Strengthening Mechanisms in Polycrystalline Multimodal Nickel-Base Superalloys

Polycrystalline γ-γ′ superalloys with varying grain sizes and unimodal, bimodal, or trimodal distributions of precipitates have been studied. To assess the contributions of specific features of the microstructure to the overall strength of the material, a model that considers solid-solution strengthening, Hall–Petch effects, precipitate shearing in the strong and weak pair-coupled modes, and dislocation bowing between precipitates has been developed and assessed. Cross-slip-induced hardening of the Ni3Al phase and precipitate size distributions in multimodal microstructures are also considered. New experimental observations on the contribution of precipitate shearing to the peak in flow stress at elevated temperatures are presented. Various alloys having comparable yield strengths were investigated and were found to derive their strength from different combinations of microconstituents (mechanisms). In all variants of the microstructure, there is a strong effect of antiphase boundary (APB) energy on strength. Materials subjected to heat treatments below the γ′ solvus temperature benefit from a strong Hall–Petch contribution, while supersolvus heat-treated materials gain the majority of their strength from their resistance to precipitate shearing.

[1]  D. Mclean.  Predicting growth of γ′ in nickel alloys , 1984 .

[2]  F. J. Humphreys,et al.  The deformation of single crystals of copper and copper-zinc alloys containing alumina particles - I. Macroscopic properties and workhardening theory , 1970, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[3]  R. Fleischer,et al.  Substitutional solution hardening , 1963 .

[4]  J. A. López,et al.  The effects of non-stoichiometry and titanium additions on the mechanical behaviour of Ni3Al (γ′) , 1970 .

[5]  P. Veyssiére,et al.  Transmission electron microscopy analysis of the early stages of damage in a γ/γ′ nickel-based alloy under low cycle fatigue , 1994 .

[6]  E. Nembach,et al.  Synergisms of grain boundary and γ′-particle strengthening in nickel-base superalloys , 1996 .

[7]  S. Matsumura,et al.  Electron microscopic observation and its interpretation of Ostwald ripening in precipitation dynamics in alloys , 1987 .

[8]  P. Voorhees,et al.  Ostwald ripening in a system with a high volume fraction of coarsening phase , 1988, Metallurgical and Materials Transactions A.

[9]  E. Nembach,et al.  The critical resolved shear stress of γ′-strengthened nickel-based superalloys with γ′-volume fractions between 0.07 and 0.47 , 1992 .

[10]  M. Vittori,et al.  On the antiphase boundary energy of Ni3(Al, Ti) particles , 1985 .

[11]  Tomoo Suzuki,et al.  Solid Solution Hardening of Ni3Al with Ternary Additions , 1986 .

[12]  W. Nix,et al.  A critical analysis of existing models for plastic flow in Ni_3Al: Comparisons with transient deformation experiments , 1992 .

[13]  D. Pope.  High Temperature Ordered Intermetallic Alloys , 1986 .

[14]  B. Wilshire,et al.  The creep and fracture behaviour of the cast, nickel-based superalloy, IN100 , 1978 .

[15]  G. Parry,et al.  Formation and structure of the potassium graphites , 1968 .

[16]  D. Dimiduk,et al.  The compositional dependence of antiphase-boundary energies and the mechanism of anomalous flow in Ni3 Al alloys , 1993 .

[17]  U. F. Kocks.  Thermodynamics and kinetics of slip , 1975 .

[18]  B. Viguier,et al.  Chapter 62 Work hardening in some ordered intermetallic compounds , 2002 .

[19]  H. Gleiter,et al.  Precipitation hardening by coherent particles , 1968 .

[20]  M. Ashby,et al.  Dispersion hardening of copper single crystals , 1966 .

[21]  M. Makin,et al.  DISLOCATION MOVEMENT THROUGH RANDOM ARRAYS OF OBSTACLES , 1966 .

[22]  P. Hirsch,et al.  The strain rate sensitivity of the flow stress and the mechanism of deformation of single crystals of Ni3(Al Hf)B , 1994 .

[23]  T. Kruml,et al.  Dislocation Structures in Ni 3 (Al, Hf) , 1996 .

[24]  Peter W Voorhees,et al.  The theory of Ostwald ripening , 1985 .

[25]  K. Chawla,et al.  Mechanical Behavior of Materials , 1998 .

[26]  D. Caillard,et al.  Thermally Activated Mechanisms in Crystal Plasticity , 2011 .

[27]  D. Dimiduk,et al.  Discrete dislocation simulations of precipitation hardening in inverse superalloys , 2006 .

[28]  A. Ardell,et al.  Superposition of Precipitation-hardening Mechanisms , 1979 .

[29]  A. Thompson.  Effect of grain size on work hardening in nickel , 1977 .

[30]  J. Jonas,et al.  Strength of metals and alloys , 1985 .

[31]  Frank Reginald Nunes Nabarro,et al.  The physics of creep : creep and creep-resistant alloys , 1995 .

[32]  F. Nabarro,et al.  Dislocations in solids , 1979 .

[33]  C. T. Liu,et al.  High-temperature ordered intermetallic alloys , 1985 .

[34]  A. Deruyttere,et al.  Multi-component solid solution hardening , 1977 .

[35]  I. Lifshitz,et al.  The kinetics of precipitation from supersaturated solid solutions , 1961 .

[36]  B. Devincre,et al.  Simulation of the plastic flow in Ni3Al : work hardening and strain-rate sensitivity , 1999 .

[37]  A. Kelly,et al.  Strengthening methods in crystals , 1971 .

[38]  O. Izumi,et al.  The relation between the defect hardening and substitutional solid solution hardening in an intermetallic compound Ni3Al , 1976 .

[39]  E. Nembach,et al.  On the additivity of solid solution and dispersion strengthening , 2001 .

[40]  K. A. Padmanabhan,et al.  Flow transients during strain rate jump tests in a titanium-modified austenitic stainless steel , 1992 .

[41]  David P. Pope,et al.  A theory of the anomalous yield behavior in L12 ordered alloys , 1984 .

[42]  Gregory B Olson,et al.  Characterization of the microstructure and phase equilibria calculations for the powder metallurgy superalloy IN100 , 2003 .

[43]  U. F. Kocks.  Kinetics of solution hardening , 1985 .

[44]  A. Mukherjee,et al.  Accelerated coarsening of microstructure during superplastic deformation , 1984 .

[45]  C. Davis,et al.  Modeling solid solution strengthening in nickel alloys , 1997 .

[46]  Brian Ralph,et al.  Observations of the fine structure of superdislocations in Ni3Al by field-ion microscopy , 1974 .