Du Sijie, Song Yang, He Yiting, Wei Chunhua, Chen Rongyou, Guo Shubo, Liang Wei, Lei Shengyuan, Liu Xiaohong
School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China.
State Key Laboratory of Featured Metal Materials and Life-Cycle Safety for Composite Structures, Guangxi University, Nanning 530004, China.
Materials (Basel). 2024 Feb 25;17(5):1060. doi: 10.3390/ma17051060.
The mechanical properties of various Ti-6Al-4V alloys are influenced by their respective microstructures. This study generated an ultrafine-grain (UFG) Ti-6Al-4V alloy featuring bimodal grain distribution characteristics achieved through initial heat treatment, multi-axial forging (MF), and annealing. The study also extensively examined the evolution process of the alloy's microstructure. By subjecting the materials to heat treatments at 900 °C with air cooling and 950 °C with air cooling, both materials were found to be consisted of primary α (α) and transformed β (α+β) regions with different proportions. Following MF, the sample treated at 900 °C displays a microstructure featuring UFGs of α+β surrounding larger micron-sized α grains. On the other hand, the sample treated at 950 °C displays a microstructure distinguished by twisted α lamellar and fragmented β grains surrounding larger micron-sized α grains. Following annealing, no significant grain growth was observed in the sample. The geometrically necessary dislocations (GNDs) within the UFGs were eliminated, though some GNDs persisted within the α grains. The samples undergoing the 900 °C heat treatment, MF, and subsequent annealing exhibited elevated strength (1280 MPa) and total elongation (10.7%). This investigation introduces a novel method for designing the microstructure of the Ti-6Al-4V alloy to achieve superior performance.
各种Ti-6Al-4V合金的力学性能受其各自微观结构的影响。本研究通过初始热处理、多轴锻造（MF）和退火制备了一种具有双峰晶粒分布特征的超细晶粒（UFG）Ti-6Al-4V合金。该研究还广泛考察了合金微观结构的演变过程。通过对材料进行900℃空冷和950℃空冷的热处理，发现两种材料均由不同比例的初生α（α）和转变β（α+β）区域组成。经过多轴锻造后，900℃处理的样品显示出一种微观结构，其特征是α+β的超细晶粒围绕着较大的微米级α晶粒。另一方面，950℃处理的样品显示出一种微观结构，其特征是扭曲的α片层和破碎的β晶粒围绕着较大的微米级α晶粒。退火后，样品中未观察到明显的晶粒长大。超细晶粒内的几何必要位错（GNDs）被消除，不过一些GNDs仍存在于α晶粒内。经过900℃热处理、多轴锻造和随后退火的样品表现出较高的强度（1280MPa）和总伸长率（10.7%）。本研究介绍了一种设计Ti-6Al-4V合金微观结构以实现优异性能的新方法。
