Synthesis and Fracture Characteristics of TiB2-TiAl Composites with a Unique Microlaminated Architecture

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2019-12, Vol.50 (12), p.5853-5865
• Main Authors: Cui, Xiping, Zhang, Yuanyuan, Yao, Yao, Ding, Hao, Geng, Lin, Huang, Lujun, Sun, Yuan
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Composite materials; Crack propagation; Electron microscopes; Fracture mechanics; Fracture toughness; Heat treating; High temperature; Intermetallic compounds; Lamellar structure; Laminates; Materials Science; Metallic Materials; Microstructure; Nanotechnology; Scanning electron microscopy; Structural Materials; Surfaces and Interfaces; Tensile properties; Thin Films; Titanium aluminides; Titanium diboride
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-019-05475-8

Microstructural evolution of as-rolled (TiB 2 /Al)-Ti laminates in the process of multistep heat treatments and microstructural characteristics of the resulting TiB 2 -TiAl composites were investigated in detail by scanning electron microscope (SEM) and transmission electron microscope. The desired TiB 2 -TiAl composites exhibited a unique microlaminated structure consisting of alternating fully lamellar α 2 -Ti 3 Al/ γ -TiAl layers and TiB 2 -rich layers. Moreover, the formation mechanism of the microlaminated structure was elucidated. It is noteworthy that the TiB 2 -TiAl composites showed improved high-temperature tensile properties and room-temperature fracture toughness due to the strengthening effect of TiB 2 particles and the structure effect of the unique microlaminated microstructure. In addition, the fracture behavior of the microlaminated TiB 2 -TiAl composites during the dynamic tensile was characterized by combining use of the three-dimensional X-ray microscope (3D-XRM) and SEM. The results indicated that pores and cracks preferred to initiate in the brittle TiB 2 -rich layer and showed a typical layered distribution, and then expanded into a nearby fully lamellar α 2 / γ layer and kept propagating through the entire α 2 / γ layer into another TiB 2 -rich layer, repeatedly, and finally the main crack propagated through all the fully lamellar α 2 / γ layers and TiB 2 -rich layers, eventually resulting in failure. Thus, the fracture mechanism of the innovative microlaminated TiB 2 -TiAl composites was proposed.