γ-TiAl alloys are excellent candidate materials for high-temperature applications, although poor hot workability limits their widespread application. In the present study, the microstructure, mechanical properties and hot workability of TiAl-Nb-Mo alloy in the as-cast and as-extruded conditions were investigated. The as-cast TiAl alloy consisted of γ/α 2 lamellae, γ and β phase distributed at colony boundaries and on the lamellar interfaces. The tiny particles of ω 0 phase were formed, transformed from β phase during HIP treatment, which dissolved after hot extrusion. The TiAl alloy exhibited improved mechanical properties and excellent hot workability after hot extrusion because of grain refinement, the introduction of β phase and the disappearance of ω 0 phase. The anomalous yield stress phenomenon occurring in as-cast material disappeared in the as-extruded condition, which was ascribed to grain refinement that reduced the resistance of grain boundaries to intragranular slip at elevated temperature. The findings demonstrate the benefits of introducing small amounts of β phase to improve hot workability of TiAl-Nb-Mo alloys, particularly when followed by heat treatment to eliminate the β phase and increase the mechanical properties.

Improvement of microstructure, mechanical properties and hot workability of a TiAl-Nb-Mo alloy through hot extrusion

Method for preparing TiAl alloy plate by argon atomization in powder metallurgy

Forging is a core process of the manufacturing industry. Being a primary metal forming process, it defines the mechanical properties of the part in the initial stage of manufacturing. An aligned grain flow pattern and a sound metal flow define a good forging. The present paper discusses the various fields of forging research. The different fields are basically the perspectives to produce a good quality product. Finally, the unexplored areas of research where further investigation is required are also given. KeywordsForging, Finite Element Analysis, Numerical Simulation, Forging Defects, Optimization

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A Review on Field Areas of Research in Forging Process using FEA

The invention discloses a high-temperature thermal extrusion moulding method of a TiAl intermetallic compound material, which relates to a thermal extrusion moulding method of a TiAl intermetallic compound material. The invention aims to solve the problems of rapid heat radiation from blank to a die, large temperature reduction of blank, large deformation resistance, serious die damage and difficult extrusion moulding existing in the process of extruding the TiAl intermetallic compound material by adopting a traditional thermal extrusion technology. The method comprises the following steps of: firstly, manufacturing an extrusion sheath and a sheath cover; secondly, placing the extrusion sheath in an inner cavity of an extrusion female die and heating both the extrusion sheath and the extrusion female die at the temperature of 200-600 DEG C; thirdly, heating the extrusion blank of a TiAl intermetallic compound to 1150-1300 DEG C, then taking out and rapidly placing into the extrusion sheath; fourthly, covering the sheath cover; and fifthly, extruding after die assembly so that the extrusion blank of the TiAl intermetallic compound is extruded and moulded in the complete cover of the extrusion sheath and the sheath cover. The invention is used for the high-temperature thermal extrusion moulding of TiAl intermetallic compound materials.

High-temperature thermal extrusion moulding method of TiAl intermetallic compound material

The invention discloses a preparation method of a gamma-TiAl-based alloy bar. The preparation method comprises the following steps: (I) preparing a gamma-TiAl alloy ingot through a vacuum melting method; (II) manufacturing a jacket, wherein the jacket comprises a jacket cylinder and jacket covers, the jacket covers are used for sealing the two end openings of the jacket cylinder, and each jacket cover is provided with a ventilating hole; (III) thermally treating the cylinder body, subsequently coating the inner wall of the cylinder body with an oxidation-resistant coating, afterwards putting the TiAl alloy ingot in the cylinder body and finally welding each jacket cover on the corresponding open end of the cylinder body; (IV) externally coating the oxidation-resistant coating, carrying out thermal treatment, subsequently extruding in an extruder to obtain the bar, and straightening the bar by letting the bar directly pass through a straightening tube; and (V) removing the jacket on the outer surface and carrying out homogenizing annealing treatment to obtain the gamma-TiAl-based alloy bar. The problem that a TiAl intermetallic compound is relatively large in brittleness and easy to oxidize in a hot working process can be solved through the preparation method disclosed by the invention, and the prepared gamma-TiAl-based alloy bar is uniform in microstructure and high in mechanical property.

Preparation method of gamma-TiAl-based alloy bar

The invention relates to a production method for a bar, in particular to a production method for a Gamma-TiAl alloy bar. The production method solves the problems that a Gamma-TiAl alloy bar produced by the prior method has the defects of surface cracks, uneven diameter, uneven size of crystal grains and easy fusion caused by the reaction of Gamma-TiAl alloy and blank at high extrusion temperature. The production method comprises the steps: heating a cast ingot, keeping temperature and annealing; cutting a cylinder in the cast ingot, packaging aluminum silicate fibers, placing in the middle of a stainless steel pipe, and sealing both ends to obtain the blank; washing the sheathed blank, drying and heating the sheathed blank, keeping temperature, placing the sheathed blank in the air, putting the sheathed blank into a cup pre-pressured by glass lubricant, putting the sheathed blank into a mould to extrude to obtain the bar; annealing the bar, taking the bar out of a blast furnace for air cooling, and obtaining the Gamma-TiAl alloy bar. The obtained bar has the advantages of no surface cracks, even diameter, even size of crystal grains and no fusion caused by the reaction of the Gamma-TiAl alloy and the sheath.

Production method for Gamma-TiAl alloy bar

The invention relates to a preparation method of TiAl alloy with fine grain full synusia tissue The invention solves the problems that the existing casting method is difficult to cast TiAl alloy with fine grain full synusia tissue in excellent mechanical property and the existing preparation method of TiAl alloy with fine grain full synusia tissue is high in cost The method includes: firstly, melting; secondly, hot isostatic pressing; thirdly, electrospark wire-electrode cutting; fourthly, sheath sealing and soldering; fifthly, heat preservation and hot extrusion, thus obtaining the TiAl alloy with fine grain full synusia tissue The organizational chart of the TiAl alloy of the invention shows that the TiAl alloy obtained by the invention has fine grain full synusia tissue; compared with the existing preparation method of TiAl alloy with fine grain full synusia tissue, the cost of the method of the invention is reduced by 50-70%

Preparation method of TiAl alloy with fine grain full synusia tissue

The invention discloses a method for improving hot processing performance of TiAl alloy, which relates to a method for improving the hot processing performance of alloy and solves the problems that the conventional method for improving the hot processing performance of the TiAl alloy has high manufacturing cost and the manufactured TiAl alloy has poor high-temperature hot processing performance and narrow hot processing window. The method comprises the following steps of: 1, smelting; 2, hot isostatic pressing; 3, homogenizing annealing; 4, electro-spark wire cutting; 5, sheathing and sealing; 6, heat preservation and hot extrusion to improve the hot processing performance of the TiAl alloy. The TiAl alloy manufactured by the method has wide hot processing window and good high-temperature hot processing performance; and compared with the conventional multi-step hot mechanical processing method for improving the hot processing performance of the TiAl alloy, the manufacturing method of the invention reduces the cost by over 50 percent.

Method for improving hot processing performance of TiAl alloy

Hot extrusion was conducted in the α+β phase region for promoting mechanical properties of Ti42Al9V0.3Y. The microstructures and tensile properties before and after hot extrusion were studied. The results show that the microstructure of the as-cast alloy mainly consists of massive γ phase in β matrix and the as-extruded alloy mainly consists of lamellar α2/γ, lamellar β/γ, and strip γ propagating from elongated β phase. In the as-cast alloy, the predominantly observed fracture mode is transgranular cleavage failure at room temperature and intergranular fracture at 650–750 °C. After hot extrusion, it transforms into transgranular cleavage-like failure, including translamellar cleavage and delamination. The excellent tensile properties of the as-extruded material are attributed to the obvious refined microstructure with broken YAl2 particles and the micro-crack shielding action of the TiAl lamellasome.

Promoting the mechanical properties of Ti42Al9V0.3Y alloy by hot extrusion in the α+β phase region *

The invention relates to a glass lubricant for gamma-TiAl alloy bar extrusion and a preparation method thereof. The invention solves the problem that the existing lubricant has poor wetting property, has very strict requirements on the initial extrusion temperature of the extrusion bar, thus causing that the thickness of the extrusion bar is uneven, the surface of the extrusion bar has crack, even is fractured and the extrusion force is large, which wastes energy. The glass lubricant is made from L glass, graphite and clay. The preparation method as follows: 1. the raw materials are weighted; 2. glass waste sludge is prepared; 3. the glass waste sludge is ground into micropowder, blended with the graphite, and then ground with balls to obtain the glass lubricant. The product has the advantages that the wetting property is good, the prepared bar has even thickness, smooth and crackless surface, low preparation cost, energy conservation and the preparation method is simple.

Hao Zhang

Papers

Production method for Gamma-TiAl alloy bar

Preparation method of TiAl alloy with fine grain full synusia tissue

Method for improving hot processing performance of TiAl alloy

Promoting the mechanical properties of Ti42Al9V0.3Y alloy by hot extrusion in the α+β phase region *

Glass lubricant for extrusion of gamma-TiAl alloy rod bar and method of producing the same