scholarly journals The Effects of Prior Austenite Grain Refinement on Strength and Toughness of High-Strength Low-Alloy Steel

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 28
Author(s):  
Xiucheng Li ◽  
Guangyi Lu ◽  
Qichen Wang ◽  
Jingxiao Zhao ◽  
Zhenjia Xie ◽  
...  
Keyword(s):  
Brittle Fracture ◽  
Fracture Surface ◽  
Alloy Steel ◽  
Prior Austenite ◽  
Low Alloy Steel ◽  
High Angle ◽  
Block Boundary ◽  
Microstructure Refinement ◽  
Austenite Grain ◽  
Prior Austenite Grain

The effects of prior austenite grain (PAG) refinement on the mechanical properties of bainitic/martensitic steels not only come from itself, but also have more complex effects by affecting the substructure formed by coherent transformation. In this study, the samples of a low-alloy steel were water quenched from different austenitizing temperatures and the bainitic/martensitic microstructures with different PAG sizes were obtained. Electron back-scattered diffraction was used to characterize the microstructure and different types of boundaries were identified and quantitatively analyzed. The tensile tests and series temperature Charpy impact tests of different heat treatment were also carried out and comprehensively analyzed with microstructure characterization works. The results show that the uniform refinement of prior austenite grain can increases the density of packet boundary and block boundary, which leads to microstructure refinement with higher density of high-angle grain boundaries with misorientation >45°. The contribution of this microstructure refinement to toughness is significant, but its contributions to strength and elongation are relatively limited. Compared to uniform refined PAG, if the PAGs are mixed crystal, the density of block boundary will be reduced, which leads to a lower density of the high-angle boundary with misorientation >45° and the positive effects of microstructure refinement on toughness improvement are weakened. The observation of fracture surface of impact specimens indicates that refining the PAG can delay the tendency of brittle fracture with the decrease in test temperature, and even in the case of brittle fracture, the cleavage facet of the fracture surface is relatively smaller. This result also verifies that PAG refinement can effectively improve toughness by inhibiting cleavage fracture.

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

Carbide composition changes in a low alloy steel

1990 ◽  
Vol 48 (2) ◽  
pp. 420-421
Author(s):  
Z. Larouk ◽  
R. Pilkington
Keyword(s):  
Alloy Steel ◽  
Prior Austenite ◽  
Creep Behaviour ◽  
Low Alloy Steel ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Heat Treated ◽  
Prior Austenite Grain Size ◽  
Composition Changes ◽  
Prior Austenite Grain

Durehete 1055 is a 1%Cr1%Mo¾%V low alloy steel used as bolting material at 565°C. It also contains 0.08%Ti and 0.005%B to improve the creep behaviour, but deleterious properties have been reported, due to the presence of trace elements such as P and Sn. The present work has been an attempt to understand this problem by examining three vacuum melted casts of this steel containing selected additions (wt.%) of 1) 0.08 Ti, 2) 0.08 Ti and 0.02 P; and 3) 0.08 Ti and 0.02 Sn. The material was heat treated for 2h at 980°C, W.Q., and tempered 4h at 680°C, giving a prior austenite grain size of 8 μm. Specimens were then crept for various times at 565°C. After test, metallographic samples were prepared from both the gauge lengths (stressed) and heads (unstressed) to enable the production of carbon extraction replicas. These replicas were examined in a Philips 400T electron microscope, and carbides analysed using EDS.

The Grain Boundary Embrittlement and De-Embrittlement Mechanism in Age Hardenable Fe-Ni-Ti Steels

2006 ◽  
Vol 118 ◽  
pp. 469-474 ◽  
Author(s):  
Min Saeng Kim ◽  
Yoon Uk Heo ◽  
Hu Chul Lee
Keyword(s):  
Electron Microscopy ◽  
Fracture Surface ◽  
Grain Boundary ◽  
Vickers Hardness ◽  
Prior Austenite ◽  
Aging Treatment ◽  
Austenite Grain ◽  
Grain Boundary Embrittlement ◽  
Prior Austenite Grain ◽  
Boundary Embrittlement

The strengthening and grain boundary embrittlement in an age hardenable Fe-20.4Ni-2.8Ti ternary alloy were investigated. The Vickers hardness and tensile properties were evaluated using a Vickers hardness and tensile tester and the precipitation behavior during aging treatment was observed by transmission electron microscopy (TEM). The fracture surface was observed using low voltage field emission scanning electron microscopy (FE-SEM). The alloy showed typical aging hardening curves with a single aging peak near 640 HV, but was found to undergo severe grain boundary embrittlement from the initial stages of aging treatment. Many fine particles were observed at the grain boundary fracture surface. These particles were identified as η-Ni3Ti precipitates nucleated at the prior austenite grain boundaries. When the aging time was extended, austenite nucleated at the interface of the matrix and η-Ni3Ti precipitate. With the formation of the austenite, the tensile ductility was recovered. It was concluded that the precipitation of the η-Ni3Ti intermetallic particles at the prior austenite grain boundaries and formation of the austenite are the main causes of embrittlement and subsequent de-embrittlement in aging of this alloy.

Sign in / Sign up

Export Citation Format

Share Document