All-Russian Institute of Aviation Materials, Moscow, Russia:

O. S. Kashapov, Head of the Laboratory of Titanium Alloys Sector, e-mail: olegkashapov@yandex.ru
T. V. Pavlova, Leading Engineer
V. S. Kalashnikov, First Category Engineer
A. V. Zavodov, Engineer

We investigated the material of large industrial forgings, made from heat-resistant near-alpha-titanium alloy VT41 (Ti – Al – Sn – Zr – Mo – Nb – W – Si – Fe – C – O), forged in a two-phase area and annealed with different cooling rates after the first annealing stage. The alloy BT41 forgings are designed to be used in manufacturing of rotor blisks of high-pressure compressors in gas turbine engines with an operating temperature of up to 600 ^оC. The cooling process was simulated under different conditions and compared with experiments and foreign sources. The results of the analysis of the forging material’s microstructure are presented by using optical and electronic transmission microscopy. The mechanical properties of the forgings are determined for different cooling conditions and different phase composition. The results of the study make it possible to justify the cooling conditions and the requirements of the forgings’ cooling rates after solution heat treatment in relation to industrial production conditions. The study of influence of cooling rate on the forging’s microstructure, carried out on 101010 mm templates, showed that the favorable microstructure is reached at a cooling rate of 10–12 ^оC/min. It was demonstrated that reaching of favorable cooling rate, e.g. under the fan, leads to high mechanical properties in large 115 mm sections similar to those reached at 45–65 mm sections of forgings that are cooled on air. The importance of optimization of heat treatment conditions for concrete forgings configuration due to specifics of cooling under the fan and preventing of unsatisfactory results, e.g. decreasing of mechanical properties, fatigue strength, durability, is noted. This way, the mechanical properties of aircooled VT41 forgings with temperatures of 20 and 600 ^оC used to be lower than for those that were cooled with a fan.
Our research work was carried out with the support of the grant of Russian Foundation for Basic Research No. 16-43-630780 «р_а» and within the realization of complex scientific field 8: Light, high-resistant corrosion-resistant welded alloys and steels, including those with high fracture toughness (Strategic ways of development of materials and technologies of their processing for the period until 2030).

1. Bubmann M., Kraus J., Bayer E. An Integrated Cost-Effective Approach to Blisk Manufacturing. XVII International Symposium On Air Breathing Engines (ISABE). MTU Aero Engines, Munich. 2005. 9 p. Available at: http://www.mtu.de (accessed: 27.11.2017)
2. Monicault J.-M., Guedou J.-Y., Soniak F. Issues and progress in manufacturing of aero titanium parts. 2008. JM de Monicaut. ITA 24.09.2008. 38 p. Available at: http://www.titanium.org/resource/resmgr/2005_2009_papers/deMonicault_JeanMichel_2008.pdf (accessed 27.11.2017)
3. Pavlova T. V., Kalashnikov V. S., Kondrateva A. R., Kochubey A. Ya. Fatigue strength of semiproducts from titanium alloys for production of gas turbine engine compressor bladed integrated disks. Vestnik mashinostroeniya. 2017. No. 4. pp. 54–59.
4. Donton W. T., Allison J. E., Lasecki J. V. The influence of thermal exposure on properties and microstructure of elevated temperature titanium alloys. Titanium' 92 : Science and Technology. 1992. pp. 295–302.
5. Evans D. J., Broderick T. F., Woodhouse J. B., Hoenigman J. R. On the synergism of 2 and silicides in Ti – 6Al – Sn – 2Cr – 2Zr – 2Mo – Si. Titanium' 95 : Science and Technology. 1995. pp. 2413–2420.
6. Davies P., Pederson R., Coleman M., Birosca S. The hierarchy of microstructure parameters affecting the tensile ductility in centrifugally cast and forged Ti-834 alloy during high temperature exposure in air. Acta Materialia. 2016. Vol. 117. pp. 51–67.
7. Popov A. A., Popova M. A. Isothermal diagrams of precipitation of silicide and aluminide phases in refractory titanium alloys. Metallovedenie i termicheskaya obrabotka metallov. 2016. No. 11. pp. 23–28.
8. Barussad A., Desvalles Y., Guedou J. Y. Control of the microstructure in large titanium discs. Application to the high pressure compressor of the GE90 aeroengine. Titanium' 95: Science and Technology. UK, The institute of Materials. 1996. pp. 1599–1608.
9. Kablov E. N. Innovative developments of FSUE «VIAM» SSC of RF on realization of «Strategic directions of the development of materials and technologies of their processing for the period until 2030». Aviatsionnye materialy i tekhnologii. 2015. No. 1 (34). pp. 3–33. DOI: 10.18577/2071-9140-2015-0-1-3-33.
10. Kablov E. N. Strategical Areas of Developing Materials and Their Processing Technologies for the Period up to 2030. Aviatsionnye materialy i tekhnologii. 2012. No. S. pp. 7–17.
11. Kablov E. N. VIAM designs for gas-turbine engines and installations. Krylya Rodiny. 2010. No. 4. pp. 31–33.
12. Kablov E. N., Kashapov O. S., Pavlova T. V., Nochovnaya N. A. Development of industrial technology manufacturing of semi-finished products from near-atitanium alloy BT41. Titan. 2016. No. 2 (52). pp. 33–42.
13. Kashapov O. S., Pavlova T. V., Nochovnaya N. A. Effect of heat treatment conditions on the structure and properties of Ti-base heat-resistant alloys for high-pressure compressor blades. Aviatsionnye materialy i tekhnologii. 2010. No. 2 (15). pp. 8–14.
14. Neal D. F. Development and evolution of high temperature titanium alloy IMI 834. Sixth world conference on titanium. France 1988. pp. 253–259.
15. Borchert B., Daeubler M. Influence of microstructure of IMI 834 on mechanical properties relevant to jet engines. Sixth world conference on titanium. 1988. pp. 467–472.
16. International titanium association. Specifications book. Fourth edition. 2005. pp. 26–36.
17. Jackson J., Rice R. Preliminary material properties Handbook. Vol. 2: SI Units. AFRL-ML-WP-TR-2001-4027. Battelle 505 King Avenue. Columbus, OH 43201-2693 Chapter 5. pp. 5–3, 5–8.
18. Lutjering G., Williams J. C. Titanium. 2nd edition. Springer-Verlag Berlin Heidelberg. 2003. 449 p.