碳含量与热处理对高铌钛铝合金微观组织及力学性能的影响

Effects of carbon content and heat treatment on microstructure and mechanical properties of TiAl alloys with high Nb

以Ti-44Al-8Nb-xC(x=0,0.3,0.6)合金为研究对象,研究了3种不同碳含量和两种不同温度的时效处理对合金的微观组织、显微硬度及高温拉伸性能的影响。结果表明:碳含量升高到0.6%时,合金中析出了Ti2AlC;时效温度从800℃升高到900℃时,含碳合金中析出了Ti_(3)AlC。碳含量的增加和时效温度的升高都有利于提升合金的显微硬度和850℃抗拉强度,显微硬度最高为(477.6±9.1)HV0.3,850℃抗拉强度最高为(605.07±5.01)MPa,较最低抗拉强度提高了32.7%。断后伸长率与合金中碳化物数量及尺寸有关,拉伸断口都表现为脆性断裂;碳含量为0.3%,经900℃时效后合金拥有最好的塑性,断后伸长率最高,为5.41%±0.42%,较最低伸长率提升了67.5%。

Taking Ti⁃44Al⁃8Nb⁃xC(x=0,0.3,0.6)alloys as the research object,the effects of three different carbon contents and two aging temperatures on the microstructure,microhardness and high⁃temperature tensile properties were studied.The results show that when the carbon content increases to 0.6%,Ti2 AlC precipitates in the alloy.When the aging temperature increases from 800℃to 900℃,Ti_(3)AlC precipitates in the alloy containing carbon.The increase in carbon content and aging temperature are all beneficial to improving the microhardness and tensile strength at 850℃of the alloy,where the highest microhardness is(477.6±9.1)HV0.3,and the highest tensile strength at 850℃is(605.07±5.01)MPa,which increases by 32.7%compored to the lowest tensile strength.The elongation is related to the number and size of carbides,and all the tensile fractures show brittle fracture.The alloy with 0.3%carbon has the best plasticity when aged at 900℃,the highest elongation is 5.41%±0.42%,which increases by 67.5%compared to the lowest elongation.