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1.
Anil K. Sachdev 《Metallurgical and Materials Transactions A》1982,13(10):1793-1797
The dynamic strain aging characteristics of two dual phase steels, a high strength low alloy (HSLA) steel, a 1008 steel and
an interstitial free (IF) steel were determined from tensile properties at temperatures in the range 295 to 460 K (22 to 187
°C) and strain rates between 6 × 10-6 to 10-2s-1. All except the IF steel were found to be susceptible to dynamic strain aging, as evidenced by increases in tensile strength.
The largest positive change was observed in the 1008 steel while the dual phase and HSLA steels showed much smaller increases.
Also, large decreases (up to 75 pct) in uniform elongation were noted for the 1008 steel while the decreases were minimal
for the dual phase and HSLA steels. The IF steel did not strain age and showed a slight increase in uniform elongation with
increasing temperature. Based upon uniform elongation as an indicator of formability, formability might be improved in dual
phase or HSLA steels by reducing the concentration of free interstitials in the ferrites through chemistry control. 相似文献
2.
A study has been made of the fatigue of a V containing dual-phase steel, whose tensile strength is equivalent to that of SAE
980X high strength, low-alloy (HSLA) steels, as a function of prestrain. It is found that the cyclic stress-strain curve,
strain-life response and notch sensitivity are little affected by pre-strains of up to 8 pct: This is in contrast to monotonie
flow strength which increases substantially with prestrain. The fatigue performance of the dual-phase steel, while different
in detail from that of other HSLA steels, is intermediate between that for SAE 950X and 980X steels. However, the notch fatigue
behavior is equivalent to that of 980X steels. The fatigue response of dual-phase steel can be understood in terms of its
high rate of work hardening which is a consequence of its ferrite plus martensite microstructure. 相似文献
3.
Various heat treatments applied to a fine-grained high strength low alloy (HSLA) steel resulted in producing different grain sizes. Optical and scanning electron microstructures of the different alloy states exhibited varying ferrite grains which have increased with the increase of annealing time and decrease of cooling rates. TEM structures of the as-received HSLA steel displayed characteristics microstructural features, distribution, and morphology of microalloy precipitates. Hardness and tensile strength values have decreased with the increase of grain sizes. Potentiodynamic electrochemical polarization of the different alloy states in 3.5 wt pct NaCl solution showed typical active metal/alloy behavior. Tensile specimens of the as-received and heat-treated alloy cathodically charged with hydrogen, followed by tensile testing, did not indicate any noticeable loss of ductility. FESEM fractographs of hydrogen-charged samples showed a few chain of voids in the presence of cup and cone ductile fracture features in tensile-tested samples without hydrogen charging as well. 相似文献
4.
Influence of microstructure on tensile properties of spheroidized ultrahigh-carbon (1.8 Pct C steel 总被引:3,自引:0,他引:3
C. K. Syn D. R. Lesuer O. D. Sherby 《Metallurgical and Materials Transactions A》1994,25(7):1481-1493
Ultrahigh-carbon steel (UHCS) containing 1.8 pct carbon was processed to create microstructures consisting of fine-spheroidized
carbide particles (0.2- to 1.5-μm size range) within a fine-grained ferrite matrix (0.3- to 5-μm range) through a variety
of thermomechanical processing and heat-treatment combinations. Tensile ductility, yield, and fracture strengths, and strain-hardening
behavior were evaluated at room temperature. Yield strengths ranged from 640 to 1450 MPa, and uniform tensile elongation ranged
from 3 to 23 pct. Quantitative analyses revealed that a Hall-Petch type relationship exists between the yield strength and
the ferrite grain size and carbide particle size within grain interiors. The fracture strength, on the other hand, was found
to be uniquely dependent on the coarse carbide particle size typically found at grain boundaries. Data from other investigators
on spheroidized carbon steels were shown to correlate well with the data for the UHCS (1.8 pct C) material. It was shown that
the tensile ductility will increase when the difference between the fracture strength and the yield strength is increased
and when the strain-hardening rate is decreased. The basis for the trends observed is that the tensile ductility is limited
by the fracture process that appears to be dictated by the nucleation of cracks at large carbide particles. The results obtained
indicate that UHCSs have significant potential for sheet applications where high strength and good ductility are primary requirements. 相似文献
5.
Influence of martensite composition and content on the properties of dual phase steels 总被引:2,自引:0,他引:2
R. G. Davies 《Metallurgical and Materials Transactions A》1978,9(5):671-679
A study has been made of the mechanical properties of dual phase (martensite plus ferrite) structures produced when Fe-Mn-C
alloys are quenched from the austenite plus ferrite phase field, so as to give a series of alloys with constant ferrite and
martensite compositions but varying percent martensites. It is found that the strength of a dual phase structure is dependent
on the ferrite grain size and the volume fraction of martensite, and is independent of the composition and strength of the
martensite. In agreement with previous work the ductility of these steels is superior to that for standard HSLA steels at
the same tensile strength. As shown in a previous paper the strength and ductility as a function of percent martensite are
in agreement with Mileiko’s theory of composites of two ductile phases. This theory and the results indicate that the superior
ductility of dual phase steels is largely a consequence of the high strength (fine grained), highly ductile (low interstitial
content) ferrite matrix. 相似文献
6.
The high strain hardening rate and formability of dual-phase steels makes them promising choices for drawing into high strength
wire. As the fundamental part of an alloy design project, dual-phase steels with several different martensite volume fractions,
particle shapes, particle sizes, compositions, and crystallographic relations with the ferrite matrix were studied. They were
wire drawn with true strains of up to 6.1. The initial microstructure, void formation tendency, drawability, and mechanical
properties of the various steels were compared and correlated. The Fe-2Si-0.1C alloy was found to be the most promising with
a suggested reduction in the carbon level to 0.06 to 0.08 pct. The double heat treatment which consists of quenching from
austenite to martensite followed by intercritical annealing and quenching produced the best microstructure for drawing into
wire. The annealing temperature should be adjusted to yield 25 to 30 vol pct martensite in the final microstructure. Stress
relief after drawing provided a substantial increase in ductility without significant loss in strength. 相似文献
7.
A. R. Marder 《Metallurgical and Materials Transactions A》1982,13(1):85-92
An investigation was made to determine the effect of volume fraction of martensite on the strength, ductility, and fracture
behavior of dual-phase steels. For both V-and Mo-bearing alloys, a linear relationship was found to exist between the amount
of martensite and both tensile strength and uniform elongation. Contrary to previous reports that predict microcracking of
martensite above 0.2 volume fraction to be responsible for a drop-off in ductility, no martensite cracking was found. Fracture
was caused by void formation at small inclusions or at the ferrite/martensite interface. In severely banded structures, the
strength/ductility relationship was detrimentally affected because of the tendency for crack propagation in the less ductile
martensite without the cracks being blunted by the ferrite matrix. 相似文献
8.
Effect of phosphorus on the formation of retained austenite and mechanical properties in Si-containing low-carbon steel sheet 总被引:1,自引:0,他引:1
The effect of phosphorus and silicon on the formation of retained austenite has been investigated in a low-carbon steel cold
rolled, intercritically annealed, and isothermally held in a temperature range of bainitic transformation followed by air
cooling. The steel sheet containing phosphorus after final heat-treatment consisted of ferrite, retained austenite, and bainite
or martensite. Phosphorus, especially in the presence of silicon, in steel was useful to assist the formation of retained
austenite. Mechanical properties, such as tensile strength, uniform elongation, and the combination of tensile strength/ductility,
were improved when phosphorus was increased up to 0.07 pct in 0.5 pct Si steel. This could be attributed to the strain-induced
transformation of retained austenite during tensile deformation. Furthermore, two types of retained austenite were observed
in P-containing steel. One is larger than about 1 μm in size and usually exists adjacent to bainite; the other one is of submicron
size and usually exists in a ferrite matrix. High phosphorus content promotes the formation of stable (small size) austenites
which are considered to be stabilized mainly by their small size effect and have a different formation mechanism from the
coarser retained austenite in the lower P steels. The retained austenites of submicron size showed mechanical stability even
after 10 pct deformation, suggesting that these small austenites have little effect on ductility. The 0.07 pct P-0.5 pct Si-1.5
pct Mn-0.12 pct C steel showed a high strength of 730 MPa and a total elongation of 36 pct. 相似文献
9.
Jun Hu Lin-Xiu Du Jian-Jun Wang Cai-Ru Gao Tong-Zi Yang An-Yang Wang R. D. K. Misra 《Metallurgical and Materials Transactions A》2013,44(11):4937-4947
Controlled rolling followed by accelerated cooling was carried out in-house to study the microstructure and mechanical properties of a low carbon dual-phase steel. The objective of the study described here was to explore the effect of cooling schedule, such as air cooling temperature and coiling temperature, on the final microstructure and mechanical properties of dual-phase steels. Furthermore, the precipitation behavior and yield ratio are discussed. The study demonstrates that it is possible to obtain tensile strength and elongation of 780 MPa and 22 pct, respectively, at the two cooling schedules investigated. The microstructure consists of 90 pct ferrite and 10 pct martensite when subjected to moderate air cooling and low temperature coiling, such that the yield ratio is a low 0.69. The microstructure consists of 75 pct ferrite and 25 pct granular bainite with a high yield ratio of 0.84 when the steel is directly cooled to the coiling temperature. Compared to the conventional dual-phase steels, the high yield strength is attributed to precipitation hardening induced by nanoscale TiC particles and solid solution strengthening by high Si content. The interphase precipitates form at a suitable ledge mobility, and the row spacing changes with the rate of ferrite transformation. There are different orientations of the rows in the same grain because of the different growth directions of the ferrite grain boundaries, and the interface of the two colonies is devoid of precipitates because of the competitive mechanisms of the two orientations. 相似文献
10.
The effect of heat treatment on the properties and structure of molybdenum and vanadium dual-phase steels 总被引:1,自引:0,他引:1
A. R. Marder 《Metallurgical and Materials Transactions A》1981,12(9):1569-1579
A systematic study was made of the effect of the heat treating parameters,(i.e., temperature, time, and cooling rate) on the properties and structure of molybdenum and vanadium bearing dual-phase steels.
The volume percent martensite was found to be the major structural factor that controls the strength and ductility of these
steels. The relationship between strength and ductility was independent of alloy addition for the alloys studied. Annealing
temperature was shown to be very important in these alloys, especially at high quench rates. The molybdenum alloy exhibited
better hardenability than the vanadium alloy for equivalent heat treating conditions. Therefore, for a given set of annealing
conditions the molybdenum alloy generally had the highest tensile strength and lowest total elongation. A minimum in the 0.2
pct yield strength was found at a specific volume fraction martensite. The increase in yield strength at the lowest volume
fraction studied can be related to a jog or discontinuity in the stress-strain curve during tensile testing. This jog was
found to be the result of the lack of a sufficient amount of free dislocations. The causes of this deficiency of the dislocations
may be: 1) an insufficient amount of transformed martensite, 2) a large martensite interparticle spacing, 3) dynamic recovery
of dislocations during cooling, and 4) pinning of dislocations by precipitates during cooling. 相似文献
11.
Heat treatments were performed using an isothermal bainitic transformation (IBT) temperature compatible with continuous hot-dip galvanizing on two high Al–low Si transformation induced plasticity (TRIP)-assisted steels. Both steels had 0.2 wt pct C and 1.5 wt pct Mn; one had 1.5 wt pct Al and the other had 1 wt pct Al and 0.5 wt pct Si. Two different intercritical annealing (IA) temperatures were used, resulting in intercritical microstructures of 50 pct ferrite (α)-50 pct austenite (γ) and 65 pct α-35 pct γ. Using the IBT temperature of 465 °C, five IBT times were tested: 4, 30, 60, 90, and 120 seconds. Increasing the IBT time resulted in a decrease in the ultimate tensile strength (UTS) and an increase in the uniform elongation, yield strength, and yield point elongation. The uniform elongation was higher when using the 50 pct α-50 pct γ IA temperature when compared to the 65 pct α-35 pct γ IA temperature. The best combinations of strength and ductility and their corresponding heat treatments were as follows: a tensile strength of 895 MPa and uniform elongation of 0.26 for the 1.5 pct Al TRIP steel at the 50 pct γ IA temperature and 90-second IBT time; a tensile strength of 880 MPa and uniform elongation of 0.27 for the 1.5 pct Al TRIP steel at the 50 pct γ IA temperature and 120-second IBT time; and a tensile strength of 1009 MPa and uniform elongation of 0.22 for the 1 pct Al-0.5 pct Si TRIP steel at the 50 pct γ IA temperature and 120-second IBT time. 相似文献
12.
Using the twin-roller type melt-quenching technique, the effects of rapid solidification on the microstructures and mechanical
properties of ferrite have been examined in 17 pct Cr and 17 pct Cr-M steels where M = Ti, Nb, Si, or Al. The melt-quenched
17 pct Cr steels have the columnar and equiaxed grains which become finer with decreasing of specimen thickness. But the yield
strength of these steels, which is about 0.48 GPa, remains almost unchanged with grain size refinement, contrary to predictions
based on Hall-Petch’s relationship. The columnar structure of the melt-quenched 17 pct Cr-M steels is very fine on alloying
with Ti and Si, while it is slightly coarse on alloying with Nb and Al. The hardness, yield strength, and fracture strength
of these 17 pct Cr-M steels increase with increased amount of alloying element, these maximum values being about 460 DPN,
1.0 GPa, and 1.35 GPa, respectively, for 17 pct Cr- 6 pct Si steel, in the ductile compositional range. These are suitable
values for a fine-gauge material having high hardness and strength as well as good ductility. 相似文献
13.
B. O. Han F. A. Mohamed Z. Lee S. R. Nutt E. J. Lavernia 《Metallurgical and Materials Transactions A》2003,34(3):603-613
In the present study, the relationships between the structure and properties of a cryomilled Al-7.5 pct Mg alloy were investigated.
The microstructure of the cryomilled Al-7.5 pct Mg alloy consisted of equiaxed grains with an approximate size of 300 nm.
Thermal treatment had only a minor effect on microstructure, as evidenced by X-ray diffraction (XRD) and transmission electron
microscopy (TEM) results. The tensile behavior was characterized by high strength, high ductility, and low-strain-hardening.
The tensile deformation was relatively uniform, with limited necking deformation, and fracture surfaces were characterized
by microdimples. The variation of strain rates from 4 · 10−4 to 4 · 10−2 s−1 had an insignificant effect on tensile behavior. Comparison of compressive and tensile behavior revealed similar moduli and
yield strengths, although the postyield behavior was markedly asymmetric. The present results indicate that grain-size effects,
solid-solution strengthening, Orowan strengthening, and dislocation strengthening contribute significantly to the properties
of a cryomilled Al-7.5 pct Mg alloy. 相似文献
14.
Manpreet Singh Anindya Das T. Venugopalan Krishnendu Mukherjee Mahesh Walunj Tarun Nanda B. Ravi Kumar 《Metallurgical and Materials Transactions A》2018,49(2):463-475
The effects of microstructure parameters of dual-phase steels on tensile high strain dynamic deformation characteristic were examined in this study. Cold-rolled steel sheets were annealed using three different annealing process parameters to obtain three different dual-phase microstructures of varied ferrite and martensite phase fraction. The volume fraction of martensite obtained in two of the steels was near identical (~ 19 pct) with a subtle difference in its spatial distribution. In the first microstructure variant, martensite was mostly found to be situated at ferrite grain boundaries and in the second variant, in addition to at grain boundaries, in-grain martensite was also observed. The third microstructure was very different from the above two with respect to martensite volume fraction (~ 67 pct) and its morphology. In this case, martensite packets were surrounded by a three-dimensional ferrite network giving an appearance of core and shell type microstructure. All the three steels were tensile deformed at strain rates ranging from 2.7 × 10?4 (quasi-static) to 650 s?1 (dynamic range). Field-emission scanning electron microscope was used to characterize the starting as well as post-tensile deformed microstructures. Dual-phase steel consisting of small martensite volume fraction (~ 19 pct), irrespective of its spatial distribution, demonstrated high strain rate sensitivity and on the other hand, steel with large martensite volume fraction (~ 67 pct) displayed a very little strain rate sensitivity. Interestingly, total elongation was found to increase with increasing strain rate in the dynamic regime for steel with core–shell type of microstructure containing large martensite volume fraction. The observed enhancement in plasticity in dynamic regime was attributed to adiabatic heating of specimen. To understand the evolving damage mechanism, the fracture surface and the vicinity of fracture ends were studied in all the three dual-phase steels. 相似文献
15.
Heat treatments were performed using an isothermal bainitic transformation (IBT) temperature compatible with continuous hot-dip
galvanizing on two high Al–low Si transformation induced plasticity (TRIP)-assisted steels. Both steels had 0.2 wt pct C and
1.5 wt pct Mn; one had 1.5 wt pct Al and the other had 1 wt pct Al and 0.5 wt pct Si. Two different intercritical annealing
(IA) temperatures were used, resulting in intercritical microstructures of 50 pct ferrite (α)-50 pct austenite (γ) and 65 pct α-35 pct γ. Using the IBT temperature of 465 °C, five IBT times were tested: 4, 30, 60, 90, and 120 seconds. Increasing the IBT time
resulted in a decrease in the ultimate tensile strength (UTS) and an increase in the uniform elongation, yield strength, and
yield point elongation. The uniform elongation was higher when using the 50 pct α-50 pct γ IA temperature when compared to the 65 pct α-35 pct γ IA temperature. The best combinations of strength and ductility and their corresponding heat treatments were as follows:
a tensile strength of 895 MPa and uniform elongation of 0.26 for the 1.5 pct Al TRIP steel at the 50 pct γ IA temperature and 90-second IBT time; a tensile strength of 880 MPa and uniform elongation of 0.27 for the 1.5 pct Al TRIP
steel at the 50 pct γ IA temperature and 120-second IBT time; and a tensile strength of 1009 MPa and uniform elongation of 0.22 for the 1 pct Al-0.5 pct
Si TRIP steel at the 50 pct γ IA temperature and 120-second IBT time. 相似文献
16.
The Bauschinger behavior after a strain reversal was evaluated for samples with microstructures representative of production
sheets for a low-carbon (LC) steel, a high-strength low-alloy (HSLA) steel, and a dual-phase (DP) steel. The microstructures
were produced in the samples by laboratory hot rolling and heat treatment. Bauschinger tests were run at strain rates of 0.0001,
0.001, and 0.01 s−1, with tensile prestrains between 1 and 7 pct. After the reversal, the samples were strained 2 pct in compression. The Bauschinger
effect is described by a Bauschinger effect parameter (BE), which is the difference between the steel strength at reversal
and the 0.05 pct offset yield strength on the reversal, normalized by the steel strength at reversal. It is found that the
Bauschinger effect is a continuous increasing function of the strength of the steel, provided the steel is prestrained at
least 2.5 pct or beyond the yield point elongation. A single trend line describes the Bauschinger effect variation with steel
strength, for all three steels in the present study and for an aluminum-killed drawing quality (AKDQ) steel from a previous
investigation. No strain rate influence on the BE was found, due to the limited strain rate range and data uncertainty. 相似文献
17.
H. Berns J. Kleff G. Krauss R. P. Foley 《Metallurgical and Materials Transactions A》1996,27(7):1845-1859
Two alloys of high-nitrogen stainless steel have been heat treated to produce dual-phase microstruc-tures. The first alloy,
N10CrNiMol7 1, a Ni-containing stainless steel, was processed conventionally. The second alloy, N20CrMol7, a Ni-free stainless
steel, was processed to obtain a higher nitrogen content by pressurized electroslag remelting. The martensite in N10CrNiMol7
1 was homogeneously distributed in the ferrite and obtained a near-constant volume fraction as a function of intercritical
annealing temperature. Microprobe analysis and microhardness measurements of the martensite con-stituent suggested that up
to 0.4 pct N was dissolved in the austenite before quenching. Austenite formation, martensite transformation, undissolved
nitrides, and retained austenite were evaluated by transmission electron microscopy (TEM). The Ni-containing alloy exhibited
classic dual-phase tensile behavior in that continuous yielding was observed together with good combinations of ultimate tensile
strength and total elongation. The martensite constituent in alloy N20CrMol7 was concen-trated within bands. Comparison of
tensile properties of the two alloys at similar volume fractions and hardness levels of martensite and ferrite showed that
the microstructure containing banded mar-tensite had inferior combinations of strength and ductility. The degradation of tensile
ductility was accompanied by a fracture mode transition from microvoid coalescence to transgranular cleavage. The deformation
and fracture behavior of both alloys were related to the microstructure. 相似文献
18.
A study has been made of an Fe-3Ni-3Mo alloy whose structure can be either ferrite or martensite or any combination of ferrite
plus martensite. By being able to measure the mechanical properties of the ferrite and martensite phases separately it is
possible, using Milieko's theory for composites of two ductile phases, to calculate the properties expected for ferrite-plus-martensite
mixtures. This theory assumes: 1) the stressstrain relationship for all structures is a power law; 2) a perfect interface
between the phases; and 3) the fibers are aligned parallel to the stress axis. The experimentally determined tensile strength
and ductility of the two-phase structures are in good agreement with the theory even though the martensite is not in the form
of aligned fibers. The ductilities obtained at tensile strengths greater than 620 MPA (90 ksi) are no better than those for
conventional HSLA steels because of the low ductility of the ferrite and low strength of the martensite. 相似文献
19.
Hsun Hu 《Metallurgical and Materials Transactions A》1982,13(7):1257-1262
Experimental studies of cold-rolled sheets from a series of silicon-phosphorus (0.07 pct P, variable Si) steels showed that,
depending on the silicon content, a dual-phase sheet can be produced with 70 ksi (483 MPa) yield strength, 100 ksi (690 MPa)
tensile strength, 15 pct elongation (in one inch), and anr
mvalue of about 1.8. The relatively low elongation value is believed to be due to quench aging. Further development to increase
hardenability and reduce the required cooling rates is expected to improve the ductility without reducingr
mvalues. 相似文献