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1.
A 0.4 pct C-2 pct Si-1 pct Cr-1 pct Mo steel was quenched and tempered at 773 K (500 °C) and deformed by multi-pass caliber rolling (i.e., warm tempforming). The microstructures and the mechanical properties of the warm tempformed steels were investigated as a function of the rolling reduction. At rolling reductions of more than 28 pct, not only extension of the martensite blocks and/or the packets in the rolling direction (RD) but also a grain subdivision became more significant, and an ultrafine elongated grain (UFEG) structure with a strong ??110??//RD fiber deformation texture was formed after 78 pct rolling. The tensile deformation behavior became significantly anisotropic in response to the evolution of UFEG structure. The longitudinal yield strength (??y) of the quenched and tempered sample increased from 1480 to 1860 MPa through the 78 pct rolling, while the transverse ??y leveled off at around 1600 MPa up to 28 pct rolling. The transverse true fracture stress was also markedly degraded in contrast to the longitudinal one. Charpy impact properties were enhanced at a rolling reduction of 52 pct or more. The 52 pct-rolled sample underwent a ductile-to-brittle transition in the temperature range from 333 K to 213 K (60 °C to ?60 °C), while the 78 pct-rolled sample showed an inverse temperature dependence of the impact toughness because of brittle delamination. The tensile and Charpy impact properties are discussed in association with the microstructural evolution. 相似文献
2.
Aging Effect on Texture Evolution during Warm Rolling of ZK60 Alloys Fabricated by Twin-Roll Casting
Jae-Hyung Cho Hong-Mei Chen Shi-Hoon Choi Hyoung-Wook Kim Suk-Bong Kang 《Metallurgical and Materials Transactions A》2010,41(10):2575-2583
ZK60(Mg-Zn-Zr) alloys experience variation of precipitates during aging. The frequency and size of rod- and disk-shaped precipitates change with aging. The effect of aging on texture evolution during warm rolling of ZK60 was investigated. Some difference was found between the texture evolution of solution heat-treated (T4) and artificially aged (T6) samples. The Aged samples had more texture variations along the thickness direction than solution heat-treated samples. The intensities of basal fibers were lower during asymmetric rolling than during symmetric rolling, although the initial intensities increased during both rolling processes. The decrease in basal fibers by asymmetric rolling was clearer at a lower temperature of 448 K (175 °C) than at 498 K (225 °C). 相似文献
3.
A direct die-filling thixoforging method is designed to fabricate aluminum thin plates with a pattern of microchannels in a single forming operation. Extruded AA2024 and AA7075 wrought aluminum billets are used. A recrystallization and partial remelting process is used to prepare the semisolid slurries required for the forming process. Under a thixoforging pressure of 70 MPa, AA7075 thin plates are successfully thixoforged in a temperature range of 883 K to 893 K (610 °C to 620 °C), corresponding to liquid fractions of ~30 to 50 pct in the semisolid slurry. AA2024 thin plate requires a thixoforging temperature range of 888 K to 898 K (615 °C to 625 °C), corresponding to the liquid fractions of ~45 to 60 pct. Final microstructures of the thin plates comprise primary α-Al equiaxed globular grains in a matrix of a solidified liquid phase. With increasing thixoforging temperature, the yield strength values continuously decrease. The ultimate tensile strength (UTS) values of the thin plates initially decrease with increasing thixoforging temperature from 883 K to 888 K (610 °C to 615 °C) and from 888 K to 893 K (615 °C to 620 °C) for the AA7075 and AA2024 thin plates, respectively. The UTS values stabilize and slightly enhance when the thixoforging temperatures are further increased to 893 K and 898 K (620 °C and 625 °C) for the AA7075 and AA2024 thin plates, respectively. Very brittle behavior (elongation value of ~1 pct) is observed for the AA7075 thin plates thixoforged at 883 K and 888 K (610 °C and 615 °C). The elongation value increases to 3 pct with increasing the thixoforging temperature to 893 K (620 °C). In contrast, larger elongation values (between 4 and 6 pct) are achieved for the AA2024 thin plates. Increasing the thixoforging pressures from 70 to 100 MPa and then to 150 MPa improves the tensile properties of the thin plates. The tensile properties of the thixoforged thin plates are linked to their microstructural characteristics and processing conditions and are discussed here in detail. 相似文献
4.
Two ferritic stainless steels (≈16.5 mass pct Cr) were hot-rolled using seven subsequent passes. The first sample was rolled
within the range 1280 °C to 750 °C,i.e., the deformation started in the ferritic region. The second sample was rolled within the range 1080 °C to 770 °C,i.e., the deformation started in the ferritic-austenitic region. In both cases, up to 40 vol pct of the ferrite transformed into
austenite during hot rolling. During the last passes, the austenite transformed into cubic martensite. After hot rolling,
these former austenitic regions were identified using a selective etching technique and examined using single orientation
determination in the scanning electron microscope. The regions which remained ferritic throughout the hot-rolling process
were investigated as well. Whereas the texture of the martensite considerably depended on the hot-rolling conditions, especially
on the temperature and on the intervals between the rollings, the texture of the ferrite was less affected. The textures of
the martensite were interpreted in terms of the crystallographic transformation rules between austenite and martensite. The
textures of the ferrite were discussed in terms of recovery and recrystallization.
M. YLITALO, formerly with the Department of Mechanical Engineering, University of Oulu, 90570 Oulu, Finland 相似文献
5.
Edwin Snape 《Metallurgical and Materials Transactions B》1970,1(5):1375-1382
The effects of hot rolling and warm working on mechanical properties and microstructure of Ni-Cu-Cb steel were investigated. In the hot rolled condition optimum strength and toughness resulted from rolling in the upper portion of the austenite plus ferrite phase field. This treatment produced a fine-grained structure consisting of equiaxed and acicular ferrite. Unusually high strength-toughness combinations were realized by warm working the hot rolled steels at 1200°F. 相似文献
6.
Pinaki Prasad Bhattacharjee M. Joshi V. P. Chaudhary J. R. Gatti M. Zaid 《Metallurgical and Materials Transactions A》2013,44(6):2707-2716
Evolution of texture during cross rolling and subsequent annealing was studied in high-purity nickel. For this purpose nickel samples were subjected to multipass cross rolling up to 90 pct reduction in thickness followed by annealing at different temperatures ranging between 673 K and 1073 K (400 °C and 800 °C). Cross rolling was carried out by rotating the samples about the normal direction (ND) by 90 deg interchanging the rolling direction and transverse direction (TD) between each consecutive pass. The development of microstructure and texture was characterized using X-ray and electron backscattered diffraction (EBSD) techniques. The deformation texture was characterized by the presence of strong brass ({110}〈112〉) and ND-rotated brass ({011}〈21 $ \overline{13} $ 13〉)) orientations. Upon annealing at 673 K (400 °C), ND||[111] fiber could be observed in the microtexture which originated from the twin formation of the recrystallized TD-rotated cube ({027}〈0 $ \overline{7} $ 2〉) grains. The fiber was weakened after annealing at 1073 K (800 °C) because of the decreased propensity for twin formation, and the microtexture was found to be weak and diffused. EBSD studies on early recrystallization stages indicated the absence of preferential nucleation of cube grains being in agreement with a weak cube texture formation in annealed cross-rolled high-purity nickel. 相似文献
7.
For the first time, hot direct rolling was applied in ferrite region in the mill and the resulting quality of the cold rolled and annealed sheet steel was as good as that hot direct rolled in austenite region with respect to microstructure and mechanical properties. In case of ferrite phase rolling, microstructure of the hot strip reveals abnormal grains and deformation bands in the grains, and elongation and r value are not so good as those rolled in the austenite phase. However, these abnormal grains left no traces and appeared to be equiaxed grains like the austenite phase rolled microstructure after 75 % cold rolling and continuous annealing at 830°C. This is attributed to the deformation bands which provide nucleation sites for recrystallization during annealing so that recrystallization occurs uniformly in the matrix. (111) texture was well developed and r value thus appeared high. 相似文献
8.
9.
Seok Su Sohn Byeong-Joo Lee Jai-Hyun Kwak Sunghak Lee 《Metallurgical and Materials Transactions A》2014,45(9):3844-3856
Effects of annealing treatment from 923 K to 1023 K (650 °C to 750 °C) prior to cold rolling on the edge cracking phenomenon of a ferritic lightweight steel were investigated. The edge cracking was severely found in the hot-rolled and 923 K (650 °C)-annealed steels after cold rolling, whereas it hardly occurred in the 1023 K (750 °C)-annealed steel. As the annealing temperature increased, lamellar κ-carbides were dissolved and coarsened, and most of the κ-carbides continuously formed along boundaries between ferrite and κ-carbide bands disappeared. Microstructural observation of the deformed region of tensile specimens revealed that the removal of band boundary κ-carbides reduced the difference in tensile elongation along the longitudinal direction (LD) and transverse direction (TD), which consequently led to the reduction in edge cracking. The 1023 K (750 °C)-annealed steel showed fine ferrite grain size, weak texture, and decomposed band structure after subsequent cold rolling and intercritical annealing, because κ-carbides actively worked as nucleation sites of ferrite and austenite. The present annealing treatment prior to cold rolling, which was originally adopted to prevent edge cracking, also beneficially modified the final microstructure of lightweight steel. 相似文献
10.
G. Fargas N. Akdut M. Anglada A. Mateo 《Metallurgical and Materials Transactions A》2011,42(11):3472-3483
The mechanical properties of rolled duplex stainless steel (DSS) products manufactured by the current industrial process exhibit
a strong anisotropy. This fact is evidently due to the two-phase nature of DSSs. During industrial rolling, not only the morphology
of the microstructure changes from coarse-grained isotropic in the cast slab to fine-grained anisotropic in the coil, with
both phases elongated in the rolling direction (RD), but also clear and intense crystallographic rolling textures develop,
especially in the ferritic phase. The objective of the present work was to modify the industrial processing route and parameters
in such a way that the strong anisotropy of DSS coils and sheets is decreased and the amount of potential applications made
from DSSs by deep drawing or roll forming operations is increased. To achieve this goal, after the industrial cold rolling,
a heat treatment is proposed with the aim of modifying the morphology and crystallographic texture of the ferritic grains
by the assistance of an enforced transformation to sigma phase. The final product obtained by this modified route showed a
microstructure with grains of austenite and ferrite randomly distributed and a significant decrease of the texture intensities
due to the retransformation of sigma into ferrite. As a result, DSS EN 1.4462 displayed an almost isotropic mechanical behavior
and an improved aptitude to deep drawing operations. 相似文献
11.
M. Papa Rao V. Subramanya Sarma S. Sankaran 《Metallurgical and Materials Transactions A》2014,45(12):5313-5317
Ultrafine-grained dual phase microalloyed V-Nb steel with ultimate tensile strength of 1371 MPa and uniform elongation of 16 pct characterized by bimodal ferrite grain structure was obtained through warm rolling and subsequent intercritical annealing. The bimodal ferrite grain structure with uniform dispersion of Nb/V carbides and strong γ-fiber texture promoted high strain hardening rate and high uniform elongation and high strength is attributed to ultrafine-grained ferrite and martensite. 相似文献
12.
P. Behjati A. Kermanpur A. Najafizadeh H. Samaei Baghbadorani L. P. Karjalainen J. -G. Jung Y. -K. Lee 《Metallurgical and Materials Transactions A》2014,45(13):6317-6328
Martensite reversion treatment was utilized to obtain ultrafine grain size in Fe-18Cr-12Mn-N stainless steels containing 0 to 0.44 wt pct N. This was achieved by cold rolling to 80 pct reduction followed by reversion annealing at temperatures between 973 K and 1173 K (700 °C and 900 °C) for 1 to 104 seconds. The microstructural evolution was characterized using both transmission and scanning electron microscopes, and mechanical properties were evaluated using hardness and tensile tests. The steel without nitrogen had a duplex ferritic-austenitic structure and the grain size refinement remained inefficient. The finest austenitic microstructure was achieved in the steels with 0.25 and 0.36 wt pct N following annealing at 1173 K (900 °C) for 100 seconds, resulting in average grain sizes of about 0.240 ± 0.117 and 0.217 ± 0.73 µm, respectively. Nano-size Cr2N precipitates observed in the microstructure were responsible for retarding the grain growth. The reversion mechanism was found to be diffusion controlled in the N-free steel and shear controlled in the N-containing steels. Due to a low fraction of strain-induced martensite in cold rolled condition, the 0.44 wt pct N steel displayed relatively non-uniform, micron-scale grain structure after the same reversion treatment, but it still exhibited superior mechanical properties with a yield strength of 1324 MPa, tensile strength of 1467 MPa, and total elongation of 17 pct. While the high yield strength can be attributed to strengthening by nitrogen alloying, dislocation hardening, and slight grain refinement, the moderate strain-induced martensitic transformation taking place during tensile straining was responsible for enhancement in tensile strength and elongation. 相似文献
13.
Jingwei Zhao Taekyung Lee Jeong Hun Lee Zhengyi Jiang Chong Soo Lee 《Metallurgical and Materials Transactions A》2013,44(8):3511-3523
In the current study, the effects of tungsten (W) addition on the microstructure, hardness, and room/low [223 K and 173 K (?50 °C and ?100 °C)] temperature tensile properties of microalloyed forging steels were systematically investigated. Four kinds of steel specimens were produced by varying the W additions (0, 0.1, 0.5, and 1 wt pct). The microstructure showed that the addition of W does not have any noticeable effect on the amount of precipitates. The precipitates in W-containing steels were all rich in W, and the W concentration in the precipitates increased with the increasing W content. The mean sizes of both austenite grains and precipitates decreased with the increasing W content. When the W content was equal to or less than 0.5 pct, the addition of W favored the formation of allotriomorphic ferrite, which subsequently promoted the development of acicular ferrite in the microalloyed forging steels. The results of mechanical tests indicated that W plays an important role in increasing the hardness and tensile strength. When the testing temperature was decreased, the tensile strength showed an increasing trend. Both the yield strength and the ultimate tensile strength obeyed an Arrhenius type of relation with respect to temperature. When the temperature was decreased from 223 K to 173 K (from ?50 °C to ?100 °C), a ductile-to-brittle transition (DBT) of the specimen with 1 pct W occurred. The addition of W favored a higher DBT temperature. From the microstructural and mechanical test results, it is demonstrated that the addition of 0.5 pct W results in the best combination of excellent room/low-temperature tensile strength and ductility. 相似文献
14.
R. Shukla S. K. Das B. Ravi Kumar S. K. Ghosh S. Kundu S. Chatterjee 《Metallurgical and Materials Transactions A》2012,43(12):4835-4845
In the current study, a novel ultra-low carbon, high-molybdenum-bearing microalloyed steel has been thermomechanically processed. Transformation of this steel during continuous cooling has been assessed. Variation in the microstructure and mechanical properties at different finish rolling temperatures has been studied. The average grain size, misorientation of grain boundary, and distribution of ferrite grains have been analyzed by using electron backscatter diffraction. The lower yield strength (251 to 377?MPa) with moderate tensile strength (406 to 506?MPa) along with high ductility (30 to 47?pct) has been achieved in the selected range of finish rolling temperatures. Superior impact toughness value in the range of 153 to 162?J is obtained in the subsize specimen even at subzero temperatures (233?K [?40?°C]), which is attributed to fine average ferrite grain size. The acicular ferrite dominated microstructure obtained at the 1023?K (750?°C) finish rolling temperature is the most attractive microstructure for pipeline applications due to its excellent combination of strength and toughness. 相似文献
15.
Sanghoon Lee Hyesung Na Byunghoon Kim Dongjin Kim Chungyun Kang 《Metallurgical and Materials Transactions A》2013,44(6):2523-2532
Pressure vessels made for petrochemical and power plants using Cr-Mo steel must be thick (≥400 mm) and have high tensile strength (≥600 MPa). However, the tensile strength in the middle portion of the vessel is very low as a result of ferrite formation. Therefore, research was performed to study the ferrite transformation that occurs in the middle portion of high-thickness Cr-Mo steel when Nb is added to it. The ferrite-formation start time of the continuous-cooling-transformation (CCT) curve decreased with an increase in Nb content until the latter reached 0.05 pct. On cooling from the austenitizing temperature, some of the NbC present at the austenitizing temperature of 1203 K (930 °C) goes into austenite solution in the temperature range of 1173 K to 1073 K (900 °C to 800 °C). However, the ferrite curve shifted to the left for the alloy containing 0.075 pct Nb. It is postulated that the surplus NbC could act as ferrite nucleation sites despite the lower cooling rate. As a result, the hardenability improved in the order of the following Nb content: 0.05 pct, 0.025 pct, 0 pct, and 0.075 pct. 相似文献
16.
Yue Wu Linda Del Castillo Enrique J. Lavernia 《Metallurgical and Materials Transactions A》1997,28(4):1059-1068
A 5083 Al alloy was synthesized using spray deposition processing with N2 as the atomization gas. It was noted that the grains that were present in as-spray-deposited 5083 Al were equiaxed with an
average size of 15.2 μm. The matrix of the material was supersaturated with Mg and Mn. The asspray-deposited microstructure
contained irregular pores with porosity in the range of 0.1 to 5.4 vol pct, depending on spatial location in the preform.
The spray-deposited alloy was thermomechanically processed using extrusion and multiple-pass warm rolling to reduce grain
size and close porosity. It was observed that spray-deposited 5083 Al exhibited superplasticity following thermomechanical
processing by extrusion followed by rolling. Superplasticity was observed in the 500 °C to 550 °C temperature range and 3
× 10−5 to 3 × 10−3 s−1 strain rate range. The corresponding strain-rate-sensitivity factors were in the 0.25 to 0.5 range and increased with decreasing
strain rate. A maximum elongation of 465 pct was noted at 550 °C and 3 × 10−5 s−1. The spray-deposited 5083 Al, thermomechanically processed by direct rolling, exhibited superplasticity in the same temperature
and strain rate ranges as those for the extruded and rolled materials. The superplastic elongation of the spray-formed and
rolled material was relatively low, being in the range of 250 to 300 pct. The deformation behavior is discussed in light of
the presence of porosity in the microstructure. 相似文献
17.
Meysam Jafari Warren M. Garrison Jr. Kaneaki Tsuzaki 《Metallurgical and Materials Transactions A》2014,45(2):647-653
A medium-carbon low-alloy steel was prepared with initial structures of either martensite or bainite. For both initial structures, warm caliber-rolling was conducted at 773 K (500 °C) to obtain ultrafine elongated grain (UFEG) structures with strong 〈110〉//rolling direction (RD) fiber deformation textures. The UFEG structures consisted of spheroidal cementite particles distributed uniformly in a ferrite matrix of a transverse grain size of about 331 and 311 nm in samples with initial martensite and bainite structures, respectively. For both initial structures, the UFEG materials had similar tensile properties, upper shelf energy (145 J), and ductile-to-brittle transition temperatures 98 K (500 °C). Obtaining the martensitic structure requires more rapid cooling than is needed to obtain the bainitic structure and this more rapid cooling promote cracking. As the UFEG structures obtained from initial martensitic and bainitic structures have almost identical properties, but obtaining the bainitic structure does not require a rapid cooling which promotes cracking suggests the use of a bainitic structure in obtaining UFEG structures should be examined further. 相似文献
18.
Correlation of rolling condition,microstructure, and low-temperature toughness of X70 pipeline steels 总被引:2,自引:0,他引:2
Byoungchul Hwang Young Min Kim Sunghak Lee Nack J. Kim Jang Yong Yoo 《Metallurgical and Materials Transactions A》2005,36(7):1793-1805
Correlation of rolling conditions, microstructure, and low-temperature toughness of high-toughness X70 pipeline steels was
investigated in this study. Twelve kinds of steel specimens were fabricated by vacuum-induction melting and hot rolling, and
their microstructures were varied by rolling conditions. Charpy V-notch (CVN) impact test and drop-weight tear test (DWTT)
were conducted on the rolled steel specimens in order to analyze low-temperature fracture properties. Charpy impact test results
indicated that the energy transition temperature (ETT) was below −100 °C when the finish cooling temperature range was 350
°C to 500 °C, showing excellent low-temperature toughness. The ETT increased because of the formation of bainitic ferrite
and martensite at low finish cooling temperatures and because of the increase in effective grain size due to the formation
of coarse ferrites at high finish cooling temperatures. Most of the specimens also showed excellent DWTT properties as the
percent shear area well exceeded 85 pct, irrespective of finish rolling temperatures or finish cooling temperatures, although
a large amount of inverse fracture occurred at some finish cooling temperatures. 相似文献
19.
N. Srisukhumbowornchai S. Guruswamy 《Metallurgical and Materials Transactions A》2004,35(9):2963-2970
The feasibility of obtaining [001] preferred texture in polycrystalline Fe85Ga15 and Fe85Al15 magnetostrictive alloys containing 1 mol pct NbC using a low-cost conventional thermomechanical processing approach is shown
in this work. Thermomechanical processing conditions examined consisted of a sequence of hot rolling, two-stage warm rolling
at 400 °C with intermediate anneal at 900 °C and texture anneal in the temperature range of 900 °C to 1300 °C for time periods
up to 24 hours. Textures present prior to and after texture annealing were characterized using orientation imaging microscopy
in a scanning electron microscope. In the case of Fe85Ga15 alloy with 1 mol pct NbC, the deformation-induced texture after a two-stage warm rolling consists of mixed {100} 〈110〉 and
{111} 〈110〉 type partial textures. Texture annealing of the Fe85Ga15 alloy with 1 mol pct NbC at 1150 °C for 2 hours changes the texture to a predominant texture that is close to {001}〈100〉.
On increasing the annealing time to 24 hours, the texture shifts toward {110}〈100〉. While texture anneal at both 1150 °C and
1300 °C produces a [001] or near-[001] preferred orientation along the rolling direction in the Fe85Ga15 alloy with 1 mol pct NbC, 1150 °C-24 hour treatment was found to provide the strongest [001] orientation among the conditions
examined. Similar trends are observed for the case of Fe85Al15 alloy with 1 mol pct NbC. 相似文献
20.
T. R. McNelley M. R. Edwards A. Doig D. H. Boone C. W. Schultz 《Metallurgical and Materials Transactions A》1983,14(7):1427-1433
Isothermal rolling of AISI 52100 steel at 923 K (650 °C) has been used to produce very fine spheroidized carbide particles
0.1 to 0.2 μm in size in a submicron grain size ferrite matrix. Pearlitic starting structures are not completely spheroidized
by such warm rolling and some isolated pearlite colonies remain after rolling. Tempered martensitic starting structures result
in more uniform structures after rolling. The effect of varying the austenitizing time and temperature and of two cycle austenitizing
treatments before rolling of tempered martensite were studied. After rolling, the room temperature yield strength was raised,
a result of the finer dispersion of carbides and the associated reduction in ferrite grain size. The presence of isolated
pearlite colonies in rolled material reduces the room temperature ductility.
Formerly Graduate Student, Department of Mechanical Engineering, United States Naval Postgraduate School 相似文献