外文资料翻译

Transformation Super plasticity of Titanium Alloy

Technology Research Connection

The outstanding characteristic of titanium is its high specific strength and

excellent corrosion resistance, while at the same time has good heat resistance

and low temperature performance, and practical application of a wide range.

As long as the materials properly, not only can greatly increase the

effectiveness of equipment, but also can bring significant economic benefits.

In regard to corrosion resistance, titanium alloys in oxidizing and neutral

media is extremely stable, the corrosion rate in sea water is far below the

stainless steel, compared with platinum, it is suitable for the petroleum,

chemical, electric power, metallurgy, agricultural chemicals, paper-making,

shipbuilding, food and medical applications and health departments.

Due to the characteristics of titanium alloy with the above, it is

particularly suitable for aircraft and spacecraft materials design is required.

Aviation Industry Development and Application of titanium alloys is the first

sector. The beginning of the fifties, the United States succeeded in the use of a

titanium aircraft, although at the time of each aircraft being used for only 1%

the weight of the structure of titanium, but titanium has opened up applications

in the aviation industry in the broad road. Now, the titanium in the world has

been widely used, small screws, nuts, such as connectors, up to the fuselage

frame, every other frame, such as structural parts, and even more than 6 meters

long, weighing two tons of the main support beam of the landing gear. For

high-speed fighters, as a result of high-speed and high maneuverability, the

aircraft structure as far as possible the requirements of light, heat capacity at

the same time; practice has proved that titanium is the most appropriate

material.

Titanium is the world's recognized difficult-to-machine materials, but the

use of super plastic forming / diffusion bonding process (SPF / DB) can be

produced by welding, riveting processes difficult to produce complex titanium

aircraft parts and components to enable integration, light weight, and lower the

cost.

Use of materials under thermal cycle repeated phase-change role in the

effects of pressure welding material so that the contact took place in super

plastic flow, so that the surface in close contact and close to the inter-atomic

forces to achieve the scope of , the realization of the material on both sides of

the interface connected to a reliable welding method known as phase-change

Super plastic diffusion bonding (Transformation Super plastic Diffusion

Bonding). Super plastic conditions, the material under stress in the smaller

plastic deformation has a very good ability to flow the process of super plastic

materials in a highly activated state of atoms, these materials will help to

remove the surface oxide film to improve the combination of the close

connections and speed up the atomic diffusion, resulting in a short period of

time to achieve a reliable connection. Be welded as long as the phase-change

material, the use of such methods can be welded. Repeated phase-change

material is produced by thermal cycling to achieve, and therefore thermal

cycling method has become the core of this welding process links.

Phase transformation super plastic diffusion bonding is a solid-phase

welding method, a general proliferation of welding and the characteristics of

welding deformation, deformation mechanisms and the proliferation of

mechanisms in the formation of welded joints are equally important role in the

process. Phase transformation super plastic diffusion bonding joints or less

after the formation of three phases.

First, physical contact with the formation of phases:

To the formation of the actual physical contact, the material must be

removed on the surface oxide film and the adsorbed layer, but in the welding

process and welding can completely clear the oxide film is of utmost

importance. Vacuum welding, the adsorbed layer and the oxide film under high

temperature description, distillation, evaporation, chemical reaction and

dissolution methods can be eliminated.

In the process of diffusion bonding, only the material near the surface of

each other, reaching between atoms can be caused by physical distance, will it

be possible to form a welded joint quality. In general, the solder materials

were processed through sophisticated, from the micro-view of its surface is

still uneven. Therefore, in the beginning stages of diffusion welding, the

welding material contact surfaces can only form of local contacts, while the

remainder of the full contact is required by the interface of the plastic

deformation of solder material, there is no part of the full contact holes are

formed, the holes on the formation of adverse effect on joint reliability.

Phase change materials in the super plastic deformation resistance under

conditions of low stress in the low to the high occurrence of plastic

deformation, welding interface of the holes can exist in the role of high-plastic

archeology to be filled rapidly. Phase-change material, the grains continue to

migration and conversion, the surface oxide film to break down quickly broken.

The use of phase-change method of super plastic diffusion bonding can be

smaller under the pressure of the rapid realization of fully welded joint

physical contact.

Second, chemical interaction of stages:

The formation of the actual contact and the surface is not enough to have

a strong connection between atoms. In order to obtain the combination of

atoms between the solid, it is necessary to activate the surface atoms.

Activation of the surface atoms will lead to the original bond (for example, the

chemical adsorption and oxygen level) of the tear, and then will it be possible

to make the electronic interactions between atoms. Under the metal in the

external force generated by shear stress and normal stress can cause the metal

surface of the plastic deformation and flow, plastic deformation and flow of

cause defects in the crystal structure (dislocations and hole) to move to the

surface at this time, defect migration the release of atomic energy will activate