Non-equilibrium Ti-Fe bulk alloys with ultra-high strength and enhanced ductility
- PDF / 439,896 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 15 Downloads / 222 Views
NN5.13.1
Non-equilibrium Ti-Fe bulk alloys with ultra-high strength and enhanced ductility Dmitri V. Louzguine-Luzgin, Larissa V. Louzguina-Luzgina1, Hidemi Kato and Akihisa Inoue Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577, Japan 1 Research and Development Project, CREST, Japan Science and Technology Agency, Sendai 985-8577, Japan ABSTRACT The high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25-40 mm in diameter and 10-15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young’s modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed. INTRODUCTION Commercial structural Ti-based alloys have an ultimate tensile strength slightly exceeding 1.0 GPa and plastic elongation of 10-15 % [1]. However, Ti-based bulk glassy alloys [2,3] exhibit strength values exceeding 2 GPa. For example, 2.2 GPa strength is obtained for the Ti50Ni20Cu23Sn7 bulk glassy alloy as a result of Sn addition [4]. A relatively low density of the main alloying element Ti (4.5 Mg/m3) implies a high strength/density ratio. Ti-based alloys also have high corrosion resistance of at room temperature. However, only a small diameter of 5-8 mm for the Ti-based bulk glassy alloys [3,5,6] has been attained so far and the low ductility restricts their applications. Recently, it also has been shown that a 3 mm diameter cylindrical rod of cast Ti60Cu14Ni12Sn4Nb10 alloy consisting of a micron–size β-Ti dendrites exhibits high ultimate compressive strength of 2.4 GPa and 14.5 % plastic strain [7]. At the same time, arc-melting is proved to be a suitable procedure for direct production of the high-strength Ti-Ni-Cu-Nb alloy samples without additional treatment [8]. As an alternative to Ti-based bulk glassy alloys which exhibit a relatively poor ductility and to Ti-Ni-Cu-Sn-Nb alloys which are very limited in size we attempted to synthesize the TiFe cast alloys. In the present work we investigate binary Ti-Fe bulk alloys exhibiting good mechanical properties obtained by melting in an arc-furnace. Some commercial Ti-based alloys like Ti-10wt.%V-2wt.%Fe-3wt.%Al [9], for example, contain a small amount of Fe but no information is available about mechanical properties of Ti-based alloys with high Fe content. EXPERIMENTAL PROCEDURE
NN5.13.2
The ingots of the Ti100-xFex alloys
Data Loading...
