Microstructure and high temperature mechanical properties of laser rapidly formed Ti-6Al-4V alloy
(1.State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
2.陕西省西安市西北工业大学凝固加工国家重点实验室)
2.陕西省西安市西北工业大学凝固加工国家重点实验室)
Abstract: Several tensile samples were prepared using laser rapid forming (LRF) with Ti-6Al-4V alloy as powder material, and the samples were annealed. The microstructure and high temperature mechanical properties of laser formed Ti-6Al-4V alloy through annealing treatment were investigated. The short-term and long-term tensile tests at 350 ℃ were performed. The results show that the microstructure of LRF samples consists of the large columnar prior β grains which grow epitaxially from the substrate along the deposition direction. There are Widmanst？tten α laths in prior β grains, but α laths in annealed microstructure are coarser, and their aspect ratio is lower than that in as-deposited microstructure. In addition, the prior β grain boundary is also coarsened and broken off through the annealing treatment. The high temperature mechanical properties of the annealed LRF samples exceed those of casting alloy significantly, especially the stress-rupture lifetime reaches 661.7 h even while the test stress increases from initial value of 490 MPa to the final stress of 800 MPa gradually.
Key words: laser rapid forming; Ti-6Al-4V; microstructure; mechanical properties; stress-rupture lifetime