粉末热压扩散与应力场耦合的力学模型

A POWDER COMPACTION MECHANICAL MODEL FOR DIFFUSION COUPLED WITH STRESS FIELD

以弹性接触应力场为初始条件,建立了热压条件下球形颗粒表面扩散与应力场耦合的力学模型.引入包含表面能项级数形式的应力函数,以描述随时间演化的表面扩散过程及扩散对应力场演化的影响.而应力场通过改变化学势梯度,又会促进(或阻止)表面扩散结合的进程.利用该模型分析了压力、温度和界面区应力场演化对致密化参数的影响.比较了满足粘着或非粘着对结合宽度和应力分布的影响,将考虑粘着的弹性接触应力场作为初始条件,分析了弹性变形和表面扩散共同驱动的粉末冶金热压烧结致密化规律.

An analytical model was developed to investigate the coupled effects of stress field and surface diffusion bonding during powder compaction taking elastic contact stress distribution as the initial condition. The stress function including the term of surface energy is introduced for describing the surface diffusion evolu- tion and its influence on stress distributions. Simultaneously, stress-induced chemical potential gradients may promote （or impede） diffusion bonding. Effects of external load amplitude, temperature and stress distribution along the bond interface are obtained using the present model. The results showed the effect of initial bonded width and stress distributions in the cases of adhesional and un-adhesional contact, respectively. Furthermore, the powder densification process was analyzed under the initial condition of stress distribution derived from elastic contact with adhesion.