激光熔覆热循环对TC4组织与力学性能的影响研究  

Influence of Laser Cladding Thermal Cycle on Microstructure and Mechanical Properties of TC4

作　　者：白文倩 陈静青[1] Bai Wenqian;Chen Jingqing(School of Materials Science and Engineering,Southwest Jiaotong University,Chengdu 610031,Sichuan,China)

机构地区：[1]西南交通大学材料科学与工程学院,四川成都610031

出　　处：《中国激光》2022年第22期191-201,共11页Chinese Journal of Lasers

摘　　要：TC4双相钛合金在相变温度附近易发生β相变及有序化转变,在激光熔覆过程中多次热循环作用会导致组织发生复杂转变。针对TC4钛合金激光熔覆组织力学性能不均匀问题,采用热模拟试验机,对TC4钛合金进行了热循环测试,探究了热循环的峰值温度、冷却速率对其组织转变及力学性能的影响。结果表明:在快速升温的热循环条件下,当峰值温度低于960℃时,材料内部发生组织粗化,随着温度的升高,一次相长宽比增大;当峰值温度达到1100℃时,晶界处亚稳β相发生同素异构转变和有序化相变,生成Ti_(3)Al有序相,一次相长宽比减小,组织细化,硬度和裂纹敏感性显著增加;当冷却速率增加时,相变类型由亚稳β相的同素异构转变为马氏体型,一次相形貌由层片状转为针状,材料硬度逐步趋于稳定,但当冷却速率大于12℃/s时,由于Ti_(3)Al的生成,材料硬度略微升高,剪切试验测得材料脆性增加。Objective TC4 titanium alloy is prone to β-phase and ordering transformation near the phase transition temperature due to its dual-phase composition characteristics. When the laser cladding is used to manufacture TC4 titanium alloy moldings, the high-temperature gradient and rapid solidification during the cladding process occur. The accumulation of thermal stress, an easy occurrence, will cause cracks to develop inside the molded part. Additionally, the structure of TC4 titanium alloy is unstable under high-temperature environments, and the rapid cooling and heating during the laser cladding process will make the base metal grains at the bottom of the molten pool epitaxial growth leading to the arrangement of the original β columnar grains along the deposition direction to form a typical solidified texture. The resulting columnar grain structure and nonequilibrium phase will further reduce the mechanical strength of the material. Furthermore, in the preparation of multilayer and multichannel samples, the change in the interlayer temperature will cause a change in the cooling rate, which will affect the transformation of the metastable β phase, and the different transformation products will affect the properties of the material. Therefore, given the uneven mechanical properties of the TC4 titanium alloy laser cladding structure during the reheating thermal cycle, the thermal simulator is used to reproduce the effect of the reheating thermal cycle during the multipass laser cladding process. The laser cladding thermal cycle and the effects of its characteristics on the microstructure and properties of TC4 titanium alloy are also investigated.Methods In this paper, the thermal simulation testing machine is used to conduct thermal cycle tests on TC4 titanium alloys to explore the effects of thermal cycle peak temperature and cooling rate on its microstructure transformation and mechanical properties. The coaxial powder feeding laser additive manufacturing(LAM) technology is used to prepare the TC4 titanium alloy

关 键 词：激光技术 钛合金 激光熔覆 热循环 显微组织 

分 类 号：TG113[金属学及工艺—物理冶金]