CN102335791B

CN102335791B - TiAl alloy brazing method for forming intermetallic compound particle-reinforced brazed seam

Info

Publication number: CN102335791B
Application number: CN 201110263928
Authority: CN
Inventors: 李玉龙; 冯艳; 何鹏; 冯吉才; 刘�文; 刘敬妍; 张华�
Original assignee: Nanchang University
Current assignee: Nanchang University
Priority date: 2011-09-07
Filing date: 2011-09-07
Publication date: 2013-03-13
Anticipated expiration: 2031-09-07
Also published as: CN102335791A

Abstract

The invention relates to a TiAl alloy brazing method for forming an intermetallic compound particle-reinforced brazed seam. The method comprises the following steps: (1) pre-placing a Ag-Cu brazing material between contact surfaces of TiAl alloy to be brazed, and placing test pieces to be brazed in a vacuum brazing furnace; (2) heating to 600-610 DEG C at a heating rate of 0.5-1.0 DEG C/s, and carrying out heat-preservation for 30-90 seconds so as to enable the temperature of the test pieces to be even; (3) heating to a temperature of 10-20 DEG C higher than the melting point of the brazing material at a heating rate of 0.5-1.0 DEG C/s, and carrying out heat-preservation for 30-90 seconds so as to form a newborn intermetallic compound thin layer; (4) continuously heating to 900-910 DEG C at a heating rate of 0.25-0.3 DEG C/s and carrying out heat-preservation for 200-300 seconds, wherein the newborn intermetallic compound thin layer crushes and enters inside a brazing seam in the process of heating and heat-preservation; and (5) cooling to the room temperature at a cooling rate of 0.5-1.0 DEG C/s, and obtaining a TiAl alloy brazed seam with dispersed intermetallic compound reinforcing particles after the brazing seam is solidified. The TiAl alloy brazing method for forming the intermetallic compound particle-reinforced brazed seam provided by the invention has the characteristics that the TiAl alloy brazed seam with dispersed intermetallic compound reinforcing particles can be obtained after heat-preservation and temperature reduction.

Description

A kind of TiAl alloy brazed method that forms intermetallic compound particle-reinforced brazed seam

Technical field

The present invention relates to a kind of TiAl alloy brazed method that forms intermetallic compound particle-reinforced brazed seam.

Background technology

The Ti-Al series intermetallic compound comprises g-TiAl, a ₂-Ti ₃Al and q-TiAl ₃Deng, specific strength height, specific stiffness are large owing to having, mechanical behavior under high temperature and antioxygenic property are good etc., and advantage is considered to Aero-Space, military affairs and motor vehicles for civilian use desirable, that have the extensive exploitation application prospect, the high temperature structural material of diesel locomotive.Wherein alloy (referred to as the TiAl alloy) specific strength and the specific stiffness take g-TiAl as base surpassed conventional high-temperature alloy and titanium alloy.But consider cost and the relatively relatively poor problem of the plasticity of TiAl alloy own, should not make large-scale or complex-shaped TiAl alloy components, therefore in order to address this problem, need development TiAl alloy self and with the interconnection technique of other structural materials, wherein soldering tech is demonstrating good prospect aspect the connection of TiAl alloy.Yet the TiAl alloy property is active, is very easy to forming thick large frangible compounds with scolder generation interfacial reaction near TiAl alloy one side in brazing process, and frangible compounds in blocks, layering can reduce the mechanical property of joint.The present invention is directed in the TiAl alloy brazed process and the problem that compound between thick large border brittle metal reduces joint mechanical property to occur easily, on the basis of carrying out theory analysis, propose to adopt the specific process butt joint microstructure evolution that runs counter to traditional soldering processes to control, obtain the TiAl alloy brazed joint of intermetallic compound particle-reinforced brazed seam.

According to existing TiAl alloy brazed documents and materials, general all is to analyze article about the generality of joint interface tissue, or the analysis of tissue and strength of joint Relations Among, and TiAl base alloy brazed joint interface tissue, boundary response layer are not had the research of the Control of the aim.If do not adopt special control technique, in the general TiAl alloy brazed joint, crisp hard intermetallic compound conversion zone generally all is to generate on the border near mother metal, the joint of this institutional framework is very easy at the inner brittle break that produces of crisp hard intermetallic compounds layer when being subjected to External Force Acting.The Typical Joints Interface Microstructure back scattering photo that the people such as famous scholar R.K.Shuie that Figure 1 shows that Taiwan obtain when adopting the Ag-Cu eutectic solder that the TiAl alloy is carried out soldering, the Al-Cu-Ti series intermetallic compound generates at solder and TiAl alloy border as shown in FIG., and the middle part of brazed seam is Ag based solid solution tissue and the Ag-Cu eutectic structure that remaining solder solidifies formation.The inner plasticity of this joint is fine, but being thickness, both sides connect into more greatly the crisp hard intermetallic fabric texture of sheet, when being subject to External Force Acting, in a single day a small amount of plastic deformation occurs and produces hardening Plastic in the good part of inner plasticity, to be easy to crack in crisp hard intermetallic compounds layer inside, border so, and crackle will be in case in mutually inner generation of fragility, will finally cause joint breaking in the rapid expansion in the inside of fragility phase.

If can reasonably control technique, make the boundary response layer thickness less, at inner intermetallic compound particle, the agglomerate that generates the disperse distribution of brazed seam, as shown in Figure 2, the characteristics that distribute according to load in the compound phase so, the comprehensive mechanical property of joint will obtain larger raising.

Be binary, the ternary alloy phase diagram of alloy and the elements such as Ag, Cu according to Ti-Al, the present invention propose a kind of TiAl base alloy self that can generate in the inside of brazed seam the intermetallic compound particle that disperse distributes and with the method for welding of other structural materials.Adopt Ag base solder, utilization in soldering heating process the Ag in the solder can be in the TiAl alloy mother metal diffusion and successively with the TiAl alloy in TiAl phase, the Ti3Al generation liquid phase of having an effect mutually, compound layer and push the inside of brazed seam between broken nascent interface metal, form the compound brazing seam structure of disperse distribution intermetallic compound particle in the brazed seam, thereby make joint obtain preferably comprehensive mechanical property.This is a kind of method of attachment of uniqueness, and other solderings of the same race and foreign material that it also forms commute compound layer between the interface metal of fragility provide a kind of new thinking and practical approach.

Through retrieval, adopt special soldering processes control to obtain the TiAl alloy brazed method of the intermetallic compound particle-reinforced brazed seam of formation disperse thereby yet there are no both at home and abroad.Background technology description of drawings: Fig. 1 TiAl/BAg-8/TiAl soldered fitting, Fig. 2 TiAl alloy and certain material soldered fitting ideal model.

Summary of the invention

The purpose of this invention is to provide a kind of TiAl alloy brazed method that forms intermetallic compound particle-reinforced brazed seam, the tissue topography of can domination property active TiAl alloy brazed process median surface intermetallic compound, thereby the mechanical property of control soldered fitting.

The present invention is achieved in that method is:

(1) the Ag-Cu scolder is preset in titanium-aluminium alloy contact surface to be welded;

(2) be warmed up to 600 ℃-610 ℃ insulation 30-90s with 0.5-1 ℃/s heating rate;

(3) be warmed up to the above 10-20 of scolder fusing point ℃ (being 790-800 ℃) insulation 30-90s with 0.5-1.0 ℃/s heating rate, form nascent intermetallic compound thin layer;

(4) continue to be warmed up to 900 ℃-910 ℃ with 0.25-0.3 ℃/s heating rate, and insulation 200-300s;

(5) cool to room temperature with 0.5-1.0 ℃/s speed.

Technique effect of the present invention is: be to increase to be provided with the special isothermal treatment for short time time after scolder just surpasses fusion temperature (790 ℃), run counter to traditional method for welding; And traditional method for welding thinks that the solder fusing only arranges a temperature retention time later, as the holding time.TiAl alloy and Ag-Cu scolder generate astable " coming into being " Al-Cu-Ti intermetallic compound thin layer under this special holding temperature.Continue to heat up, because Ag-Cu liquid solder and TiAl alloy mother metal interaction, astable nascent intermetallic compound thin layer can occur broken under the actings in conjunction such as the hydraulic shock of liquid solder, element counterdiffusion, thermograde, concentration gradient, thereby makes nascent Al-Cu-Ti intermetallic compound thin layer broken and enter into weld seam inside.900 ℃ of-910 ℃ of insulations, the nascent intermetallic compound of these fragmentations will form intermetallic compound and strengthen particle as the core of forming core, and insulation and cooling will obtain the TiAl alloy brazed weld seam that intermetallic compound strengthens the particle dispersion distribution later.

Description of drawings

Fig. 1 TiAl/BAg-8/TiAl soldered fitting.

Fig. 2 TiAl alloy and certain material soldered fitting ideal model.

Fig. 3 is special process curve map of the present invention.

Fig. 4 is for adopting the TiAl alloy brazed joint microstructure interface of " the TiAl alloy brazed method that forms intermetallic compound particle-reinforced brazed seam " soldering.The photograph instrument is light microscope (Olympus, model: XTZ-E), amplify 200 times of shootings.

The specific embodiment

Process for soldering step of the present invention is as follows:

(2) be warmed up to 600 ℃ of insulation 90s with 0.5 ℃/s heating rate;

(3) be warmed up to 795 ℃ of insulation 90s with 0.5 ℃/s heating rate, form nascent intermetallic compound thin layer;

(4) continue to be warmed up to 905 ℃ with 0.25 ℃/s heating rate, and insulation 300s;

(5) cool to room temperature with 0.5 ℃/s speed.

Such as Fig. 1, Fig. 2, Fig. 3, shown in Figure 4, programming rate is 0.5-1 ℃/s first, is warmed up to below the solder fusion temperature, and namely 600-610 ℃ is incubated, temperature retention time 30-90s, and purpose is to make whole workpiece temperature to be welded even.For the second time programming rate is 0.5-1 ℃/s, is warmed up to the above 10-20 of solder fusion temperature ℃, temperature retention time 30s-90s, and purpose is Ag parent metal and the TiAl alloy mother metal intermetallic compound that generation comes into being that reacts under this temperature.Programming rate is 0.25-0.3 ℃/s for the third time, be warmed up to 900 ℃-910 ℃, under this temperature, be incubated 200s-300s: heat up for the third time and insulating process in astable nascent intermetallic compound thin layer under the actings in conjunction such as the hydraulic shock of liquid solder, Elements Diffusion, thermograde, concentration gradient, can occur brokenly, and enter into weld seam inside; 900 ℃-910 ℃ are incubated in the temperature-fall period that reaches subsequently, the nascent intermetallic compound of these fragmentations will form intermetallic compound and strengthen particle as the core of forming core, will obtain the TiAl alloy brazed weld seam that intermetallic compound strengthens the particle dispersion distribution after cooling to room temperature.

Claims

1. TiAl alloy brazed method that forms intermetallic compound particle-reinforced brazed seam is characterized in that method step is as follows:

(2) 0.5-1 ℃/s heating rate is warmed up to 600 ℃-610 ℃ insulation 30-90s;

(3) be warmed up to the above 10-20 of scolder fusing point ℃ with 0.5-1.0 ℃/s heating rate, namely 790-800 ℃, insulation 30-90s forms nascent intermetallic compound thin layer;

(4) continue to be warmed up to 900 ℃-910 ℃ with 0.25 ℃ of-0.3 ℃/s heating rate, and insulation 200-300s;

(5) cool to room temperature with 0.5-1.0 ℃/s speed.