August 31 st to September 4 th , 2014 L3-71 EXTENDED ABSTRACT Structure Property relationship in High Manganese steels Authors: Dinesh Kumar 1* , S. B. Singh 2 Affiliation: 1,2 Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, India, 721302 dinesh.iitkgp10@gmail.com Abstract: In present work different compositions of high Mn steels is selected with varying carbon (range from 0.15-0.5) content after homogenization and forging of steels at 1150°C for 4 hours. One part part of experiment is done for deformation study and other is for transformation study. Cold rolling, compression and tensile test is done for all steels to check the formation of deformation induced martensite ε and α΄ and quenching test for the formation of thermal induced martensite. It was found in result that ε martensite is useful for enhancing the tensile strength along with elongation as compared to presence of α΄ or ε and α΄ martensite simultaneously. Cold rolling and tensile testing is found to be more pronounced to trigger twinning or martensite formation as compared to compression test. Thus transformation induce higher fraction of martensite as compared with deformation process depending on chemical composition of steels. Key words: ε and α΄ martensite, quenching test, cold rolling, tensile test, compression test 1. Introduction Steels with Mn content (15-30wt%) and alloying elements C (≤0.6wt%), Al(0-3 wt%) and Si(0- 3%) possess high strength and excellent formability due to the formation of extensive deformation twins under mechanical load which leads to formation of deformation twins (Twinning induced plasticity steel (TWIP)) or can go through multiple martensitic transformations such as γ fcc (austenite) →ε hcp (hcp-martensite) →α' bcc (bcc-martensite) depending on stacking fault energy [1-4]. For twinning to occur, it is usually necessary for the steel stacking fault energy (SFE) to be in the range of 18-35 mJ/m2. If the SFE is <18 mJ/m2, twinning is replaced by martensitic transformation. However, if it is >35 mJ/m2, then the slipping processing will be the only mechanism that contributes to the plastic deformation of steel [ 5,6]. In order to understand the stability of austenite and formation of ε and α΄ martensite in high maganese steels, we have taken five different compositions having magnese content (14-25 wt%) and carbon content (0.1-0.35 wt%). One part of the study focuses on the effect of quenching medium on the formation of martensite in these high manganese steels which includes cooling rate and grain size. Second part of the work is concerned with strain induced martensitic transformation during cold rolling, tensile testing and compression testing of forged steels and comparing the stress induced martensite formation during quenching test with strain induced martensitic transformation during straining. Effect of thermal martensite ε and α΄ martensite on mechanical properties is also studied. 2. Materials and Methods High maganese steels were prepared in open casting and cast in a rectangular ingot which was 110mm x 60mm x 25 mm in size. Each ingot was 2.5 kg and chemical composition is listed in table 1. A 25mm thick plate was cut from ingot and homogenizes at 1200ºC for 4 hour than forged the sample for 50% of its initial thickness followed by air cooling.