SiCp/Al复合材料增强颗粒尺寸效应的细观分析

Meso analysis on size effect of SiCp/Al MMCs

运用Voronoi方法建立了反映金属基颗粒增强复合材料(MMCp)微结构的多晶集合体代表性单元(RVE);采用Taylor关系推导了包含颗粒结构尺寸和体积分数参数的位错滑移硬化函数;建立了由300个平均粒度约为20μm的晶粒组成的多晶集合体代表性单元,并对MMCp3.5-5、MMCp3.5-10、MMCp10-5、MMCp10-10四种具有不同粒径和体积分数的铝基SiC颗粒增强复合材料在宏观均匀变形条件下的应力应变响应进行了数值模拟。计算结果表明:复合材料的应力应变模拟曲线与试验曲线吻合得较好,说明所推导的模型和硬化模式能够合理地描述颗粒增强尺度效应的变化趋势;多晶体模型也能够合理地表现复合材料内部应力应变在空间分布上的细观不均匀性。数值模拟结果反映了颗粒增强区承载着较大的载荷份额,而非颗粒存在区(基体)则承受着高达18%的应变,在两个区域的交界处出现了高达310MPa的应力集中,与已有文献试验观测的结果比较吻合。

Representative volume element(RVE) of polycrystalline aggregation embodying microstructure of MMCp material is established by utilizing Voronoi method; and the hardening function of dislocation slip is derived, including the parameters of particle diameter and volume fraction, by using Taylor's formula. It is simulated that the stress-strain response of four SiCp/Al composites with different particle diameters and volume fractions e.g., MMCp3.5-5, MMCp3.5-10, MMCp10-5 and MMCp10-10 under the macroscopic homogeneous deformation with RVE including 300 grains of average size of about 20μm. The results show the simulation curves of stress-strain response are in good agreement with the experimental ones. It reveals that the polycrystalline model and hardening function can effectively represent the variation tendency of particle size effect. The polycrystalline model displays the microscopic heterogeneity of the space distribution of stress and strain in the MMCp. The analyses of numerical simulation results reveal that the reinforced matrixes with particles bear more loading than the core region of crystal grain without particle; and the matrixes without particle undergo more deformations up to 18% strain. The higher stress concentration and strain gradient are found to emerge in the border of grains, stress up to 310MPa, which is in agreement with the comments in existing literatures.