Fabrication and Characterization of Graphene Reinforced Titanium Matrix Composites

Abstract

Titanium matrix composites (TMCs) represent a cutting-edge class of materials renowned for their exceptional strength-to-weight ratio, high-temperature resistance, and excellent corrosion properties. The fabrication of TMCs involves embedding reinforcing materials such as ceramic, metallic, or carbon fibers within a titanium matrix through various techniques, including powder metallurgy, solid-state diffusion bonding, and liquid phase sintering. These fabrication methods allow for precise control over the microstructure and properties of the resulting composite, tailoring it to specific applications. The properties of TMCs are highly desirable in numerous industries, including aerospace, automotive, biomedical, and defense. In aerospace, TMCs find extensive applications due to their lightweight nature coupled with high strength, making them ideal for components subjected to high loads and extreme temperatures. In automotive engineering, TMCs offer promising avenues for lightweight, leading to enhanced fuel efficiency and performance. Moreover, in biomedical applications, the biocompatibility of titanium (Ti) combined with the mechanical properties of TMCs make them suitable for implants and prosthetic devices, providing long-term stability and compatibility within the human body. Furthermore, TMCs exhibit remarkable thermal stability and corrosion resistance, rendering them suitable for use in aggressive environments such as chemical processing plants and marine applications. Recent advancements in the field of TMCs include the development of novel fabrication techniques, optimizing microstructural properties, and exploring hybrid composites combining multiple reinforcing materials. Additionally, computational modeling and simulation advancements have facilitated the design of TMCs for specific applications, further expanding their potential utility across various industries. In conclusion, titanium matrix composites represent a promising class of materials with a wide range of applications and significant potential for further advancements. Continued research and development efforts aimed at optimizing fabrication techniques, enhancing properties, and exploring new applications will undoubtedly propel the utilization of TMCs in diverse fields, contributing to technological innovation and sustainable engineering solutions. Much work is carried out to develop TMCs using ceramic reinforcements (boron carbide, silicon carbide, aluminum oxide). The densities of most of the ceramic reinforcing materials are higher than Ti/Ti alloy. Therefore, improvement in the mechanical properties of titanium matrix composite (TMC) comes with a slight increase in their density. In addition,

iv various researchers reported that the high chemical reactivity of titanium at high temperatures makes traditional fabrication techniques unfeasible for the fabrication of TMCs. Recently, many efforts have been made to use graphene (GR) as a better substitute for ceramic reinforcing material. GR is a 2D carbon material (single atomic layer of sp2 - hybridized carbon atoms) with excellent mechanical, thermal, self-lubrication, low density, and electrical properties. Spark plasma sintering (SPS) is gaining popularity for fabricating TMCs due to its fast heating rates, short sintering time, high densification, and limited grain growth. However, minimal literature on the fabrication of Ti alloy (Ti6Al4V) reinforced with multilayer graphene (MLG) via the SPS process is available. The detailed mechanical, tribological, corrosion, and finishing experimental studies still need to be done. To address the above stated challenges, in the current work Ti6Al4V/MLG nanocomposites have been fabricated via the SPS process. Detailed experimental studies were performed to study the effect of the input parameters, viz., MLG content and SPS process sintering temperature on the various output responses of the fabricated TMCs. The content of MLG in Ti6Al4V nanocomposites is varied between 0 % to 1.36 %, while sintering temperature varied from 787 °C to 1212 °C. The present work explores the influence of input parameters by investigating fabricated nanocomposites' properties. Microstructural study reveals an in-situ reaction between a carbon source from MLG and Ti from the Ti6Al4V to form a secondary phase TiC. It is evident from the results obtained that MLG plays a vital role in improving the microstructural, mechanical, tribological and corrosion properties of sintered nanocomposites. A detailed parametric study is performed to develop regression equations of the output responses, viz., hardness, elastic modulus, wear rate and corrosion current density (Icorr) as a function of input parameters, i.e., sintering temperature and wt. % of MLG. Analysis of variance showed that % contribution of sintering temperature and wt. % of MLG was 42.15 % and 55.40 %, respectively for hardness. Also, the % contribution for the elastic modulus was 49.24 % for sintering temperature and 48.61 % for wt. % of MLG. Maximum value of hardness and elastic modulus achieved for TMCs is 5.37 GPa and 138.90 GPa, respectively. A minimum wear rate of 14.50 x 10-6

g/m and Icorr of 1.45

1.45 μAcm-2

, corresponding to a 54.40 % and 53.82 % improvement compared to bare Ti6Al4V, is achieved for Ti6Al4V /0.8 wt. % MLG fabricated at 1000 °C. In-house developed abrasive flow finishing process setup and abrasive media successfully finished the TMCs with a maximum improvement of 73.20 % in surface roughness.