Y元素对铸造Ti-6Al-4V合金微观组织与力学性能的影响

Effect of Y addition on the microstructure and mechanical properties of the as-cast Ti-6Al-4V alloy

摘要:

本文研究了Y元素合金化对铸造Ti-6Al-4V合金微观组织与力学性能的影响。铸态合金微观组织与力学性能分别利用金相显微镜、扫描电镜、透射电镜和拉伸试验进行表征。结果显示，Ti-6Al-4V合金呈现典型的魏氏组织特征。添加Y元素后，合金中形成Y2O3颗粒并分布在初生β晶粒的晶界处，同时在晶界两侧形成平行的α/β层片结构，而晶粒内部形成相互交叉的α/β层片结构，即Y2O3明显改变了Ti基体片层组织形貌。相比于Ti-6Al-4V合金，添加Y元素之后，合金的屈服强度和抗拉强度稍有提高，但是平行的α/β层片结构和Y2O3颗粒引起合金由解理断裂向延晶断裂转变，进而导致延伸率显著减小。所以，Ti基体微观组织变化对合金力学性能同样具有重要作用。

Abstract:

The effects of yttrium (Y) addition on microstructures and properties of the as-cast Ti-6Al-4V alloys were studied. The microstructure and mechanical properties were characterized by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile testing. Ti-6Al-4V alloy showed typical Widmanstatten structure. With Y addition, Y2O3 particles formed and primarily distributed along the prior-β grain boundaries, and it induced the formation of special paralleled α/β lamellas on either side of the prior-β grain boundaries, that was the influence of Y2O3 particles on the Ti matrix. While it exhibited alternate α/β lamellas inside the grains of Ti-6Al-4V-0.3Y alloys. Comparing with Ti-6Al-4V, the Y addition improved the strength slightly, both the paralleled α/β lamellas and Y2O3 caused the transformation from cleavage fracture to intergranular fracture and the significant decrease of elongation. Therefore, the variation of the microstructure of Ti matrix caused by Y2O3 also played an important role in the ductility of the alloys.