Discontinuously Reinforced Titanium Matrix Composites

For centuries, scientists have been conducting investigations to develop materials which are “stronger, stiffer, lighter, and hotter.”

In order to overturn the situation of inferior mechanical properties of discontinuously reinforced metal matrix composites (DRMMCs) fabricated by conventional powder metallurgy (PM), one quasi-continuous network microstructure of DRTMCs was successfully designed.

After success of design and fabrication of network structured pure Ti matrix composites, it is necessary to fabricate titanium alloy matrix composites in order to further improve strength for extensive industrial applications. Certainly, the Ti6Al4V (Ti64) alloy was selected as matrix, not only due to its availability and superior combination of mechanical properties but also because of its wide applicability in the industry.

In order to better understand mechanical behaviors of the network-structured TiBw/Ti64 composites with inhomogeneous microstructure, Vickers microhardness testing was carried out on the different positions of the composites. The Vickers microhardness testing results show that the value of the Vickers microhardness at the center of Ti64 particle in the composite is 330, which is a little higher than that of the monolithic alloy (325), which may be due to the increase of alloy elements and the α phase content.

It is encouraging that the novel network-structured TiBw/Ti6Al4V composites with a combination of superior strengthening and toughening effects were successfully designed and fabricated in our previous work. Compared with the monolithic Ti6Al4V alloy fabricated by the same process, the ultimate tensile strength of the as-sintered 5 vol.% TiBw/Ti6Al4V composites with a novel network microstructure was increased by 34% (1090 MPa) aligned with 3.6% elongation.

In order to further investigate the effects of the subsequent heat treatment on the microstructure and mechanical properties of TiBw/Ti6Al4V composites with a novel network microstructure, heat treatment was performed on the typical 5vol.%TiBw/Ti6Al4V (200 μm) composite with a network microstructure.

Except for the above TiBw/Ti, TiBw/Ti6Al4V composites, network-structured TiCp/Ti6Al4V (Huang et al. in Mater Sci Eng A 528(6):2859–2862, (2011) [1]), (TiCp+TiBw)/Ti6Al4V (Huang et al. in Mater Sci Eng A 527(24–25):6723–6727, (2010) [2]), (Ti₅Si₃+TiC)/Ti (Huang et al. in Compos Sci Technol 82:23–28, (2013) [3]), (TiC+Ti₃SiC₂+Ti₅Si₃)/Ti6Al4V (Liu et al. in Adv Eng Mater 17(7):933–941, (2015) [4]), (TiBw+Ti₅Si₃)/Ti6Al4V (Jiao et al. in Sci Rep, (2016) [5]), TiBw/Ti60 (Wang et al. in Mater Sci Eng A 648:443–451, (2015) [6]), two-scale network-laminated (TiBw/Ti)-Ti composites (Liu et al. in Compos Sci Technol 126:94–105, (2016) [7]; Liu et al. in J Alloy Compd 602(25):87–192, (2014) [8]) were also successfully fabricated to improve their performance. To fabricate TiCp/Ti6Al4V composite with a network microstructure requires the raw powder materials with a large difference in size to be low-energy milled instead of high-energy ball milling as used in the conventional powder metallurgy route.

In order to further enhance the mechanical properties of titanium-based materials, much attention has been paid on titanium matrix composites (TMCs) due to its superior properties, such as high-specific strength, high-specific modulus, and high temperature durability.