VT15 Alloy Research Articles

Temperature dependence of the plasticity of hydrogenated commercial titanium and VT3-1 and VT15 alloys

1. For technological titanium containing 0.025% H after hardening causing the transition of hydrogen to a solid solution, are characteristic two plasticity minima, at +20 and −80°C. The biggest decrease of relative contraction is observed at −80°C. After aging for a year hydrogen changes to hydrides. Here the plasticity of the commercial titanium decreases with falling temperature but its value remains higher than the minimum plasticity of hardened specimens at corresponding temperatures. 2. For VT3-1 α+β-alloy containing 0.03% H alongside with the minimum of ψ in the range of 0 to −20°C is observed its sharp decrease at −60 to −80°C. At lower temperatures ψ increases. 3. In the VT15 β-alloy hydrogen embrittlement appears at temperatures of 0 and −40°C.

The corrosion behavior of high-strength VT15 alloy in sulfuric acid

The corrosion behavior of high-strength VT15 alloy in sulfuric acid

Determining the conditions for the appearance of reversible hydrogen brittleness in metals

1. With the assumption that cracks form according to the method proposed by Cottrell, equations were obtained determining the development of reversible hydrogen brittleness as a result of movement of the hydrogen atoms by dislocations moving along the slip planes. 2. The equations obtained make it possible to explain all of the basic rules of reversible hydrogen brittleness. 3. The conditions for the development of reversible hydrogen brittleness calculated using the proposed equations for VT-15 alloy were found to give satisfactory agreement with experimental data.

Effect of quenching temperature on the fine structure and properties in mechanicothermal treatment of the VT 15 alloy

1. A heating temperature of 800°C before quenching is insufficient to homogenize the β-phase of the VT15 alloy. The β-phase does not decompose in the grain boundaries during aging because the grain boundaries are enriched in molybdenum and chromium and impoverished in aluminum. 2. When the quenching temperature is increased from 800 to 1200°C the homogenization of the β-phase increases. 3. With increasing degrees of homogenization the recrystallization temperature of the β-phase increases and decomposition during aging is slowed down. This favors the establishment of temperaturetime conditions conducive to the development of the subgranular structure, providing a favorable combination of the mechanical properties and their restoration. 4. When the quenching temperature is increased from 800 to 1200°C the volume effect during aging decreases. Decomposition of the β-phase during aging at 480°C requires a longer time effer quenching from 1200°C than after quenching from 800°C. 5. An increase of the aging temperature to 520°C after quenching from 1200°C leads to embrittlement of the metal because of the selective precipitation of intermetallic compounds of titanium and chromium in the grain boundaries.

Heat treatment of the VT14, VT16, and VT15 alloys

1. A small increase in strength resulting from cold plastic deformation of annealed and quenched VT14 and VT16 alloys is accompanied by a sharp decrease in ductility. This method of strengthening semi-finished products and articles of these alloys has no advantage. 2. Deformation of the annealed and quenched VT15 alloy increases its strength. 3. Deformation after strengthening of the VT15 and VT16 alloys by heat treatment increases their strength. This method can be used in manufacturing high strength semi-finished products and articles.

Effect of heat treatment on the structure and properties of welded joints in the VT15 alloy

1. It was found that the best strengthening heat treatment for welded VT15 alloys is as follows: heating to 800°C and cooling in water after 15 min at this temperature, aging at 500°C fo 10 h, and repeated heating at 560°C for 10 min. Quenching and aging after welding increases the ultimate strength, but decreases the ductility. 2. An increase in the aging time to 10 h at 500°C strengthens the weld seam and the base metal more than the heat affected zone. A longer aging time increases the hardness of the heat affected zone without strengthening the seam or the base metal.

Singularities of heat treatment of the cladded VT15 alloy

1. The optimum quenching temperature of cladded sheets of the VT15 alloy 3 mm thick is 800°C. 2. The cooling rate during quenching must be no lower than 3 deg/min. 3. Since the cladding has a certain passivating effect, the rate of phase transformations in the base metal is slowed down. 4. The areas of the metal close to the cladding layer are enriched in molybdenum and consist of undecomposed β-phase.

Effect of oxygen and hydrogen on the mechanical properties of the VT1, OT4, and VT15 alloys

Effect of oxygen and hydrogen on the mechanical properties of the VT1, OT4, and VT15 alloys

Thermomechanical treatment of the VT15 alloy

1. High temperature thermomechanical treatment consisting of hot deformation at 1050°C and quenching in water improves the mechanical properties after aging at 450 and 560°C. 2. Preliminary cold working of the β-solid solution is responsible for its uniform decomposition during aging following high temperature thermomechanical treatment and is responsible for the considerable fragmentation of the products of decomposition, which improves the mechanical properties.

Strengthening of the VT15 alloy by heat treatment

Strengthening of the VT15 alloy by heat treatment

Effect of high temperature thermomechanical treatment on the resistance of the VT15 alloy to biaxial elongation

High temperature thermomechanical treatment improves the structure and increases the strength of barrels made of the VT15 alloy subjected to biaxial elongation.