梯度异质结构CoCrNi中熵合金的设计及变形机理研究

Design and deformation mechanism of CoCrNi medium entropy alloy with gradient heterostructure

CoCrNi是一种典型的中熵合金,其具有塑性高但拉伸强度较低的特点,这种强塑性权衡问题限制了其工程应用范围。本文采用轧制退火和旋转加速喷丸工艺,在CrCoNi中熵合金中引入梯度晶粒尺寸和孪晶的异质结构。结果表明,这种设计实现了优良的强塑性,其屈服强度和抗拉强度分别为665 MPa和950 MPa,同时断裂塑性达到40.6%。在拉伸变形过程中,梯度晶粒异质结构能够产生非均匀变形诱导硬化,提升合金屈服强度的同时,保持高的加工硬化率和优异的延展性。因此,基于轧制退火和旋转喷丸工艺,引入梯度晶粒异质结构是克服合金强度-延展性失衡问题的有效途径。

CoCrNi is a typical medium entropy alloy with high plasticity but low tensile strength.The trade⁃off problem limits its engineering applications.In this work,the heterogeneous structure of the gradient grain and twin was introduced into a CrCoNi medium entropy alloy by rolling annealing and rotating accelerated shot peening.The result show that this design achieves an excellent strong plasticity with the yield strength,tensile strength and fracture plasticity of 665 MPa,950 MPa and 40.6%,respectively.During tensile deformation,the gradient heterostructure can produce the hetero deformation⁃induced hardening,improve the yield strength of the alloy,and maintain a high work hardening rate and an excellent ductility.Therefore,the introduction of the gradient heterostructure based on rolling,annealing,and rotating shot peening is an effective way to overcome the trade⁃off between strength and ductility.