Ti、Al混合粉在放电等离子烧结过程中的相变

Phase transformation of blended Ti and Al powders during spark plasma sintering

将Ti、Al混合粉以100℃/min的升温速率在400～980℃采用放电等离子方式进行烧结。通过XRD以及EPMA分析了烧结试样中的相和组织形貌,研究了Ti、Al混合粉在放电等离子烧结过程中的相变规律。结果表明,Ti、Al混合粉烧结中发生的相变符合Ti、Al粉体扩散反应的一般规律,即反应是由Al向Ti的扩散主导的。烧结过程可分为4个阶段:颗粒软化阶段、Al3Ti形成阶段、中间相生成阶段、最终产物生成及致密化阶段。在低于Al的熔点温度烧结时生成Al3Ti;Al消耗完之后,Al3Ti中的Al继续向Ti颗粒扩散,导致Al3Ti减少,并在界面上生成Ti2Al5、Al2Ti、TiAl及Ti3Al。在生成Al3Ti阶段,Al的熔化加快了反应速率。同时,适当施压可抑制Al的反致密化效果,得到致密度为98%的块体。

Blended Ti and Al powders were sintered by spark plasma sintering（SPS） with 100℃/min at 400-980 ℃. Phase identification and microstructural evaluation of sintered samples were carried out by XRD and EPMA. The results show that the phase transformation process during sintering of blended Ti and Al powders meets the general principle of reaction between Ti and Al powders. That is, reaction is dominated by the diffusion of Al into Ti. The sintering process is divided into four stages：particles softening, Al3Ti formation, intermediate phases formations and final product formation with densification. Al3Ti is formed below the melting point of Al and when Al is used up,Al in AI3 Ti diffuses into Ti particles,with the amount of Al3 Ti decreasing and phases Ti2 AI~, Al2 Ti, TiAl and Ti3 Al forming along the interface. The reaction in stage of Al3Ti formation is accelerated because of the appearance of melted Al. Otherwise, the dense bulk with 98% theoretical density is gained by way of properly pressing to restrain the anti-densification effect of Al.