论文部分内容阅读
采用溶胶-喷雾干燥法制备纳米晶(W,Ni,Fe,La)复合粉末,研究了粉末在烧结过程中La对抑制鼓泡和晶粒长大的作用机理,通过XRD与SEM分析了La在烧结过程中的相转变规律和在合金中的存在形式,讨论了稀土La对合金液相烧结过程中扩散的影响。结果表明:稀土La在纳米复合粉末中主要以La2WO6与La4W2O15的形式存在。经液相烧结后,稀土La主要以二次相颗粒的形式分布于粘结相中,生成高温下能稳定存在的La4W2O15相,该相对杂质元素Ca、O具有很好的亲和力,起到晶界净化和晶内净化的作用。同时二次相颗粒存在于粘结相中,抑制了W在粘结相中的扩散,降低了W在粘结相中的溶解度,使得液相烧结溶解-析出过程减慢,从而抑制液相烧结阶段的晶粒长大和鼓泡现象。
The composite powders of nanocrystalline (W, Ni, Fe, La) were prepared by sol-spray drying method. The mechanism of La on the inhibition of bubbling and grain growth during the sintering process was studied. The effect of La on The phase transformation during sintering and the existing forms in the alloy were discussed. The effect of rare earth La on the diffusion during liquid phase sintering was discussed. The results show that rare earth La exists mainly in the form of La2WO6 and La4W2O15 in the nano-composite powders. After liquid phase sintering, the rare earth La mainly distributes in the phase of the secondary phase particles in the binder phase to form the stable La4W2O15 phase at high temperature. The relative impurity element Ca, O has a good affinity and reaches the grain boundary Purification and purification of the role of the crystal. While the secondary phase particles are present in the binder phase, inhibiting the diffusion of W in the binder phase, decreasing the solubility of W in the binder phase, slowing the liquid phase dissolution dissolution-precipitation process, and suppressing the liquid phase sintering Phase of grain growth and bubbling phenomenon.