热暴露对Cr-12Nb合金组织与性能的影响

Effect of Thermal Exposure on Microstructure and Properties of Cr-12Nb Alloy

采用机械合金化+热压工艺制备出成分为Cr-12Nb的Cr/NbCr2合金。对该合金进行800℃保温不同时间的真空热暴露实验,研究了热暴露对合金组织与性能的影响。结果表明,合金在前30h的热暴露过程中析出了细小的Laves相NbCr2,随热暴露时间的延长,Laves相NbCr2不再析出,并发生聚集长大。Cr-12Nb合金的致密度在热暴露过程中稍有增加,而维氏硬度随热暴露时间的延长先升高后下降,但整体均高于热暴露前,维氏硬度在热暴露50h后达到6.1GPa,较未热暴露提高了3.3%。Cr-12Nb合金的室温压缩屈服强度、抗压强度和塑性应变随热暴露时间的延长先上升后下降,屈服强度和抗压强度整体而言均高于未热暴露时的强度。热暴露50 h后合金的屈服强度和抗压强度分别从热暴露前的1843MPa和1911MPa提高至1884MPa和2372MPa。塑性应变在热暴露10h后达到最大值13.2%,热暴露50h后下降至8.1%,较热暴露前下降了33.6%。

Abstraet：Cr/NbCr2 alloy with the composition of 88at% Cr and 12at%Nb （Cr-12Nb） was prepared by mechanical alloying and hot pressing. Then, the effects of thermal exposure on microstructure and properties were investigated after thermal exposure at 800 ℃ in vacuum for different time, respectively. The results indicate that some microscopic NbCr2 Laves phase particles are precipitated within 30 h treatment. Then, with the thermal exposure time further increasing, no more NbCr2 particles are precipitated and the former NbCr2 particles appear to certain coarsening. While, the relative density of Cr-12Nb alloy increases slightly during the whole treatment process. After thermal exposure, the mechanical properties of the alloy also show different from the original alloy. The value of Vickers hardness of Cr-12Nb alloy increases firstly and then declines with the increase of thermal exposure time. Vickers hardness of Cr-12Nb alloy can reach 6.1 GPa at 50 h which increases by 3.3% than that of original alloy. With the prolong of thermal exposure time the yield strength, compressive strength and strain of Cr-12Nb alloy show the same trend, firstly increase and then decrease with the prolong of thermal exposure time. Compared with original alloy, the yield strength and compressive strength of exposed Cr-12Nb alloy show higher. After 50 h thermal exposure, the yield strength and compressive strength vary from 1843 MPa and 1911 MPa to 1884 MPa and 2372 MPa, respectively. While, the strain reaches maximum value 13.2% at 10 h and then declines to 8.1% which is reduced by 33.6% than that of original alloy at 50h.