Abstract This paper analyzes the heating of TiAl powders at particle scale in spark plasma sintering (SPS). During SPS processing, the powder particles are subjected to uniaxial pressing and small contact areas are formed between particles. Numerical simulations are performed on a representative cell of the material and qualitatively compared to experiments. In order to understand the heating mechanisms involved in SPS, two models are analyzed. The first one considers only heat diffusion in the material. The second one associates local Joule heating due to current concentration and heat diffusion. In TiAl alloys, the γ-α phase transition at 1335°C was used as marker of the temperature reached locally. More than 100 particle necks of several samples of 100μm diameter Ti48Al48Cr2Nb2 powders processed by SPS were investigated to detect overheating marks. Simulations clearly show high current concentration in and close to the necks, but both simulations and experiments show that there is no heat concentration close to the necks for this size of particles. Simulations show that this is due to fast heat dissipation in small particles: centimetric or higher size particles would be required to observe significant overheating.

中文翻译：

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放电等离子烧结中颗粒接触处局部过热的理论和实验研究

摘要 本文分析了 TiAl 粉末在放电等离子烧结 (SPS) 中颗粒尺度的加热。在SPS加工过程中，粉末颗粒受到单轴压制，颗粒之间形成小的接触面积。对材料的代表性电池进行数值模拟，并与实验进行定性比较。为了了解 SPS 中涉及的加热机制，我们分析了两个模型。第一个只考虑材料中的热扩散。第二个与由于电流集中和热扩散引起的局部焦耳加热有关。在 TiAl 合金中，1335°C 的 γ-α 相变被用作局部达到温度的标志。对经 SPS 处理的几个直径为 100μm 的 Ti48Al48Cr2Nb2 粉末样品的 100 多个颗粒颈部进行了研究，以检测过热痕迹。模拟清楚地显示颈部内和颈部附近的高电流集中，但模拟和实验都表明，对于这种尺寸的粒子，颈部附近没有热量集中。模拟表明，这是由于小颗粒的快速散热：需要厘米或更大尺寸的颗粒才能观察到明显的过热。