Network-Strengthened Ti-6Al-4V/(TiC+TiB) Composites: Powder Metallurgy Processing and Enhanced Tensile Properties at Ele
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TRODUCTION
STIMULATED by the rapid development in aerospace engineering, there has been growing effort in investigating advanced metallic-based materials with excellent specific mechanical properties and outstanding physicochemical stability at elevated temperatures.[1] With regard to this, Ti-based alloys have attracted broad attention owing to their unique combination of low density, superior strength, and desirable chemical corrosion resistance.[2–4] Figure 1 summarizes the
SHAOLOU WEI is with the School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, P.R. China and also with the Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA. LUJUN HUANG, XINTING LI, YANG JIAO, WEI REN, and LIN GENG are with the School of Materials Science and Engineering, Harbin Institute of Technology. Contact e-mails: [email protected]; [email protected] Manuscript submitted January 21, 2019. Article published online May 21, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
specific strength with respect to service temperature for conventional engineering materials. In the temperature range from ambient value up to 400 C, Ti-based alloys exhibit more favorable specific strength compared to Al-based alloys, heat-resistant stainless steels, and polycrystalline Ni-based superalloys. Nonetheless, their specific strengths display a dramatic decreasing trend as the service temperature approaches 600 C, which largely hinders their potential applications. Moreover, Ti-based alloys often possess strong oxidation propensity at elevated temperatures, which further expedites their degradation due to the formation of porous TiO2 oxide scale or the embrittlement problem induced by oxygen-rich a phase.[5,6] In an effort to improve these shortcomings, appreciable investigations have been accomplished toward compositional optimization,[7,8] microstructural modulation,[9–11] and surface modification.[12–14] Although these strategies have enabled property enhancement of Ti-based alloys, challenges still exist from a processing perspective, since the aforementioned approaches either require the addition of highcost alloying elements or involve precise control of thermomechanical treatment conditions. VOLUME 50A, AUGUST 2019—3629
Over the past decades, the development of Ti-matrix composites (TMCs) has paved a novel cost-effective way for the improvement of high-temperature performances.[15] By incorporating commercial engineering ceramic reinforcers, such as SiC, TiB, and TiC, a variety of TMCs have been successfully developed and examined to achieve desirable properties at both ambient and elevated temperatures.[16–18] Based on the characteristics of reinforcers, the development of TMCs can be categorized into three stages[15,19]: (1) continuously reinforced TMCs with homogenously distributed reinforcers, (2) discontinuously reinforced TMCs with homogenously distributed reinforcers, and (3) discontinuously reinforced TMCs with inhomogenously distributed reinforcers. In
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