环境氧含量对激光定向能量沉积TC4合金组织及性能的影响

Effects of Atomtmosphere Oxygen Content on Microstructure and Mechanical Properties of TC4 Titanium Alloy Prepared by Laser Directed Energy Deposition

摘要:

研究了环境气氛氧含量对激光定向能量沉积TC4钛合金组织及力学性能的影响，通过OM、SEM和TEM及硬度实验、拉伸实验对成形试样的显微组织、力学性能和断口进行分析。结果表明：当成形气氛氧含量从50ppm、500ppm、2000ppm到5000 ppm逐渐提高，试样表面氧化程度增加，TC4钛合金试样表面颜色由由银白色逐渐过渡到黄色、蓝色和深灰色，XRD衍射图谱结果表明，试块表面氧化物种类增多，氧化层的厚度也逐渐增加；试样显微组织逐渐由网篮状组织转变为针状马氏体α′组织，板条粗化，长宽比减小；TC4钛合金试样的硬度和室温抗拉强度随成形气氛氧含量的增加逐渐提高，受金属晶格畸变及冷却速度的影响，沉积态成形试样的抗拉强度由920 MPa增加到982 MPa，延伸率由12.4%减小到10.9%。

Abstract:

TC4 titanium alloy specimens were prepared by laser directed energy depositon in different oxygen contents of inert atmosphere. The effects of oxygen content in the argon shielding gas on microstructure, fracture surface and mechanical properties of TC4 titanium alloy by laser directed energy depositon have been investigated by optical microstructure (OM), scanning electron microscopy (SEM) , transmission electron microscope (TEM), microhardness testing and tensile testing. The results show that the oxidation degree of the samples surface increase, and the surface color of TC4 titanium alloy samples gradually change from silver white to yellow, blue and dark gray with the increasing of the oxygen content of the atmosphere. From XRD analysis, the types of oxides on the sample surface increase, and the thickness of the oxide layers also increase gradually. The microstructure of the specimens gradually change from basket structure to acicular martensite α" structure, the laths are coarsened and the aspect ratios are reduced. The hardness and tensile strength at room temperature of TC4 titanium alloy samples increase gradually with the increase of oxygen content in the forming atmosphere. Due to the influence of metal lattice distortion and cooling rate, the tensile strength of the deposition samples increase from 920 MPa to 982 MPa and the elongation decreased from 12.4% to 10.9%.