选区激光熔化成形Ti-6Al-4V合金的力学各向异性

Mechanical Anisotropy of Ti-6Al-4V Alloy Fabricated by Selective Laser Melting

摘要:

为了阐明选择性激光熔化成形Ti-6Al-4V合金的各向异性，研究了合金不同方向对应试样的压缩力学性能、显微硬度、显微组织和晶体取向。分析了力学性能的各向异性，并利用EBSD技术分析了不同晶粒类型和取向对不同尺度应力应变分布的影响。结果表明，室温下，当应变率为10^-3 s^-1时，合金的抗压缩屈服强度和显微硬度随方向变化，呈现出各向异性。合金显微组织为柱状，沿沉积方向表现出等轴晶，其为内部致密六方（hcp）结构的α/α'马氏体结构。α'相择优取向近似<0001>。由于柱状晶长/宽比高，hcp织构弱，对称性差，导致了各向异性。

Abstract:

To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting (SLM), the compressive mechanical properties, microhardness, microstructure, and crystallographic orientation of the alloy across different planes were investigated. The anisotropy of SLM-fabricated Ti-6Al-4V alloys was analyzed, and the electron backscatter diffraction technique was used to investigate the influence of different grain types and orientations on the stress-strain distribution at various scales. Results reveal that in room-temperature compression tests at a strain rate of 10^-3 s^-1, both the compressive yield strength and microhardness vary along the deposition direction, indicating a certain degree of mechanical property anisotropy. The alloy exhibits a columnar microstructure; along the deposition direction, the grains appear equiaxed, and they have internal hexagonal close-packed (hcp) α/α' martensitic structure. α' phase has a preferential orientation approximately along the <0001> direction. Anisotropy arises from the high aspect ratio of columnar grains, along with the weak texture of the microstructure and low symmetry of the hcp crystal structure.