TOPICAL COLLECTION: ADVANCES IN MATERIALS MANUFACTURING AND PROCESSING
Characterization of X80 and X100 Microalloyed
Pipeline Steel Using Quantitative X-ray Diffraction
J.B. WISKEL, X. LI, D.G. IVEY, and H. HENEIN
Quantitative X-ray diﬀraction characterization of four (4) X80 and three (3) X100 microalloyed
steels was undertaken. The eﬀect of through-thickness position, processing parameters, and
composition on the measured crystallite size, microstrain, and J index (relative magnitude of
crystallographic texture) was determined. Microstructure analysis using optical microscopy,
scanning electron microscopy, transmission electron microscopy, and electron-backscattered
diﬀraction was also undertaken. The measured value of microstrain increased with increasing
alloy content and decreasing cooling interrupt temperature. Microstructural features
corresponding to crystallite size in the X80 steels were both above and below the detection
limit for quantitative X-ray diﬀraction. The X100 steels consistently exhibited microstructure
features below the crystallite size detection limit. The yield stress of each steel increased with
increasing microstrain. The increase in microstrain from X80 to X100 is also associated with a
change in microstructure from predominantly polygonal ferrite to bainitic ferrite.
Ó The Minerals, Metals & Materials Society and ASM International 2018
characterization of a micro-
alloyed pipeline steel can take many forms,
optical microscopy (OM), scanning electron microscopy
(SEM), transmission electron microscopy (TEM), and
electron-backscattered diﬀraction (EBSD). Due to the
complexity of the microstructure inherent in microalloyed
steels, most, if not all, of these techniques are used in a
complimentary way to characterize this material.
Microstructural features in microalloyed steels can
include the presence of several co-existing complex
phases (e.g., ferrite, acicular ferrite, or bainite),
dislocation density variations associated with the diﬀer-
in grain size and/or subgrain size.
tural features are directly related to the composition of
and to the thermomechanical controlled
processing (TMCP) conditions employed, including
ﬁnish rolling temperature (FRT) and coiling interrupt
and ultimately with the mechan-
ical properties of the material.
Previous work by the authors
X-ray diﬀraction (QXRD) to quantify the mean size and
atomic composition of nanosize precipitates in microal-
loyed steels. This paper focuses on applying the general
QXRD technique to the characterization of microstruc-
ture, speciﬁcally crystallite size (D
), microstrain (e
and texture index (J), for four (4) X80 and three (3)
X100 microalloyed pipeline steels. These speciﬁc QXRD
microstructure features are related to grain/subgrain
size, dislocation density and texture, respectively.
The measured QXRD values of crystallite size (D
), and texture index (J) are correlated
with CIT, FRT, composition, and both yield strength
) and the yield strength-to-tensile strength ratio (Y/
TS). OM, SEM, TEM, and EBSD analysis of the steel
microstructures was also undertaken to assess the
crystallite size measurements obtained in the analysis.
The use of QXRD as a complementary characterization
technique for microalloyed steels is assessed.
Quantitative X-ray diﬀraction (QXRD) is an indirect
microstructure characterization technique that is used in
this contribution to quantify crystallite size, microstrain,
and the relative magnitude of preferred orientation (via
a J index term) in a crystalline material. This section will
brieﬂy describe the basics of QXRD and then review the
concepts associated with crystallite size, microstrain,
and preferred orientation.
J.B. WISKEL, X. LI, D.G. IVEY, and H. HENEIN are with the
Department of Chemical and Materials Engineering, University of
Alberta, Edmonton, AB, T6G 1H9, Canada. Contact e-mail:
Manuscript submitted January 29, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B