Alpha case formation mechanism in Ti-6Al-4V alloy investment castings using YFSZ shell moulds

Show simple item record

dc.contributor.author Bauristhene, A.M.
dc.contributor.author Mutombo, Kalenda
dc.contributor.author Stumpf, Waldo E.
dc.date.accessioned 2014-02-28T11:50:37Z
dc.date.available 2014-02-28T11:50:37Z
dc.date.issued 2013-04
dc.description.abstract Ti-64, which accounts for more than 50% of the worldwide titanium tonnage, has found commercial importance in industries requiring components with high specific strength and resistance to corrosion. Investment casting is the preferred production method due to the difficult machinability of the alloy. This study was aimed at investigating the mechanism and the extent of alpha case formation on Ti- 64 components cast using the investment casting method with YFSZ (yttria fully-stabilized zirconia) shell moulds after vacuum induction melting. The extent of the reaction between the mould hot face and the molten metal has been studied by varying parameters such as soaking temperature and mould hot face composition, and examining their effects on the reaction with the mould. An increase in the soaking temperature had an effect on the alpha case, both in appearance and hardness, but had no effect on contamination levels by carbon, oxygen, and nitrogen. The depth of alpha case increased with soaking temperature, increasing from 35 m to 161 m with an increase in temperature from 1200°C to 1400°C. The micro-hardness profiles provided insight into the effect of the alpha case on the mechanical properties of the Ti-64 alloy by displaying hardness values of 1000 HV0.1 and above, but could not be solely utilized to determine the alpha case penetration depth due to microstructural differences in the unaffected Ti-64, in particular the martensitic microstructure that formed with a fast cooling rate from a higher temperature. Levels of expected contaminants such as Zr, Y, O, and C were low. The addition of the colloidal zirconia binder affected the interfacial reactions. YFSZ proved to be a thermodynamically stable refractory material, with the alpha case possibly forming as a result of segregation. en
dc.description.librarian am2014 en
dc.description.librarian ai2014
dc.description.uri http://www.saimm.co.za/ en
dc.identifier.citation Bauristhene, AM, Mutombo, K & Stumpf, WE 2013, 'Alpha case formation mechanism in Ti-6Al-4V alloy investment castings using YFSZ shell moulds', Journal of The Southern African Institute of Mining and Metallurgy, vol. 113, no. 4, pp. 357-361. en
dc.identifier.issn 0038-223X (print)
dc.identifier.issn 2225-6253 (online)
dc.identifier.uri http://hdl.handle.net/2263/37006
dc.language.iso en en
dc.publisher Southern African Institute of Mining and Metallurgy en
dc.rights © The Southern African Institute of Mining and Metallurgy, 2013 en
dc.subject Ti-6Al-4V en
dc.subject Alpha case en
dc.subject Investment casting en
dc.subject YFSZ shell moulds en
dc.subject.lcsh Titanium alloys -- Founding en
dc.subject.lcsh Precision casting en
dc.subject.lcsh Zirconium oxide en
dc.title Alpha case formation mechanism in Ti-6Al-4V alloy investment castings using YFSZ shell moulds en
dc.type Article en


Files in this item

This item appears in the following Collection(s)

Show simple item record