TC4钛合金电子束连接组织与性能演变

Microstructure and Performance Evolution of Electron Beam Bonding of TC4 Titanium Alloy

对厚20 mm的TC4钛合金板真空电子束连接过程温度场进行数值模拟,并对其进行了退火处理。采用光学显微镜、显微硬度仪、拉伸试验机、冲击试验机等分析了退火前后电子束接头的显微组织和力学性能。结果表明,TC4钛合金真空电子束连接过程中连接区及其附近热影响区存在较大的温度梯度,可高达1000℃;退火处理后接头组织为针状马氏体α'相,热影响区组织为针状马氏体α'相和原始的α相与β相,电子束接头显微组织组成相未发生变化,但其晶粒尺寸细化;退火处理消除了电子束接头热影响区到母材区的硬度突变现象,接头抗拉强度达到母材的98%,冲击韧度较退火前提高了6.0%以上。

The temperature field of TC4 titanium alloy plate with thickness of 20 mm during vacuum electron beam bonding was numerically simulated,and subsequent annealing treatment was performed.The microstructures and mechanical properties of the joint before and after annealing were analyzed by optical microscope,microhardness tester,tensile tester and impact tester.The results indicate that there exists a large temperature gradient in the joining zone and adjacent heat affected zone during vacuum electron beam bonding of TC4 titanium alloy,which reaches up to 1000℃.After annealing treatment,the microstructure of the joint is composed of acicular martensiteα'phase,and that of heat-affected zone consists of acicular martensiteα'phase and the originalαandβphases.The phase composition of electron beam joint remains stable,while grain size is refined.The abrupt phenomenon of hardness from the heat affected zone to the base metal zone of the electron beam joint is eliminated by annealing treatment,where the tensile strength of the electron beam joint reaches 98%of base metal,and the impact toughness is over 6.0%higher than that of ones before annealing.