热锻温度对TG6高温钛合金显微组织和力学性能的影响

来源期刊：金属学报2010年第8期

论文作者：王涛 郭鸿镇 张永强 姚泽坤 谭立军

文章页码：913 - 920

关键词：高温钛合金； 近等温锻造； 显微组织； 力学性能

Key words：high temperature titanium alloy； near-isothermal forging； microstructure； mechanical property

摘    要：在850-1075℃范围内,采用恒定的应变速率和变形程度,对TG6合金进行了近等温锻造实验.利用OM和金相图像分析软件等手段分别测定了TG6合金锻前保温、锻后空冷和锻后热处理试样的显微组织中初生α相的含量,以及热处理锻件组织中次生片状α相的厚度.结果表明,与锻前保温的合金相比,较低温度(低于1000℃)下锻造的锻件及其热处理锻件中初生α相含量减少,且减少程度随锻造温度升高而降低;而较高温度(大于1000℃)下锻造的锻件及热处锻件中初生α相含量增加,且增加幅度随锻造温度的升高而增加.提高锻造温度减小了次生α相形核密度,造成片状α相厚度随锻造温度的升高而增加.当在1075℃锻造时,由于β晶粒过分长大,造成显微组织不均匀.研究了合金锻件的室温和600℃拉伸性能、冲击韧性及断裂韧性.结果表明,合金拉伸强度对锻造温度不敏感,塑性随锻造温度升高而减小,而室温断裂韧性则随温度升高而增加,两相区锻造的合金冲击韧性无明显变化,但当锻造温度接近β相变点时呈现降低趋势.采用SEM,TEM及OM等手段分析了合金锻件力学性能变化的原因.

Abstract: Near-isothermal forging experiments of the TG6 titanium alloy have been conducted at the deformation temperatures ranging from 850 to 1075℃ with a constant strain rate and deformation degree.The primary α phase content in the alloy after solution,deformation and heat treatment,and the thickness of lamellarαphase in the alloy after heat treatment were measured by OM and image analyzer.The results show that compared to solution state,both forging and forging+heat treatment cause the decrease or increase of primary α phase content when forging temperatures are below or over 1000℃.The thickness of the lamellar α phase increases with the increase of forging temperature, which is caused by the decrease of nucleation density of secondaryαphase.The β phase grains are so big when the forging temperature is 1075℃,while their microstructures are non-uniform.The room temperature and 600℃ tensile properties,impact property and fracture toughness of TG6 alloy have also been measured.It is found that the tensile strength of the TG6 alloy is not very sensitive to forging temperature.The plasticity decreases but the fracture toughness increases with the increase of forging temperature.There is no obvious change in the impact toughness when forging in the α and β double phase field,however it decreases when forging temperature is near the β transformation temperature.The change in mechanical property was explained by SEM,TEM and OM experiments.