Relation Between Microstructures and Constitutive Behavior of Advanced Tempered Martensitic Steels

2001 ◽  
Vol 679 ◽  
Author(s):  
Philippe Spätig ◽  
Robin Schäublin ◽  
Max Victoria
Keyword(s):  
Strain Hardening ◽  
Prior Austenite ◽  
Martensitic Steels ◽  
Heterogeneous Distribution ◽  
Austenite Grain ◽  
Transmission Electron ◽  
Dislocation Mechanics ◽  
Distribution Of Dislocations ◽  
Prior Austenite Grain ◽  
Dislocation Path

ABSTRACTIn an effort to better understand the plasticity of the tempered martensitic steels, the strain-hardening of two 7-9Cr steels is examined in terms of dislocation mechanics. It is shown that, over the temperature range investigated (173K-523K), the strain-hardening as a function of stress can be described by an equation taking account the dislocation storage and annihilation. The model of strain-hardening used in this study is based on the original Kocks description of the dislocation density evolution with plastic strain but the heterogeneous distribution of dislocations resulting from the lath boundaries and prior austenite grain boundaries is taking into account. The effect of stress and temperature on the storage and annihilation is discussed. The relation between the determined mean dislocation path associated to the heterogeneous lath dislocation structure and the transmission electron microscope observations performed on the two different steels is outlined.

scholarly journals Microstructure of Z-Phase Strengthened Martensitic Steels: Meeting the 650°C Challenge

2016 ◽  
Vol 879 ◽  
pp. 1147-1152 ◽  
Author(s):  
Fang Liu ◽  
Masoud Rashidi ◽  
John Hald ◽  
Lutz Reißig ◽  
Hans Olof Andrén
Keyword(s):  
Electron Microscopy ◽  
Atom Probe Tomography ◽  
Prior Austenite ◽  
Atom Probe ◽  
Martensitic Steels ◽  
Austenite Grain ◽  
Transmission Electron ◽  
Governing Factor ◽  
The Impact ◽  
Prior Austenite Grain

We studied three series of Z-phase strengthened steels using scanning electron microscopy, transmission electron microscopy, and atom probe tomography to reveal the detailed microstructure of these steels. In particular, the phase transformation from M(C,N) to Z-phase (CrMN) was studied. Carbon content in the steels is the governing factor in this transformation. The impact toughness of some test alloys was rather low. This is attributed to the formation of a continuous W-rich film along prior austenite grain boundaries. Cu and C addition to the test alloys changed Laves phase morphology to discrete precipitates and improved toughness dramatically. BN particles were found in some steels. Formation of BN is directly linked to the B concentration in the steels.

Strengthening and Toughening Mechanisms in Martensitic Steel

2014 ◽  
Vol 922 ◽  
pp. 350-355 ◽  
Author(s):  
Shane C. Kennett ◽  
Kip O. Findley
Keyword(s):  
Prior Austenite ◽  
Controlled Rolling ◽  
Recrystallization Temperature ◽  
Low Carbon ◽  
Martensitic Steels ◽  
Toughening Mechanisms ◽  
Austenite Grain Size ◽  
Direct Quenching ◽  
Austenite Grain ◽  
Prior Austenite Grain

Low carbon martensitic steels are often produced by reaustenitizing and quenching (RA/Q). Direct quenching (DQ) has gained interest in the past few decades and requires quenching immediately after working above or below the austenite recrystallization temperature to form martensitic microstructures. In the current study, microalloyed ASTM A514 steel is used to produce martensite from either equiaxed or pancaked prior austenite grain (PAG) microstructures. The equiaxed PAG conditions simulate microstructures produced by RA/Q and the pancaked PAG conditions simulate microstructures produced by controlled rolling (CR) before DQ. Controlled rolling followed by DQ was simulated with double hit compression in a Gleeble® 3500. The prior austenite grain size (PAGS) was varied between 9 and 75 μm prior to controlled rolling. The strengthening and toughening mechanisms are being investigated in the as-quenched (AsQ), low temperature tempered (LTT: 200 °C), and high temperature tempered (HTT: 600 °C) conditions. The equiaxed PAG condition has a Hall-Petch (H-P) relationship between yield strength (or microhardness) and PAGS in the AsQ condition. There is not a H-P relationship between PAGS and microhardness in the CR-DQ conditions. The CR-DQ conditions generally exhibit higher microhardness than the RA/Q conditions with similar PAGS, with the most significant differences in the larger PAGS conditions. Toughness was only measured in the equiaxed PAG conditions. The smallest PAGS has the lowest ductile-to-brittle transition temperature (DBTT) with the highest strength in the AsQ and LTT conditions. The smallest PAGS has the lowest DBTT and the lowest strength in the HTT condition.

Effect of prior austenite grain size on the abrasive wear resistance of ultra-high strength martensitic steels

Wear ◽  
2020 ◽  
Vol 454-455 ◽  
pp. 203336
Author(s):  
Oskari Haiko ◽  
Vahid Javaheri ◽  
Kati Valtonen ◽  
Antti Kaijalainen ◽  
Jaakko Hannula ◽  
...  
Keyword(s):  
Grain Size ◽  
Wear Resistance ◽  
Prior Austenite ◽  
High Strength ◽  
Abrasive Wear Resistance ◽  
Martensitic Steels ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

scholarly journals A New Systematic Approach Based on Dilatometric Analysis to Track Bainite Transformation Kinetics and the Influence of the Prior Austenite Grain Size

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 324
Author(s):  
David San-Martin ◽  
Matthias Kuntz ◽  
Francisca G. Caballero ◽  
Carlos Garcia-Mateo
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Prior Austenite ◽  
Bainitic Transformation ◽  
Transformation Rate ◽  
Transformation Kinetics ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

This investigation explores the influence of the austenitisation heat treatment and thus, of the prior austenite grain size (PAGS), on the kinetics of the bainitic transformation, using as A case study two high-carbon, high-silicon, bainitic steels isothermally transformed (TIso = 250, 300, 350 °C), after being austenised at different temperatures (γTγ = 925–1125 °C). A methodology, based on the three defining dilatometric parameters extracted from the derivative of the relative change in length, was proposed to analyse the transformation kinetics. These parameters are related to the time to start bainitic transformation, the time lapse for most of the transformation to take place and the transformation rate at the end of the transformation. The results show that increasing the PAGS up to 70 µm leads to an increase in the bainite nucleation rate, this effect being more pronounced for the lowest TIso. However, the overall transformation kinetics seems to be weakly affected by the applied heat treatment (γTγ and TIso). In one of the steels, PAGS > 70 µm (γTγ > 1050 °C), which weakly affects the progress of the transformation, except for TIso = 250 °C, for which the enhancement of the autocatalytic effect could be the reason behind an acceleration of the overall transformation.

A quantitative atom probe study of the Nb excess at prior austenite grain boundaries in a Nb microalloyed strip-cast steel

2012 ◽  
Vol 60 (13-14) ◽  
pp. 5049-5055 ◽  
Author(s):  
Peter J. Felfer ◽  
Chris R. Killmore ◽  
Jim G. Williams ◽  
Kristin R. Carpenter ◽  
Simon P. Ringer ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Prior Austenite ◽  
Cast Steel ◽  
Atom Probe ◽  
Austenite Grain ◽  
Strip Cast ◽  
Prior Austenite Grain

Nb segregation at prior austenite grain boundaries and defects in high strength low alloy steel during cooling

2017 ◽  
Vol 115 ◽  
pp. 165-169 ◽  
Author(s):  
Xianglong Li ◽  
Ping Wu ◽  
Ruijie Yang ◽  
Shoutian Zhao ◽  
Shiping Zhang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Alloy Steel ◽  
Prior Austenite ◽  
High Strength ◽  
Low Alloy Steel ◽  
Austenite Grain ◽  
Prior Austenite Grain
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