正火温度对电弧增材制造Ti-6Al-4V组织与性能的影响

Effect of normalizing temperature on microstructure and properties of Ti-6Al-4V fabricated by arc additive manufacturing

关键词:  TC4(Ti-6Al-4V)|正火处理|TIG电弧增材制造|显微组织|力学性能

Key words:  TC4 (Ti-6Al-4V)|normalizing treatment|TIG arc additive manufacturing (TIG AAM)|microstructure|mechanical properties

摘要:

利用TIG电弧增材制造技术制备了TC4钛合金样件，并对样件进行了正火处理. 结果表明，经正火处理后的试样组织由α相和β相组成；在750 ~ 950 ℃范围内，随着正火温度的升高，针状初生α相变短变粗，并逐渐向网篮组织方向转变；在950 ~ 1 050 ℃温度范围内，随着温度的升高，部分初生α相聚合长大，并向着“伪等轴晶”方向转化，在1 050 ℃形成了“伪等轴晶”初生α相 + 细小针状初生α相 + 细小针状初生α相之间的α + β组织，针状初生α相随着温度的升高变短变细. 最佳条件(850 ℃/2 h/空冷)下y方向的抗拉强度900.4 MPa、屈服强度820.4 MPa、断后伸长率9.3%、断面收缩率27.4%，z方向的抗拉强度890.1 MPa、屈服强度790.1 MPa、断后伸长率10.8%、断面收缩率31.0%，其性能接近锻件标准要求；沉积态与正火处理态的硬度值变化不大；拉伸试样(y和z方向)断口形貌均布满韧窝，属于塑性断裂.

Abstract:

The samples of TC4 titanium alloy were prepared by TIG arc additive manufacturing, and the samples were normalized. The results show that the microstructure of the sample is composed of α phase and β phase after normalizing treatment. And the acicular primary α phase becomes shorter and thicker with the increase of normalizing temperature at the range of 750 ~ 950 °C, and gradually changes to the direction of net basket structure. At the range of 950 ~ 1 050 °C, some primary α phases develop toward "pseudo-equiaxed crystals", and form structures which comprises the "pseudo-equiaxed crystals" primary α phase + the fine needle-like primary α phase + (α + β) structures between the fine needle-like primary α phases at 1 050 °C. The better mechanical properties of the present work (in conditions of 850 °C/2 h/AC) show that tensile strength, yield strength, elongation and reduction of the area in y direction are 900.4, 820.4 MPa, 9.3%, and 27.4% respectively, and tensile strength, yield strength, elongation and reduction of the area in z direction are 890.1, 790.1 MPa, 10.8%, and 31.0% respectively, which is close to the standard requirements for forgings. The hardness of sedimentary state and normalizing state has little changes. The fracture morphology of tensile specimen (z tensile specimen and y tensile specimen) is full of dimples and belongs to plastic fracture.