Abstract
The hot deformation and fracture behavior of TiB/nano-sized particulate reinforced titanium matrix composites were investigated. The effect of reinforcement contents and initial structures on the isothermal deformation and fracture characteristic were investigated through microstructure analysis, tensile tests and crack propagation tests. It was found that the optimal working parameters for Ti composites is determined at 900-950°C/0.01-0.1 s-1, which is associated with the continuous dynamic recrystallization of primary a grains and dynamic globularization of lamellar α. The necklace recrystallization was observed in β phase region, and the instability mechanisms include inhomogeneous deformation and breaking or debonding of TiB whiskers. Additionally, the addition of reinforcements refines α phases, decreasing the lamellar α width. The aspect ratio of TiB is much higher with the increase of reinforcement content. Higher content (2.5 vol. % and 5 vol. %) brings about more broken reinforcements and defects, which result in brittle fracture in Ti composite. Reinforcements and defects are believed to be the key factors to determine the crack propagation. Intergranular cracking is the main cracking way in the region where there are few reinforcements. Defects caused by fractured TiB play a dominant role in diverting intergranular cracking to transgranular cracking. Key words: Hot deformation, dynamic globularization, dynamic recrystallization, Titanium matrix composites
Highlights
The hot deforma on and fracture behavior of TiB/nano-sized par culate reinforced tanium matrix composites were inves gated
The result of X-ray diffrac on analysis confirms that the TiB +La2O3/Ti composite could be fabricated by the common cas ng technique, which was using the chemical reac on between tanium matrix and the addi on of LaB6 powder
And 5b, a large quan ty of low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) distribute in primary a grains. It seems that new DRXed grains in primary α are developed by the in situ evolu on of subgrains with the growth of LAGBs to HAGBs, which is associated with the typical con nuous dynamic recrystalliza on (CDRX) mechanism
Summary
The hot deforma on and fracture behavior of TiB/nano-sized par culate reinforced tanium matrix composites were inves gated. The deforma on and fracture behavior of in situ Ti composite reinforced with TiB and nano-sized par cles with different ini al structures through isothermal deforma on were studied. The ini al microstructure consisted of approximately 85% elongated α phases, and TiB fibers were oriented along the hot forging direc on It is about 2μm in thickness, and the La2O3 par cles were 200-700nm in diameter, which were distributed uniform in the matrix of Ti composite
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