scholarly journals Effects of the Austenite Grain Size and Deformation in the Unrecrystallized Austenite Region on Bainite Transformation Behavior and Microstructure.

1995 ◽  
Vol 35 (8) ◽  
pp. 1020-1026 ◽  
Author(s):  
Sadahiro Yamamoto ◽  
Hiroyasu Yokoyama ◽  
Katsumi Yamada ◽  
Masakazu Niikura
Keyword(s):  
Grain Size ◽  
Transformation Behavior ◽  
Bainite Transformation ◽  
Austenite Grain Size ◽  
Austenite Grain

scholarly journals Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 988 ◽  
Author(s):  
Liangyun Lan ◽  
Zhiyuan Chang ◽  
Penghui Fan
Keyword(s):  
Grain Size ◽  
Prior Austenite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Bainite Transformation ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

The simulation welding thermal cycle technique was employed to generate different sizes of prior austenite grains. Dilatometry tests, in situ laser scanning confocal microscopy, and transmission electron microscopy were used to investigate the role of prior austenite grain size on bainite transformation in low carbon steel. The bainite start transformation (Bs) temperature was reduced by fine austenite grains (lowered by about 30 °C under the experimental conditions). Through careful microstructural observation, it can be found that, besides the Hall–Petch strengthening effect, the carbon segregation at the fine austenite grain boundaries is probably another factor that decreases the Bs temperature as a result of the increase in interfacial energy of nucleation. At the early stage of the transformation, the bainite laths nucleate near to the grain boundaries and grow in a “side-by-side” mode in fine austenite grains, whereas in coarse austenite grains, the sympathetic nucleation at the broad side of the pre-existing laths causes the distribution of bainitic ferrite packets to be interlocked.

Effect of Austenite Grain Size on the Mechanical Properties in Air-Cooled 0.1C-5Mn Martensitic Steel

2014 ◽  
Vol 783-786 ◽  
pp. 1027-1032 ◽  
Author(s):  
Toshihiro Hanamura ◽  
Shiro Torizuka ◽  
Soutaro Tamura ◽  
Shohei Enokida ◽  
Hiroshi Takech
Keyword(s):  
Grain Size ◽  
True Strain ◽  
Air Cooling ◽  
Transformation Behavior ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Lath Width ◽  
True Fracture ◽  
Strength And Ductility ◽  
Martensite Structure

In 0.1C-5Mn steels, 5%Mn addition increases hardening ability and makes 100% martensitic transformation even in air cooling without water quenching. Their Ms and Mf temperatures are in the range of 350-250°C, and subzero treatment is not needed. This makes it possible to measure Ms and Mf temperatures accurately by dilatometry. Utilizing a newly developed experimental technique that makes it possible to examine phase transformation behavior and conduct tensile testing with the same specimen, we examined these relationships with identical specimens and obtained the following results. Ms temperature decreases as much as 40 K with a decrease in austenite grain size from 254 to 30 m. Regarding martensite structure, the packet size and the block length decrease, while the lath width does not change, with the refinement of austenite grain size by about one tenth. True stress - true strain curves obtained up to fracture elucidates that the austenite refinement substantially improves true fracture strength and greatly increases true fracture strain of martensite, potentially invalidating the conventional concept of a trade-off balance between strength and ductility.

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