Development of Testing Machine for Mechanical Properties at Ultra High Temperature using Impulse Electron Irradiation

研制了超高温耐火材料力学性能试验机。为脉冲电子轰击系统搭建了专门的真空室。电子辐照是在30KV真空条件下进行的。为了在力学测试中保持试件，使用陶瓷托架。利用该加热系统获得的最高温度约为2000min C，升温速率为500min C/ﾟ。力学试验的热稳定性小于2ﾟC。由于金属材料的试验样品是通过电子辐照直接加热的，因此可以在超高温下进行力学试验。对于陶瓷试件，用钽管对试件表面进行转化，然后再进行高温处理。试件上下两侧的温度梯度很小。在拉伸或压缩试验中，使用激光测量试件的位移。利用该试验机研究了过渡金属硅化物MoSi2和NbSi2的力学性能，它们是在2000ﾟC左右工作的耐火材料的候选材料。MoSi2和NbSi2在1200ﾟC以上表现出反常强化，少量第三元素的加入使反常峰向高温方向移动。并对TiAl合金的力学性能进行了研究。利用这台机器可以很容易地获得这些合金的强度和塑性的温度依赖关系。

Testing machine for mechanical properties of ultra high-temparture refractory materials has been developed. Special vacuum chamber was built for impulse electron bombardment system. Electron irradiation was carried out at 30kV in vacuum. To hold the specimen during mechanical testing, ceramic holder was used. The maximum temperature which was obtained using this heating system was around 2000ﾟC.High heating rate of 500ﾟC/min was obtained. The thermal stability during mechanical test was less than 2ﾟC.Since test specimens of metallic materials were directly heated by electron irradiation, mechanical test at ultra high temperature could be done. For ceramic specimens the specimen surface was convered by tantalum tube and then high temperature was realozed. The thermal gradient between upper and bottom sides of specimens was very small. The displacement of specimens during tesile or comression tests was measured using laser light. Mechanical properties of transition metal silicides such as MoSi_2 and NbSi_2 which are attractive candidates for refractory materials operating around 2000ﾟC were investigated by means of this testing machine. MoSi_2 and NbSi_2 showed anomalous strengthening above 1200ﾟC and the anomalous peak was shifted to higher temperture by addition of small amounts of third element. Mechanical properties of TiAl alloys were also investigated. The temperature dependence of strength and ductility of these alloys was easily obtained using this machine.