中温轧制对新型镍基高温合金微观组织和高温力学性能的影响

Effect of Warm Rolling on Microstructure Evolution and High Temperature Mechanical Properties of a Novel Ni-based Superalloy

合金的微观组织与加工方法有关,并进一步决定了合金的力学性能。基于此,采用EBSD、SEM、TEM和准静态高温拉伸试验研究了不同中温轧制变形量与新型镍基高温合金微观组织和高温(760℃)力学性能之间的内在联系。中温轧制变形量的增大会显著提高合金的高温力学性能:相比于固溶+双级时效处理试样的高温力学性能(σ_(y)=860 MPa,σ_(uts)=973 MPa和ε_(f)=3.5%),当中温轧制变形量为10%时,合金的σ_(y)提高了230 MPa,σ_(uts)提高了166 MPa,ε_(f)变化不明显,为4.1%;而当中温轧制变形量为80%时,合金的σ_(y)提高了190 MPa,σ_(uts)提高了165 MPa,ε_(f)大幅度增加,为22.5%。微观组织分析表明,随着中温轧制变形量的增加,合金的主要变形机制由孤立层错剪切向微孪生转变,微孪晶的形成既保证了合金的高温强度,又有利于延伸率的提高,是实现合金高温强塑性匹配的主要原因。本研究为获得良好高温强塑性匹配的镍基高温合金提供了一种新策略。

Based on the theory that the microstructure depends on the processing method and further determines the mechanical properties of the alloy,the intrinsic relationship of different warm rolling deformation degrees with the microstructure evolution and high temperature(760 oC)mechanical properties of a novel Ni-based superalloy were investigated by EBSD,SEM,TEM and quasi-static high temperature tensile tests.The results show that the increase in the reduction of warm rolling significantly improves the high temperature mechanical properties.The yield strength,ultimate tensile strength and elongation of Ni-based superalloy processed by the warm rolling with the deformation reduction of 10%,are increased by 230 MPa,166 MPa,and 4.1%,respectively,compared with that of samples processed by solution and aging treatments.Further rolling deformation processing(80%)causes the evident increase(22.5%)in elongation.The microstructural analysis shows that with the increase in warm rolling deformation degree,the main deformation mechanism transforms from isolated stacking fault to microtwinning.The formation of microtwins not only ensures the high-temperature strength,but also is beneficial to improve the elongation which is the main reason to achieve the high temperature tensile strength-ductility matching.The present study provides a new strategy to obtain the satisfactory high temperature tensile strength-ductility matching of Ni-based superalloy.