ORAL

SESSION: AdvancedMaterialsMonAM-R6	Marquis International Symposium on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development(3rd Intl Symp. on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development)
Mon Oct, 23 2017	Room: Condesa IA
Session Chairs: Jan Seidel; S. Ravi P. Silva; Session Monitor: TBA

12:00: [AdvancedMaterialsMonAM03]
Effect of Heat Treatment Paths on the Microstructure and Mechanical Properties of High Cr Containing Ultrahigh Strength Steels
G.bae Park¹ ; Yunik Kwon¹ ; K.h. Kwon² ; Nack Kim¹ ; ¹POSTECH, Pohang, Korea (Republic of [South] Korea); ²RIST, Pohang, Korea (Republic of [South] Korea);
Paper Id: 112 [Abstract]

Ultrahigh-strength steels are needed in many demanding applications including aircraft landing gears. For such applications, the steels should have high strength, high fracture toughness, and high-stress corrosion cracking resistance. However, most of the commercial alloys such as 4340, 300M, and AerMet100 generally have poor corrosion resistance and require the use of cadmium coating to prevent corrosion, which raises serious problem during maintenance. For the steels to have excellent corrosion resistance, a fairly large amount of Cr is needed in the alloy composition. However, high Cr content in the steels can cause serious problems such as degraded fracture toughness and corrosion resistance due to a possible formation of Cr-containing particles along grain boundaries. In the present study, Fe-Cr-0.2C steels with other additional alloying elements have been subjected to various heat treatment paths such as quenching and tempering (Q&T), quenching and partitioning (Q&P), and austempering. The microstructure has been analyzed by detailed TEM studies and correlated with mechanical properties including stress corrosion cracking resistance for a selected steel.

SESSION: AdvancedMaterialsMonAM-R6	Marquis International Symposium on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development(3rd Intl Symp. on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development)
Mon Oct, 23 2017	Room: Condesa IA
Session Chairs: Jan Seidel; S. Ravi P. Silva; Session Monitor: TBA

15:00: [AdvancedMaterialsMonAM06]
Development of Precipitation Hardened Austenitic High Mn Steels for Automotive Applications
Yunik Kwon¹ ; Nack Kim¹ ; ¹POSTECH, Pohang, Korea (Republic of [South] Korea);
Paper Id: 109 [Abstract]

Recently, there has been a great interest in high strength steels that can improve the performance of automobiles by reducing the fuel consumption and the emission of exhaust gasses. Austenitic high Mn steels usually show high work hardening rate and accordingly excellent combination of ultimate tensile strength and ductility that are suitable for automotive applications. However, in spite of such excellent tensile properties, these austenitic high Mn steels usually show low yield strength as compared to other conventional ferritic high strength steels. Therefore, there is a great need for improving yield strength of austenitic high Mn steels without sacrificing other properties. In the present study, an attempt has been made to improve yield strength by utilizing precipitation hardening as well as grain refinement. Among the possible alloying elements that can induce the precipitation of carbides, V was chosen since it has a relatively large solubility in austenite at high temperatures. The model alloys containing various amounts of Mn, C, and V were fabricated and their microstructure and tensile properties were evaluated after annealing of cold rolled sheets. It shows that the cooling rate after annealing as well as alloy composition have a large effect on precipitation behavior of carbides and accordingly tensile properties. Details of microstructural evolution in these alloys have been investigated by EBSD, SEM, TEM, and 3DAP and correlated with tensile properties.