深冷处理对TC4钛合金退火过程中微观组织和力学性能的影响  

Effect of deep cryogenic treatment on microstructure and mechanical properties of TC4 titanium alloy during annealing

作　　者：李晓琛 王世颖 华天宇 陈智栋 Li Xiaochen;Wang Shiying;Hua Tianyu;Chen Zhidong(School of Materials Science&Engineering,Changzhou University,Changzhou Jiangsu 213164,China;School of Petrochemical Engineering,Changzhou University,Changzhou Jiangsu 213164,China)

机构地区：[1]常州大学材料科学与工程学院,江苏常州213164 [2]常州大学石油化工学院,江苏常州213164

出　　处：《金属热处理》2022年第6期46-53,共8页Heat Treatment of Metals

基　　金：国家自然科学基金(51601020,51574047)。

摘　　要：采用液氮直冷法在-196℃下分别对10%、20%和40%压下量的TC4双相钛合金进行12 h的深冷处理并进行500℃不同时间退火处理。利用光学显微镜对晶粒尺寸进行表征;利用扫描电镜(SEM)对α相和β相体积分数进行表征;利用维氏硬度仪、电子万能试验机分别对硬度和拉伸性能进行表征。通过晶粒尺寸以及α相和β相组织结构的变化,来分析材料的硬度和拉伸性能的变化原因。结果表明,随着退火时间的延长,深冷退火试样晶粒尺寸呈先下降后上升的规律,β相的体积分数逐渐减少,转变为α相。深冷12 h轧制态TC4钛合金经过1 h的退火处理后,晶粒尺寸出现小幅度的下降,这与退火过程中产生的较小晶粒有关,并且材料在轧制后继续深冷使得材料的变形能更高,在退火过程中容易产生更多的小晶粒,同时更有利于促进β相向α相转变,材料在500℃退火1 h时综合力学性能表现优异。当退火时间超过1 h后,材料内α相和β相两相体积分数的变化逐渐趋于平缓,并且随着退火时间的延长,晶粒粗化现象比较明显。因此,材料的强度和硬度均低于退火1 h时的强度和硬度。冷轧变形的TC4合金经12 h深冷后在500℃退火1 h较为理想,可获得较好的综合力学性能。TC4 dual-phase titanium alloy with 10%, 20% and 40% compression was subjected to 12 h cryogenic treatment at-196 ℃ by liquid nitrogen and then annealed at 500 ℃ for different time. The grain sizes were characterized by optical microscope, the volume fraction of α and β phases was measured by scanning electron microscope, the hardness and tensile properties were tested by Vickers hardness tester and electronic universal testing machine, respectively. Through the change of grain size and the structure of α phase and β phase, the changes of the hardness and tensile properties were explained. The results show that the grain size decreases first and then increases, and the volume fraction of β phase gradually decreases and transforms into α phase with the annealing time increases. When annealed for 1 h, the grain size decreases slightly, which is related to the smaller grains produced during the annealing process, and the continued cryogenic treatment after rolling makes more deformable, and more small grains are easily produced during the annealing process which is more conducive to promote the transition from β phase to α phase. So the alloy has excellent comprehensive mechanical properties when annealed at 500 ℃ for 1 h. When the annealing time exceeds 1 h, the volume fraction of α and β phases does not change significantly, and with the extension of the annealing time, the grain coarsening phenomenon is more obvious. Therefore, the strength and hardness of the material are lower than that when annealed for 1 h. It is concluded that annealing at 500 ℃ for 1 h is an ideal processing for the cold rolled TC4 titanium alloy after deep cryogenic treatment for 12 h, under which can obtain preferable comprehensive mechanical properties.

关 键 词：深冷处理 TC4双相钛合金 微观组织 力学性能 退火处理 

分 类 号：TG146.2[一般工业技术—材料科学与工程]