Copper-Base Alloys Processed by Rapid Solidification and Ion Implantation
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COPPER-BASE ALLOYS PROCESSED BY RAPID SOLIDIFICATION AND ION IMPLANTATION J.V. Wood and C.J. Elvidge, Department of Materials,
The Open University,
Milton Keynes, UK. E. Johnson, A. Johansen, L. Sarholt-Kristensen and 0. Henriksen, Physics Laboratory II, University of Copenhagen, Denmark. ABSTRACT Alloys of Cu-Sn and Cu-B have been processed by both melt spinning and ion implantation. In some instances (eg Cu-Sn alloys) rapidly solidified ribbons have been subjected to further implantation. This paper describes the
similarities and differences in structure of materials subjected to a dynamic and contained process. For example in Cu-B alloys (up to 2wt% Boron) extended solubility is found in implanted alloys which is not present to the same degree in rapidly solidified alloys of the same composition. Likewise the range and nature of the reversible martensitic transformation is different in both cases as examined by electron microscopy and differential scanning calorimetry. INTRODUCTION The production of extended solubilities and non-equilibrium phases (including amorphous structures) are characteristics of both rapid solidification and ion implantation. This paper presents some preliminary data for copper alloys processed by both techniques. Previous work on copper alloys has concentrated either on their 'model' properties for analysing various rapid solidification techniques (1)or has been confined to compositions found to display a shape memory effect (2-4). In the latter instance the temperature of the martensitic transformation associated with the shape memory behaviour, is lowered in comparison with cast and wrought products. This depression is linked with retained defect concentrations and the refinement of grain size. In this investigation we report on two simple binary copper alloys: Cu-B and Cu-Sn which have been processed by both techniques. The first represents an investigation into a system where boron can act substitutionally and interstially and extensions in solid solubility would be expected. Cu-Sn by contrast is a system which has a number of complex phase boundaries and for compositions around 14 at.% there is a potential for formation of metastable martensite. ION IMPLANTATION All experiments for Cu-Sn were undertaken on pure Cu single crystal spark machined into discs with surface normal. Implantations at random incidencg were performed at room j•m2ratuye in a heavy ion isotope separator below 2.10 Pa. A beam flux of 3.10 m sec ensured that the samples were not heated during implantation. Analyses were made by combining Rutherford backscattering (RBS) and channeling techniques. For Cu-B, single crystal and polycrysMllIne sampleý 1 of 2 Cu were implanted with 40 keV boron ions to fluences of 5.10 l and 8 210l m . Nuclear reaction analyses were performed using the reaction 5 B(po) 8Be which has two resonance peaks. The broad peak at 660 keV was used for latti&e location analysis of the implanted boron atoms. The lower peak at 163 keV which is very narrow,was used to determine boron implant conce
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