Materials Science and Engineering A 527 (2010) 961–966 Contents lists available at ScienceDirect Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea High temperature deformation behavior of hot isostatically pressed P/M FGH4096 superalloy Yongquan Ning a,∗ , Zekun Yao a , Hui Li a , Hongzhen Guo a , Yu Tao b , Yiwen Zhang b a Northwestern Polytechnical University, PR China b China Iron and Steel Research Institute Group, Beijing 100081, PR China article info Article history: Received 23 April 2009 Received in revised form 4 September 2009 Accepted 4 September 2009 Keywords: P/M superalloy High temperature deformation Constitutive modeling Processing map DRX abstract The hot deformation behavior of hot isostatically pressed (HIPd) P/M superalloy FGH4096 has been char- acterized by isothermal compression testing in the temperature range of 1050–1140 ◦ C and strain rate range of 0.002–1.0 s -1 . The apparent activation energy of deformation was calculated to be 418 kJ/mol, and constitutive equation that described the flow stress as a function of the strain rate and deformation temperature was proposed for high temperature deformation of the alloy. The processing map was calcu- lated to evaluate the efficiency of the forging process in the temperatures and strain rates investigated and to recognize the instability regimes. It was found that the strain has no significant effect on the processing maps. The optimum processing conditions were in the strain rates of around 0.01–0.2 s -1 and temper- atures of 1080–1110 ◦ C, the efficiencies are higher compared to other stable regimes. The DRX occurs at the temperatures of 1050–1130 ◦ C and strain rate range 0.005–0.2 s -1 . At the processed temperature of 1080 ◦ C, lower than dissolution temperature of  ′ phase about 30 ◦ C, undissolved  ′ phase particles were contributed to restricting the coarsening of complete recrystallized grains. Plasticity instability was expected in the regime of strain rate higher than 0.4 s -1 and temperature range of 1090–1130 ◦ C. Crown Copyright © 2009 Published by Elsevier B.V. All rights reserved. 1. Introduction Precipitation-hardened nickel-based superalloys have been widely used as high-temperature structural materials in gas turbine engine applications for more than 50 years [1]. Powder metallurgy (P/M) technology was introduced as an innovative manufactur- ing process to overcome the severe segregation, and P/M process produces a fine, homogenous and macrosegregation-free structure [2–6]. FGH4096 superalloys is a new P/M alloy that is used as tur- bine discs [7,8], owing to its good tensile and creep properties and microstructural stability up to 750 ◦ C for extended periods of expo- sure. But this alloy is rather difficult to deform because of its poor workability. Thus, the characterization of deformation behavior is essential for the optimization of hot forging process for this alloy. In the past 20 years, processing map had been used to optimize the processing parameters in hot working of metallic materials. Balasubrahmanyam and Prasad [9] determined the deformation behavior of Ti–10V–4.5Fe–1.5Al alloy and optimized the process- ing parameters through processing map. Rao and Prasad [10,11] established the processing map of Mg–3Sn–1Ca alloy obtained ∗ Corresponding author. Tel.: +86 29 88493744; fax: +86 29 88491619. E-mail address: ningke521@163.com (Y. Ning). the instability domains of plastic deformation and optimized the hot working extruded parameters. And numerous investigations characterized the high temperature deformation behavior of super- alloys and P/M superalloys through processing map technology, such as nimonic 75, nimonic 85A, nimonic 90, P/M IN-100 and IN718 [12–16]. Somani et al. [13] investigated the influence of the processing parameters on the flow stress behavior, performed the constitutive modeling of the working process for P/M IN-100 superalloy, and established the effect of processing conditions on structure evolution. Cai et al. [15,16] developed the processing map for superalloy 718 and pointed out that the strain had a slight effect on the processing map. In this paper, isothermal compression of P/M FGH4096 super- alloy has been conducted at different strain rates and hot working temperatures. The approach of processing map has been adopted to understand the mechanisms during processing, and to optimize hot forming process for this alloy. The technique of processing maps is based on the dynamic materials model, the principles of which have been described in detail [17–19]. Briefly, the work-piece undergoing hot deformation is considered to be a dissipator of power supplied by a particular source. The stress–strain ( vs. ε) curve and the flow behavior of materi- als are strongly dependent on the strain rate and temperature. The general form of the flow behavior at constant strain and tempera- 0921-5093/$ – see front matter. Crown Copyright © 2009 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2009.09.011