Ti-60钛合金电子束焊接接头高温下的失效与变形行为

FAILURE AND DEFORMATION BEHAVIORS OF ELECTRON BEAM WELDMENT OF TITANIUM ALLOY Ti-60 AT ELEVATED TEMPERATURE

在600℃拉伸条件下,Ti-60钛合金电子束焊接接头的熔合区和热影响区抗变形能力强于母材区(BM),试样断裂于母材区.在600℃持久条件下,当加载应力(?)550 MPa时,接头变形以扩散控制的位错攀移为主,变形能力取决于显微组织中的板条边界密度,板条越细,边界密度越高,变形能力越大,断裂位置在接头熔合区;当加载应力接近或>550 MPa(母材区屈服强度附近)时,接头的变形以位错滑移为主,断裂位置在母材区.在600℃高周疲劳条件下,疲劳裂纹易萌生于接头母材区,裂纹形核位置在试样的表面或次表面.TEM观察表明,接头母材区的变形以贯穿板条集束的位错滑移为主;而接头熔合区中的位错则局限在单个马氏体板条内部,位错运动特征为攀移及少量滑移.

The failure location of the 600 ℃ tensile specimens of EBW weldment of Ti-60 alloy was found to be in the base metal （BM） region, which was attributed to the superior antideformabilities of fusion zone （FZ） and heat-affected zone （HAZ） during tensile testing. The creep rupture property at 600 ℃ was found to be related to the level of creep stress applied： the fracture location shifted from FZ to BM region when the applied stress reached 550 MPa, at or above which the deformation mechanism changed from dislocation climbing to dislocation slipping. Fatigue cracks at 600 ℃ fatigue test were found to initiate at the surface or sub-surface of the specimen at BM region, TEM observation revealed that the deformation in BM region is mainly caused by dislocation gliding through α-phase laths, while the deformation in FZ is caused by dislocation climbing and limited dislocation slipping within the laths.