Abstract
Ti-55511 billet with the acicular α initial microstructure was hot rolled (HR sample) and then heat treated (HR+HT sample) at 750 °C. The effects of HR and HT on the anisotropy of microstructure, texture, and tensile properties were investigated. The tensile results show that there are obvious anisotropic tensile properties between RD and TD. The anisotropic elongation of HR sample is related to the morphology of α phase. After HR, the acicular α is parallel to RD. As for RD specimen, the transgranular propagation of microcrack passing through the acicular α phase leads to the ductile fracture, thus showing the higher ductility than TD specimen. While the intergranular propagation of microcrack passing by the equiaxed α phase in TD specimen causes the brittle fracture. The anisotropic strength of HR sample depends on the relationship among texture type of α phase, slip system, and loading direction. The maximum texture intensity at TD leads to the easy activation of basal slip system in RD and that of prismatic slip system in TD, and then causes the lower strength of RD specimen than TD specimen. After HT, the decreased anisotropy of elongation and strength can be attributed to the increased α size and the decreased texture intensity of α phase. These results demonstrate that anisotropic tensile properties mainly depend on the morphology and texture of α phase.
Highlights
Titanium and titanium alloys with super specific strength, good resistance to corrosion, and high biocompatibility have attracted much attention and are widely used in industrial areas such as aerospace, vessel and biomedicine [1,2]
Anisotropy increasing of strain, the engineering stress in four curves increase rapidly to reach the peak value, Figure22shows showsthe theengineering engineeringstress-strain stress-straincurves curvesofofdifferent differentsamples samplesatatroom roomtemperature
The changed anisotropy of tensile properties can be related to the evolution of texture and microstructure after HR
Summary
Titanium and titanium alloys with super specific strength, good resistance to corrosion, and high biocompatibility have attracted much attention and are widely used in industrial areas such as aerospace, vessel and biomedicine [1,2]. Some researchers investigated the effect of α grain orientation on the anisotropic ductility in near-α and α+β titanium alloys. Rolling causes the intense crystallographic texture in α and β phase and further results in the obvious anisotropic mechanical properties in titanium alloys [15,16]. Due to the high contents of β stabilizer and special c/a ratio in HCP crystal structure [21], the texture and activation of slip systems in near β Ti-55511 alloy may be different from other titanium alloys. It’s necessary to study the effect of special texture on the anisotropic mechanical property of Ti-55511 rolled plate. The current work focuses on illustrating the effects of hot rolling and heat treatment on the anisotropy of microstructure and tensile properties of Ti-55511. Our work enriches researches about anisotropic tensile properties of titanium alloys and can offer a helpful guidance for industrial production
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