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: AdvancedMaterialsMonPM-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: Yunik Kwon; Nack Kim; Session Monitor: TBA

14:30: [AdvancedMaterialsMonPM05] Keynote
High Specific Strength Alloys for Sustainable Society
Nack Kim¹ ; ¹POSTECH, Pohang, Korea (Republic of [South] Korea);
Paper Id: 107 [Abstract]

The world currently faces significant challenges in energy conservation and environmental protection. Materials and their manufacturing processes have a pivotal and ubiquitous impact on meeting these global challenges. Among various end-use sectors of energy, the transportation sector is the second in energy consumption and the first in the energy-related CO2 emissions. Therefore, there exists a strong need for the significant improvement in fuel economy and reduction in pollutants emissions of the transportation systems. One of the most effective ways to overcome such problems associated with transportation systems is the use of high strength, lightweight alloys, i.e., high specific-strength alloys, as structural components of vehicles. High specific strength alloys are also important for improving the efficiency of hybrid-type vehicles because they offset the weight of power systems such as batteries and electric motors. This presentation discusses the recent progress in the development of high specific strength alloys, with particular examples on newly developed lightweight steels and Mg alloys.

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.

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

15:30: [AdvancedMaterialsMonAM07]
Effect of Deformation Twins on Recrystallization Behavior of Magnesium Alloy Sheets
Jae H. Kim¹ ; Byeong-chan Suh² ; Ji Hyun Hwang³ ; Myeong-shik Shim¹ ; Nack Kim¹ ; ¹POSTECH, Pohang, Korea (Republic of [South] Korea); ²NIMS, Tsukuba, Japan; ³Pohang University of Science and Technology, Pohang, Korea (Republic of [South] Korea);
Paper Id: 110 [Abstract]

In recent years, there has been a great interest in the weight reduction of automobiles for energy conservation and environmental protection. One of the most effective ways to reduce the weight of vehicles is the use of lightweight materials such as Mg alloys as structural components in vehicles. Mg alloys have the lowest density among commercially available structural alloys and recent studies have shown that some Mg alloys have good mechanical properties comparable to those of Al alloys. However, Mg alloys have a critical shortcoming that needs to be overcome, poor formability at room temperature mainly originated from strong basal texture developed during thermomechanical processing. Although several Mg alloys show random/weak texture and accordingly good room temperature formability, most of such alloys rely on the usage of expensive rare earth elements. In the present work, an attempt has been made to modify the texture of Mg alloys by utilizing deformation twins as nuclei for recrystallization. The main impetus for such approach comes from the idea that various deformation twins formed in Mg alloys have different orientation relationship with the matrix and accordingly can induce the formation of recrystallized grains with different orientations. The orientation relationship between parent grain, deformation twins, and recrystallized grains has been analyzed by ex-situ heating EBSD in both as-rolled and annealed conditions to understand how deformation twins affect the orientation of recrystallized grains.

SESSION: AdvancedMaterialsMonAM-R7	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 IB
Session Chairs: Toshinori Okura; Carlos Enrique Schvezov; Session Monitor: TBA

15:30: [AdvancedMaterialsMonAM07]
Effect of Alloying Element on Deformation Behavior of Binary Magnesium Alloys
Ji Hyun Hwang¹ ; Byeong-chan Suh² ; Jae H. Kim³ ; Myeong-shik Shim³ ; B. J. Lee¹ ; Jaimyun Jung¹ ; H. S. Kim¹ ; Nack Kim³ ; ¹Pohang University of Science and Technology, Pohang, Korea (Republic of [South] Korea); ²NIMS, Tsukuba, Japan; ³POSTECH, Pohang, Korea (Republic of [South] Korea);
Paper Id: 111 [Abstract]

As the lightest of structural alloys, Mg alloys offer significant potential for weight reduction, but have yet to see the significant application in automobiles, particularly in sheet form. One of the major drawbacks preventing such application is their poor formability at room temperature, originating from their strong basal texture and the limited number of slip systems. Therefore, numerous studies have been conducted to improve the formability of Mg alloys by alloy modification and weakening/randomizing the texture. Although the effect of alloying elements on the modification of texture is relatively well understood, the intrinsic effect of alloying elements on the deformation behavior of Mg alloys is not clearly understood yet. The present work is aimed at having a better understanding of the effect of alloying elements on the deformation behavior of Mg alloys. Among various elements utilized in Mg alloys, four representative alloying elements have been chosen; Al and Zn that are most commonly used alloying elements in Mg alloys, Sn that is known to increase ductility and promote significant precipitation hardening in Mg alloys, and Y that represents rare earth elements used in numerous Mg alloys. The binary alloys containing these elements have been cast and subjected to various thermomechanical treatment to have the similar grain size. Their deformation behavior has been analyzed by in-situ tensile test with EBSD, and the result has been compared with the VPSC simulation analysis to identify the role of each alloying element in the deformation behavior.