%A TAN Yaqin, WANG Xiaoming, ZHU Sheng, QIAO Junwei %T Research Progress on Strengthening and Ductilizing High-Entropy Alloys %0 Journal Article %D 2020 %J Materials Reports %R 10.11896/cldb.18100188 %P 5120-5126 %V 34 %N 5 %U {http://www.mater-rep.com/CN/abstract/article_2520.shtml} %8 2020-03-10 %X High-entropy alloys (HEAs) have displayed promising application potential as structural materials owing to their excellent mechanical properties, such as high strength, high hardness, good corrosion and wear resistance. The research upon mechanical properties optimization for HEAs has provoked considerable attention and some preliminary achievements have been made.
  Traditionally, the strengthening mechanisms of alloys can be classified as solid-solution strengthening, dislocation hardening, grain-boundary strengthening and secondary-phase hardening. Because HEAs have high tendency to form solid solution, solid-solution strengthening is consi-dered as a major and effective way for HEAs. In this regard, we can use one of the principal elements or an element similar to other principal elements to generate substitution solid solution. Or we can add some atoms with small radius, such as C, N, and B, so the lattice distortions can be obtained. Thermo-mechanical techniques, as commonly used prior treatment method, are also applicable for HEAs, in which cold-rolling, for-ging, recrystallization annealing, etc. all can significantly increase dislocation density and refine grains. In addition, there is a more prevailing way in recent years-secondary-phase hardening. We can easily determine the annealing temperature by thermodynamic analysis to obtain secondary phase particles, and even to control their size and morphology. Thus HEAs' mechanical properties can be improved due to the interaction between dislocations and secondary phase particles, with either shearing mechanism or Orowan-bypassing mechanism. Apart from changing internal structure, surface treatment is also helpful in strengthening and ductilization. For HEAs with fine plasticity, carburizing & nitriding and coating generally facilitate to obtaining the structure with hard surface and ductile interior. The hardening effect of carburizing & nitriding stems from interstitial solid solution and secondary phase precipitation, while the role of coating process depends on the strong adhesion between coating and alloy substrate.
  This paper gives an elaborate description of strengthening and ductilizing effects of element doping and thermal treatment on HEAs, from the perspective of internal enhancing mechanism. It also involves some typical surface treatment methods favorable for mechanical improvement of HEAs.