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ANALYSISOFSTEELSVM339B, depending on the testing tempera-ture. The reason is perhaps, as explained ear-lier, air cooling has more detrimental effect ontoughness, most likely related to Nb precipita-tion.CONCLUSIONSIn conclusion, the mechanical properties andmicrostructure were investigated to find outthe suitability of the nickel-free manganesesteels to be used at low temperatures. Theexperimental results are summarised below.1. It is clear that VM339A is tougher thanVM339B. It has higher impact resistance, forexample 61 J at -20°C in the as quenched con-dition. The alloying elements such as carbon,titanium and aluminium in alloy VM339Bmake the alloy more brittle. These elementshave significant effect on the hardness of thealloy.2. The tempering at 450oC up to 100 hoursdoes not affect the toughness of the alloys sig-nificantly. This is an added advantage whencompared with other cryogenic alloys thatneed a precise heat treatment and tempering.A further study is required to substantiate thatthe nickel free steels form a potential candi-date for cryogenic applications. These alloysare cheaper than the present 9% nickel alloys.It is found from this research that temperinghas no effect on the alloys, which may be use-ful for welding works. Therefore, weldingeffects can be investigated under hot and coldworking condition to study the suitability forthe applications.REFERENCES1.Roberts, M. J., Owen, W. S. The strength of martensitic iron-nickel alloys. ASM Trans. Quart. 60:687-692, 1967.2.Floreen, S., Haynes, H. W., Devine, T. M. Cleavage initiationin Fe-Ni alloys. Metall. Trans. 2:1403-1406, 1971.3.Avery, R. E., Parsons, D. Welding stainless and 9% nickelsteel cryogenic vessels. Welding Journal 74(11):45-50, 1995.4.Oshima, T., Habara, Y., Kuroda, K. Efforts to save nickel inaustenitic stainless steels. ISIJ Int. 47, 359-364, 2007.5.Qiu, C. M., Wang, Y. F., Yu, J. Effect of asynchronous rollingon wear-resisting performance of high manganese steel.Adv. Mater. Res. 146-147:340-344, 2011.6.Holden, A., Bolton, J. D., Petty, E. R. Structure and propertiesof iron-manganese alloys. J. Iron Steel Inst. 209, 721-728,1971.7.Nikbakht, F., Nasim, M., Davies, C., Wilson, E. A., Adrian, H.Isothermal embrittlement of Fe-8Mn alloys at 450°C. Mater.Sci. Technol. 26:552-558, 2010.8.Roberts, M. J. Effect of transformation substructure on thestrength and toughness of Fe-Mn alloys. Metall. Trans.1:3287-3294, 1970.9.Vaynman, S., Isheim, D., Kolli, R.P., Bhat, S.P., Seidman, D.N.,Fine, M.E., 2008. High-strength low-carbon ferritic steelcontaining Cu-Fe-Ni-Al-Mn precipitates. Metall. Mater.Trans. A 39:363-373, 2008.10.Sathiya, P., Aravindan, S., Ajith, P. M., Arivazhagan, B., Haq,A. N. Microstructural characteristics on bead on platewelding of AISI 904 L super austenitic stainless steel usinggas metal arc welding process. Int. J. Eng. Sci. Technol.2(6):189-199, 2010.11.Berns, H., Theisen, W. Ferrous Materials: Steel and Cast Iron,Springer, Berlin, pp. 1-418, 2008.12.Subramanyam, D. K., Swansiger, A. E., Avery, H. S. Austeniticmanganese steels. In Properties and Selection: Irons, Steels,and High-Performance Alloys, vol. 1, ASM Handbook. ASMFigure 1: Scanning electron microscope images of the fracture surface of alloy VM339A, 850oC for1 h, water quenched, and then impact tested at 20oC: mainlyductile failure, impact energy 71 joules. (a) Low magnification. (b) High magnification. MICROSCOPY AND ANALYSISNOVEMBER 201119Figure 2: Scanning electron microscope images of the fracture surface of alloy VM339B, 850oC for1 h, water quenched, and then impact tested at 20oC: mainlyductile failure, impact energy 54 joules. (a) Low magnification. (b) High magnification.Figure 3: Charpy impact energy as a function of specimen temperature at testing for the Fe-8.46%Mn-0.24%Nb-0.038%C alloy.International, Materials Park, OH, pp. 822-840, 1990.13.Bolton, J. D., Petty, E. R., Allen, G. B. The mechanicalproperties of ??-phase low-carbon Fe-Mn alloys. Metall.Trans. 2:2915-2923, 1971.14.Nasim, M., Edwards, B. C., Wilson E. A. A study of grainboundary embrittlement in an Fe-8%Mn alloy. Mater. Sci.Eng. A 281:56-67, 2000.15.Wilson, E. A., Ghosh, S. K., Scott, P. G., Hazeldine, T. A.,Mistry, D. C., Chong, S. H. Low cost grain refined steels asalternative to conventional maraging grades. Mater.Technol. 23:1-8, 2008.16.Nasim, M., Wilson E. A. The effect of thermal cycling on theimpact toughness of an Fe-8Mn alloy. In PhaseTransformations, Vol. 1, The Institution of Metallurgists,York, pp. v21-v25, 1979.©2011 John Wiley & Sons, Ltdababcone-shaped dimpletearing

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