Transmission Electron Microscopy of RSP FE/CR/MN/MO/C Alloy
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TRANSMISSION ELECTRON MICROSCOPY OF RSP FE/CR/MN/MO/C ALLOY 3. 3. RAYMENT AND G. THOMAS Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720 ABSTRACT Rapid solidification processing (RSP) has been carried out on an Fe/Cr/Mn/Mo/C alloy using both electron-beam melting and pistonand-anvil techniques. Preliminary TEM results show RSP produces a refined duplex microstructure of ferrite and martensite, with a typical ferrite grain size of 0.50 - 3.0 microns. This RSP microstructure is significantly different from that observed in the conventionally austenitized and quenched alloys--a lath martensitic microstructure with thin films of retained interlath austenite. The morphological change produced by RSP is accompanied by an increase in hardness from 48R to 61R (- 480 to 720 VHN). It is intended to use electron-beam specimens to examine the potential beneficial effect of RSP upon sliding wear resistance and, by careful TEM studies, it will be possible to characterize the microstructure and its role in the hardness and wear behavior of the RSP alloy. INTRODUCTION Over the past few years, an extensive research program has been carried out at Berkeley on the microstructural and mechanical properties of Fe/Cr/Mn/C based alloys [1,2 ]. By optimizing both alloying element content and heat treatment, a refined microstructure has been produced with a corresponding high strength and high toughness. These properties are desirable for many engineering applications, in particular, mining and mineral processing, in which a strong, tough material is required with good wear resistance.
The aim of the present work is to try and improve the sliding wear resistance
of an Fe/Cr/Mn/Mo/C alloy, through RSP, and to characterize the wear resistance as a function of microstructure. This paper represents a preliminary transmission electron microscopy (TEM) examination of the RSP alloy. EXPERIMENTAL DETAILS The alloy, Fe-3wt%Cr-2wt%Mn-0.5wt%Mo-0.3wt%C which was supplied by Daido Steel company of Japan, was air melted into 201b ingots and subsequently rolled to I" thick by 25" wide bars. Homogenization of these bars occurred at 12009C for 24 hrs. Specimens suitable for rapid solidification were cut from these bars. Prior to electron-beam melting, specimens were austenitized at 1100°C for 1 hr, oil-quenched and then tempered at 2009C for 1 hr with a final brine quench. This heat treatment was carried out in order for the substrate material to have the microstructure found previously to give the optimum combination of mechanical properties [2]. Rapid solidification was performed using a piston-and-anvil technique and electronbeam melting technique. Both techniques have been adequately described elsewhere [3,4]. The operational parameters for the electron-beam melting were 60 cycles beam frequency, 300 watts beam power, 5cm/sec linear velocity and 0.3mm focussed beam diameter. Microhardness testing was carried out using a Leitz microhardness tester with a Vickers diamond indentor
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