【作者】 孙巧艳； 谭长生； 肖林； 孙军；

【Author】 Sun Qiaoyan;Tan Changsheng;Xiao Lin;Sun Jun;State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University;

【机构】 金属材料强度国家重点实验室西安交通大学；

【摘要】 TC2l合金是我国自主研发的两相高强高韧性钛合金,主要用于飞机的结构件。本文研究了TC2l合金经过固溶处理和固溶+时效处理的组织在拉伸载荷作用下的变形行为及特性,揭示了β相强化的微观机制。将双态组织的TC2l合金分别进行以下处理:900℃固溶4.5小时、900℃固溶4.5小时+600℃时效6小时,获得的组织具有相同的α相形貌与分布,但是前者的β相二次a相的析出,后者β相有二次α析出。对以上两种组织状态的合金进行拉伸试验(试样采用板状试样,拉伸前抛光腐蚀,显示微观组织),观察并分析了随着变形量的增加,合金滑移带的形成、扩展规律,揭示了β相中二次α相存在对滑移的显著阻碍作用。通过对变形试样的TEM的观察分析,发现α相启动了柱面滑移和基面滑移,对于无二次α相析出的β相,滑移穿过α/β界面,将启动β滑移并穿过β相,进入相邻α相滑移,α/β界面强化作用较弱;对于时效后β相有二次α相析出,初始α相的滑移阻碍在α/β界面处,滑移无法穿过有二次α相析出的β相,此时α/β界面阻碍位错滑移并起到强化效果。α/β界面处应力足够大的情况下β相发生孪晶变形以协调应力集中,从而避免界面裂纹产生。更多还原

【Abstract】 In present work different interaction between slip and α/β interphase in TC21 alloy and strengthening mechanism from α/β interphase are discussed with respect of existence of the second acicular a phase.TC21 alloy with duplex microstructure were subjected to solid solution treated at 900℃ for 4.5 hours to get coarse α phase and plate-like β phase,and another group of sample were annealed at 600℃ to nucleation second acicular a phase in plate-like β phase.The dog-bone tensile sample were polished and etched before tensile tests so that the slip bands in a and β phase can be observed.The results show that slip starts in a phase and with increasing strain the slip band go cross the α phase.Whether the slip bands penetrate α/β interphases depends on the existence of second α phase in plate-like β phase.The slip can penetrate α/β phase easily and reactive slip in beta phase when there is no second a in beta phase,while slip stop at α/β phase when second acicular a existence in β phase.As a result,the latter interphase brings about strengthening for titanium alloy.The slip systems are prismatic slips in(10-10) prismatic plane in a phase and slip in(111) plane in beta phase.Twinning is activated in beta phase with second acicular a phase to relax the stress concentration at interphase which can avoid formation of crack at interphases.更多还原