Structure and Properties of Semifinished Sheet Products Made of an Intermetallic Refractory Alloy Based on Ti 2 AlNb
- PDF / 2,006,575 Bytes
- 6 Pages / 594 x 792 pts Page_size
- 93 Downloads / 166 Views
STRUCTURE AND PROPERTIES OF SEMIFINISHED SHEET PRODUCTS MADE OF AN INTERMETALLIC REFRACTORY ALLOY BASED ON Ti 2 AlNb S. V. Skvortsova,1,2 А. А. Il’in,1 А. М. Mamonov,1 N. А. Nochovnaya,1 and О. Z. Umarova1
UDC 669.018.44:669.295
We study the influence of two-stage thermal treatment on the formation of the phase composition, structure, and mechanical properties of semifinished sheet products made of VTI-4 refractory alloy based on the Ti 2 AlNb intermetallic compound. It is shown that, changing the temperature of heating in the first stage of treatment and the temperature of subsequent aging, it is possible to affect the strength and plasticity characteristics of the material in broad ranges. It is demonstrated that, in order to obtain a structure guaranteeing a relative elongation of 8–12%, the temperature of the first stage of treatment must remain in the (β + α 2 + O) three-phase region and the procedure of cooling down to room temperature or to the temperature of the second stage of treatment (800–850°С) should be realized together with the furnace. To get high levels of short- and long-term strength at 650°С with preservation of moderate values of plasticity (3–5%), it is necessary to perform cooling after isothermal treatment in the three-phase region in air. The subsequent procedure of aging should be carried out within the temperature range 800–850°С for 7 h. Keywords: refractory titanium ortho-alloy, thermal treatment, structure, phase composition, strength, plasticity.
Recent years are marked by the extensive investigations and technological advances aimed at the creation and implementation of refractory alloys based on titanium aluminide and intended for long-term operation within the temperature range 600–700°С under the conditions of intense corrosive action of gas atmospheres and high alternating loads. These materials have higher specific strengths at temperatures of up to 700°С than nickel alloys and refractory steels. Moreover, they have better ranges of working temperatures than the commercial refractory titanium alloys [1–3]. To improve the mechanical properties of Ti 3Al and TiAl intermetallic compounds, it is customary to perform their multicomponent alloying with active refractory β -stabilizing elements (Nb, Mo, V, Ta, and W) enhancing the elastic and strength characteristics of the analyzed materials and reducing the intensity of oxidation. In recent years, the alloys based on TiAl (gamma-alloys) prove to be most promising under the conditions of ultimate working temperatures. They are characterized by high heat resistance but have extremely low characteristics of plasticity at room temperature [4, 5]. The alloys based on the Ti3Al intermetallic compound (super-alpha-2-type alloys) are deformed in the hot state but only for low levels of strains and rates and have quite poor casting properties [6, 7]. At present, the ortho-alloys based on the Ti 2 AlNb intermetallic compound are regarded as be most promising. Moreover, they can be used as an alternative to fire-dangerous titanium alloys [8–1
Data Loading...
