Microstructure and mechanical properties of Ti‐6Al‐4V produced by electron beam melting of pre‐alloyed powders

Emerald - Tập 15 Số 3 - Trang 171-178 - 2009
Luca Facchini1, Emanuele Magalini2, Pierfrancesco Robotti2, Alberto Molinari1
1Department of Materials Engineering and Industrial Technologies, University of Trento, Trento, Italy
2Eurocoating SPA, Ciré di Pergine, Italy

Tóm tắt

Purpose

The purpose of this paper is the microstructural and mechanical characterization of a biomedical Ti‐6Al‐4V alloy produced by electron beam melting, and the study of the stability of the as‐built microstructure upon heat treatment.

Design/methodology/approach

Ti‐6Al‐4V alloy produced by electron beam melting has been mechanically characterized through tensile and fatigue testing. Its microstructure has been investigated by optical observation after etching and by X‐ray diffractometry analysis. The stability of the microstructure of the as‐built material has been deepened carrying out suitable heat treatments, after an analysis by dilatometry test.

Findings

The microstructure of a Ti‐6Al‐4V alloy produced by electron beam melting has a very fine and acicular morphology, because of the intrinsically high‐solidification rate of the process. This microstructure is very stable, and the traditional thermal treatments cannot modify it; the microstructure changes significantly only when an amount of strain is introduced in the material. However, the mechanical properties of the alloy produced by electron beam melting are good.

Originality/value

The paper provides evidence of the microstructural stability of the material produced by electron beam melting. Even if the microstructure of the as‐built material is not recommended by the specific ISO standard, the related mechanical properties are fully satisfactory. This is a significant indication from the point of view of the production of Ti‐6Al‐4V orthopaedic and dental prostheses by electron beam melting.


Tài liệu tham khảo

ASM Metals Handbook (1985a), Heat Treating, 9th ed, Vol. 4, American Society for Metals, Metals Park, OH, pp. 763‐74. ASM Metals Handbook (1985b), Properties and Selection: Stainless Steels, Tool Materials and Special‐Purpose Metals, 9th ed, Vol. 3, American Society for Metals, Metals Park, OH. Bourell, D., Wohlert, M., Harlan, N., Das, S. and Beaman, J. (2002), “Powder densification maps in selective laser sintering”, Advanced Engineering Materials, Vol. 9 No. 4, pp. 663‐9. Cormier, D., Harrysson, O. and West, H. (2002), “Characterization of H13 steel produced via electron beam melting”, Rapid Prototyping Journal, Vol. 10 No. 1, pp. 35‐41. Facchini, L., Magalini, E., Robotti, P. and Molinari, A. (2007), “Microstructural and mechanical characterization of Ti‐6Al‐4V biomedical components produced by electron beam sintering”, working paper, Proceedings of the 21st European Conference on Biomaterials, Brighton, UK, 10 September. Gil Mur, F.X., Rodríguez, D. and Planell, J.A. (1996), “Influence of tempering temperature and time on the α′‐Ti‐6Al‐4V martensite”, Journal of Alloy and Compounds, Vol. 234, pp. 287‐9. Hollander, D.A., von Walter, M., Wirtz, T., Sellei, R., Schmidt‐Rohlfing, B., Paar, O. and Erli, H. (2006), “Structural, mechanical and in‐vitro characterization of individually structured Ti‐6Al‐4V produced by direct laser forming”, Biomaterials, Vol. 27, pp. 955‐63. Jovanović, M.T., Tadić, S., Zec, S., Mišković, Z. and Bobić, I. (2006), “The effect of annealing temperatures and cooling rate on microstructure and mechanical properties of investment cast Ti‐6Al‐4V alloy”, Materials and Design, Vol. 27, pp. 192‐9. Kobryn, P.A. and Semiatin, S.L. (2003), “Microstructure and texture evolution during solidification processing of Ti‐6Al‐4V”, Journal of Materials Processing Technology, Vol. 135, pp. 330‐9. Kubiak, K. and Sieniawski, J. (1998), “Development of the microstructure and fatigue strength of two phase titanium alloys in the processes of forging and heat treatment”, Journal of Materials Processing Technology, Vol. 78, pp. 117‐21. Leyens, C. and Peters, M. (2003), Titanium and Titanium Alloys, Wiley‐Vch, Weinheim. Malinov, S., Sha, W., Guo, Z., Tang, C.C. and Long, A.E. (2002), “Synchrotron X‐ray diffraction study of the phase transformations in titanium alloys”, Materials Characterization, Vol. 48, pp. 279‐95. Mitchell, A. (1999), “The electron beam melting and refining of titanium alloys”, Materials Science and Engineering, Vol. A263, pp. 217‐23. Over, C., Meiners, W., Wissenbach, K., Hutfless, J. and Lindemann, M. (2003), “Rapid manufacturing of metal parts and tools using laser melting”, Proceedings of the Second International WLT‐Conference on Lasers in Manufacturing, Munich, Germany, June. Ping Li, J., de Wijn, J.R., van Blitterswijk, C.A. and de Groot, K. (2006), “Porous Ti6Al4V scaffold directly fabricating by rapid prototyping: preparation and in‐vitro experiment”, Biomaterials, Vol. 27, pp. 1223‐35. Ponader, S., Vairaktaris, E., Heinl, P., von Wilmowsky, C., Rottmair, A., Körner, C., Singer, R.F., Holst, S., Schlegel, K.A., Neukam, F.W. and Nkenke, E. (2007), “Effect of topographical surface modifications of electron beam melted Ti‐6Al‐4V titanium on human fetalosteoblasts”, Journal of Biomedical Materials Research Part A, Vol. 84A No. 4, pp. 1111‐9. Semiatin, S.L., Stefansson, N. and Doherty, R.D. (2005), “Prediction of the kinetics of static globularization of Ti‐6Al‐4V”, Metallurgical and Materials Transactions A, Vol. A36, pp. 1372‐6. Wirtz, T., von Walter, M., Schulz, O. and Wissenbach, K. (2003), “New possibilities for the design and manufacturing of bone implants with external and internal functional architecture”, Proceedings of the Second International WLT‐Conference on Lasers in Manufacturing, Munich, Germany, June.