TY - JOUR
T1 - Obtaining bimodal microstructure in laser melting deposited Ti-5Al-5Mo-5V-1Cr-1Fe near β titanium alloy
AU - Liu, C. M.
AU - Tian, X. J.
AU - Wang, H. M.
AU - Liu, D.
PY - 2014/7/15
Y1 - 2014/7/15
N2 - Bimodal microstructures, consist of equiaxed primary α (αp) and lamellar secondary α (αs), usually lead to good comprehensive properties for wrought titanium alloys. However, for laser melting deposited titanium alloys, only lamellar microstructures are usually obtained, which result in relative low ductility. In this paper, to improve the ductility of laser melting deposited Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy, we try to introduce equiaxed α and obtain bimodal microstructures by heat treatments. Firstly, two kinds of heat treatment are applied to obtain equiaxed α i.e., subtransus anneal treatment and subtransus multi-anneal treatment. The subtransus anneal treatment is found to be able to promote α phase globularization, and the underlying mechanism is proposed by diffusion theory. However, it only leads to the elongated α phase with aspect ratio about 3.5. Then, inspired by the globularization mechanism, a novel subtransus multi-anneal treatment is designed, which can lead to near equiaxed α with the aspect ratio about 1.7. Afterwards, the subtransus multi-anneal and aging treatment are applied to obtain bimodal microstructure with near equiaxed αp and lamellar αs, which increases the elongation of the alloy to 11.5%, compared to 6.7% for the stress-relief anneal treated samples.
AB - Bimodal microstructures, consist of equiaxed primary α (αp) and lamellar secondary α (αs), usually lead to good comprehensive properties for wrought titanium alloys. However, for laser melting deposited titanium alloys, only lamellar microstructures are usually obtained, which result in relative low ductility. In this paper, to improve the ductility of laser melting deposited Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy, we try to introduce equiaxed α and obtain bimodal microstructures by heat treatments. Firstly, two kinds of heat treatment are applied to obtain equiaxed α i.e., subtransus anneal treatment and subtransus multi-anneal treatment. The subtransus anneal treatment is found to be able to promote α phase globularization, and the underlying mechanism is proposed by diffusion theory. However, it only leads to the elongated α phase with aspect ratio about 3.5. Then, inspired by the globularization mechanism, a novel subtransus multi-anneal treatment is designed, which can lead to near equiaxed α with the aspect ratio about 1.7. Afterwards, the subtransus multi-anneal and aging treatment are applied to obtain bimodal microstructure with near equiaxed αp and lamellar αs, which increases the elongation of the alloy to 11.5%, compared to 6.7% for the stress-relief anneal treated samples.
KW - Bimodal microstructure
KW - Laser melting deposition
KW - Subtransus multi-anneal treatment
KW - Titanium alloy
UR - http://www.scopus.com/inward/record.url?scp=84901231668&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2014.05.010
DO - 10.1016/j.msea.2014.05.010
M3 - Article
AN - SCOPUS:84901231668
SN - 0921-5093
VL - 609
SP - 177
EP - 184
JO - Materials Science and Engineering: A
JF - Materials Science and Engineering: A
ER -