Invention content
In view of the deficienciess of the prior art, the object of the present invention is to provide a kind of low temperature ultrasonics to assist magnesium alloy weldingMethod completes entire ultrasonic welding process in atmospheric environment, shortens the time of isothermal solidification to the utmost, required heating temperatureSpend relatively low, weld interval is short, and the joint mechanical property obtained is strong, reduces process complexity, reduces welding cost.
To achieve the goals above, the technical solution adopted in the present invention is：A kind of low temperature ultrasonic auxiliary magnesium alloy weldingMethod, include the following steps：
Surface treatment step, base material to be welded are only limitted to magnesium alloy or magnesium-based composite material, by the to be welded of base material to be weldedJunction carries out mechanical grinding and ultrasonic cleaning；
Assembling steps before welding, select thin shape or the zinc foil of sheet as intermediate reaction material layer, by intermediate reaction materialLayer is clamped in the weld interface of upper and lower two base materials to be welded, forms a component to be welded；
Component to be welded, is placed on the processing platform of ultrasonic welding system by upper machine fixing step, and makes Ultrasonic probe pressureTightly on the top of component to be welded；Ultrasonic probe is applied into pressure, pressure value 0.1-0.2MPa to component longitudinal direction to be welded；
Load ultrasound and sensing heating step will be welded ultrasonic wave by Ultrasonic probe and conducted to component to be welded, weldingThe power control of ultrasonic wave is welded the FREQUENCY CONTROL of ultrasonic wave and is set in 10-30kHz, while by sensing heating in 200-500WStandby to heat component to be welded, induction heating equipment power control is in 4-6kW, and induction heating equipment FREQUENCY CONTROL is in 200-250kHz；
Component temperature to be welded is heated to 335-345 DEG C, passes through Ultrasonic probe pair by intermediate reaction material layer collapsing stepComponent ultrasonication to be welded makes intermediate reaction material layer be generated under ultrasound and temperature action with base material to be welded and reacts, intermediateIt disappears after the reaction of the reaction wood bed of material, after the weld interface of upper and lower base material to be welded forms compound layer and molten solid layer, ultrasoundTool heads fail, wherein molten solid layer includes first layer and the second layer, and first layer is Zn atoms to inside base material to be weldedSolid-state diffusion layer；The second layer is α-Mg (Zn) crystal grain of precipitation during weld seam liquid metal solidification；
Component temperature to be welded is heated to 365-375 DEG C by rich magnesium conversion step, and Ultrasonic probe is super to component to be welded againSound acts on, and weld seam liquid metal reaches the hypoeutectic ingredient of rich Mg, and α-Mg (Zn) mutually depend on base material to be welded and are precipitated and grow up；
Component temperature to be welded is down to 335- by eutectic conversion step by Ultrasonic probe to component ultrasonication to be welded345 DEG C, eutectic reaction occurs for weld seam liquid metal：L→Mg51Zn20+MgZn；
Without eutectoid cooling step, when component temperature to be welded drops to 295-305 DEG C, Mg the and Zn atom quilts in component to be weldedLimitation movement；
Weld assembly step is completed, welding finished product is obtained.
In further technical solution, the intermediate reaction material collapsing step, the Ultrasonic probe is to described to be weldedComponent ultrasonication 1-3 seconds, the intermediate reaction material layer generate instead with the base material to be welded under ultrasound and temperature actionIt answers, disappears after the reaction of intermediate reaction material layer；
The richness magnesium conversion step, component temperature to be welded are heated to 365-375 DEG C, Ultrasonic probe to component to be welded afterContinuous ultrasonication 100-125 seconds, weld seam liquid metal reaches the hypoeutectic ingredient of rich Mg, and α-Mg (Zn) mutually depend on mother to be weldedMaterial is precipitated and grows up；
The eutectic conversion step, component temperature to be welded drop to 335-345 DEG C, continue to component to be welded in Ultrasonic probeEutectic reaction occurs for ultrasonication 2-3 seconds, weld seam liquid metal：L→Mg51Zn20+MgZn；
The no eutectoid cooling step, component to be welded temperature in 1-3 seconds drop to 295-305 DEG C, in component to be weldedMg and Zn atoms are moved by limitation.
In further technical solution, the richness magnesium conversion step, the component temperature to be welded is heated to 365-375 DEG C,After the Ultrasonic probe continues component to be welded to keep ultrasonication 100-125 seconds, Ultrasonic probe stops ultrasonication；
Component temperature to be welded is down to 335-345 DEG C by the eutectic conversion step, and Ultrasonic probe is to component to be welded
Ultrasonication is restarted, the ultrasonication time is 2-3 seconds.
In further technical solution, the intermediate reaction material layer is more than the weld interface of the base material to be welded.
In further technical solution, before the welding in assembling steps, the zinc foil selects zinc foil made of pure zinc,The thickness of zinc foil is 45-55 μm.
In further technical solution, in the surface treatment step, to the described to be welded of the base material to be weldedFace is polished, and the sand paper of 1000-1500 mesh is selected to polish surface to be welded.
In further technical solution, in the surface treatment step, the base material to be welded is positioned over a concentration of 90-It is cleaned by ultrasonic in 100% acetone soln and using cleaning ultrasonic wave, it is 10-20 minutes to be cleaned by ultrasonic the time.
In further technical solution, in load ultrasound and sensing heating step, the work(of the welding ultrasonic waveRate is controlled in 300W, welds the FREQUENCY CONTROL of ultrasonic wave in 20kHz, while described to be welded by induction heating equipment heatingComponent, induction heating equipment power control is in 5kW, and induction heating equipment FREQUENCY CONTROL is in 225kHz.
In further technical solution, in the upper machine ultrasonic welding step, by the pressure value of the Ultrasonic probeIt is set as 0.15MPa.
In further technical solution, the temperature of the component to be welded is heated to 365 DEG C, when the welding ultrasonic activationBetween be 120 seconds.
The invention has the advantages that compared with the prior art,：
1. using zinc foil as intermediate reaction material layer and by welding ultrasonic wave auxiliary, completing magnesium alloy in atmospheric conditionsOr the high quality transition liquid-phase diffusion connection of magnesium-based composite material, reduce the complexity and processing cost of technique, very big limitThe time of the solidifications such as ground shortening, required heating temperature is relatively low, and weld interval is short, and the joint mechanical property obtained is strong.
2. using zinc foil relatively thin as intermediate reaction material layer, in the welding process, ultrasonic losses are smaller so that ultrasound is madeWith being enhanced.
3. the vibration in the welding process, welding ultrasonic wave can effectively abolish interface oxidation film, promote Mg-Zn eutectics anti-It answers, accelerate isothermal solidification process and forms the connector of typical microstructures structure, shearing strength of joint is made with welding ultrasonic waveIncreased with the extension of time, and base material to be welded realizes effectively connection.
Specific implementation mode
It is only below presently preferred embodiments of the present invention, is not intended to limit the scope of the present invention.
A kind of method of low temperature ultrasonic auxiliary magnesium alloy welding, includes the following steps：
Surface treatment step, base material 3 to be welded are only limitted to magnesium alloy or magnesium-based composite material, by waiting for for base material 3 to be weldedWelding surface carries out mechanical grinding and ultrasonic cleaning；
Assembling steps before welding, select thin shape or the zinc foil of sheet as intermediate reaction material layer 4, by intermediate reaction materialLayer 4 is clamped in the weld interface of upper and lower two base materials 3 to be welded, forms a component to be welded；
Component to be welded, is placed on the processing platform of ultrasonic welding system by upper machine fixing step, and Ultrasonic probe 1 is made to pressTightly on the top of component to be welded；Ultrasonic probe 1 is applied into pressure, pressure value 0.1- to component longitudinal direction to be welded0.2MPa；Shown in Fig. 1.
Load ultrasound and sensing heating step will be welded ultrasonic wave by Ultrasonic probe 1 and conducted to component to be welded, weldingThe power control of ultrasonic wave is welded the FREQUENCY CONTROL of ultrasonic wave and is set in 10-30kHz, while by sensing heating in 200-500WStandby 2 heating component to be welded, 2 power control of induction heating equipment is in 4-6kW, and 2 FREQUENCY CONTROL of induction heating equipment is in 200-250kHz；
Component temperature to be welded is heated to 335-345 DEG C, passes through Ultrasonic probe 1 by intermediate reaction material layer collapsing stepTo component ultrasonication to be welded, so that intermediate reaction material layer 4 is generated under ultrasound and temperature action with base material 3 to be welded and reacts,Intermediate reaction material layer 4 disappears after reacting, and compound layer and molten solid layer are formed in the weld interface of upper and lower base material 3 to be weldedAfterwards, Ultrasonic probe 1 stops ultrasonication, wherein molten solid layer includes first layer and the second layer, and first layer is Zn atoms to waiting forSolid-state diffusion layer inside welding base metal 3；The second layer is α-Mg (Zn) crystal grain of precipitation during weld seam liquid metal solidification；
Component temperature to be welded is heated to 365-375 DEG C by rich magnesium conversion step, and Ultrasonic probe 1 is again to component to be weldedUltrasonication is carried out, weld seam liquid metal reaches the hypoeutectic ingredient of rich Mg, and α-Mg (Zn) mutually depend on base material 3 to be welded and are precipitatedAnd it grows up；
Component temperature to be welded is down to 335- by eutectic conversion step by Ultrasonic probe 1 to component ultrasonication to be welded345 DEG C, eutectic reaction occurs for weld seam liquid metal：L→Mg51Zn20+MgZn；
Without eutectoid cooling step, when component temperature to be welded drops to 295-305 DEG C, Mg the and Zn atom quilts in component to be weldedLimitation movement；
Weld assembly step is completed, welding finished product is obtained.
Wherein more specifically,
In surface treatment step, base material 3 to be welded selects MB8 magnesium alloys or AZ31 magnesium alloys, treats welding base metal 3Surface to be welded is polished, and the sand paper of 1000-1500 mesh is selected to polish surface to be welded.The polishing of base material 3 to be welded is completedAfterwards, base material 3 to be welded is positioned in a concentration of 90-100% acetone solns and is cleaned by ultrasonic using cleaning ultrasonic wave, surpassedSound scavenging period is 10-20 minutes.Wherein, cleaning ultrasonic wave is the ultrasonic wave of ultrasonic generator generation and conducts to ultrasonic workHas the ultrasonic wave of head 11 and service sink.
Before welding in assembling steps, zinc foil selects zinc foil made of pure zinc, and the thickness of zinc foil is 45-55 μm.It is intermediate anti-Material layer 4 is answered to be more than the weld interface of base material 3 to be welded.
In upper machine ultrasonic welding step, it sets the pressure value of Ultrasonic probe 1 to 0.15MPa.
In load ultrasound and sensing heating step, the power control of ultrasonic wave is welded in 300W, welds the frequency of ultrasonic waveRate is controlled in 20kHz, while heating component to be welded by induction heating equipment 2, and 2 power control of induction heating equipment is in 5kW, senseAnswer 2 FREQUENCY CONTROL of heating equipment in 225kHz.
In intermediate reaction material layer collapsing step, 335- is heated to the temperature of component to be welded by induction heating equipment 2345 DEG C, Ultrasonic probe 1 to component ultrasonication to be welded 1-3 seconds, intermediate reaction material layer 4 and base material 3 to be welded in ultrasound andReaction is generated under temperature action, intermediate reaction material layer 4 disappears after reacting；It is formed in the weld interface of upper and lower base material 3 to be weldedAfter compound layer and molten solid layer, Ultrasonic probe 1 fails, wherein and molten solid layer includes first layer and the second layer, and firstLayer is Zn atoms to the solid-state diffusion layer inside base material 3 to be welded；The second layer is precipitation during weld seam liquid metal solidificationα-Mg (Zn) crystal grain；
Rich magnesium conversion step, component temperature to be welded are heated to 365-375 DEG C, continue to component to be welded in Ultrasonic probe 1Ultrasonication 100-125 seconds, weld seam liquid metal reach the hypoeutectic ingredient of rich Mg, and α-Mg (Zn) mutually depend on base material to be welded3 are precipitated and grow up；At this point, Ultrasonic probe 1 can continue to carry out ultrasonication to component to be welded or Ultrasonic probe 1 stops ultrasoundEffect.
Eutectic conversion step, when component temperature to be welded drops to 335-345 DEG C, Ultrasonic probe 1 is again to component to be weldedIt carries out ultrasonication 2-3 seconds or Ultrasonic probe 1 continues ultrasonication 2-3 seconds to component to be welded, weld seam liquid metal occurs altogetherCrystalline substance reaction：L→Mg51Zn20+MgZn；
Without eutectoid cooling step, component to be welded temperature in 1-3 seconds drops to 295-305 DEG C, because cooling velocity is very fast, waits forMg the and Zn atoms welded in component are moved by limitation.
It combines and can be seen that from table and Figure 10, when base material 3 to be welded is when ultrasonication is less than 120s, the shearing of connector is strongDegree can enhance with the extension of ultrasonication time；When base material 3 to be welded is when being more than 120s the ultrasonication time, connectorShear strength is maintained at same level.It follows that it is optimal to treat the ultrasonication time control of welding base metal 3 in 120sValue.
The experimental principle analysis of the present invention is, with the extension of the action time of welding ultrasonic wave, to generally include following threeThe variation of aspect：
One, in the welding process, with the extension of welding ul-trasonic irradiation time, the Microstructure of Joint structure of acquisitionVariation is generated therewith, is broadly divided into the following four stage：
Intermediate reaction material layer 4 disappears the stage, as shown in Fig. 2, when it is 1 second to weld the ul-trasonic irradiation time, it is originalThe interfaces Mg-Zn show bending, show that interface oxidation film has completely removed.Original zinc foil completely disappears, anti-by Mg-Zn institutesThe compound answered replaces completely.In conjunction with EDS and XRD analysis, as shown in figure 8, the object to the compound layer mutually judges, greyMatrix compounds be Mg51Zn20, and needle-shaped or granular white compound mutually be MgZn.Compound layer with it is to be weldedThe interface of base material 3 forms one layer of α-Mg (Zn) solid solution layer.By amplifying observation it can be found that the solid solution layer actually dividesIt is two layers：Close to base material 3 to be welded first layer be Zn atoms to the solid-state diffusion layer inside base material 3 to be welded, because of the layerIt is interior there is the precipitate reinforced phase of some whites, and the white reinforced phase inside these reinforced phases and original base material 3 to be weldedIt is very much like；The second layer close to compound layer by α-Mg (Zn) crystal grain for being precipitated during weld seam liquid metal solidification, becauseIt is showed for these crystal grain and depends on the form that 3 surface of base material to be welded is precipitated and is grown to liquid metal.
Rich magnesium changes phase, when welding the ul-trasonic irradiation time after 1 second, by the institutional framework of weld seam and as schemedMg-Zn phasors shown in 9 is it is found that the liquid metal among weld seam can reach a kind of hypoeutectic ingredient of richness Mg, such as institute in Fig. 9Show, region shown in Z points.α-Mg (Zn) are mutually directly attached to the precipitation of base material 3 to be welded and grow up in cooling procedure.
The eutectic reacting condition stage, when being cooled to 341 DEG C of the eutectic reaction temperature of Mg-Zn, remaining liquid phase in weld seamEutectic reaction directly occurs：L→Mg51Zn20+MgZn.
Without eutectoid cooling stage, there is no generations by subsequent eutectoid reaction Mg51Zn20 → α-Mg (Zn)+MgZn, this is mainIt is because faster cooling velocity limits the movement of Mg and Zn atoms.
Two, in the welding process, with the extension of welding ul-trasonic irradiation time, the layer structure of microstructure also withVariation, be mainly reflected in the change width of compound layer, solid solution layer and connector.
(1) when welding ul-trasonic irradiation 1 second, as shown in Fig. 2, the width difference of compound layer, solid solution layer and connectorIt is 56 μm, 12 μm and 81 μm.
(2) when it is -5 seconds 3 seconds to weld the ul-trasonic irradiation time, as shown in Figure 3-4, it can be found that the width base of solid solution layerThis is constant, and quickly reducing occurs in the width of compound layer and connector.The process shows during welding ultrasonic activation,Solid-state magnesium-liquid weld seam-solid-state magnesium sandwich structure is acted on by the superaudible periodical extrusion pressure for welding ultrasonic wave,A large amount of eutectic liquid phase is extruded, so that compound layer is obviously thinning.
(3) after the welding ul-trasonic irradiation time being more than 5 seconds, as illustrated in figs. 5-7, the overall width variation of connector is little,And the width of compound layer is reduced, the thickness of solid solution layer accordingly increases.
(4) when it is 30 seconds to weld the ul-trasonic irradiation time, as shown in figure 5, compound layer thickness is reduced to 10 μm；
(5) when the welding ul-trasonic irradiation time further extending to 60 seconds, as shown in fig. 6, compound layer becomes not connectIt is continuous；
(6) it when reaching 120 seconds the welding ul-trasonic irradiation time, as shown in fig. 7, compound layer completely disappears, entirely connectsHead is made of solid solution layer completely.
The practical differentiation of this microstructure is an isothermal solidification process.It can be found that it should by amplifying observationSolid solution layer can equally be divided into two layers：I layers close to base material 3 to be welded are similarly Zn atoms divergent contour into solid magnesium alloyAt solid solution；And intermediate III layers are isothermal solidification α-Mg (Zn) solid solution that solidification is precipitated in situ.III layers of Crack causeMainly by Zn atoms to the diffusion inside base material 3 to be welded caused by, while at this stage, the extrusion for welding ultrasonic wave is madeWith equally existing, only welding ul-trasonic irradiation at this stage does not have the welding ul-trasonic irradiation of early period apparent.Because of equivalentZn elements can form wider connector when forming α-Mg (Zn) solid solution completely.
Three, as shown in Figure 10, in the welding process, with the extension of welding ul-trasonic irradiation time, shearing strength of jointAnd the thickness of each layer tissue also changes therewith in connector.
(1) when it is 1-5 seconds ranges to weld the ul-trasonic irradiation time, strength of joint is quick with the increase of ultrasonication timeIncrease, this be mainly compound layer and weld width in connector it is rapid reduce caused by.From welding ul-trasonic irradiation 5 secondsFracture apperance can find that the fracture mode mainly shows brittle fracture, and fracture takes place mostly in inside compound layer, such as Figure 11It is shown.
(2) when welding ul-trasonic irradiation time lengthening is later to 5 seconds, as illustrated by figs. 12-13, strength of joint increases slowSlowly, this is mainly influenced by the reduction of compound layer thickness and the increase of solid solution layer thickness.
(3) when it is 30 seconds and 60 seconds to weld the ul-trasonic irradiation time, the fracture of connector betides compound layer and solid solutionInside body layer, as shown in figure 12.As welding sonication times extend, the region for betiding solid solution layer internal break is increased.
(4) when the welding ul-trasonic irradiation time reaching 120 seconds, connector is made of solid solution layer completely, and connector is averagely cutShearing stress reaches maximum value 106.4MPa, close to the intensity of base material 3 to be welded.The fracture behaviour of the connector betides to be weldedInside base material 3, as shown in figure 13.
Primary structure, principle and effect of the present embodiment are identical as embodiment one, and which is not described herein again.
Beneficial effects of the present invention are：
(1) with 45-55 μm of zinc foil make intermediate reaction material layer 4 and by welding ultrasonic wave auxiliary in atmospheric conditions atWork(realizes the high quality transition liquid-phase diffusion connection of magnesium alloy or magnesium-based composite material.
(2) there are large effects for welding ul-trasonic irradiation time butt joint institutional framework.On the one hand, welding ultrasonic wave shakesKinetic energy is enough effectively to abolish interface oxidation film, promotes Mg-Zn eutectic reactions, and accelerate isothermal solidification process.On the other hand, connectorTypical microstructures structure is：Magnesium alloy or magnesium-based composite material/interface α-Mg (Zn) solid solution layer/Mg51Zn20's and MgZn is mixedPolymerisable compounds layer/interface α-Mg (Zn) solid solution layer/magnesium alloy or magnesium-based composite material.With prolonging for welding ul-trasonic irradiation timeLong, the compound layer in weld seam is quickly reduced and solid solution layer is constant, and subsequent compound layer is slowly reduced until disappearing and solid solution layerThe process being slowly increased.
(3) shearing strength of joint with welding the ul-trasonic irradiation time extension and increase, and with intermetallic compound,There are certain correspondences for solid solution layer and weld width.When weld the ul-trasonic irradiation time be 120 seconds when, connector completely byα-Mg (Zn) solid solution layer is constituted, and the average shear strength of connector is up to 106.4MPa, and is broken and betides magnesium alloy or magnesiumInside based composites.
The above content is only presently preferred embodiments of the present invention, for those of ordinary skill in the art, according to the present inventionThought, there will be changes in the specific implementation manner and application range, and the content of the present specification should not be construed as to the present inventionLimitation.