反应烧结高Nb-Al_3Ti合金的组织演变机理

Microstructure Evolution Mechanism of High Nb Content Al_3Ti Alloy by Reaction Sintering

摘要:

采用放电等离子热压烧结技术(SPS)制备高Nb-Al_3Ti合金,研究了315和645℃预烧结处理以及885～1130℃范围内不同反应烧结温度对Al_3Ti合金显微组织的影响,分析了不同烧结温度下合金组织的变化过程并绘制组织转变示意图。结果表明,经过315与645℃的预烧结处理,原料颗粒表面氧化物溶解并发生固相扩散生成少量的Al_3Ti使相界钝化; 885～1130℃的反应烧结过程主要发生液相烧结与晶粒生长,熔融液相Al与难熔Ti、Nb_2Al的相界处发生包晶反应生成Al_3Ti和Al_3Nb,新生Al_3Ti相阻碍Al元素扩散使内部与Ti反应的Al含量降低导致Al_2Ti的生成;随着烧结温度升高,反应速率加快,反应原料快速完成合金化过程并进行晶粒生长,Al_3Ti与Al_3Nb的晶体结晶度得到提高。

Abstract:

A high Nb content Al_3 Ti alloy was prepared by spark plasma sintering technology to study the effects of 315 ℃and 645 ℃ pre-sintering and different reaction sintering temperatures at 885-1130 ℃ on the microstructure of Al_3 Ti alloy. The microstructure transformation process at different sintering temperatures was analyzed and the schematic diagram of microstructure transformation was drawn. The results show that after the pre-sintering treatment at 315 and645 ℃,the surface oxide of the raw material particles dissolves,and the solid phase diffusion occurs and a small amount of Al_3 Ti is generated to make the phase boundary passivation. The liquid-phase sintering and grain growth occurs in the reaction sintering process at 885-1130 ℃,the peritectic reaction between molten Al and refractory Ti and Nb2 Al results in the formation of Al_3 Ti and Al_3 Nb,and the formation of Al2 Ti is attributed to the fact that the Al_3 Ti phase hinders the diffusion of Al element and reduces the Al content of the reaction with Ti. With the increase of sintering temperature,the reaction rate is accelerated and the alloying process and grain growth of the reaction materials is rapidly completed,resulting the improvement of the crystallinity of Al_3 Ti and Al_3 Nb.