基于微结构动态演化机制的单晶镍基高温合金晶体塑性本构及其有限元模拟

MICROSTRUCTURE EVOLUTION MECHANISM BASED CRYSTAL-PLASTICITY CONSTITUTIVE MODEL FOR NICKEL-BASED SUPERALLOY AND ITS FINITE ELEMENT SIMULATION

因其优异的高温力学性能,镍基单晶高温合金在航空航天和能源等领域得到了广泛的应用.镍基单晶高温合金优异的高温性能来源于其特有的两相微结构.基于代表体胞模型及分块均匀化方法,以位错密度为主要内变量,发展了一个包含两相微结构和位错演化信息的单晶镍基高温合金塑性行为的本构模型.该本构模型充分考虑了镍基单晶合金中位错在基体相和沉淀增强相中的多种演化机制,例如,基体位错八面体滑移、立方滑移、位错攀移、交滑移、位错弓出、位错切过沉淀增强相以及位错Kear-Wilsdolf(K-W)锁形成与解锁等.在商用有限元软件ABAQUS的框架下,编制了UMAT用户材料子程序.利用该用户子程序,对单晶和多晶镍基高温合金在不同温度、不同加载方向下的单调塑性、循环塑性、蠕变等典型行为进行了计算模拟.结果表明:该晶体塑性本构模型能"统一地"刻画镍基高温合金在不同温度、不同方向下的多种变形行为,并与实验结果具有良好的一致性.

The nickel-based superalloy has been widely used in turbine engines of aerospace and marine industries for its excellent strength and high resistance to creep and oxidation at elevated temperature.These excellent mechanical behaviors root in its unique two-phases microstructure.Based on the homogenization method and representative volume cell(RVC)model,a crystal-plasticity(CP)constitutive model with information of two-phases microstructure and dislocation evolution was developed for nickel-based superalloys.By introducing various dislocation densities as major internal variables,the present constitutive model fully considered a series of dislocation mechanisms,including octahedral glide,cubic slip,climb,cross slip and bowing-out in the phase,and precipitate shearing and the Kear-Wilsdolf lock formation in the0phase.Based on this,a user material subroutine(UMAT)for this CP constitutive model was realized in the FEM software ABAQUS.By using this UMAT module,the creep,monotonic and cyclic mechanical behaviors of single-crystalline and poly-crystalline nickel-based superalloys were modeled under di_erent temperatures and various loading orientations.The computationally obtained results were in good accordance with the experimental data,indicating that the present CP constitutive model with information of microstructures and dislocations evolution could uniformly describe various mechanical behaviors of nickel-based superalloys under di_erent temperatures and loadings,including the monotonic plasticity,creep and cyclic plasticity.