純鈦低溫力學性能的影響
( 1. 西安交通大學 金屬材料強度國家重點實驗室， 西安 710049;
2. 西安理工大學 材料科學與工程學院， 西安 710048;
3. 西北有色金屬研究院 鈦合金研究所， 西安 710016)
摘 要: 對工業(yè)純鈦（TA2）在液氮介質(zhì)中機械孿晶隨應變量的變化規(guī)律以及孿晶對晶粒尺寸的依賴性進行了研究。結(jié)果表明： 在靜拉伸過程中孿晶分數(shù)隨應變量的增加而增加， 孿晶的形成主要在均勻塑性變形階段， 尤其在塑性變形的初期， 頸縮后孿晶分數(shù)增加緩慢。 孿晶形貌的演化規(guī)律為：在變形的初始階段生成孿晶的尺寸比較大， 在隨后的塑性變形中又發(fā)生破碎， 最終形成一些孿晶密集的區(qū)域。 低溫下純鈦的塑性變形方式為孿生和滑移共同作用。 粗晶粒（55 μm）和細晶粒（18 μm）的純鈦在室溫和低溫下的拉伸實驗結(jié)果表明， 晶粒的粗化沒有降低純鈦的塑性， 低溫下粗、 細晶粒純鈦的塑性均比室溫下的高。這種現(xiàn)象與純鈦低溫下活躍的孿生密切相關(guān)。
關(guān)鍵字: 工業(yè)純鈦； 機械孿晶； 塑性； 力學性能
mechanical behavior of commercial titanium
at cryogenic temperature
（ 1. State Key Laboratory for Mechanical Behavior of Materials,
Xi'an Jiaotong University, Xi'an 710049, China;
2. School of Materials Science and Engineering,
Xi'an University of Technology. Xi'an 710048, China;
3. Research Center for Titanium Alloy,
Northwest Institute for Nonferrous Metals Research, Xi'an 710016, China）
Abstract: Twinning behavior in tensile deformation of commercial pure titanium as well as its grain size dependence were investigated. The microstructure after deformation was observed by use of optical microscope and transmission electron microscope, and the twin fraction was obtained as well. The results show that twins appear mainly at the stage of strain hardening and twin fraction increases with increase of the plastic deformation. The size of twins at early stage of plastic deformation is larger than that at latter stage, however, larger twins will break under large deformation, which forms some zones with high density of twins together with small twins. The microstructures also show that twinning cooperates with slip in the deformation of titanium at cryogenic temperature. Commercial pure titanium with grain size of 18 μm and 55 μm were obtained after annealed at 650 ℃ and 800 ℃, respectively. The tensile properties show that ductility of titanium increases with increase of grain size from 18 μm to 55 μm at room temperature and -196 ℃, and twinning seems to become more common in coarsening grains. All the results imply that higher ductility in coarsening grain is related to the mechanisms of twinning induced plasticity.
Key words: commercially pure titanium; mechanical twinning; ductility; mechanical behavior
