Determination of equilibrium transformation temperatures Ae3 and Ae1 for low-carbon steels using the in situ high-temperature X-ray diffraction technique

This paper describes a method to determine the equilibrium transformation temperatures in low C steels using the in situ high-temperature X-ray diffraction technique. The samples were heated and then cooled from 1000 to 720 °C in a stepwise manner decreasing to −10 °C. Austenite and ferrite fractions were determined by a quantitative method using the integrated intensities of austenite (111)γ and ferrite (110)α peaks from X-ray diffraction patterns. The effect of the temperature on interplanar d spacings of (111) and (110) crystallographic planes was determined using 2θ maximum positions of the austenite (111)γ and ferrite (110)α peaks. The equilibrium transformation temperatures were determined to be Ae1=720 °C and Ae3=950 °C. The results are in excellent agreement with those obtained by dilatometric analysis and Thermo-Calc phase diagram simulation software. In addition, the results were supported by microstructural observations: the formation of thin ferrite films (5–10 μm) was observed at temperatures near to experimental Ae3.

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In-situ High-temperature X-ray Diffraction on the .GAMMA..RAR..ALPHA. Transformation in Low-carbon Steels.

ISIJ International ◽

10.2355/isijinternational.42.94 ◽

2002 ◽

Vol 42 (1) ◽

pp. 94-99 ◽

Cited By ~ 4

Author(s):

A. Bodin ◽

L. Woning ◽

J. Sietsma ◽

S. van der Zwaag

Keyword(s):

High Temperature ◽

Carbon Steels ◽

Low Carbon ◽

X Ray Diffraction ◽

Low Carbon Steels ◽

X Ray

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An In Situ High-Temperature X-Ray Diffraction Study of Phase Transformations in Maraging 300 Steel

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.371.73 ◽

2017 ◽

Vol 371 ◽

pp. 73-77 ◽

Cited By ~ 1

Author(s):

Adriano Gonçalves Reis ◽

Danieli Aparecida Pereira Reis ◽

Antônio Jorge Abdalla ◽

Antônio Augusto Couto ◽

Jorge Otubo

Keyword(s):

High Temperature ◽

Room Temperature ◽

Volume Fraction ◽

X Ray Diffraction ◽

Austenite Transformation ◽

X Ray ◽

Xrd Diffraction ◽

Temperature Solution ◽

Diffraction Patterns

An in situ high-temperature X-ray diffraction (HTXRD) study in maraging 300 steel was carried out to study the martensite to austenite transformation and effect of time of exposure in the austenite reversion below austenite start temperature. Solution annealed materials were subjected to controlled heating-holding cycles. The first sample was heated at a rate of 10 oC/min from room temperature to 800 oC, showing that the microstructure is completely martensitic (α’110) until 600 oC. From 650 oC until 800 oC, the microstructure is gradually changing from martensitic to austenitic, showed by the increasing peaks of γ111 and reducing peaks of α’110. At 800 oC the microstructure is completely austenitic (γ111). Another sample was heated at 10 oC/min from room temperature to 600 oC and held for 4 hours. At 600 oC, at 0 h time of exposure, only a martensitic peak was observed. An austenite peak can be observed after some time of exposure at this temperature. The volume fraction of austenite increased with increasing time of exposure at 600 oC, reaching 50/50 volume fraction after 4 hours of exposure. XRD diffraction patterns for the same sample that was held for 4 hours at 600 oC and then cooled down in air to room temperature showed the same intensity of austenite and martensitic peaks found in situ at 600 oC for 4 hours (retained austenite), with the volume fraction of 50/50 of austenite and martensite phases. The HTXRD technique can be used to identify and quantify martensite to austenite transformation and austenite retention.

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In Situ High Temperature X-Ray Studies on Bainitic Transformation of Austempered Silicon Alloyed Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.3086 ◽

2010 ◽

Vol 638-642 ◽

pp. 3086-3092 ◽

Cited By ~ 4

Author(s):

Esa Vuorinen ◽

Xiang Chen

Keyword(s):

High Temperature ◽

Volume Fraction ◽

Early Stage ◽

Bainitic Transformation ◽

Experimental Results ◽

Low Carbon ◽

X Ray Diffraction ◽

Heterogeneous Distribution ◽

X Ray

The in-situ X-ray diffraction observations of the bainitic transformation of silicon alloyed steels were performed using the high temperature X-ray diffraction technique. The experimental results have shown that the volume fraction and carbon content of austenite remains a constant value which indicate that the transformation is almost finished after the early stages of austempering transformation. Asymmetry diffraction peaks are obtained for samples at the early stage of transformation due to a heterogeneous distribution of carbon in different regions of austenite and thus exists two types of austenite: low-carbon austenite (γLC) and the high-carbon austenite (γHC). The experimental results supports that the bainite growth is by a non-diffusive mechanism when austempering temperature is in the lower bainite transformation temperature.

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