Creep rupture life of in situ synthesized (TiB+TiC)/Ti matrix composites
Introduction
The addition of ceramic particles to titanium matrix alloy can improve mechanical properties and service temperature. Titanium matrix composites reinforced with ceramic particles are conventionally prepared by powder technology 1, 2 or liquid metallurgy [3], where the ceramic particles are directly incorporated into solid or liquid matrices, respectively. Recently, particle reinforced titanium matrix composites fabricated by in situ processes have been extensively studied due to their potentially low fabrication cost and high mechanical properties. Self-propagating high-temperature synthesis (SHS) 4, 5, mechanical alloying [6], powder metallurgy 7, 8, 9, 10 and rapid solidification processing 11, 12 have been used to produce the titanium matrix composites by in situ technique. The following SHS reactions between Ti and C, B4C have been utilized to produce the titanium matrix composites 4, 5: Based on the above reactions, we highlight a novel in situ process in which traditional ingot metallurgy plus SHS techniques were used to produce (TiB+TiC)/Ti matrix composites [13]. The mechanical properties of in situ synthesized titanium matrix composites at room- and elevated-temperature have been extensively studied 10, 11, 12, 14. However, the research on creep properties is very limited, especially for creep rupture life 4, 15. In this paper, the creep rupture life of in situ synthesized (TiB+TiC)/Ti matrix composites has been discussed.
Section snippets
Experimental procedure
On the basis of the former paper [13], the titanium matrix composites reinforced with two different mole ratios between TiB and TiC (4:1 and 1:1) were fabricated by consumable vacuum arc remelting. The nominal alloy composition is Ti-6Al-2Sn-4Zr-2Mo-0.2Si. The volume percentage of reinforcements is 8%. The compositions of the raw materials and the theoretical volume percentage of the reinforcements are listed in Table 1. The processing technology can be expressed as following. Stoichiometric
Results and discussion
The optical microstructures of the titanium matrix composites reinforced with different mole ratios between TiB and TiC after the hot-forging were shown in Figure 1. Figure 1(a) and Figure 1(b) show the microstructures of the titanium matrix composites reinforced with TiB:TiC = 4:1 at longitudinal and transverse cross-section. Figure 1(c) and Figure 1(d) show the microstructures of the titanium matrix composites reinforced with TiB:TiC = 1:1 at longitudinal and transverse cross-section. They
Conclusions
From above discussions, the following conclusions can be obtained. The interfacial microstructures of in situ synthesized titanium matrix composites are very stable during the creep deformation, so they are very valuable to improve the creep rupture life. The creep rupture life of the titanium matrix composites was significantly higher than that of the matrix alloy throughout the ranges of stress and temperature. The compatibility of deformation between the TiB and the titanium matrix alloy is
Acknowledgements
We would like to acknowledge financial support provided by the National Nature Science Foundation of China under Grant No: 59631080 and the New Materials Center of Shanghai.
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