooled and slow-cooled. Light microscopy can give a fast and precise measurement of the phase proportions and reveals important features related to the morphology of the phases, but in the samples where the austenite content is low, quantification becomes difficult and imprecise.

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Instituto de Fisica, Universidade Federal do Ceara, Campus do Pici, Caixa Postal 6030, CEP 60455-760 Fortaleza/CE (Brazil). E-mail: marcus@fisica.ufc.br
  2. Instituto de Fisica, Universidade Federal do Ceara, Campus do Pici, Caixa Postal 6030, CEP 60455-760 Fortaleza/CE (Brazil)
  3. PGMEC/TEM, Universidade Federal Fluminense, Rua Passo da Patria, 156, CEP 24210-240, Niteroi/RJ (Brazil)
  4. Depto. Engenharia Meca-hat nica, Universidade Federal do Ceara (Brazil)
  5. Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil)
Publication Date:
OSTI Identifier:
20748750
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 54; Journal Issue: 4-5; Other Information: DOI: 10.1016/j.matchar.2004.12.009; PII: S1044-5803(05)00011-2; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AUSTENITE; FERRITE; MAGNETIZATION; MICROSTRUCTURE; MORPHOLOGY; OPTICAL MICROSCOPY; SATURATION; SOLUTIONS; STAINLESS STEELS; TEMPERATURE RANGE 1000-4000 K; TEXTURE; X-RAY DIFFRACTION

Citation Formats

Ribeiro Miranda, M.A., Sasaki, J.M., Tavares, S.S.M., de Abreu, H.F.G., and Neto, J.M.. The use of X-ray diffraction, microscopy, and magnetic measurements for analysing microstructural features of a duplex stainless steel. United States: N. p., 2005. Web. doi:10.1016/j.matchar.2004.12.009.
Ribeiro Miranda, M.A., Sasaki, J.M., Tavares, S.S.M., de Abreu, H.F.G., & Neto, J.M.. The use of X-ray diffraction, microscopy, and magnetic measurements for analysing microstructural features of a duplex stainless steel. United States. doi:10.1016/j.matchar.2004.12.009.
Ribeiro Miranda, M.A., Sasaki, J.M., Tavares, S.S.M., de Abreu, H.F.G., and Neto, J.M.. 2005. "The use of X-ray diffraction, microscopy, and magnetic measurements for analysing microstructural features of a duplex stainless steel". United States. doi:10.1016/j.matchar.2004.12.009.
@article{osti_20748750,
title = {The use of X-ray diffraction, microscopy, and magnetic measurements for analysing microstructural features of a duplex stainless steel},
author = {Ribeiro Miranda, M.A. and Sasaki, J.M. and Tavares, S.S.M. and de Abreu, H.F.G. and Neto, J.M.},
abstractNote = {X-ray diffraction, light optical microscopy, and magnetization saturation measurements were employed to analyse the microstructural features of a UNS S31803 duplex stainless steel modified by high-temperature treatments. The samples were heated to 1300 deg. C and cooled by different ways to produce five different microstructures. Solution treatments at 1000 deg. C were also employed to produce another five conditions. Three methods were employed to determine the austenite/ferrite proportions. X-ray diffraction gave higher austenite values than the other methods, due to the influence of texture, but can be successfully used to determine the microstrain level in each phase. Magnetic saturation measurement is a very simple and precise method for quantification of austenite and ferrite volume fractions in samples that were fast-cooled and slow-cooled. Light microscopy can give a fast and precise measurement of the phase proportions and reveals important features related to the morphology of the phases, but in the samples where the austenite content is low, quantification becomes difficult and imprecise.},
doi = {10.1016/j.matchar.2004.12.009},
journal = {Materials Characterization},
number = 4-5,
volume = 54,
place = {United States},
year = 2005,
month = 5
}
  • The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite wasmore » detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.« less
  • In the hot deformation of the duplex stainless steels, the complexity of the microstructure evolution and mechanical response is increased as compared with those of single-phase ferritic or austenitic stainless steels. In the present work, plane strain compression and torsion deformation modes have been used to analyze the microstructural evolution and the mechanical behavior of a duplex stainless steel in as-cast and wrought conditions, as a function of spatial phase distribution, the nature of interface, and the relative mechanical properties of both phases. The law of mixtures has been used to explain the different flow curves obtained when changing themore » phase distribution and/or the deformation mode. On deforming as-cast microstructures, the deformation partitions vary heterogeneously between both phases and some austenite areas act as hard nondeforming particles. Cracks have been observed to occur at the interface of such regions, from relatively low strains, for which the initial Kurdjumov-Sachs orientation relationship between ferrite and austenite is still present.« less
  • The machining of super duplex stainless steel castings is usually complicated by the difficulty involved in maintaining the dimensional tolerances required for given applications. Internal stresses originating from the solidification process and from subsequent heat treatments reach levels that exceed the material's yield strength, promoting plastic strain. Stress relief heat treatments at 520 deg. C for 2 h are an interesting option to solve this problem, but because these materials present a thermodynamically metastable condition, a few precautions should be taken. The main objective of this work was to demonstrate that, after solution annealing at 1130 deg. C and watermore » quenching, stress relief at 520 deg. C for 2 h did not alter the duplex microstructure or impair the pitting corrosion resistance of ASTM A890/A890M Grade 6A steel. This finding was confirmed by microstructural characterization techniques, including light optical and scanning electron microscopy, and X-ray diffraction. Corrosion potential measurements in synthetic sea water containing 20,000 ppm of chloride ions were also conducted at three temperatures: 5 deg. C, 25 deg. C and 60 deg. C.« less
  • Time Resolved X-Ray Diffraction (TRXRD) measurements are made in the Heat Affected Zone (HAZ) of 2205 Duplex Stainless Steel (DSS) spot welds. Both the {gamma} {yields} {delta} and {delta} {yields} {gamma} transformations are monitored as a function of time during the rapid spot weld heating and cooling cycles. These observations are then correlated with calculated thermal cycles. Where the peak temperatures are highest ({approx}1342 C), the {gamma} {yields} {delta} transformation proceeds to completion, leaving a ferritic microstructure at the end of heating. With lower peak temperatures, the {gamma} {yields} {delta} transformation proceeds to only partial completion, resulting in a microstructuremore » containing both transformed and untransformed austenite. Further analyses of the individual diffraction patterns show shifts in the peak positions and peak widths as a function of both time and temperature. In addition, these changes in the peak characteristics are correlated with measured changes in the ferrite volume fraction. Such changes in the peak positions and widths during the {gamma} {yields} {delta} transformation provide an indication of changes occurring in each phase. These changes in peak properties can be correlated with the diffusion of nitrogen and other substitutional alloying elements, which are recognized as the primary mechanisms for this transformation. Upon cooling, the {delta} {yields} {gamma} transformation is observed to proceed from both the completely and partially transformed microstructural regions in the TRXRD data. An examination of the resulting microstructures confirms the TRXRD observation as the evidence shows that austenite both nucleates and grows from the ferritic microstructure at locations closest to the fusion zone boundary and grows from untransformed austenite grains at locations further from this boundary.« less