基于二维离散位错动力学的颗粒强化机制建模

Modeling of particle strengthening mechanics based on two-dimension discrete dislocation dynamics

基于二维离散位错动力学方法,以含有L12型长程有序γ′沉淀相的镍基合金为研究对象,根据材料实际的晶体结构建立了相应的模型。研究了颗粒体积分数与平均半径对金属及合金强度的影响,实现了材料临界分切应力的预测。为了使有限元模型与实际Ostwald熟化晶体中的颗粒分布更为接近,模型考虑了颗粒的LSW分布规律。此模型中颗粒简化为球形,其在三维空间中的体积分数分别为5.5%、8%和10.5%,平均半径分别为16b、25b和36b(b为位错的柏氏矢量大小),位错与颗粒之间的交互作用基于位错切过机制。结果表明,欠时效状态下γ′沉淀相的体积分数或平均半径的增大都会导致镍基合金的临界分切应力增大。临界分切应力一定程度上体现了材料强度,临界分切应力越大,材料强度越高,因此可以通过增大颗粒体积分数和平均半径提高材料强度。

Based on the method of two-dimension discrete dislocation dynamic (2DDD),the Ni-base alloy with L12 long-range ordered γ′ precipitate was taken as study object,the corresponding model was built based on the real crystal structure.The effects of volume fraction and mean radius of particles on strengthening of metals and alloys were investigated,the critical resolved shear stress (CRSS)of the material was predicted.In order to make the finite element model close to distribution of particles of an actual Ostwald-ripened crystal,the LSW distribution of particles was considered in the model.In the model,the particles were simplified to be spherical.The volume fraction of particles in three dimensions was 5.5%,8.0%and 10.5%,and the mean radius of particles was 16b,25b and 36b (b is the value of burgers vector),respectively.The interaction between dislocation and particles was based on the dislocation cutting mechanism.The result shows that in under-aged situation the higher volume fraction or higher mean radius of γ′ precipitates can both enlarge the CRSS of Nibase alloy.To some extent the strengthening of material is determined by CRSS,which rises with the increase of CRSS.Therefore,the strength of the material can be improved by increasing volume fraction and average radius of particles.