Segregation of boron at prior austenite grain boundaries in a quenched martensitic steel studied by atom probe tomography

2015 ◽  
Vol 96 ◽  
pp. 13-16 ◽  
Author(s):  
Y.J. Li ◽  
D. Ponge ◽  
P. Choi ◽  
D. Raabe
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 ◽  
...  

2016 ◽  
Vol 879 ◽  
pp. 1147-1152 ◽  
Author(s):  
Fang Liu ◽  
Masoud Rashidi ◽  
John Hald ◽  
Lutz Reißig ◽  
Hans Olof Andrén

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.


2017 ◽  
Vol 115 ◽  
pp. 165-169 ◽  
Author(s):  
Xianglong Li ◽  
Ping Wu ◽  
Ruijie Yang ◽  
Shoutian Zhao ◽  
Shiping Zhang ◽  
...  

The cavitational mode of failure of prior austenite grain boundaries in bainitic creep-resisting low alloy steels is now well established as a principal factor in the high incidence of cracking problems which has developed on modern power plant in recent years. The microstructural features dominating the cavitation process at the reheat temperature in a ½CMV bainitic steel of high classical residual level have been determined. The prior austenite grain boundaries become zones of comparative weakness ca . 1 pm thick at 700 °C and are incapable of sustaining significant shear loads. Deformation is therefore initiated by a relaxation of load, through a process of prior austenite grain boundary zone shear, from inclined to transverse boundaries such that a concentration of normal stress develops across the latter. The overall deformation is thereafter determined by cavitation of the transverse boundary zones, the necessary inclined boundary displacements being accommodated by further grain boundary zone shear. Transverse boundary cavitation is shown to be an essentially time-independent process of localized ductile microvoid coalescence resulting from the plastic deformation of the boundary zone.


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