环境湿度及氢气压力对U-2.5%Nb合金拉伸性能的影响

Effect of Environment Humidity and Hydrogen Pressure on the Tensile Property of U-2.5%Nb Alloy

研究了U-2.5%Nb合金(质量分数,下同)在相对湿度分别为3.5%、50%、100%、水浸、热水和水蒸气环境,氢气压力分别在0.4,1.0,2.0MPa条件下的拉伸性能及断口形貌。结果表明:拉伸速率在3×10-5/s时,随环境湿度及氢气压力的增加,U-2.5%Nb合金的抗拉强度降低,规定非比例延伸强度增加,塑性急剧下降。同样在水浸环境,3×10-5/s与1×10-4/s的拉伸速率相比,U-2.5%Nb合金断后伸长率下降约84%,断面收缩率下降约79%。拉伸速率在3×10-5/s时,合金在2.0与0.4MPa的氢气压力相比,断后伸长率下降约20%,断面收缩率下降约13%。在相对湿度3.5%的环境下,U-2.5%Nb合金试样断口边缘呈韧窝状,有一定的韧性特征。在水浸环境下,试样断口边缘韧窝明显减少,有一定的脆断特征。在水蒸气环境中,试样断口边缘有明显的解理脆断特征。在氢气环境中,试样断口的脆断特征随氢气压力的增加而增强。

The tensile property and fracture appearance of U-2.5%Nb alloy（mass fraction） were studied under the conditions with relative humidity of 3.5%,50%,100%,underwater,hot water and water vapor,together with hydrogen pressure of 0.4,1.0,and 2.0 MPa.The results show that when the strain rate is 3×10-5/s,with the environment humidity and hydrogen pressure increasing,the tensile strength of U-2.5%Nb alloy decreases,the proof strength non-proportional extension increases,and the plasticity decreases sharply.In the underwater environment,at the strain rate of 3×10-5/s the elongation after fracture decreases by about 84% and the reduction of area decreases by about 79% compared with those at the strain rate of 1×10-4/s.At the strain rate of 3×10-5/s and in the 2.0 MPa hydrogen pressure environment,the elongation after fracture decreases by about 20% and the reduction of area decreases by about 13% compared with those in the 0.4 MPa hydrogen pressure environment.The fracture surface of U-2.5%Nb alloy shows a ductile feature in the environment with 3.5% relative humidity.However,dimples of the alloy fracture surface reduce obviously and a brittle fracture appears in the underwater environment.The fracture surface of the alloy shows an evident cleavage and brittle feature in water vapor environment.The brittle feature of the alloy fracture surface is enhanced with the hydrogen pressure increasing.