The Effect of Ultra-Fast Heating on the Microstructure, Grain Size and Texture Evolution of a Commercial Low-C, Medium-Mn DP Steel

The effect of ultra-fast heating on the microstructures of steel has been thoroughly studied over the last year as it imposes a suitable alternative for the production of ultra high strength steel grades. Rapid reheating followed by quenching leads to fine-grained mixed microstructures. This way the desirable strength/ductility ratio can be achieved while the use of costly alloying elements is significantly reduced. The current work focuses on the effect of ultra-fast heating on commercial dual phase grades for use in the automotive industry. Here, a cold-rolled, low-carbon, medium-manganese steel was treated with a rapid heating rate of 780 °C/s to an intercritical peak temperature (760 °C), followed by subsequent quenching. For comparison, a conventionally heated sample was studied with a heating rate of 10 °C/s. The initial microstructure of both sets of samples consisted of ferrite, pearlite and martensite. It is found that the very short heating time impedes the dissolution of cementite and leads to an interface-controlled α → γ transformation. The undissolved cementite affects the grain size of the parent austenite grains and of the microstructural constituents after quenching. The final microstructure consists of ferrite and martensite in a 4/1 ratio, undissolved cementite and traces of austenite while the presence of bainite is possible. Finally, it is shown that the texture is not strongly affected during ultra-fast heating, and the recovery and recrystallization of ferrite are taking place simultaneously with the α → γ transformation.

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STRUCTURAL CHARACTERISTICS OF (Ba,Sr)TiO3 THIN FILMS BY RAPID THERMAL ANNEALING

Surface Review and Letters ◽

10.1142/s0218625x07009153 ◽

2007 ◽

Vol 14 (01) ◽

pp. 141-145

Author(s):

Q. Y. ZHANG ◽

S. W. JIANG ◽

Y. R. LI

Keyword(s):

Thin Films ◽

Grain Size ◽

Heating Rate ◽

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Rapid Heating ◽

Structural Characteristics ◽

High Heating Rate ◽

Duration Time ◽

Temperature Heating

The rapid thermal annealing (RTA) process was adapted to crystallize the amorphous ( Ba,Sr ) TiO 3 thin films prepared on Si (111) substrates by RF magnetic sputtering deposition. The effect of annealing temperature, heating rate and duration time on crystallization was studied through X-ray diffraction and atomic force microscopy. The result shows that the crystallinity and grain size were strongly dependent on the temperature, heating rate, and duration time. Higher heating rate leads to smaller grain size. In high heating rate, the grain size shows different dependence of temperature from that of low heating rate. For a heating rate of 50°C/s, the grain size decreased with temperature increasing below 700°C, while after that temperature, the grain size increased slightly with the temperature increasing. At a certain temperature, the crystallinity and surface roughness improved with increase in annealing time, while grain size changed little. The effect of rapid heating rate on the nucleation and grain growth has been discussed, which contributes to the limited grain size of the annealed ( Ba,Sr ) TiO 3 thin films.

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The effect of heating factors on the properties of heat-induced surimi gel under ohmic heating

Can Tho University Journal of Science ◽

10.22144/ctu.jen.2021.028 ◽

2021 ◽

Vol 13 (2) ◽

pp. 32-42

Author(s):

Van Nguyen

Keyword(s):

Electrical Conductivity ◽

Heating Rate ◽

Salt Concentration ◽

Ohmic Heating ◽

Heating Time ◽

Holding Time ◽

Water Bath ◽

Heating Rates ◽

Fast Heating ◽

Water Bath Heating

Ohmic heating (OH) is a method that heat is generated within the food due to its electrical resistance, resulting in a relatively linear heating rate and uniform temperature distribution. Because surimi-based paste contains water and salts, the conductivity is sufficiently good for the ohmic effect. Gelation induced by OH greatly depends on heating conditions such as heating speed, heating time, or electrical conductivity. However, the detailed information obtained is quite limited. Therefore, in order to clarify how ohmic heating affects the physical properties of surimi gel under OH, gels from croaker surimi (SA grade) were obtained using different heating conditions (heating speed, heating time, or salt concentration - electrical conductivity). Furthermore, the gels heated by ohmic heating were compared with the gel obtained by conventional water-bath heating. The results showed that, at the same heating rates, higher salt concentration generated better surimi gels for croaker surimi. Gels cooked ohmically at a slow heating rate performed significantly better than those cooked at a fast heating rate or heated conventionally in a water bath. There was little discernible difference in protein pattern between gels heated by OH and conventional water bath heating at fast heating rates with two different salt concentrations. The results also indicated that holding time at target temperature showed no effect on the gel. These results suggested that the properties of heat-induced surimi gels by OH are affected by not only heating speed but also holding time at maximum temperature and salt content.

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Bake Hardening Properties of Ultra-Rapid Annealed Ultra-Low Carbon Bake Hardening Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.941-944.127 ◽

2014 ◽

Vol 941-944 ◽

pp. 127-131 ◽

Cited By ~ 1

Author(s):

De Chao Xu ◽

Jun Li ◽

Yan Dong Liu ◽

Xiang Wei Kong

Keyword(s):

Grain Size ◽

Heating Rate ◽

Rolling Reduction ◽

Temper Rolling ◽

Low Carbon ◽

Heating Rates ◽

Bake Hardening ◽

Soaking Time ◽

Rapid Annealing ◽

Bake Hardening Steel

Ultra-rapid annealing (URA) experiments were carried out to study the effect of heating rate on the recrystallization kinetics, grain size and Bake-hardening (BH) properties of Ultra-low carbon Bake Hardening Steel annealing with different heating rates followed by gas cooling (about 100°C/s) with variation of soaking times. It was shown that the degree of grain refinement is controlled by the parameters of heating rates and soaking time of the Ultra-rapid annealing cycles. For the steels investigated, the final grain size decreases with increasing heating rate and increases with increasing soaking time. The effects of dislocation density, varied by means of non-temper rolling reduction and a temper rolling reduction of 1% on the Bake-hardening properties were investigated within an aging temperature of 170°C for 20 min.

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The Effect of Final Annealing Heating Rate on Abnormal Grain Growth in a Fe-3.5%Si Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.350 ◽

2016 ◽

Vol 879 ◽

pp. 350-355

Author(s):

Fatayalkadri Citrawati ◽

Md Zakaria Quadir ◽

Paul Munroe

Keyword(s):

Grain Size ◽

Heating Rate ◽

Grain Growth ◽

Growth Kinetics ◽

Annealing Time ◽

Annealing Temperature ◽

Rapid Heating ◽

Secondary Recrystallization ◽

Recrystallization Annealing ◽

Final Annealing

In this study the effects of heating rate on the sharpness and size of Goss oriented ({110}<001>) grains during secondary recrystallization annealing at 900 °C was observed. The results show that, at the same annealing temperature, rapid heating of the samples to this temperature generates a higher drag force compared to a slower heating rate (5°C/min). The two groups of samples show different growth kinetics for Goss grains, in which at the longest annealing time, the rapid heating sample exhibits larger maximum Goss grain size compared to the slower heated samples.

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Microwave sintering of ZnO at ultra high heating rates

Journal of Materials Research ◽

10.1557/jmr.2001.0393 ◽

2001 ◽

Vol 16 (10) ◽

pp. 2850-2858 ◽

Cited By ~ 44

Author(s):

Geng-fu Xu ◽

Isabel K. Lloyd ◽

Yuval Carmel ◽

Tayo Olorunyolemi ◽

Otto C. Wilson

Keyword(s):

Grain Size ◽

Heating Rate ◽

Microwave Heating ◽

Grain Growth ◽

Rapid Heating ◽

Microwave Sintering ◽

Complete Suppression ◽

Heating Rates ◽

High Heating ◽

Size Uniformity

In this paper, a unique processing approach for producing a tailored, externally controlled microstructure in zinc oxide using very high heating rates (to 4900 °C/min) in a microwave environment is discussed. Detailed data on the densification, grain growth, and grain size uniformity as a function of heating rate are presented. With increasing heating rate, the grain size decreased while grain size uniformity increased. At extremely high heating rates, high density can be achieved with almost complete suppression of grain growth. Ultrarapid microwave heating of ZnO also enhanced densification rates by up to 4 orders of magnitude compared to slow microwave heating. The results indicate that the densification mechanisms are different for slow and rapid heating rates. Since the mechanical, thermal, dielectric, and optical properties of ceramics depend on microstructure, ultrarapid heating may lead to advanced ceramics with tailored microstructure and enhanced properties.

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A TEM study of the influence of microstructure on the superplastic behavior of a U-5.8 wt.% Nb alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144310 ◽

1986 ◽

Vol 44 ◽

pp. 568-569

Author(s):

G. Mackiewicz Ludtka

Keyword(s):

Grain Size ◽

Heating Rate ◽

Phase Field ◽

Single Phase ◽

Superplastic Behavior ◽

Two Phase ◽

Single Phase Field

Historically, metals exhibit superplasticity only while forming in a two-phase field because a two-phase microstructure helps ensure a fine, stable grain size. In the U-5.8 Nb alloy, superplastici ty exists for up to 2 h in the single phase field (γ1) at 670°C. This is above the equilibrium monotectoid temperature of 647°C. Utilizing dilatometry, the superplastic (SP) U-5.8 Nb alloy requires superheating to 658°C to initiate the α+γ2 → γ1 transformation at a heating rate of 1.5°C/s. Hence, the U-5.8 Nb alloy exhibits an anomolous superplastic behavior.

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