Different from previous research works on cryogenic titanium alloys with a lamellar microstructure, this study focused on cryogenic tensile properties and the related deformation mechanism of a fine-grained near alpha titanium alloy of equiaxed microstructure. The fine-grained equiaxed Ti–3Al–3Mo–3Zr alloy exhibited a remarkably enhanced cryogenic tensile strength until 20 K, but cryogenic ductility decreased sharply as temperature drops. Ultimate tensile strength jumped from 740 MPa at 298 K to 1290 MPa at 77 K and to 1535 MPa at 20 K, while elongation-to-fracture dropped from 20.0% to 12.5% and to 4.0%, respectively. Sharp decline of cryogenic ductility was considered to be directly influenced by the high-angle misoriented equiaxed α-Ti grains. Because dislocation motion got much difficult and twinning could not operate extensively in the fine equiaxed microstructure at cryogenic temperatures. Besides, slip and twinning could not transfer across α-Ti grain boundaries or α/β phase interfaces, resulting in premature cracking. Different from deformation of traditional counterpart with a lamellar microstructure, prismatic and basal slips invariably dominated at 298, 77 and 20 K. Only in certain α-Ti grains whose <0001> parallel to loading direction, {10 1‾ 2} type tension twins operated at 77 and 20 K. The present fine-grained near α-Ti alloy with an equiaxed microstructure is suggested to be applied at temperature not lower than 77 K. 

Cryogenic tensile properties and deformation behavior of a fine-grained near alpha titanium alloy with an equiaxed microstructure

Cryogenic Tensile Properties and Deformation Behavior of a Fine-Grained Near Alpha Titanium Alloy with an Equiaxed Microstructure

Ultrahigh cryogenic strength and exceptional ductility at 20 K in a TWIP Ti–15Mo alloy

Effects of hybrid reinforcements to the high temperature tensile and creep properties of a (TiB + TiC + Y2O3)/α-Ti composite

Effect of TiB, TiC and Y2O3 on tensile properties and creep behavior at 650 ℃ of titanium matrix composites

In order to investigate the influence of service temperature on the mechanical properties of Ti–5Al-2.5Sn ELI titanium alloy, the tensile tests were performed on the polycrystalline Ti–5Al-2.5Sn ELI titanium alloy samples under a wide temperature range from 20 K to 300 K. The scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) tests were conducted to analyze the fracture behavior evolution, crystallographic orientation, grain boundary characterization and dislocation configuration of the samples. Besides, the deformation mechanism of Ti–5Al-2.5Sn ELI titanium alloy was also thoroughly investigated. Experimental results indicate that the Ti–5Al-2.5Sn ELI titanium alloy displays the single dislocation slipping deformation behavior at room temperature, whereas the coupling of dislocation slipping and twinning deformation behaviors dominate at the cryogenic temperature. The twinning deformation improves the plastic deformation capacity of Ti–5Al-2.5Sn ELI titanium alloy by coordinating the crystallographic orientation, promoting the boundary rotating and the dislocation slipping abilities, which induces the acceptable low-temperature elongation and occurs frequently with the decreasing test temperature. On the other hand, the dislocation strengthening effect resulting from a large number of dislocation structures also contributes to promoting the ultimate tensile strength of the Ti–5Al-2.5Sn ELI titanium alloy under cryogenic temperature.

Investigation on the deformation mechanism of Ti–5Al-2.5Sn ELI titanium alloy at cryogenic and room temperatures

Spheroidization behavior of (TiB+TiC+Y2O3)/α-Ti alloy during annealing

The invention discloses a wall thickness homogenization method adopting isothermal stamping for a titanium alloy thick-wall spherical shell. Through divisional design on friction coefficients of a male die and a to-be-formed plate, the male die and pull rings are heated separately so that a temperature gradient is formed, the wall thickness homogenization of the titanium alloy thick-wall sphericalshell is ensured, the spherical bottom reduction rate is reduced from 50% in conventional forming to below 15%, the overall wall thickness fluctuation of a housing does not exceeds 30% of the wall thickness of a blank and the size is stable. Since the reduction of the spherical bottom is inhibited effectively, the extent of damage of the mechanical property at the spherical bottom is reduced substantially, the overall mechanical property of the titanium alloy thick-wall spherical shell is better, the titanium alloy thick-wall spherical shell is particularly applicable to development and production of a TA7 low-temperature titanium alloy gas cylinder product for a carrier rocket, and is also applicable to the development and production of titanium alloys in other fields and other trademarks and the like products, and the wall thickness homogenization method is very practical.

Shi Wei

Papers

Investigation on the deformation mechanism of Ti–5Al-2.5Sn ELI titanium alloy at cryogenic and room temperatures

Spheroidization behavior of (TiB+TiC+Y2O3)/α-Ti alloy during annealing

Wall thickness homogenization method adopting isothermal stamping for titanium alloy thick-wall spherical shell