脉冲频率和热输入对电弧增材制造TC4钛合金形貌和组织的影响

The anisotropy caused by columnar β grains are main challenges in arc additive manufacturing of Ti-6Al-4V alloy. In order to handle these issues, multilayer walls were deposited with different pulse frequencies and heat inputs. Combined with finite element analysis, the influence of pulse frequency and heat input on macrostructure and microstructure of deposited Ti-6Al-4V alloy were investigated. The results indicate that with the increase of pulse frequency, the widths of deposited walls decrease rapidly at first, and then increase slightly; The columnar β grains transform from columnar into equiaxed β grains and are refined, but α phases have no obvious variation. Increasing heat input is beneficial to obtaining equiaxed β grains, but the wall width increases and α phases become coarser. The width of the specimen is determined by the dimension of the molten pool, which is influenced by the average heat input and the input heat in peak time period. Improving pulse frequency can break the dendrites and reduce the temperature gradient, which is conducive to increasing the nucleation rate. Besides, higher heat input can reduce the temperature gradient as well. Therefore, equiaxed β grains are formed with the increase of pulse frequency and heat input. The morphology of α phases is mainly associated with the cooling rate. Reducing heat input can increase cooling rate and refine α phases.