Recovery, recrystallization, grain growth and phase stability of a family of FCC-structured multi-component equiatomic solid solution alloys

Abstract The equiatomic high-entropy alloy FeNiCoCrMn is known to crystallize as a single phase with the face-centered cubic (FCC) crystal structure. To better understand this quinary solid solution alloy, we investigate various binary, ternary and quaternary alloys made from its constituent elements. Our goals are twofold: ( i ) to investigate which of these lower order systems also form solid solution alloys consisting of a single FCC phase, and ( ii ) to characterize their phase stability and recovery, recrystallization, and grain growth behaviors. X-ray diffraction (XRD) and scanning electron microscopy with backscattered electron images showed that three of the five possible quaternaries (FeNiCoCr, FeNiCoMn and NiCoCrMn), five of the ten possible ternaries (FeNiCo, FeNiCr, FeNiMn, NiCoCr, and NiCoMn), and two of the ten possible binaries (FeNi and NiCo) were single-phase FCC solid solutions in the cast and homogenized condition, whereas the others either had different crystal structures or were multi-phase. The single-phase FCC quaternary, FeNiCoCr, along with its equiatomic ternary and binary subsidiaries, were selected for further investigations of phase stability and the thermomechanical processing needed to obtain equiaxed grain structures. Only four of these subsidiary alloys—two binaries (FeNi and NiCo) and two ternaries (FeNiCo and NiCoCr)—were found to be single-phase FCC after rolling at room temperature followed by annealing for 1 h at temperatures of 300–1100 °C. Pure Ni, which is FCC and one of the constituents of the quinary high-entropy alloy (FeNiCoCrMn), was also investigated for comparison with the higher order alloys. Among the materials investigated after thermomechanical processing (FeNiCoCr, FeNiCo, NiCoCr, FeNi, NiCo, and Ni), FeNiCo and Ni showed abnormal grain growth at relatively low annealing temperatures, while the other four showed normal grain growth behavior. The grain growth exponents for all five of the equiatomic alloys were found to be ∼0.25 (compared to ∼0.5 for unalloyed Ni), suggesting that solute drag may control grain growth in the alloys. For all five alloys, as well as for pure Ni, microhardness increases as the grain size decreases in a Hall-Petch type way. The ternary alloy NiCoCr was the hardest of the alloys investigated in this study, even when compared to the quaternary FeNiCoCr alloy. This suggests that solute hardening in equiatomic alloys depends not just on the number of alloying elements but also their type.

[1]  D. Horton,et al.  Grain growth phenomena in nickel , 1994 .

[2]  R. Birringer,et al.  On the room-temperature grain growth in nanocrystalline copper , 1994 .

[3]  S. Avner Introduction to Physical Metallurgy , 1964 .

[4]  C. Liu,et al.  Effect of valence electron concentration on stability of fcc or bcc phase in high entropy alloys , 2011 .

[5]  N. Hwang,et al.  Grain boundary faceting and abnormal grain growth in nickel , 2000 .

[6]  C. Woodward,et al.  Microstructure and Room Temperature Properties of a High-Entropy TaNbHfZrTi Alloy (Postprint) , 2011 .

[7]  Sheng Guo,et al.  Solid solutioning in equiatomic alloys: Limit set by topological instability , 2014 .

[8]  I. Shabanova,et al.  High-temperature ordering-phase separation transition in the Fe50Co50 alloy , 2008 .

[9]  Zushu Hu,et al.  Microstructures and compressive properties of multicomponent AlCoCrFeNiMox alloys , 2010 .

[10]  J. Szpunar,et al.  A role of fractions of mobile grain boundaries in secondary recrystallization of Fe–Si steels , 1999 .

[11]  J. Drolet,et al.  The impurity-drag effect on grain growth , 1968 .

[12]  C. Schwink,et al.  Investigations of the yield region of concentrated CuGe and CuZn single crystals—I. Critical resolved shear stress, slip line formation and the true strain rate , 1977 .

[13]  C. Dunn Cold-rolled and primary recrystallization textures in cold-rolled single crystals of silicon iron , 1954 .

[14]  E. George,et al.  Tensile properties of high- and medium-entropy alloys , 2013 .

[15]  John C. Horwath,et al.  Absence of long-range chemical ordering in equimolar FeCoCrNi , 2012 .

[16]  L. Battezzati,et al.  Kinetics of abnormal grain growth in pure iron , 1979 .

[17]  Y. Zhou,et al.  Solid solution alloys of AlCoCrFeNiTix with excellent room-temperature mechanical properties , 2007 .

[18]  B. Günther,et al.  Secondary recrystallization effects in nanostructured elemental metals , 1992 .

[19]  Yi Qiao,et al.  Novel microstructure and properties of multicomponent CoCrCuFeNiTix alloys , 2007 .

[20]  H. Tsai,et al.  Evolution of microstructure, hardness, and corrosion properties of high-entropy Al0.5CoCrFeNi alloy , 2011 .

[21]  Y. Ustinovshikov,et al.  Phase separation and ordering in the Fe-Co system , 2006 .

[22]  T. G. Nieh,et al.  Grain growth and the Hall–Petch relationship in a high-entropy FeCrNiCoMn alloy , 2013 .

[23]  B. Murty,et al.  Alloying behavior in multi-component AlCoCrCuFe and NiCoCrCuFe high entropy alloys , 2012 .

[24]  G. Eggeler,et al.  The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy , 2013 .

[25]  R. Brick,et al.  Behavior of Metals At Low Temperatures , 1953 .

[26]  H. W. King Quantitative size-factors for metallic solid solutions , 1966 .

[27]  Mats Hillert,et al.  On the theory of normal and abnormal grain growth , 1965 .

[28]  T. Shun,et al.  Nanostructured High‐Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes , 2004 .

[29]  Sheng Guo,et al.  Anomalous solidification microstructures in Co-free AlxCrCuFeNi2 high-entropy alloys , 2013 .

[30]  D. Miracle,et al.  Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys , 2011 .

[32]  A. Wolfenden The energy stored in polycrystalline copper deformed at room temperature , 1971 .

[33]  H. Bei,et al.  Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys , 2013 .

[34]  C. Schwink,et al.  Precision measurements of critical resolved shear stress in CuMn alloys , 1986 .

[35]  P. Liaw,et al.  Refractory high-entropy alloys , 2010 .

[36]  K. T. Aust,et al.  The four stages of grain growth , 1971 .

[37]  J. E. Burke,et al.  RECRYSTALLIZATION AND GRAIN GROWTH , 1952 .

[38]  C. Dunn Secondary recrystallization textures and their origin in cold-rolled single crystals of silicon iron , 1953 .

[39]  T. Langdon,et al.  Influence of stacking fault energy on microstructural development in equal-channel angular pressing , 1999 .

[40]  E. Nes,et al.  Subgrain growth in heavily deformed aluminium—experimental investigation and modelling treatment , 1995 .

[41]  M. Edirisinghe,et al.  The Effects of Particles and Solutes on Grain Boundary Migration and Grain Growth , 1992 .

[42]  H. Berns,et al.  High nitrogen steels : structure, properties, manufacture, applications , 1999 .