B_4C对Nb-NbCr_2合金热稳定性的影响研究

Effect of B_4C on Thermal Stability of Nb-NbCr_2 Alloy

采用机械合金化和热压工艺制备添加原子分数为0.5%B_4C的Nb-NbCr_2合金,在1 200℃对其分别进行30~100 h的真空热暴露实验,研究B_4C对Nb-NbCr_2合金热稳定性的影响。结果表明,热暴露后的B_4C/Nb-NbCr_2合金未发生明显的物相变化;热暴露100 h后的致密度从98.6%升高至98.7%,其变化幅度明显小于未添加B_4C的合金;热暴露后的Laves相NbCr2颗粒存在少许聚集长大现象,但比未添加B_4C的合金的聚集长大现象要轻微许多;热暴露50 h和100 h后的维氏硬度与热暴露前相比分别下降10.1%和1.7%,但其变化幅度明显较小未添加B_4C的合金;热暴露100 h后的抗压强度和塑性应变分别由热暴露前的3 048 MPa和12.7%变化至2 788 MPa和20.7%,其变化幅度要小于未添加B_4C的合金。添加B_4C颗粒可在一定程度上提高Nb-NbCr_2合金的热稳定性。

The Nb-NbCr_2 alloy with 0. 5at. % B_4C was prepared by mechanical alloying and hot pressing. To investigate the effects of B_4C on thermal stability of Nb-NbCr_2 alloy,the samples were thermally exposed at 1 200 ℃ for 30 ~ 100 h in vacuum,respectively.The results show that composition phases of B_4C/Nb-NbCr_2 alloy have no obvious change after the thermal exposure process. The relative density of B_4C/Nb-NbCr_2 alloy increases from 98. 6% to 98. 7% and the change is significantly smaller than Nb-NbCr_2 alloy without B_4C addition. Laves phase NbCr_2 particles of B_4C/Nb-NbCr_2 alloy have a little aggregation and growth after the thermal exposure process,but the phenomenon of aggregation and growth of Laves phase NbCr_2 particles is much less than Nb-NbCr_2 alloy without B_4C addition. After thermal exposure for 50 h,the Vickers hardness of B_4C/Nb-NbCr_2 decreases by 10. 1% after the first 50 h and decreases by only 1. 7% after the later 50 h,and the change is significantly smaller than Nb-NbCr_2 alloy without B_4C addition.After thermal exposure for 100 h,the compressive strength and plastic strain of B_4C/Nb-NbCr_2 alloy change from 3 048 MPa and12. 7% to 2 788 MPa and 20. 7%,respectively,and the change is significantly smaller than Nb-NbCr_2 alloy without B_4C addition. Ingeneral,it can be seen that the B_4C particles can improve the thermal stability of Nb-NbCr_2 alloy.