超声波对BT20钛合金激光沉积修复作用机制探究

Effect of ultrasonic on laser deposition repairing of BT20 titanium alloy

通过ANSYS有限元数值模拟和试验相结合,研究了超声波对BT20钛合金激光沉积修复过程的作用。结果表明,超声波振幅为0.2-0.55μm时,能得到成形质量较好的修复层;当超声波振幅为0.4μm时,超声波对熔池的作用主要表现为超声的机械作用和热作用,而不是超声空化效应;超声的机械作用使得组织的气孔率降低,但是其机械作用不足以克服修复层晶粒外延生长的驱动力,没能阻止β柱状晶沿沉积方向的生长;超声的机械作用将晶粒片层组织中的α板条打断,而热作用使得熔池凝固速度降低,从而使α板条变短变粗。

The effect of ultrasonic on laser deposition process in repaired components of BT20 titanium alloy was investigated by using finite element simulation and experimental test. The results show that when ultrasonic amplitude was 0.2-0.55 μm, the forming quality of repaired layers was better; When ultrasonic amplitude was 0.4 μm, the effect of ultrasonic on molten pool was mainly about mechanical effect and thermal effect, not ultrasonic cavitation effect. The mechanical effect declines the porosity rate of organization, but the mechanical force was less than the epitaxial growth driving force of crystalline grain in repaired layers so that the growth of /3-columnar grain along the direction of deposition could not be blocked; The mechanical effect breaks the a-lath of lamellar microstructure and the thermal effect makes the solidification speed slow, as a result, the a-lath was becoming short and thick.