Effect of carbon addition on creep behavior of cast TiAl alloy with hard-oriented directional lamellar microstructure
- PDF / 2,546,101 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 81 Downloads / 199 Views
ORIGINAL PAPER
Effect of carbon addition on creep behavior of cast TiAl alloy with hard‑oriented directional lamellar microstructure Xi‑wen Zhang1,2 · Yu‑ling Tang2 · Wen‑juan Wan1 · Chun‑lei Zhu1 · Ji Zhang1 Received: 1 September 2019 / Revised: 30 October 2019 / Accepted: 7 November 2019 © China Iron and Steel Research Institute Group 2020
Abstract Two TiAl alloys, Ti–47.5Al–3.7(Cr, V, Zr) and Ti–47.5Al–3.7(Cr, V, Zr)–0.1C (at.%), were prepared by cold crucible levitation melting to couple the hard-oriented directional lamellar microstructure with carbon microalloying strengthening. The creep behavior and mechanism for the improvement in creep properties by carbon addition were investigated by mechanical tests and electron microscopy characterizations. The results show that obvious improvements on the creep properties at 760 °C and 276 MPa are achieved by 0.1 at.% C addition into TiAl alloy with directional lamellar microstructure, which promotes the creep strain and minimum creep rate decreasing with a large content. The minimum creep rate is reduced from 4.37 × 10−8 to 3.97 × 10−9 s−1, and the duration entering into creep acceleration is prolonged for more than 10 times. The mechanism for creep property improvement by 0.1% C addition is attributed to two aspects. The first one is that T i2AlC is found to be strong obstacles of 1/2[110] dislocations when moving across the lamellar interface in the carbon containing alloy. The other one is that the interfacial dislocations are effectively impeded and the release process is hindered by dynamic precipitation of T i3AlC, which is proposed to be the special mechanism for creep resistance improvement of this hard-oriented directional lamellar microstructure. Keywords Cast titanium aluminide · Lamellar microstructure · Creep behavior · Carbon addition · Dynamic precipitation
1 Introduction The titanium aluminide (TiAl) alloy is a promising lightweight high-temperature structural material with the properties of low densities, superior high-temperature specific strength and oxidation resistance [1]. And TiAl alloys have already been successfully applied to the last-stage low-pressure turbine blades in aero engine [2] and turbochargers in automobile [3]. With the increase in working temperature and service life of TiAl alloy structural components, the demand for improving the high-temperature creep properties becomes more and more urgent.
* Chun‑lei Zhu [email protected] 1
Beijing Key Laboratory of Advanced High Temperature Materials, China Iron and Steel Research Institute Group, Beijing 100081, China
National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
2
Among the typical microstructures, the fully lamellar microstructures exhibit the best high-temperature behavior [4, 5], but the creep resistance is still not yet competent to fulfill the coming requirements. The method of adding minor carbon can reduce the creep rate and delay the onset of tertiary creep sta
Data Loading...
