MATEC Web Conf.
Volume 321, 2020The 14th World Conference on Titanium (Ti 2019)
|Number of page(s)||6|
|Published online||12 October 2020|
Strengthening of Ti-6Al-7Nb alloy by high-pressure torsion processing
1 Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 101-0062 Tokyo, Japan
2 Department of Materials Science and Engineering, Kyushu University, 819-0395 Fukuoka, Japan
3 WPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 819-0395 Fukuoka, Japan
A Ti-6Al-7Nb alloy with three different initial microstructures was processed by high-pressure torsion (HPT) and the resultant microstructure and mechanical properties of the alloy after HPT processing were investigated. The microstructure of the as-received alloy was an equiaxed (α+β) microstructure. The rods were subjected to solution treatment and aging (STA) treatment to obtain a bi-modal microstructure consisting of an equiaxed α phase and lamellar α+β phases, and those to solution treatment and quenching (STQ) treatment to obtain a bi-modal microstructure consisting of equiaxed α-phase and acicular α’-phase. Disks were cut from those rods and were processed by HPT under a pressure of 6 GPa. After HPT processing through 20 revolutions, the alloy with each of the three initial microstructures showed ultrafine grains with a size of ~70 nm. The alloy resulted in a higher tensile strength (1350 MPa) in both the bi-modal microstructures than that (1250 MPa) in the alloy with equiaxed α+β microstructure after HPT processing. It was shown that the Ti-6Al-7Nb alloy with the bi-modal microstructure was strengthened more than with the equiaxed α+β microstructure when the alloy was processed by HPT. Furthermore, the alloy with bi-modal microstructure consisting of equiaxed α-phase and acicular α’-phase showed a good balance between the tensile strength (1280 MPa) and the elongation to fracture (22%) after HPT processing through 1 revolution. In summary, therefore, large strength and elongation of the Ti-6Al-7Nb alloy were simultaneously achieved by HPT processing.
© The Authors, published by EDP Sciences, 2020
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