α+β型钛合金惯性摩擦焊接头焊态/热处理态组织演变及性能研究

Microstructure evolution and mechanical properties of inertia friction welding joint of α+β titanium alloy in welding state/post-weld heat treatment

摘要:

文中采用SEM、EBSD及TEM等表征手段分析了惯性摩擦焊接头在焊态及焊后热处理态下的微观组织形貌与分布特征，并研究了焊后热处理态下的接头力学性能。结果表明，焊缝区为单一等轴α晶粒，在焊态下由板条状马氏体α′相+晶界片状αp相+亚稳态β相构成，并伴随着(0001)//ND丝织构。热处理后转变为晶界片状αp相+晶内片状αs+β相，在原有丝织构的基础上形成了(21 ?1 ?3)[21 ?1 ?9]取向织构；焊缝区显微硬度最高，随着向母材区过度显微硬度逐渐降低，焊后热处理可降低焊缝区硬度，使接头硬度分布较为均匀。接头在室温下的拉伸试验均断裂于远离焊缝中心的母材区。

Abstract:

The SEM, EBSD and TEM were used for analyze the microstructure morphology and distribution characteristics of inertial friction welded joint in welding state and post-welding heat treatment state. In addition, the mechanical properties of the joint in post-welding heat treatment state were studied. The results showed that the weld zone was single equiaxed α grains, which is composed of lamellar martensite α" phase + grain boundary lamellar αP phase + metastable β phase in welding state, and with (0001)//ND fiber texture. The microstructure was consisted of grain boundary lamellar αP phase + intragranular lamellar αS +β phase after post-weld heat treatment. The (21 ?1 ?3)[21 ?1 ?9] orientation texture was also formed on the basis of the original fiber texture. Under the effect of welding pressure and thermal cycling, the equiaxed αP phase in thermo-mechanically affected zone had been transformed into a rod and approximately paralleled to the welding interface. The equiaxed αP phase in thermal affected zone still maintained original shape. The weld zone had the highest microhardness, which gradually decreased from weld zone to base metal. The post-weld heat treatment can reduce the hardness of the weld zone and obtain uniform hardness distribution in welded joint. The tensile specimens at room temperature failed in the base metal away from weld center line.