Microstructural Study of a High Bainite Dual Phase (HBDP) Steel Austempered at Different Temperatures

2010 ◽  
Vol 297-301 ◽  
pp. 62-67 ◽  
Author(s):  
R. Bakhtiari ◽  
A. Ekrami
Keyword(s):  
Impact Energy ◽  
Volume Fraction ◽  
Salt Bath ◽  
Total Elongation ◽  
Air Cooling ◽  
Dual Phase ◽  
Severe Reduction ◽  
Steel Bars ◽  
Different Temperatures ◽  
Austempering Temperature

4340 steel bars were austenitized at 850oC for 1 hour followed by heating at 700oC (ferrite and austenite region) for 90 min and quenching into a salt bath with different temperatures of 300, 350, 400 and 450oC. The steel bars were held for 1 hour at these temperatures before air cooling to room temperature. Various ferrite-bainite microstructures with 34% volume fraction of ferrite and different bainite morphologies were obtained. The results of SEM studies showed that by increasing the austempering temperature, the morphology of bainite varies from lower to upper bainite. According to the T-T-T diagram of the studied steel, the bainite transformation will not complete for the holding time of 1 hour at 400 and 450oC austempering temperatures and there can be 9 and 23Vol% of martensite at these temperatures respectively. Microstructural studies of specimens austempered at these temperatures showed complex microstructures of ferrite, bainite and martensite. Mechanical testing results showed reduction in yield and ultimate tensile strengths, hardness, uniform and total elongations and impact energy with increase of the austempering temperature from 300 to 400oC. But for dual phase steel austempered at 450oC, the yield and tensile strengths and hardness increased and a severe reduction in total elongation and impact energy was obtained. This brittle behaviour was related to martensite formation during cooling from this austempering temperature.

scholarly journals Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Hadi Torkamani ◽  
Shahram Raygan ◽  
Carlos Garcia Mateo ◽  
Yahya Palizdar ◽  
Jafar Rassizadehghani ◽  
...  
Keyword(s):  
Carbon Content ◽  
Volume Fraction ◽  
Block Size ◽  
Tensile Tests ◽  
Total Elongation ◽  
Martensite Phase ◽  
Low Carbon ◽  
Steel Increase ◽  
Different Temperatures ◽  
The Impact

AbstractIn this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite.

Deformation Behaviour of Martensite in a Low-Carbon Dual-Phase Steel

2006 ◽  
Vol 15-17 ◽  
pp. 774-779 ◽  
Author(s):  
M. Mazinani ◽  
Warren J. Poole
Keyword(s):  
Dual Phase Steel ◽  
Volume Fraction ◽  
Deformation Behaviour ◽  
Dual Phase ◽  
Low Carbon ◽  
Heating Rates ◽  
Dp Steel ◽  
Martensite Content ◽  
High Heating ◽  
Different Temperatures

The deformation behaviour of martensite and its effect on tensile properties of a lowcarbon dual-phase (DP) steel were investigated. DP steel samples with different martensite contents and morphologies were produced after intercritical annealing at different temperatures using low and high heating rates. Two distinct martensite morphologies were obtained for low and high heating rates. The investigated steel showed the unusual results that the true fracture stress and strain were found to increase with the martensite volume fraction. The plastic deformation of martensite was considered to be responsible for these results. Experimentally, it was observed that the martensite in DP steels with greater than 25-30% martensite can deform plastically during tensile straining. Finally, the effect of tempering on the martensite plasticity was also evaluated. It was found that the tempering process and an increase in the martensite content have a similar effect on promoting martensite plasticity.

The Influence of Quenching Temperature on the Mechanical Properties of a Dual-Phase Steel with 0.094% C and 0.53% Mn

2015 ◽  
Vol 808 ◽  
pp. 28-33 ◽  
Author(s):  
Constantin Dulucheanu ◽  
Nicolai Bancescu ◽  
Traian Severin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Dual Phase Steel ◽  
Volume Fraction ◽  
Total Elongation ◽  
Metallographic Analysis ◽  
Dual Phase ◽  
Quenching Temperature ◽  
Offset Yield Strength ◽  
Martensite Structure

In this article, the authors have analysed the influence of quenching temperature (TQ) on the mechanical properties of a dual-phase steel with 0.094 % C and 0.53% Mn. In order to obtain a ferrite-martensite structure, specimens of this material have been the subjected to intercritical quenching that consisted of heating at 750, 770, 790, 810 and 830 °C, maintaining for 30 minutes and cooling in water. These specimens have then been subjected to metallographic analysis and tensile test in order to determine the volume fraction of martensite (VM) in the structure, ultimate tensile strength (Rm), the 0.2% offset yield strength (Rp0.2), the total elongation (A5) and the Rp0.2/Rm ratio.

Effect of Austempering Temperature on High Cycle Fatigue Behavior of an Austempered Ductile Iron (ADI)

2010 ◽  
Vol 457 ◽  
pp. 493-498 ◽  
Author(s):  
Sasan Yazdani ◽  
Amir Sadighzadeh Benam ◽  
Behzad Avishan
Keyword(s):  
Fatigue Life ◽  
Volume Fraction ◽  
Fatigue Behavior ◽  
Salt Bath ◽  
Fatigue Tests ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Test Pieces ◽  
Rotating Bending Fatigue ◽  
Austempering Temperature

Ductile irons with chemical compositions of Fe-3.6%C-2.6%Si-0.50%Cu-0.51%Ni were cast into standard keel blocks. Austenitizing heat treatment was carried out on test pieces at 875°C followed by austempering at 320, 365 and 400°C for times within the austempering processing window in a salt bath furnace. Rotating bending fatigue tests were performed with Roell Amsler UBM 200™ equipment at 3500 rpm at room temperature. Metallography and X-ray diffraction techniques were used to evaluate the fatigue life. Results indicate an increase of 10, 20 and 24% in fatigue life for specimens austempered at temperatures of 320, 365 and 400°C respectively, compared to that of as cast samples. According to the XRD test results; there is an increase in volume fraction of high carbon austenite by increasing the austempering temperature.

scholarly journals Mechanical characteristics evaluation of dual phase and related hardening techniques on AISI 4340 steel

2018 ◽  
Vol 12 (4) ◽  
pp. 4018-4029
Author(s):  
Sathyashankara Sharma ◽  
B. M Gurumurthy ◽  
U. Achutha Kini ◽  
Ananda Hegde ◽  
Ajinkya Patil
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Salt Bath ◽  
Air Cooling ◽  
Dual Phase ◽  
Aisi 4340 Steel ◽  
Treatment Processes ◽  
4340 Steel ◽  
Wide Range ◽  
Aisi 4340

Steel has wide range of applications and is used in various machinery and general metallic components. Depending on the particular application, steels with tailorable and appropriate properties are used. This requires various methods which can be used to alter the properties based on the requirements. Generally, mechanical properties of the steel are improved by conducting the heat treatment processes. The aim of the present work is to experimentally investigate the effects of conventional heat treatments and special hardening techniques for dual phase structure on mechanical properties of AISI 4340 steel. The test specimens are machined as per ASTM standards and hardness, tensile, impact and microstructure analysis were carried out after the heat treatment processes. Dual phase heat treatment to obtain ferrite-bainite structure is performed by heating the as-bought specimen to the intercritical temperature for two hours followed by isothermal holding in fusible salt bath containing sodium nitrate and sodium nitrite at subcritical temperature for 30 minutes and cooling in air to room temperature. Similarly, ferrite-martensite structure is obtained by air cooling after holding isothermally in the salt bath for 10 seconds.  Ferrite-bainite steel was observed to be soft, whereas ferrite-martensite steel was relatively harder. Austempered steel has high toughness with optimum hardness and conventionally hardened steel is the hardest among all. Microstructure shows colony of bainite and martensite in ferrite matrix of ferrite-bainite and ferrite-martensite dual phase structures respectively. An increase in brittleness was observed with the increase in hardness due to the conventional hardening to display lesser impact strength compared to austempered steel.

Physical Simulation of Thermo-Mechanical Processing of Ferritic-Bainitic Dual Phase (FBDP) Steel

2016 ◽  
Vol 879 ◽  
pp. 495-501 ◽  
Author(s):  
Taher El-Bitar ◽  
Eman El-Shenawy ◽  
Maha El-Meligy
Keyword(s):  
Strain Hardening ◽  
Physical Simulation ◽  
Volume Fraction ◽  
Rolling Process ◽  
Recrystallization Temperature ◽  
Air Cooling ◽  
Dual Phase ◽  
Mechanical Processing ◽  
Allotropic Transformation ◽  
Gleeble 3500

The present work is dealing with a physical simulation of thermo-mechanical processing of ferritic-bainitic dual phase (FBDP) steel alloy containing 0.1% C, 0.3% Si, 0.9% Mn and 0.7% Cr. The microstructure changes and allotropic transformations during thermo-mechanical simulation are investigated. A series of heating – cooling cycles to detect the critical and allotropic transformation temperature by dilatation were carried out on the thermo-mechanical simulator (Gleeble 3500). On the other hand, five – consecutive hits were used during the physical simulation of hot rolling process. Two hits were representing the roughening stage followed by three ones representing finish rolling. Holding at 500°C for 5, 7, 10, 12 and 15 min. after last hit has been applied and then followed by air cooling. Dilation curves appear that Ac1= 766 °C, while Ac3 was detected as 883 °C. Baintic allotropic transformation temperatures were clearly noticed as 618 °C for Bs and 542 °C for Bf. The recrystallization temperature was also detected as 1035 °C. Holding for 5-7 min. at 500 °C was concluded as the optimum for creation a bainite volume fraction. Rough hot deformation a higher temperature above the recrystallization temperature is essential, where no strain hardening and possibility for achieving high strains without excessive loads. Finishing deformation at temperature lower than Tr would create fine bainitic structure. The flow curve of the steel ensures continuous strain hardening. The strain hardening rate (σf/ε) was directly proportional to temperature difference from pass to pass.

Experimental Approach for Investigation of Micro Void Behavior on Dual Phase Steel during Plastic Deformation

2013 ◽  
Vol 535-536 ◽  
pp. 393-396
Author(s):  
Takashi Ishikawa ◽  
T. Ishiguro ◽  
N. Yukawa ◽  
H. Yoshida ◽  
N. Fujita
Keyword(s):  
Dual Phase Steel ◽  
Experimental Approach ◽  
Volume Fraction ◽  
Alloy Element ◽  
Total Elongation ◽  
Heat Treatment Condition ◽  
The Other ◽  
Dual Phase ◽  
Phase Volume Fraction ◽  
Initial Stage

In this research, micro void behavior of DPS, which has different phase volume fraction, is investigated experimentally. Prepared specimens have different amount of alloy element and heat treatment condition. Although both these specimens have almost the same strength and total elongation, these showed quite different local elongations, hole expanding ratio and bending ductility. In order to observe micro void behavior specimens, that have different strain levels, are prepared. These sectional areas are observed by laser microscope after cutting and polishing. The change ratio of micro void volume fraction of DPS, which showed high local ductility, is lower than that of the other DPS. Concerning low ductility DPS, small size void (less than 3µm diameter) increases rapidly not only at grain boundary but in the ferrite grain, especially at initial stage of deformation. On the other hand, nucleation of micro void of high ductility DPS is inhibited.

Effect of Microstructure on Mechanical Properties and Abrasive Wear Behavior of Low Carbon Dual-Phase Steels

2014 ◽  
Author(s):  
Mehmet Çağrı Tüzemen ◽  
Elmas Salamci
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Wear Behavior ◽  
Steel Specimen ◽  
Total Elongation ◽  
Dry Sliding Wear ◽  
Dual Phase ◽  
Low Carbon ◽  
Wear Properties ◽  
Dp Steels

The mechanical properties and wear behavior of Dual Phase (DP) steels have been investigated and compared with those observed in normalized (N) steel that has the same chemical composition. The DP steels having different content and morphology of martensite were produced by varying intercritical annealing temperature and initial microstructures. Mechanical properties of four different DP steels and N steel have been investigated by carrying out tensile and macrohardness tests. Dry sliding wear tests have been conducted on four different the DP steels and the N steel using pin-on-plate to investigate their wear characteristics. It has been found that the yield and tensile strengths and macrohardness increase with increasing martensite content and decreasing martensite size. The yield and tensile strengths and macrohardness of the N steel were significantly lower than the DP steels whereas percentage of total elongation was higher. Wear properties are improved by increasing martensite volume fraction and size in the DP steels. The N steel specimen showed the highest wear rate.

scholarly journals Microstructure Evolution during Recrystallization in Dual-Phase Steels

2012 ◽  
Vol 715-716 ◽  
pp. 13-22 ◽  
Author(s):  
Nicola Peranio ◽  
Franz Roters ◽  
Dierk Raabe
Keyword(s):  
Plane Strain ◽  
Volume Fraction ◽  
Salt Bath ◽  
Dip Coating ◽  
Time Range ◽  
Dual Phase ◽  
Dual Phase Steels ◽  
Heating And Cooling ◽  
Temperature Regimes ◽  
Hot Rolled

The microstructure and texture of rolled and annealed dual-phase steels with 0.147 wt. % C, 1.868 wt. % Mn, and 0.403 wt. % Si were analyzed using SEM, EDX, and EBSD. Hot rolled sheets showed a ferritic-pearlitic microstructure with a pearlite volume fraction of about 40 % and ferrite grain size of about 6 µm. Ferrite and pearlite were heterogeneously distributed at the surface and distributed in bands at the center of the sheets. The hot rolled sheets revealed a through-thickness texture inhomogeneity with a plane-strain texture with strong α-fiber and γ-fiber at the center and a shear texture at the surface. After cold rolling, the ferrite grains showed elongated morphology and larger orientation gradients, the period of the ferrite-pearlite band structure at the center of the sheets was decreased, and the plane-strain texture components were strengthened in the entire sheet. Recrystallization, phase transformation, and the competition of both processes were of particular interest with respect to the annealing experiments. For this purpose, various annealing techniques were applied, i.e., annealing in salt bath, conductive annealing, and industrial hot-dip coating. The sheets were annealed in the ferritic, intercritical, and austenitic temperature regimes in a wide annealing time range including variation of heating and cooling rates.

scholarly journals The Investigation of Effects of Temperature and Nanoparticles Volume Fraction on the Viscosity of Copper Oxide-ethylene Glycol Nanofluids

2017 ◽  
Author(s):  
Mohammad Hemmat Esfe
Keyword(s):  
Ethylene Glycol ◽  
Copper Oxide ◽  
Volume Fraction ◽  
Relative Viscosity ◽  
Experimental Results ◽  
Different Temperatures ◽  
Nanoparticles Volume Fraction ◽  
Effects Of Temperature ◽  
Nanofluid Viscosity ◽  
Experimental Values

In the present article, the effects of temperature and nanoparticles volume fraction on the viscosity of copper oxide-ethylene glycol nanofluid have been investigated experimentally. The experiments have been conducted in volume fractions of 0 to 1.5 % and temperatures from 27.5 to 50 °C. The shear stress computed by experimental values of viscosity and shear rate for volume fraction of 1% and in different temperatures show that this nanofluid has Newtonian behaviour. The experimental results reveal that in a given volume fraction when temperature increases, viscosity decreases, but relative viscosity varies. Also, in a specific temperature, nanofluid viscosity and relative viscosity increase when volume fraction increases. The maximum amount of increase in relative viscosity is 82.46% that occurs in volume fraction of 1.5% and temperature of 50 °C. Some models of computing nanofluid viscosity have been suggested. The greatest difference between the results obtained from these models and experimental results was down of 4 percent that shows that there is a very good agreement between experimental results and the results obtained from these models.

Sign in / Sign up

Export Citation Format

Share Document