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Title: Flash® RA – Maximum Strength Steel w/ Retained Austenite Made in <10 Seconds

  1. SFP Works, LLC, Washington Twp, MI (United States)
Publication Date:
Research Org.:
SFP Works, LLC, Washington Twp, MI (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
Report Number(s):
Final Report
DOE Contract Number:
Type / Phase:
Resource Type:
Technical Report
Country of Publication:
United States
36 MATERIALS SCIENCE; Steel; Advanced High Strength Steel; AHSS; Flash Processing; Flash; Bainite

Citation Formats

Cola, Gary M. Flash® RA – Maximum Strength Steel w/ Retained Austenite Made in <10 Seconds. United States: N. p., 2015. Web.
Cola, Gary M. Flash® RA – Maximum Strength Steel w/ Retained Austenite Made in <10 Seconds. United States.
Cola, Gary M. 2015. "Flash® RA – Maximum Strength Steel w/ Retained Austenite Made in <10 Seconds". United States. doi:.
title = {Flash® RA – Maximum Strength Steel w/ Retained Austenite Made in <10 Seconds},
author = {Cola, Gary M},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2015,
month = 3

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  • The relationships between microstructure, mechanical, and fracture properties were investigated for thick sections (up to 15 cm) following air cooling and tempering in a silicon-modified 4340, 300-M. This steel, which has high pearlite hardenability achieves high strength levels after very slow cooling. Slow cooling also leads to high levels of retained austenite (up to 30 percent). Properties were determined for microstructures equivalent to those developed through air cooling and tempering of 2.5, 5.0, 10.0 and 15 cm thick plates. Simulated slow cooling was performed on small specimens to model the thicker sections. Fracture toughness and Charpy V-notch behavior were usedmore » to evaluate fracture properties while both round and flat tensile specimens were used to measure mechanical properties. Emphasis was placed on determining the role of the austenite on these properties. The morphology, amount, and mechanical stability of the austenite were characterized using transmission electron microscopy and magnetic saturation techniques. It was found that the stability of the austenite, which changed with tempering treatment, had a major influence on the fracture properties. Specifically, if the austenite was stable the material had good fracture resistance, while if the austenite was unstable the fracture toughness was poor. Destabilization of the austenite after tempering was found to be associated with tempered martensite embrittlement. Finally, it was found that for 300-M there was an optimum slow cooling rate which led to a good combination of strength, ductility and fracture resistance.« less
  • The purpose of this work was to assess the effects of the amount of retained austenite content on the ductile-to-brittle transition temperature of martensitic precipitation strengthened stainless steels for four different precipitation strengthening systems, one utilizing NiTi strengthening and three utilizing R-phase strengthening. The retained austenite contents in the four systems were varied by varying composition. The austenite content in the NiTi strengthened system was varied by varying the chromium content and the austenite content in the R-phase strengthened Systems was varied by varying the nickel content. The room temperature toughness levels of the NiTi strengthened system were quite lowmore » and it was decided not to pursue this system further. The three R-phase strengthened systems had sufficient room temperature toughness and strength to be of further interest. Of these three systems the primary focus was on the 12Cr/12Co/5Mo system. In this system four alloys, identical except for variations in nickel content, were the primary focus of the work. These alloys achieved, on tempering at 5250 C for 3.16 hours, yield strengths on the order of 210 ksi and ultimate tensile strengths of 235 ksi. The effect of test temperature on the Charpy impact energy was investigated for two tempering temperatures for these four alloys. It was found for both tempering conditions that lower ductile-to-brittle transition temperatures were favored by increasing amounts of austenite in the structure. In fact, the ductile-to-brittle transition temperature was quite low, about -750 C, for the tempered at 5250 C for 3.16 hours microstructure of the alloy in this series which contained the highest nickel and the highest amount of retained austenite after quenching. At this point it is believed the austenite content is an important contributor to the low ductile-to-brittle transition temperature of this microstructure.« less