Superplastic Behavior of ATI 718Plus Superalloy

Abstract:

Complex shaped, ultra thin-walled parts can be manufactured using superplastic forming. Hot working temperature for the production of fine-grained billets (d=5-15 μm) out of ATI Allvac 718Plus^® superalloy is in the range of 982-1038°C. An ultrafine-grained structure (d=0.3 μm) was produced by multi-axial forging with a gradual decrease of the forging temperature from 950 to 700°C. Superplastic properties of the alloy were carried out in the temperature interval of 700-950°C. It has been revealed that the fine-grained alloy provided superplastic elongations about 300% at 950°C and strain rate of 10^-4 s^-1. The highest elongation of ultrafine-grained alloy was about 1450% and very low flow stresses were reached at 900°C and strain rate of 3×10^-4 s^-1. The ultrafine-grained alloy showed superplastic properties also at 700°C (0.62T_m). The microstructure and superplastic properties of the alloys 718 and 718Plus are compared.

• Periodical: Materials Science Forum (Volumes 838-839)
• Pages: 557-562
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.838-839.557
• Online since: January 2016
• Authors: Shamil Kh. Mukhtarov, Farid Z. Utyashev
• Keywords: ATI 718Plus, Multi-Axial Forging, Nickel-Based Superalloy, Superplasticity, Ultrafine-Grained Structure

References

[1] R. Kennedy, Allvac® 718PlusTM, superalloy for the next forty years, Superalloys 718 & Derivatives (2005) 1-14.

DOI: 10.7449/2005/superalloys_2005_1_14

[2] M.W. Mahoney, Superplastic properties of Alloy 718, Superalloy 718 - Metallurgy and Applications (1989) 391-405.

DOI: 10.7449/1989/superalloys_1989_391_405

[3] G.A. Salishchev, O.R. Valiakhmetov, V.A. Valitov, Sh. Kh. Mukhtarov, Submicrocrystalline and nanocrystalline structure formation in materials and search for outstanding superplastic properties, Mater. Sci. Forum 170-172 (1994) 121-130.

DOI: 10.4028/www.scientific.net/msf.170-172.121

[4] Sh. Mukhtarov, N. Dudova, V. Valitov, Processing and mechanical properties of bulk nanostructured nickel-based alloys, Mater. Sci. Eng. A 503 (2009) 181-184.

DOI: 10.1016/j.msea.2008.02.058

[5] Information on http: /www. atimetals. com/products/718plus-alloy/Pages/Specifications. aspx.

[6] Sh. Mukhtarov, V. Valitov, M.F.X. Gigliotti, PR Subramanian, J.S. Marte, N. Dudova, Influence of severe thermomechanical treatment on formation of nanocrystalline structure in Ni 718 and Ni 718Plus alloys and their mechanical properties, Mater. Sci. Forum 584-586 (2008).

DOI: 10.4028/www.scientific.net/msf.584-586.458

[7] O.A. Kaibyshev, F.Z. Utyashev, Superplasticity: Microstructural Refinement and Superplastic Roll Forming, Futurepast, Arlington, (2005).

[8] N.C. Eurich, P.D. Bristowe, Thermodynamic stability and electronic structure of h-Ni6Nb(Al, Ti) from first principles, Scr. Mater. 77 (2014) 37-40.

DOI: 10.1016/j.scriptamat.2014.01.012

[9] E.J. Pickering, H. Mathur, A. Bhowmik, O.M.D.M. Messé, J.S. Barnard, M.C. Hardy, R. Krakow, K. Loehnert, H.J. Stone, C.M.F. Rae, Grain-boundary precipitation in Allvac 718Plus, Acta Mater. 60 (2012) 2757-2769.

DOI: 10.1016/j.actamat.2012.01.042

[10] Sh. Mukhtarov, V. Valitov, N. Dudova, Properties of bulk and sheet micro-, submicro-, and nanocrystalline Alloy 718, Superalloys 718, 625, 706, and Various Derivatives (2005) 507-516.

DOI: 10.7449/2005/superalloys_2005_507_516

[11] Sh. Mukhtarov, Effect of Grain Size on the Superplastic Behavior of a Nanostructured Nickel-Based Superalloy, Mater. Sci. Forum 633-634 (2010) 569-575.

DOI: 10.4028/www.scientific.net/msf.633-634.569

[12] V.A. Valitov, Sh. Kh. Mukhtarov, Yu.A. Raskulova, Processing and superplastic properties of nanocrystalline Alloy 718 during warm deformation, Rev. Adv. Mater. Sci. 11 (2006) 159-166.

[13] R.Z. Valiev, R.K. Islamgaliev, I.V. Aleksandrov, Bulk nanostructured materials from severe plastic deformation, Prog. Mater. Sci. 45 (2000) 103-189.

DOI: 10.1016/s0079-6425(99)00007-9

[14] Aerospace Structural Metals Handbook, CINDAS, LLC, West Lafayette, Indiana, (2013).

[15] V.A. Valitov, O.A. Kaibyshev, Sh. Kh. Mukhtarov, B.P. Bewlay, M.F.X. Gigliotti, Processing and properties of microcrystalline, submicrocrystalline and nanocrystalline alloy 718, Superalloys 718, 625, 706 and Derivatives (2001) 313-321.

DOI: 10.7449/2001/superalloys_2001_313_321

[16] V.A. Valitov, Sh. Mukhtarov, A.P. Zhilyaev, O.A. Ruano, Evolution of microstructure during low temperature superplastic deformation of bulk nanostructured Ni-Cr-Fe-Nb base superalloy, Rev. Adv. Mater. Sci. 25 (2010) 148-154.

[17] M. Kumar, A.J. Schwartz, W.E. King, Microstructural evolution during grain boundary engineering of low to medium stacking fault energy fcc materials, Acta Mater. 50 (2002) 2599-2612.

DOI: 10.1016/s1359-6454(02)00090-3

[18] D. Huber, C. Sommitsch, M. Stockinger, Comparison between microstructure evolution in IN718 and ATI Allvac®718PlusTM - simulation and trial forgings, Adv. Mater. Res. 278 (2011) 168-173.

DOI: 10.4028/www.scientific.net/amr.278.168