Materials Science and Engineering A 398 (2005) 128–136 Effect of heat treatment on microstructures and tensile properties of Ni-base superalloy M963 L.Z. He a,b,∗ , Q. Zheng a , X.F. Sun a , H.R. Guan a , Z.Q. Hu a , A.K. Tieu b , C. Lu b , H.T. Zhu b a Department of Superalloys, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, PR China b School of Mechanical, Materials and Mechatronics, University of Wollongong, Wollongong, NSW 2522, Australia Received 13 November 2004; accepted 11 March 2005 Abstract The effect of solution treatment (ST) on tensile properties of M963 Ni-base superalloy tested at 800 ◦ C has been investigated. The detailed microstructures, fracture surfaces and dislocation structures are examined through energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). With increasing solution treated temperature, the yield strength (YS) and ultimate tensile strength (UTS) increase, however, the elongation decreases. Microstructural observations show that the morphologies of carbide, primary  ′ and re-precipitated  ′ change significantly with increasing solution treated temperature. The main deformation mode is  ′ by-pass when solution treated temperature is lower than 1220 ◦ C, and changes to  ′ shearing at 1230 ◦ C. The interface of carbide with matrix is the main site of crack initiation and propagation under all testing conditions. © 2005 Elsevier B.V. All rights reserved. Keywords: M963 alloy; Heat treatment; Microstructures; Tensile properties 1. Introduction Ni-base superalloys, strengthened by  ′ precipitates and solution additions, are produced in various forms suitable for application at high temperature, due to their excellent creep and fatigue strength, good corrosion resistance. Many researches have been focused on the effect of heat treat- ment on the microstructures and creep properties of some commercial superalloys [1–10], but its effect on the tensile properties is limited [11–14]. M963, used as a material for blades and vanes in gas turbine engine, is a cast polycrys- talline Ni-base superalloy, contains a large amount of the re- fractory elements tungsten, molybdenum and niobium. It has been reported that the conventionally solution treated alloy has low ductility at 800 ◦ C [15–17]. The same behavior was also observed in other superalloys [18–21]. However, up to now, few attentions have been paid to improve the low duc- tility for certain superalloys [9,11,13]. The purpose of this work is to investigate the effect of heat treatment on the mi- ∗ Corresponding author. Tel.: +61 2 42214809; fax: +61 2 42213101. E-mail address: cybhlz@163.net (L.Z. He). crostructures and tensile properties of M963 superalloy tested at 800 ◦ C, to find a way to improve ductility of the alloy at 800 ◦ C. 2. Experimental procedure The chemical composition of M963 alloy used in this work is listed in Table 1. Minor elements are 8 wt. ppmP, 10 wt. ppmS, 3 wt. ppmO and 6 wt. ppmN. The master alloy was re-melted in a VIM25F vacuum induction furnace and then cast into test bars. Some test bars were used as cast condition, others were solution treated at 1200, 1210, 1220 and 1230 ◦ C for 4h followed by air cooling, respectively. The temperature during heat treatment was controlled within ±1 ◦ C Specimens for tensile test with a diameter of 5 mm and a gage length of 25 mm were machined longitudinally from the cast and solution treated bars. The tensile tests were conducted in air at 800 ◦ C using a SHIMADZU Universal testing machine Autograph AG-250KNE with furnace attachment. Specimens were induction heated and a temperature gradient not exceeding ±2 ◦ C was maintained 0921-5093/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2005.03.021