热处理对激光焊接β钛合金组织及性能的影响

Influence of heat treatment on microstructure and properties of laser welded β titanium alloy

采用激光焊焊接Ti-3Al-6Mo-2Fe-2Zr(wt.%)β钛合金,研究热处理对接头显微组织和拉伸性能的影响。由于激光焊接的冷却速率可达553 K/s,远大于β相向其他物相转变的临界冷却速率,所以焊缝显微组织由柱状晶形态的单一β相构成。在近热影响区,初生α相和次生α相均转变为β相,且β相晶粒尺寸增大;在远热影响区,尺寸较大的初生α相得以保留。780℃/1 h/WQ热处理后,焊缝中生成厚度约为150~350 nm、长度约为1~3μm短棒状α相,焊接头强度和延伸率有所提高;780℃/1 h/WQ+500℃/6 h/FC热处理后,焊缝中生成厚度约为30~40 nm,长度约为150~300 nm的α相,接头强度进一步提高,但断裂发生在弹性变形阶段。

Laser welding was used to weld Ti-3Al-6Mo-2Fe-2Zr(wt.%) β titanium alloy to study the effect of heat treatment on the microstructure and tensile properties of the joint. Since the cooling rate of laser welding can reach 553 K/s,which is much greater than the critical cooling rate for the transformation of β phase to other phases,the microstructure of the weld is composed of a single β phase with columnar crystals. In the near-heat-affected zone,both the primary α-phase and the secondary α-phase transform into β-phase,and theβ-phase grain size increases;in the far-heat-affected zone,the larger primary α-phase remains. After the 780 ℃/1 h/WQ heat treatment,α phase with the thickness of 150 ~350 nm and length of 1 ~3 μm is formed in the fusion zone. Both the strength and elongation-to-failure of the joints increase after the 780℃/1 h/WQ heat treatment. After the 780 ℃/1 h/WQ+500 ℃/6 h/FC heat treatment,α phase with the thickness of 30~40 nm and length of 150~300 nm is formed in the fusion zone. The strength of the joints is further improved with fracture in tensile deformation stage.