热处理对激光沉积TC4组织和性能的影响

Effect of Heat Treatment on Microstructure and Properties of Laser Deposition TC4

摘要:

通过对激光沉积TC4钛合金沉积态和热处理态的显微组织、静载力学性能及显微硬度进行对比研究，探索改善激光沉积TC4钛合金组织，进而提高综合力学性能的途径。研究结果表明，沉积态试样在970 ℃热处理后初始连续的晶界α相已经彻底破碎；随着固溶时间的延长，球状α相进一步长大且增多，α板条充分生长且显著增大；在970℃固溶2h后再进行时效热处理后，组织是一种由等轴α，网篮α和转变β相构成的三重混合组织，使得组织参数达到最优化。与沉积态和退火态相比，固溶时效处理后的试样，由于组织中的等轴组织起着变形协调的作用，网篮组织可以降低位错的塞积作用进而提高塑性，使得塑性有很大的提高且强度又降低不多，综合力学性能得到显著的提高。激光沉积制造TC4钛合金的沉积态、退火态、固溶时效态和固溶态（固溶温度相同）的显微硬度依次升高，但是当固溶温度进一步提高至相变点以上进行热处理时，由于再结晶后的晶内组织发生了重排，试样的显微硬度将会明显下降。

Abstract:

By comparing the microstructures,static mechanical properties and microhardness of laser deposition TC4 alloy in the as-deposited and heat-treated states, the approaches to perfect the microstructure of laser deposition TC4 alloy are explored. Results show that after the as-deposited sample undergoes 970℃ heat treatment, the grain boundary α is thoroughly broken which is continuous initially; with the extension of solution time, globular α phases are more and bigger, and their laths are in full growth and increase dramatically; two hours later, when the sample undergoes aging treatment, its structure turns to be constituted by equiaxed α, basketweave α and transformed β phase, which results in the optimized textural parameters. Compared with as-deposited and annealed samples, the plasticity of the solution aging sample is enhanced significantly and the strength is decreased slightly, and their integrated mechanical properties improved remarkably. Its equiaxed structure performs coordinating function and its basketweave structure can reduce the dislocation pile-up to improve the plasticity. The microhardness is gradually increased in laser deposition TC4 alloy in the as-deposited, annealing, solution aging and solid-solution. But when the solution temperature rises to the transformation point, the microstructure of the sample rearranges after crystallizing, leading to marked decline in microhardness.