激光功率对激光熔化沉积Ti-6Al-4V-0.25C合金组织和性能的影响

Effect of Laser Powder on the Microstructure and Properties of Ti-6Al-4V-0.25C Alloys by Laser Melting Deposition

采用含0.25%C(质量分数)的Ti-6Al-4V预合金粉末进行激光熔化沉积试验,研究了激光功率对Ti-6Al-4V-0.25C合金组织和性能的影响。结果表明,Ti-6Al-4V-0.25C合金微观结构为等轴β晶粒,晶粒内部形成了层状α+β结构,并且平均晶粒尺寸和α板条尺寸均随着激光功率的增加而逐渐增加。此外,随着激光功率的增加,合金拉伸性能得到明显提升,特别是在激光功率为1500 W时制备的合金样品,抗拉强度、屈服强度及伸长率分别为1191 MPa、1129 MPa和8.3%。一方面,这是由于激光功率增加使得合金孔隙率显著降低;另一方面,Ti-6Al-4V合金中含有微量的C元素,在冷却/凝固过程中,大多数的C原子固溶在Ti基体中,造成固溶强化。

The effect of laser power on microstructure and properties of Ti-6Al-4V-0.25C alloy was studied by laser melting deposition of Ti-6Al-4V-0.25C prealloy powder containing 0.25wt% C. The results show that the microstructure of Ti-6Al-4V-0.25C alloy is equiaxed grain morphology, and layered α+β structure is formed inside the grains. The average grain size and α lath size increase gradually with the increase of laser power. In addition, with the increase of laser power, the tensile properties of the alloy are obviously improved, especially the ultimate tensile strength, yield strength and elongation of the alloy prepared at the laser power of 1500 W are 1191 MPa, 1129 MPa and 8.3%, respectively. On the one hand, the porosity of the alloy decreases with the increase of laser power. On the other hand,Ti-6Al-4V alloy contains trace element C. During the cooling/solidification process, C atoms are solidly dissolved in Ti matrix, resulting in solid solution strengthening.