Formation of (Ferrite+Cementite) Microduplex Structure by Warm Deformation in High Carbon Steels

2007 ◽  
Vol 539-543 ◽  
pp. 155-160 ◽  
Author(s):  
Tadashi Furuhara ◽  
Takuto Yamaguchi ◽  
Shoji Furimoto ◽  
Tadashi Maki
Keyword(s):  
Dynamic Recrystallization ◽  
Critical Strain ◽  
Dynamic Recovery ◽  
Carbon Steels ◽  
Duplex Structure ◽  
High Carbon ◽  
Tempered Martensite ◽  
Warm Deformation ◽  
Microstructure Change ◽  
Microduplex Structure

The microstructure change by warm deformation in high-carbon steels with different initial ferrite (α) + cementite (θ) duplex microstructures has been examined. Three kinds of initial structures, i.e., pearlite, α+spheroidized θ and tempered martensite, were prepared using Fe-0.8C-2Mn and Fe-1.0C-1.4Cr alloys and compressed by 30-75% at 973K at a strain rate of 5x10-4 s-1. Equiaxed fine α grains, approximately 2μm in diameter and mostly bounded by high-angle boundaries, are formed with spheroidized θ by dynamic recrystallization during compression of the pearlite by 75%. When the (α+θ) duplex structure containing spheroidized θ was deformed, the original α grains become elongated and only subgrains are formed within them by dynamic recovery. For the tempered martensite, equiaxed α grains similar to those in the deformed pearlite were obtained after 50% compression. This indicates that the critical strain needed for the completion of dynamic recrystallization of α is smaller for the tempered martensite than for the other structures.

scholarly journals Microstructure Evolution of Allotropic Materials during Thermomechanical Processing

2012 ◽  
Vol 710 ◽  
pp. 93-100 ◽  
Author(s):  
Cecilia Poletti ◽  
Fernando Warchomicka ◽  
Martina Dikovits ◽  
Simon Großeiber
Keyword(s):  
Phase Transformation ◽  
Dynamic Recrystallization ◽  
Constitutive Equations ◽  
Power Dissipation ◽  
Hot Deformation ◽  
Power Efficiency ◽  
Dynamic Recovery ◽  
Carbon Steels ◽  
Processing Maps ◽  
Strain And Strain Rate

The microstructure developed during hot deformation is the result of deformation mechanisms such as dynamic recovery and dynamic recrystallization. Hot deformation can also result in damage and flow localisation, especially in multiphase metal based materials. Several models have been proposed to correlate the parameters of the deformation process (temperature, strain and strain rate) with the flow behaviour such as the processing maps. They were developed based on the dynamic materials model (DMM) and later a modified DMM introduced some changes in the calculation of the processing maps. The correlation of the relevant microstructural changes with thermodynamic parameters are tested and discussed. The data was obtained by using the Gleeble simulator with in situ quenching facilities. Microstructural studies related to the hot deformation of metals were carried out based on alpha-beta and near beta titanium alloys and on low carbon steels. The results are correlated with the efficiency of power dissipation, and the constitutive equations. In diffusion controlled processes such as dynamic recovery, dynamic recrystallization, phase transformation and pore coarsening are related to high power efficiency, and to low n exponent. The efficiency of power dissipation is more sensitive to the deformation parameters than the constitutive equations for materials with phase transformation.

20#,60Si2Mn,9Cr18MoV Steel Ferrite Area Dynamic Recovery and Recrystallization Research

2013 ◽  
Vol 690-693 ◽  
pp. 197-201
Author(s):  
Liang Li ◽  
Wen Kai Xiao ◽  
Tao Tao Fan ◽  
Zhou Quan Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Dynamic Recovery ◽  
Strain Curve ◽  
Carbon Steels ◽  
Test Machine ◽  
Simulation Test ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Deformation Activation Energy ◽  
Strain Storage

By using the Gleeble - 1500 hot simulation test machine we studied 20#, 60Si2Mn, 9Cr18MoV the three kinds of low, medium and high carbon steels to observe the dynamic recovery and recrystallization of ferrite while in the process of thermoplastic deformation. We calculated the hot deformation activation energy of each kind of steel by combining the stress-strain curve we got in the experiment and the theoretical model of Z parameter. It turns out Q9Cr18MoV<Q20#<Q60Si2Mn. In the meanwhile, microstructure observation through transmission electron microscope shows that the dynamic recrystallization of ferrite is more likely to happen in 9Cr18MoV steel than in 20# steel and in 60Si2Mn steel. These results indicate that the dynamic recrystallization of ferrite is not only determined by stacking fault energy but also closely related with the strain storage energy release degree.

Precipitation at the transformation interface of pearlite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 912-913
Author(s):  
F. A. Khalid ◽  
D. V. Edmonds
Keyword(s):  
Thin Foil ◽  
Carbon Steels ◽  
Model Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Growth Interface ◽  
Medium Carbon ◽  
Interphase Precipitation ◽  
Solution Treated ◽  
Wide Range

The austenite/pearlite growth interface in a model alloy steel (Fe-1lMn-0.8C-0.5V nominal wt%) is being studied in an attempt to characterise the morphology and mechanism of VC precipitation at the growth interface. In this alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the precipitation of VC at the austenite/ferrite interface, which reaction, termed interphase precipitation, occurs in a number of low- carbon HSLA and microalloyed medium- and high- carbon steels. Some observations of interphase precipitation in microalloyed low- and medium- carbon commercial steels are also reported for comparison as this reaction can be responsible for a significant increase in strength in a wide range of commercial steels.The experimental alloy was made as 50 g argon arc melts using high purity materials and homogenised. Samples were solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised at 1300 °C for 15 min. and isothermally transformed at 620 °C for 10-18hrs. and WQ. Specimens of microalloyed commercial steels were studied in either as-rolled or as- forged conditions. Detailed procedures of thin foil preparation for TEM are given elsewhere.

Sintered High Carbon Steels: Effect of Thermomechanical Treatments on their Mechanical and Wear Performance

2008 ◽  
Vol 591-593 ◽  
pp. 271-276 ◽  
Author(s):  
M.A. Martinez ◽  
R. Calabrés ◽  
J. Abenojar ◽  
Francisco Velasco
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Powder Metallurgy ◽  
Thermomechanical Treatment ◽  
Bending Strength ◽  
Carbon Steels ◽  
Tool Steels ◽  
High Carbon ◽  
Wear Performance ◽  
Metallographic Study

In this work, ultrahigh carbon steels (UHCS) obtained by powder metallurgy with CIP and argon sintered at 1150°C. Then, they were rolled at 850 °C with a reduction of 40 %. Finally, steels were quenched at 850 and 1000 °C in oil. In each step, hardness, bending strength and wear performance were evaluated. Obtained results are justified with a metallographic study by SEM. Both mechanical properties and wear resistance are highly favoured with the thermomechanical treatment that removes the porosity of the material. Moreover, final quenching highly hardens the material. The obtained material could be used as matrix for tool steels.

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