激光焊接近α型Ti60合金高温力学行为
High-temperature Mechanical Behavior of Laser Welded Near α Ti60 Alloy
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摘要: 针对高温钛合金焊接结构在大推力、高推重比飞行器中的高可靠性服役需求, 研究了激光焊接钛合金高温力学性能及变形机制。结果表明, 受焊接热循环影响, 焊接接头各区域的组织类型及形态、稀土相分布、晶粒尺寸、再结晶组织体积分数等存在显著差异。室温和600 ℃条件下维氏硬度由大到小依次为焊缝区、热影响区、母材区, 焊缝区高硬度主要源于其内部形成的细小针状α'相。高温导致接头各区域的硬度值下降约20%。室温和600 ℃条件下接头拉伸试样均断裂于母材区, 断口呈现出韧窝生长的穿晶断裂模式。接头试样的屈服强度和抗拉强度与母材相当, 而延伸率有所降低, 其源于焊缝区和热影响区的变形量较少。高温下母材和接头试样的强度均降低, 高温塑性变形以回复和再结晶致应变软化为主。Abstract: The high-temperature mechanical properties and deformation behavior of laser welded Ti60 alloy were investigated aiming at the high reliable service requirements of Ti60 laser welded structures for high thrust and high thrust/weight ratio aircraft. Results show that influenced by the welding thermal cycle, there are significant differences in the microstructure type, morphology, rare earth phase distribution, grain size, and volume fraction of recrystallization structure in different zones of welded joints. The average Vickers hardness can be ranked in terms of the decreasing value as weld zone > heat affected zone > base metal zone. The high hardness of the weld zone mainly arises from the fine needle α' phases. The high temperature induces the decrease of the hardness of different zones of joints by about 20%. The base metal is the failure path for welded joint specimens subjected to room and high temperature loading. The fracture surfaces are characterized by dimple growth induced transgranular fracture mode. The yield strength and tensile strength of welded joints are equivalent to those of the base metal. However, the elongation of welded joints is reduced. This can be attributed to the less deformation in weld zone and heat affected zone. The strength of the base metal and welded joints decrease when subjected to high temperature loading. The high temperature plastic deformation is mainly characterized by recovery and recrystallization induced strain softening.