Tensile and Creep Properties of Rapidly Solidified Titanium Alloys Containing Complex Matrices and Fine Dispersoids
- PDF / 2,849,906 Bytes
- 9 Pages / 417.6 x 639 pts Page_size
- 56 Downloads / 222 Views
TENSILE AND CREEP PROPERTIES OF RAPIDLY SOLIDIFIED TITANIUM ALLOYS CONTAINING COMPLEX MATRICES AND FINE DISPERSOIDS M.F.X.Gigliotti*, R.G.Rowe*, G.E.Wasielewski**, G.K.Scarr**, and J.C.Williams*** * General Electric Corporate Research and Development, Schenectady, NY ** General Electric Aircraft Engine Business Group, Evendale, OH *** Carnegie-Mellon University, Pittsburgh, PA
ABSTRACT
Titanium alloys containing alpha matrices with various rare earth compound dispersions were prepared by melt extraction. The melt extracted material was HIPped, extruded, and thermally exposed to yield various microstructures including transformed beta and equiaxed alpha. Tensile and creep tests were conducted on material in the different microstructural conditions. Trends in mechanical behavior as a function of alloy chemistry and process history are discussed. The alloys with a transformed beta microstructure had superior creep resistance. Alloys containing dispersoids had better tensile ductilities compared with those which did not contain a dispersoid. Portions of this work were carried out under Air Force Contract F3361583-C-5034.
INTRODUCTION Rapid solidification and deformation processing of titanium alloys containing rare earth additions have been used to produce a fine dispersion of the rare earth phase in titanium alloys [1-3]. Various binary and ternary titanium alloys have been evaluated to assess the role of rare earth compound dispersoids on strengthening [4]. Elements of the lanthanide series, or rare earth elements, have low solubilities in alpha titanium, and appear to be good dispersion strengthening candidates. For those rare earth elements whose phase diagrams with titanium are known, there appear two distinct alloy classes. If the rare earth's melting point is less than 1100 C, the binary diagram with titanium is a monotectic. If the rare earth's melting point is above 1300 C, the binary system is a simple eutectic. Since there is little solubility of rare earths in titanium, there will be liquid rare earth phase above the minimum melting point of the alloy. Many rare earths have too low a melting point to be useful dispersiods in titanium, since those molten below 1000 C would coarsen during consolidation or thermomechanical processing. However, in the presence of oxygen, stability is likely to be enhanced by oxide formation. This should allow low melting point rare earth elements to form oxides and exhibit stability above their melting point. Those rare earths most promising would include Gd and Er, and by extension -- Tb, Dy, Y, Ho, Tm and Lu. Some interest has been shown in rare earth additions using conventional ingot metallurgy. Kaschuk and Svetlov [5] found considerable grain refining in a Ti - 5 Al alloy with minor additions of rare earths, with an increase in tensile strength and oxidation resistance.
Mat. Res. Soc. Symp. Proc. Vol. 58. ' 1986 Materials Research Society
344
Sastry et al., using rapid solidification (r.s.), have shown that higher levels of rare earth additions produce dispersoids w
Data Loading...
