Metallurgical Abstracts on Light Metals and Alloys vol.55

Phase transformations in Al-Ti-Mg powders consolidated by high-pressure torsion: Experiments and first-principles calculations

Yongpeng Tang^a,b, Mitsuhiro Murayama^c,d, Kaveh Edalati^a, Qing Wanga^e, Satoshi Iikubo^e, Takahiro Masuda^f, Yuji Higo^g, Yoshinori Tange^g, Yasuo Ohishi^g,
Masaki Mito^b and Zenji Horita^a,b,h,i
^aWPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan
^bGraduate School of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
^cDepartment of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
^dInstitute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8580, Japan
^eDepartment of Life and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan
^fDepartment of Mechanical Engineering and Materials Science, Yokohama National University, Yokohama 240-8501, Japan
^gJapan Synchrotron Radiation Research Institute, Hyogo 679-5798, Japan
^hMagnesium Research Center, Kumamoto University, Kumamoto 860-8555 Japan
ⁱSynchrotron Light Application Center, Saga University, Saga 840-8502, Japan

[Published in Journal of Alloys and Compounds Vol. 889 (2021), 161815]

https://doi.org/10.1016/j.jallcom.2021.161815
E-mail: mitoh[at]mns.kyutech.ac.jp
Key Words: Al-Ti-Mg alloys, high-pressure torsion, first-principles calculations

A powder mixture of Al-Ti-Mg with an equal atomic fraction was subjected to severe plastic deformation using high-pressure torsion (HPT) under 6 GPa at room temperature for full consolidation. Microstructural evolution with respect to straining and annealing was examined by X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy. The XRD analysis revealed that Ti prevails in the consolidated sample and a phase transformation occurs from α phase to ω phase during HPT processing while the total fraction of the ω phase increases with straining. Grain refinement to ~100 nm was achieved through the HPT processing for 100 revolutions as well as the formation of nanograined intermetallics such as Al₃Ti, AlTi₃ and TiAl. The hardness gradually increases with straining, and further increases by annealing at 573 K for 1.5 h due to the formation of an Al₁₂Mg₁₇ phase despite the fact that the harder ω phase was reversely-transformed to the softer α phase and grains were coarsened to ~450 nm. First-principles calculations show that Al and Mg elements are dissolved into the ω-Ti during HPT processing.

TEM high-resolution lattice images and diffractograms of (a) Al, Al₃Ti, and AlTi₃, and (b) AlTi and ω-Ti in sample processed by HPT for 100 revolutions.