锻造变形对Ti-5Al-6.5Mo-1.5Fe低成本钛合金组织性能演化的影响研究

Effect of Forging Deformation on Evolution of Microstructure and Properties of Ti-5Al-6.5Mo-1.5Fe Low-Cost Titanium Alloy

摘要:

进行了Ti-5Al-6.5Mo-1.5Fe低成本钛合金不同锻造参数下微观组织与拉伸性能演化的分析研究，发现合金在不同锻造参数下的组织性能之间存在明显关联。结果表明：合金在两相区锻造时，组织中等轴初生α相（α_p）含量随温度升高逐渐降低、尺寸减小，抗拉强度和塑性略有波动；随锻造变形量增大，组织中α_p相形态发生明显改变，合金抗拉强度和塑性稳定性较好，α_p相内部呈现出连续的取向差累积，促进了球化和再结晶，β相在变形力作用下取向逐渐转变为Cube织构｛001｝<100>。在单相区锻造时，原始α_p相完全消失，β晶粒粗大，长条状晶界α相（α_GB）析出，晶内次生α相（α_s）增多，合金拉伸塑性急剧下降。组织内可协调变形的等轴α_p相和显著提高强度的纳米级α_s相的共存可同时实现高强度和高韧性，使得合金在两相区锻造能够获得更好的力学性能，而β粗晶是造成合金单相区锻造后塑性下降的主要原因，试样拉伸断裂机制从两相区锻造变形后的单一韧窝断裂转变为β单相区锻造后的解理-韧窝混合断裂。

Abstract:

The evolution of microstructure and tensile properties of Ti-5Al-6.5Mo-1.5Fe low-cost titanium alloy under different forging parameters was studied, and it is found that there is a significant correlation between the microstructure and properties of the alloy under different forging parameters. The results show that when the alloy is forged in α+β phase region, the content and size of the equiaxed primary α phase (α_p) in the microstructure decrease gradually with increase in temperature, and the tensile strength and plasticity fluctuate slightly. As the forging deformation increases, the morphology of α_p phase in the microstructure changes obviously, and the strength and plasticity of the alloy remain stable. There is a continuous accumulation of misorientation inside the α_p phase to promote spheroidization and recrystallization. The orientation of β phase gradually transforms into the Cube texture {001}<100> under deformation force. When forged in the single β phase region, the alloy obtains coarse original β grains, the α_p phase completely disappears, the intragranular secondary α phase (α_s) increases, the long strip grain boundary α phase (α_GB) precipitates, and the plasticity of the alloy drops sharply. The coexistence of equiaxed α_p phase, which can coordinate deformation, and nanoscale α_s phase, which significantly improves the strength of the alloy in the microstructure, can achieve high strength and high toughness at the same time, allowing the alloy to obtain better mechanical properties in α+β phase region. The β coarse grain is the main reason for the decrease in plasticity after forging in the single β phase region of the alloy, and the tensile fracture mechanism of the specimen changes from single dimple fracture after forging in α+β phase region to cleavage-dimple mixed fracture after forging in single β phase region.