Introduction of ZTC3(α-β) casting titanium alloy material

Overview of ZTC3
ZTC3 alloy is a Ti-Al-Mo cast titanium alloy containing eutectic element Si and rare earth element Ce, thus increasing the effect of refractory particle strengthening on the basis of traditional strengthening. The alloy has good comprehensive properties, excellent thermal strength below 500℃ (high temperature strength, creep resistance, etc.), high strength at room temperature, good casting technology, good fluidity, no hot cracking tendency. Castings are used in annealed or hot isostatic pressing.
The alloy can be used to manufacture engine casing, bracket, impeller and other structural parts, and its long-term operating temperature can reach 500℃.
ZTC3 technical standard
GJB 2896 -- 1997 Specification for Titanium and Titanium Alloy Investment Precision Castings
HB 5448 -- 1990 "Titanium and Titanium alloy investment Precision Castings"
Q/6S 448 -- 1985 "Aviation ZT3 casting titanium alloy"
Q/6S 449-1985 "ZT3 Casting of Titanium Alloy Compressor Casing Casting"
Q/12BY 2237 -- 1998 "Technical Conditions for castings of ZT3 titanium alloy Grade 4-5, Grade 6-7 compressor casing for Aero engine"

ZTC3 heat treatment system
(1) Stress-free annealing: 650°C, 1-3h, air-cooled or furnace cooled.
(2) Hot isostatic pressing treatment: 920℃±10°C, 100-140MPa, 3-3.5h, with the furnace cooling to 300℃ below the oven.
ZTC3 smelting and casting supply
The master alloy ingot smelted twice by vacuum consumable electrode arc furnace, or the forged bar smelted twice by vacuum consumable electrode and the oxide skin removed, is remelted in vacuum consumable electrode arc shell furnace. According to the shape, size and quality requirements of the cast, gravity casting or centrifugal casting is adopted. According to the casting size, wall thickness, quantity and quality requirements, choose the machined graphite type, or compacted (graphite) type, or investment precision casting.
ZTC3 application overview
High pressure compressor parts cast with ZTC3 alloy have been mass produced for more than 10 years, and can also be used for other aerospace structural parts working under 500℃.
ZTC3 special requirements
(1) The oxygen content in the base alloy has a great influence on the mechanical properties of the alloy, especially on the plasticity and weldability. With the increase of oxygen content, the plasticity and weldability of the alloy become worse. Therefore, attention should be paid to the oxygen content in the preparation and smelting process of the master alloy.
(2) -- Normal castings can be supplied in annealed state, but the class I and Ⅱ castings used in aerospace must be treated by hot isostatic pressing.
ZTC3 process properties and requirements
(1) Formability
Alloy casting performance is good, no hot cracking tendency, can be used graphite type or investment casting shell, according to the shape, structure, size and quality requirements of the casting, centrifugal casting or gravity casting method casting of various sizes of special-shaped castings.
(2) Welding performance
The alloy has good weldability. The strength of the joint welded with TIG welding in the TIG welding box shall not be lower than that of the matrix. For complex or important castings, stress removal annealing at 650℃ is required after welding and repair welding.
(3) Heat treatment process of parts
According to the quality requirements of castings, non-vacuum annealing at 650℃ or vacuum annealing can be used, holding for 1-3h, direct air cooling or furnace cooling to 250°C and then air cooling. The castings of class Ⅰ and Ⅱ used in aviation must be treated by hot isostatic pressing, and then stress relief annealing can be carried out according to the need.
ZTC3 use recommendations
It is suggested that ZTC3 alloy should be used to make special-shaped structural castings in aerospace equipment with operating temperature below 500℃.
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