WC粒度分布对WC-Co硬质合金力学性能影响的模拟分析

Numerical Investigation about Influence of WC Grain Distribution on Mechanical Properties of WC-Co Cemented Carbide

本文旨在建立基于WC-Co硬质合金真实微观组织的力学性能预测有限元分析方法,进而分析WC颗粒粒度分布对微区变形和力学行为的影响。实验设计和制备了具有Co含量相同,WC晶粒分布均匀和非均匀的两种WC-Co硬质合金,并进行维氏硬度测试和用SEM进行组织观测。通过对合金组织的SEM形貌照片进行WC颗粒边界的重构,建立WC和Co两相真实组织的二维有限元模型。通过有限元模拟对两种合金的弹性模量、泊松比和强度等力学性能进行预测和微观变形机理分析。有限元模拟结果表明均匀合金强度高于非均匀合金,与实验测试的硬度所揭示的规律相吻合。对微观变形机理分析揭示了均匀合金应力分布更均匀是强度较高的主要内在机理,而WC/WC邻接界面的应力集中是弱化力学性能的主要机制。

Aiming at a finite element analysis approach for the estimation of mechanical properties in the real microstructure of WC-Co cemented carbide, the influences of WC grain distribution on the local deformation and mechanical behaviors were investigated in this research. Experimentally, two types of uniform alloy and nonuniform alloy with different WC grain sizes but same Co content, were designed and produced, and their hardness and microstructure were investigated by Vickers indentation test and SEM, respectively. The reconstruction of WC grain boundaries based on the SEM images was conducted to establish the finite element models of the real microstructures of WC grains and Co binder for the alloy. The mechanical properties, including E-modules, Poisson ratio and strength of the cemented carbide, were assessed, and the local deformation mechanisms were investigated by the finite element analysis （FEA）. The FEA results show that the uniform alloy presents larger strength, which is consistent with the trend revealed by the measured hardness. Moreover, the FEA on the local deformation reveals that the more uniform stress distribution of the uniform alloy is the main mechanism for the enhancement in strength, and the stress concentration occurring at the WC/WC interfaces significantly deteriorates the mechanical behaviors.