FR3114987A1 - Additive manufacturing process of an aluminum alloy blank with structural hardening - Google Patents

Abstract

Process for the additive manufacturing of a structurally hardened aluminum alloy blank Process for the additive manufacturing of a structurally hardened aluminum alloy blank part, comprising the step consisting in depositing the said alloy, in the state of melting, layer by layer, on a base substrate, said alloy, the deposition step being implemented by using arc welding equipment with wire electrode in an inert gas atmosphere (MIG) with current and filler material pulsed according to a short-circuit metal transfer (CMT) process, the filler material being an aluminum alloy with age hardening, all or part of the parameters of the welding equipment, in particular the speed of the filler material, the rate of deposition and the composition of the protective gas forming the inert gaseous atmosphere, being controlled so as to stabilize the deposit. Figure for abstract: Fig. 1

Description

Additive manufacturing process of an aluminum alloy blank with structural hardening

The present invention relates to the field of metallurgy, in particular that of the metallurgy of aluminum alloys with structural hardening. In particular, the invention presents a process for the manufacture of an aluminum alloy blank with structural hardening as well as a blank obtained according to such a process. The invention also relates to a process for manufacturing a structurally hardened aluminum alloy part from such a blank as well as a part produced according to such a process.

To produce metal parts, in particular parts in structurally hardened aluminum alloy, it is known to forge or machine a block of metal or metal alloy. These methods have the disadvantage of generating material loss.

It is also possible to produce metal parts by welding parts of parts together. However, the age hardened aluminum alloys of the 6000 and 7000 series are not weldable, in a homogeneous manner, by conventional welding processes without leading to the formation of cracks in the weld zone.

FR 2 980 382 discloses a process for hardfacing aluminum metal parts of a turbomachine by means of welding equipment comprising a pulsed current generator and a flow rate of pulsed filler metal wire. The hardfacing is carried out by means of a filler metal wire whose composition is of the same nature as the composition of the aluminum alloy of the part to be hardened, the pulsed metal wire flow rate and the hardfacing speed of the metal part of the turbomachine being adapted so as to carry out hardfacing without hot cracking. This process makes it possible to reconstruct a portion of a part to be hardfaced, for example a retention casing flange of an aluminum alloy turbomachine without hot cracking.

There is thus a need to produce, entirely, aluminum parts with structural hardening without cracks whose mechanical characteristics are acceptable.

Process for manufacturing an aluminum alloy preform with structural hardening

To meet all or part of these needs, the present invention proposes, according to one of its aspects, a process for the additive manufacturing of a blank of an aluminum alloy part with structural hardening.

According to the invention, the method comprises the step of depositing said alloy, in the molten state layer by layer, on a base substrate, the deposit step being implemented by the use of a gas inert (MIG) wire arc welding equipment with pulsed current and filler material using a short circuit metal transfer (CMT) process, the filler material being an alloy of aluminum with structural hardening, all or part of the parameters of the welding equipment, in particular the speed of the filler material, the speed of deposition and preferably the composition of the protective gas forming the inert gaseous atmosphere, being controlled so as to stabilize the deposit.

Advantageously, the filler material is chosen from the group consisting of a wire, a strip, a bar, preferably a wire, or a mixture of these.

The term "structurally hardened aluminum alloy" means aluminum alloys chosen from the group consisting of aluminum alloys of the 2000, 6000, 7000 series, preferably of the 6000 or 7000 series, and a mixture of those -this. Unlike other aluminum alloys, alloys with age hardening have higher mechanical strengths.

The method according to the invention therefore makes it possible to obtain blanks whose mechanical strength is high while saving material. The process can also make it possible to obtain blanks with complex geometries, for example not achievable by machining and/or forging.

The speed of the filler material and the speed of deposition are preferably adapted so as to produce a blank without hot cracking.

By "speed of the filler material", we mean the average speed of movement of the filler material within the welding equipment, in the direction of the blank.

By "deposition rate" is meant the average rate of deposition of said alloy for the production of the blank.

For a speed of the filler material of between 3.5 and 6.5 m/min approximately, in particular between 3.9 and 5.5 m/min approximately, the stabilization of the deposit is advantageously achieved with a deposition speed of between 10 and 120 cm/min approximately, in particular between 20 and 100 cm/min.

The speed of the filler material and the deposition speed are preferably coupled in order to guarantee the quality of the deposition. In other words, the speed of the filler material and the deposition speed are preferably determined as a function of each other in order to guarantee the quality of the deposition.

Alternatively, the filler material velocity and the deposition velocity are independent of each other.

During the step of depositing the structurally hardened aluminum alloy on the base substrate or on the preceding layer, a part of the filler material, moving in the direction of deposition, periodically passes into a state of fusion, that is to say changes from a solid state to a liquid state, in particular at the end of the filler material which is close to the base substrate or the previous layer. At least part of the aluminum alloy of the molten filler material is then deposited on the base substrate or the previous layer, locally forming a molten pool on the blank. Thus, melts are periodically deposited. As the filler material moves in the direction of deposition, the locally deposited weld pools cool down, changing from a liquid state to a solid state. When a puddle is deposited on a previous layer of the blank, it fuses with it as it cools.

The periodic passage of part of the filler material into a state of fusion is caused by a pulsed electric current, passing through the filler material, oscillating between a low intensity and a high intensity or peak intensity, the frequency of pulsation being advantageously between 40 Hz and 60 Hz. Preferably, for a voltage between 10 V and 15 V, the electrical intensity varies periodically between a low intensity, for example approximately 15 A, and a high intensity or current peak of approximately 150 A, for example.

In a first phase called intensity peak I, the filler material is not in contact with the blank or the substrate and advances in the direction of the blank or the substrate. In this peak phase, the intensity I which crosses the filler material is at its peak, which allows the formation of an electric arc between the filler material and the blank, in a manner known per se. In this phase, part of the filler material passes into a state of fusion and forms a drop of molten material at one end of the filler material, in particular at the end of the filler material which is close to the base substrate. or the previous layer.

In a second phase called waiting, the drop of molten material is held at the end of the filler material. In this phase, the filler material is still moving in the direction of the blank and the intensity passing through the filler material is reduced to reach a plateau.

In a third so-called short-circuit phase, the drop of molten material carried to the end of the filler material comes into contact with the blank or with the substrate. A short-circuit then forms which triggers a second decrease in the intensity I. The short-circuit triggers a slight recoil of the filler material in the welding equipment, which allows the deposit of the drop of molten material, forming thus a molten pool. Once the weld pool has been deposited on the blank, the filler material is again moved in the direction of the blank or the substrate.

By "stabilizing the deposit", it is meant that the parameters of the welding equipment, in particular the speed of the filler material, the speed of deposition and the composition of the protective gas forming the inert gaseous atmosphere, are controlled in such a way that that the melts deposited have substantially the same mass of filler material and substantially the same shape, that is to say substantially the same height and substantially the same width. In particular, during the short-circuit phase, the rate of penetration of the filler material into the molten pool must be controlled so as to limit the projection of materials in a molten state, before the intensity peak. Turbulence within the weld pool is thus limited while stabilizing the flow of the quantity of material deposited, which optimizes the evacuation of porosities.

Advantageously, in the implementation of the method, at the deposition step, the parameters of the welding equipment are controlled so as to form a synergy together, in particular in order to optimize the mechanical characteristics of the blank, in particular in order to minimize its porosity. For example, it is sought to obtain a porosity such that the ratio between the volume of the pores in the blank and the volume of the blank is less than 0.1%.

These welding equipment parameters include in particular the deposition rate, the filler material rate, the composition of the protective gas forming the inert gaseous atmosphere and improvement parameters chosen from the group consisting of the cycle pulse frequency intensity, the peak intensity, the duration of the peak intensity phase, the instantaneous deposition rate in the waiting phase, the intensity in the waiting phase, the intensity in the short-circuit, the temporal variation of intensity between the short-circuit phase and the peak phase, the temporal variation of intensity between the peak phase and the standby phase, the voltage, the duration of the variation of the intensity between the intensity in the short-circuit phase and the intensity in the peak phase, the flow of protective gas, the correction of the arc height, the pre-gas duration, the duration of post-gas, filler material retraction correction time, and inter-pass time.

The speed of the filler material preferably conditions all or part of the synergy parameters.

Preferably, the aluminum alloy with structural hardening is chosen from the 6000 series, in particular the aluminum alloys 6005, 6060, 6061, 6063, 6082, 6101 and 6262, or the 7000 series, in particular the alloy of 7075 aluminum.

To implement the method with a filler material comprising an aluminum alloy with structural hardening 6061 and having a diameter equal to approximately 1.2 mm, in which for a speed of the filler material of between 3.8 and 5.3 m/min approximately, in particular between 4 and 4.9 m/min approximately, stabilization of the deposit is advantageously achieved with a deposition rate of between 40 cm/min and 80 cm/min approximately.

Preferably, the composition of the protective gas comprises a mixture of argon and helium, in particular a mixture by volume of approximately 80% argon (Ar) and 20% helium (He). Such a mixture makes it possible to minimize the viscosity of the weld pool, which facilitates the evacuation of porosities. The flow rate of protective gas Ar80%He20% is preferably between 10 L.min ^-1 and 25 L.min ^-1 approximately, preferably equal to 15 L.min ^-1 approximately.

The duration of the current peak phase corresponds to the time to pass from the short-circuit phase to the standby phase. During this phase of the peak, the passage from the low intensity of the short-circuit phase to the intensity of the peak is done according to a temporal variation of predetermined intensity, in particular between 100 A/ms and 300 A/ms approximately , preferably equal to approximately 220 A/ms, for a measured predetermined variation duration, preferably equal to approximately 0.5 ms. Once at the peak, the intensity is constant until the waiting phase. The duration of the intensity peak phase is preferably between 1 ms and 50 ms approximately, better still between 1 ms and 10 ms approximately, better still equal to 1.8 ms approximately.

The length of the electric arc in the peak current phase must be neutral, i.e. neither too short nor too long. The correction of the arc height, a parameter making it possible to vary the length of the electric arc, should preferably be close to 0%.

In the standby phase, the current changes from the peak to a standby phase current value, preferably of the order of approximately 60 A, according to a measured predetermined intensity temporal variation, preferably comprised between 100 A/ms and 300 A/ms approximately, preferably equal to 220 A/ms approximately. In the waiting phase, the instantaneous deposition rate is reduced, preferably almost zero.

The waiting phase ends when the short circuit occurs. The intensity is then lowered to reach a selected short-circuit phase intensity, advantageously between 15 A and 100 A approximately, preferably equal to 15 A approximately.

Before the formation of the electric arc in the peak intensity phase, it is possible to send a protective gas in the direction of the blank for a predetermined measured pre-gas time. Preferably, no protective gas is sent in the direction of the blank before the formation of the electric arc, which corresponds to a pre-gas duration equal to 0 s.

After each deposition of a drop of molten filler material, a protective gas is preferably sent in the direction of the blank for a predetermined measured post-gas time in order to protect the molten puddle. The post-gas duration is preferably equal to approximately 3s.

To limit the risks of sticking between the filler material and the drop of molten filler material in the short-circuit phase, the electrical intensity is preferably maintained at the value of the intensity plateau of the short-circuit phase. waiting for a predetermined measured duration of yarn retraction correction, preferably between 0.01 s and 0.5 s approximately, preferably equal to 0.06 s approximately.

After the deposition of a layer, it is possible to leave a waiting time before the possible deposition of a new layer for a predetermined measured duration called the inter-pass duration. The duration between passes is preferably between 4 s and 60 s approximately, preferably equal to 10 s approximately.

Preferably, the cooling system, i.e. the water box, is regulated at a predetermined temperature, in particular around 20°C.

In a particular embodiment, the base substrate is made of the same material as the filler material or is made of a material of the same composition. In this case, the substrate forms part of the blank.

In a particular embodiment, the method comprises a step of pickling the substrate. The step of stripping the substrate consists for example of scraping the deposition surface of the substrate using a scraper, so as to reduce the quantity of pollutant-rich alumina present on this deposition surface, and/or perform degreasing, for example using a solvent, in particular acetone and/or 80% alcohol.

In a particular embodiment, the base substrate comprises a backing support slat. The backing support slat can be made, for example, of a thermally conductive refractory material or of cooled copper. During the deposition of the molten pool, the backing support slat makes it possible to retain the molten pool without merging with it. As the weld pool cools, the aluminum alloy changes from a liquid state to a solid state. It is then possible to easily separate the backing support slat and the aluminum alloy, for example without using a cutting tool or pliers. The method may include the step of separating the base substrate, in particular formed by a backing support slat, from the structurally hardened aluminum alloy blank.

The method advantageously comprises a step of heat treatment of the blank. Such a heat treatment can make it possible to improve the mechanical characteristics of the blank, in particular to increase its hardness. The heat treatment is preferably chosen from the group consisting of solution treatment followed by quenching or annealing, natural ripening or tempering, annealing, complete heat treatment called T6 and a mixture of these. , preferably a full T6 heat treatment.

In the case of a heat treatment comprising solution treatment, the residual stresses, of a thermomechanical nature, within the blank, formed during the manufacturing process of the blank, are relaxed.

By "complete heat treatment called T6", is meant a heat treatment comprising solution treatment, preferably at approximately 530° C. for approximately 1 hour, annealing, for example in water or in air, and tempering , preferably at approximately 175° C. for approximately 8 hours.

Structurally hardened aluminum alloy blank

Another subject of the invention, according to another of its aspects, in combination with the foregoing, is an aluminum alloy blank with structural hardening produced according to the method as defined above.

The process makes it possible to obtain a blank which does not exhibit hot cracking.

The blank may have undergone, during the process, a heat treatment as defined above. Such a heat treatment can make it possible to improve the hardness of the blank and its mechanical resistance.

The blank is advantageously in the form of several superimposed layers of structurally hardened aluminum alloy, due to its manufacturing process. The blank may include the base substrate, preferably fabricated from the same age-hardened aluminum alloy as the layers of the blank. Alternatively, the blank may not include a base substrate on which it was made, the base substrate, for example formed by a backing support slat, having been separated therefrom.

The blank may have a rectangular shape. As a variant, the blank can have another shape, geometric or not, integrating for example reliefs, rounded parts, rectilinear parts and/or others.

The volume of the blank can be between 0.0001 m ³ and 10 m ³ approximately, for example.

Process for manufacturing a structurally hardened aluminum part

Another subject of the invention, according to another of its aspects, in combination with the foregoing, is a method for manufacturing an aluminum part with structural hardening, from a blank produced according to the method as defined above. , comprising a step of finishing the blank, preferably chosen from the group consisting of machining and forging.

The process makes it possible to obtain an aluminum alloy part with structural hardening while limiting the loss of material during the finishing stage.

To this end, the blank can be made in such a way as to limit the quantity of material to be removed from the blank during the finishing step.

The method may include the step consisting in carrying out a heat treatment of the part, in particular when no heat treatment has been implemented on the blank or in addition to the heat treatment carried out on the blank.

Such a heat treatment is preferably chosen from the group consisting of solution treatment followed by quenching or annealing, natural ripening or tempering, annealing, complete T6 heat treatment and a mixture thereof , preferably a full T6 heat treatment. Such a heat treatment can make it possible to improve the hardness of the part and/or its mechanical strength.

When the finishing step consists of machining, the blank can be heat treated before machining.

When the finishing step consists of forging, the part can be heat treated after forging. The forging can consist of a stamping.

Structurally hardened aluminum alloy part

Another subject of the invention, according to another of its aspects, in combination with the foregoing, is a structurally hardened aluminum alloy part made according to the method as defined above.

Such a part does not show any cracking thanks to the invention. In addition, it has a high mechanical resistance due to the fact that it is entirely made of aluminum alloy with structural hardening.

The invention may be better understood on reading the detailed description which follows, non-limiting examples of implementation thereof, and on examining the appended drawing, on which

there schematically shows in perspective an installation for implementing the process for manufacturing a blank according to the invention,

there represents a graph of the measurement of the intensity passing through the filler material in the implementation of the method for manufacturing a blank according to the invention,

there represents a graph of the measurement of the tension between the filler material and the blank in the implementation of the method according to the invention,

there represents a graph with different photographs in side view of cross-sections of blanks produced with a method according to the invention with different filler material speeds and different deposition speeds,

there represents a map illustrating the aspect ratio of the cooled molten pool in the implementation of the method according to the invention as a function of the deposition rate and the filler material rate,

there represents a map illustrating the acceptability criterion in the implementation of the method according to the invention as a function of the deposition rate and the filler material rate,

there represents a graph with different top view photographs of blanks made with a process according to the invention with different filler material speeds and different deposition speeds,

there is a top view photograph of a longitudinal section of a blank made with a blank manufacturing process without parameter control as in the process according to the invention,

there is a photograph of an installation during the implementation of the method according to the invention,

there is another photograph of the installation of the at another time,

there is another photograph of the installation of Figures 9 and 10 at another time,

there is a top view photograph of a longitudinal section of another example of a blank produced with the method according to the invention,

there is an enlargement of a detail VI of the ,

there is a photograph of a blank made with a method according to the invention,

there is an x-ray of the outline of the ,

there represents a graph illustrating the hardness as a function of the location within a blank produced according to the method of the invention,

there represents a graph similar to that of the a blank that has undergone heat treatment,

there represents a graph similar to that of the a blank having undergone another heat treatment,

there represents a graph similar to that of the a blank having undergone another heat treatment,

there represents a graph similar to that of the of a blank having undergone another heat treatment, and

there represents a part produced according to the method of the invention.

detailed description

In the remainder of the description, identical elements or identical functions bear the same reference sign. For the purpose of conciseness of the present description, they are not described with regard to each of the figures, only the differences between the embodiments being described.

It has been illustrated at an installation 1 allowing the implementation of the blank manufacturing process according to the invention.

Installation 1 comprises arc welding equipment with wire electrode in MIG inert gas atmosphere (MIG for Metal Inert Gas in English) with pulsed current and filler material according to a method of metal transfer by short circuit CMT (CMT for Cold Metal Transfer in English). In the example shown, the protective gas forming the inert atmosphere is a mixture of argon and helium in an 80%/20% ratio.

This installation 1 comprises a torch 2 bringing the filler material 3, in this example a wire with a diameter equal to approximately 1.2 mm. The installation 1 further comprises a support 4 and a base substrate 6. In this example, the installation 1 comprises two jaws 5 making it possible to hold the base substrate on the support 4. On the base substrate 6, a blank 10 in accordance with the method according to the invention. On the , a blank 10 is displayed during manufacture using the method according to the invention.

The installation 1 makes it possible to implement the method according to the invention to produce the blank 10. The filler material 3 comprises an aluminum alloy with structural hardening of the 6061 type in the example illustrated.

The method according to the invention comprises the step consisting in depositing in the molten state in layer 11 by layer 11, on the base substrate 6, the aluminum alloy with structural hardening of the filler material 3. The filler material velocity, the deposition rate and the composition of the protective gas forming the inert gas atmosphere are controlled so as to stabilize the deposition. Thanks to the invention, a blank 10 is obtained which has no cracks and whose mechanical strength, due to the use of an aluminum alloy with structural hardening, is high.

On the , the direction is visualized, along a longitudinal axis X, of deposition of the material, that is to say of deposition of the structurally hardened aluminum alloy, horizontal in the example illustrated. The direction, along a Y axis, of displacement of the filler material 3 is also displayed which, in this example, is perpendicular to the direction of deposition of the material and vertical.

Always on the , an arrow parallel to the axis X is displayed illustrating the direction of movement of the torch 2 for the deposition of material to produce the layer 11n being deposited. As this layer 11n is not the first layer, it is deposited on an underlying layer 11, layer 11n-1. It should be noted that the first deposited layer, layer 11a, is deposited directly on the base substrate 6.

The base substrate 6 can be made of the same structurally hardened aluminum alloy as the blank 10. In this case, after the completion of the production of the blank 10, the base substrate 6 remains integral with the draft 10.

Also in this case, the method may include a step of pickling the base substrate 6, for example by scraping the deposition surface of the substrate 6 in combination with degreasing with acetone.

We have illustrated on the an example of periodic temporal variation of the intensity I which passes through the filler material 3 during the implementation of the method. In this example, the pulse frequency is 60 Hz.

In a first phase 30 called the peak of intensity I, the filler material 3 is not in contact with the blank 10 or the base substrate 6 and advances in the direction of the blank 10 or of the substrate 6 In this peak phase 30, the intensity I which passes through the filler material 3 is at its maximum, that is to say at its peak, in this example the intensity at the peak is approximately 150 A, this which allows the formation of an electric arc between the filler material 3 and the blank 10. In this phase 30, part of the filler material 3 passes into a state of fusion and forms a drop of molten material at a end of the filler material 3, in this example at the end 33 of the filler material 3.

In a second so-called waiting phase 31, the drop of molten material is held at the end 33 of the filler material 3. In this phase 31, the filler material is still moving in the direction of the blank and the current passing through filler material 3 is reduced to reach a plateau, which is at 50 A in the example of .

In a third so-called short-circuit phase 32, the drop of molten material carried to the end 33 comes into contact with the blank 10 or with the substrate 6. A short-circuit then forms which triggers a second decrease in intensity I. In the example of the , the current drops to 25 A. The short-circuit triggers a slight recoil of the filler material in the welding equipment, which allows the drop of molten material to be deposited, thus forming a molten pool.

The tension between the welding material and the blank is constant during the implementation of the process as illustrated in the graph of the , where the voltage is maintained at approximately 12 V.

We have illustrated on the graph of the various cross-sections of blank 10 during manufacture, in aluminum alloy 6061, obtained after depositing a layer of filler material on a base substrate 6. In these examples, the deposits are made in an atmosphere of argon and helium in an 80%/20% ratio at a flow rate of approximately 15 L.min-1. Depending on the speed Vd of deposition and depending on the speed of the filler material Vf, the shape of the deposition of the layer of filler material deposited on the substrate 6 is displayed.

There is obtained by calculating, as a function of the deposition velocity Vd and as a function of the filler material velocity Vf, the ratio R of the height h of deposition to the width l of deposition, R= h/l for the same layer 11, h and l being illustrated for layer 11n-1 on the . The ratio R is preferably close to 1, for example between 0.8 and 1.2.

The ratio R is included in this range of preferential values in the non-hatched areas 34. In the other areas, the ratio R is not acceptable. There is a collapse of the weld pool, i.e. an R ratio of less than 0.8, in zone 35 and a lack of penetration of the weld pool, i.e. an R ratio greater than 1.2 in zone 36. Such a collapse of the molten pool can be seen in certain blanks during manufacture illustrated in the , for example the blank 10i. One also visualizes such a lack of penetration of the molten pool in certain blanks in the course of manufacture illustrated on the , for example the blank 10a. Finally, blanks 10 during manufacture are visualized which are acceptable, such as for example the blank 10e.

On the , the quality of the blank 10 obtained is displayed, as a function of the deposition speed Vd and as a function of the speed of the filler material Vf, for the same deposition conditions as in FIGS. 4 and 5. Thus, it can be seen that only certain ranges of combinations of deposition rate Vd and filler material rate Vf are acceptable. As can be seen, the graph is divided into several zones illustrating the acceptability or otherwise of the blank obtained as a function of the deposition and filler material speeds. Among the zones A, B, C, D and E visible on the , zone A is preferred while zones B, C and D remain acceptable. Zone E, for its part, does not make it possible to obtain an acceptable draft. Zone A is also shown in Figures 4 and 5.

The acceptability criterion represents the quantity of projection and the continuity of the deposit. When large projections and/or discontinuities are obtained, the acceptability criterion is worth 0. Conversely, when there is neither projection nor discontinuity, the acceptability criterion is worth 1. In the case of zone D, the acceptability criterion is between 0 and 0.3. In the case of zone C, the acceptability criterion is between 0.3 and 0.6. In the case of zone B, the acceptability criterion is between 0.6 and 0.9. Finally, in the case of zone A, the acceptability criterion is greater than 0.9 and preferably greater than 0.9 as is the case for zone A.

It can be seen for example that zone A covers, for a speed V _f between approximately 4.8 and 5.2 m/min, a range of speeds V _d between approximately 20 and 35 cm/min. Zone A also covers, for a speed V _f of between approximately 3.8 and 5.2 m/min, a range of deposition speeds V _d of between approximately 38 and 85 cm/min. Zone A also covers, for a speed V _f of between approximately 4.4 and 5.2 m/min, a range of deposition speeds V _d of between approximately 85 and 100 cm/min.

There also represents, delimited by dotted lines, this zone A. The top views are thus displayed, illustrated by photographs of preferred blanks 10, with speeds Vd and Vf being in zone A.

On the , a blank 10 made of a 6061 aluminum alloy is displayed without having checked the parameters of the welding equipment so as to stabilize the deposit. This blank has a porosity equal to approximately 2%. The pores P are visualized. Such a blank 10 has weak mechanical characteristics.

Stabilization of the deposit is obtained when the parameters of the welding equipment, in particular the speed of the filler material, the speed of deposition and the composition of the protective gas forming the inert gaseous atmosphere, are controlled in such a way that the baths fusion deposited have substantially the same mass of filler material and substantially the same shape, that is to say substantially the same height and substantially the same width. This stabilization can be verified by capturing high-speed photographs of the installation during the implementation of the process, as seen in Figures 9 to 11.

The photograph of the is taken during the peak intensity phase 30. The photograph of the is taken during the waiting phase 31. The photograph of the is taken during the short-circuit phase 31. These various photographs make it possible to ensure that the projection of materials in a state of fusion is limited.

On the , the blank 10, also visible on the in magnification, has a porosity of less than about 0.5%. Such a blank was obtained by controlling the parameters of the welding equipment, in particular the speed of the filler material, the speed of deposition and the composition of the protective gas forming the inert gaseous atmosphere, so as to stabilize the deposit.

The difference in porosity between the blanks 10 of FIGS. 8 and 12 is thus linked to an optimization of the parameters in the implementation of the method according to the invention. The speed of the filler material Vf conditions a synergy of parameters of the welding equipment used in the implementation of the method to produce the blank 10 of the . These parameters include the deposition rate Vd, the filler material rate Vf and the composition of the protective gas forming the inert gas atmosphere. Parameters may include enhancement parameters, including intensity cycle pulse frequency, peak intensity, duration of peak intensity phase, instantaneous deposition rate in standby phase 31, the intensity in the standby phase 31, the intensity in the short-circuit phase 32, the time variation of intensity between the short-circuit phase 32 and the peak phase 30, the duration of the variation of the intensity between the intensity in the short-circuit phase 32 and the intensity in the peak phase 30, the temporal variation of intensity between the peak phase 30 and the standby phase 31, the voltage , shielding gas flow, arc height correction, horizontal pulse cycle, pre-gas time, post-gas time, wire retraction correction time, and inter-gas time. passes.

An example of synergy that can reduce porosity and therefore improve the mechanical characteristics of the blank can be:

• intensity cycle pulse frequency: 60 Hz,
• current at peak: 150 A
• duration of phase 30 of the intensity peak: 1.8 ms,
• instantaneous deposition rate in the waiting phase 31: 0 cm/min,
• current in standby phase 31: 60 A,
• current in the short-circuit phase 32: 15 A,
• temporal variation in intensity between the short-circuit phase 32 and the peak phase 30: 220 A/ms,
• duration of the intensity variation between the intensity in the short-circuit phase 32 and the intensity in the peak phase 30: 0.5 ms,
• temporal variation in intensity between the peak phase 30 and the standby phase 31: 220 A/ms,
• voltage: 12V,
• deposition rate: 4 cm/min,
• filler material speed: 4.5 m/s,
• type of gas atmosphere; Ar80% He20%,
• protective gas flow: 15 L/min,
• arc height correction: 0%,
• horizontal pulse cycle: 0.6,
• pre-gas duration: 0 s,
• post-gas duration: 3 s,
• thread retraction correction time: 0.06 s, and
• inter-pass duration: 10 s.

We have illustrated on the an X-ray of another example of a blank 10 made of alloy 6061 produced according to the method of the invention, the blank 10 being visible on the . On this X-ray, it is possible to see the different pores P.

There are illustrated in Figures 16 to 20, various graphs illustrating the hardness of a blank 10 made with the method according to the invention.

In the case of the , only the step of depositing the layers 11 to form the blank 10 has been carried out without carrying out any subsequent heat treatment of the blank 10 thus produced. It can then be seen that the hardness of the base substrate 6 located over a range between 0 and 20 mm is much greater than the hardness of the layers 11 deposited to form the blank 10, which extends over a range between 26 and 55 mm in this example. Two very distinct hardness plateaus are observed between the base substrate 6 and the blank 10. It is observed that the average hardness is approximately 88 HV (Vickers hardness, in English "Hardness Vickers" homogeneous at kg.F/mm² ).

In the example of the , after production of the blank 10, it has been subjected to a heat treatment consisting of a hyperquenching, that is to say a heat treatment of solution heat treatment at 530° C. for one hour, followed by sudden cooling in water at room temperature for a few minutes. We see, looking at the graph of the , that the hardness of the blank 10 is greater than that of the base substrate 6 and that the blank has few porosities illustrated by the frame. The average hardness is 81 HV.

In the case of the , the blank 10 was subjected to another heat treatment. , the blank 10 was subjected to a temperature of 175° C. for eight hours. This corresponds to a complete heat treatment called T6. The average hardness is around 107 HV. We thus observe on the that the hardness obtained after the complete heat treatment T6 is much higher than that of the after the annealing heat treatment.

In the case of the , the blank 10 was subjected to an over-ageing treatment, called SRV treatment. The average hardness obtained is then approximately 121 HV.

Finally, in the case of , a sub-ageing treatment, called SSV, has been subjected to the blank 10. The average hardness is then approximately 105 HV.

We have illustrated on the an example of part 20 that can be obtained from the blank 10 of the by carrying out a step of finishing the blank 10. In this example, the finishing state consists of a machining of the blank 10. This finishing step comprises in this example a polishing of the whole of the blank 10 as well as the realization of two non-through windows 15 and 16.

The invention is not limited to the examples which have just been described.

We do not depart from the scope of the invention if the part 20 is made by forging the blank 10.

The heat treatment possibly implemented on the blank 10 can take place after the blank 10 has been produced. Alternatively, in particular in the context of forging, it is the part 20 and not the blank 10 which can such heat treatment.

The base substrate 6 can be made of a backing support slat, for example made of cooled copper or of a thermally conductive refractory material, so as to be able to be separated from the blank 10, in particular after the latter has been produced.

The base substrate 6 can be made from another material without departing from the scope of the invention, for example from another structurally hardened aluminum alloy.

The filler material may include another structurally hardened aluminum alloy.

Claims (12)

Process for the additive manufacturing of a blank (10) of a structurally hardened aluminum alloy part (20), comprising the step of depositing said alloy, in the molten state, layer (11) by layer ( 11) on a base substrate (6), the deposition step being implemented by using arc welding equipment with wire electrode in an inert gas atmosphere (MIG) with current and filler material pulsed according to a short-circuit metal transfer process (CMT), the filler material (3) being an aluminum alloy with structural hardening, all or part of the parameters of the welding equipment, in particular the speed of the material intake, the rate of deposition and the composition of the protective gas forming the inert gas atmosphere, being controlled so as to stabilize the deposit. Process according to Claim 1, in which, for a speed of the filler material of between 3.5 and 6.5 m/min approximately, preferably between 3.9 and 5.5 m/min approximately, the stabilization of the deposition is achieved with a deposition rate of between 10 and 120 cm/min approximately, in particular between 20 and 100 cm/min approximately. A method according to any preceding claim, wherein the protective gas composition comprises a mixture of argon and helium, in particular a mixture by volume of 80% argon and 20% helium. Method according to any one of the preceding claims, in which the method comprises a preliminary step of pickling the base substrate (6). Method according to any one of the preceding claims, in which the base substrate (6) is made of the same material as the filler material (3), the base substrate (6) forming part of the blank (10 ). Method according to any one of the preceding claims, in which the base substrate (6) is a backing support batten, for example made of a thermally conductive refractory material or of cooled copper and in which the method comprises the step consisting in separating the base substrate (6) from the preform (10) of age hardened aluminum alloy. A method according to any preceding claim, in which the parameters of the welding material are controlled so as to form a synergy together, the parameters including the velocity of the filler material, the deposition rate and the composition of the protective gas forming inert gas atmosphere and enhancement parameters selected from the group consisting of intensity cycle pulsation frequency, peak intensity, duration of peak intensity phase, instantaneous deposition rate in the waiting phase, the intensity in the waiting phase, the intensity in the short-circuit phase, the temporal variation of intensity between the short-circuit phase and the peak phase, the temporal variation d intensity between the peak phase and the standby phase, the voltage, the duration of the variation of the intensity between the intensity in the short-circuit phase and the intensity in the peak phase, the flow rate of shielding gas, height correction r of arc, the pre-gas time, the post-gas time, the filler material retraction correction time and the inter-pass time. Process according to any one of the preceding claims, comprising a step of heat treatment of the blank (10), the heat treatment preferably being chosen from the group consisting of solution treatment followed by quenching or annealing , natural cure or tempering, annealing, T6 full heat treatment, preferably full heat treatment, and a mixture thereof. A method according to any preceding claim, wherein the age hardened aluminum alloy is selected from the 6000 series, including aluminum alloys 6005, 6060, 6061, 6063, 6082, 6101 and 6262, or 7000 series, including 7075 aluminum alloy. Process according to any one of the preceding claims, the filler material comprising an aluminum alloy with structural hardening 6061 and having a diameter equal to approximately 1.2 mm, in which for a speed of the filler material of between approximately 3.8 and 5.3 m/min, in particular between approximately 4 and 4.9 m/min, the stabilization of the deposit is achieved with a deposition speed of between 40 cm/ min and 80 cm/min approximately. Method of manufacturing a part (20) from a blank (10) produced by implementing the method according to any one of the preceding claims, comprising a step of finishing the blank (10), chosen from preferably from the group consisting of machining and forging. Method according to the preceding claim, comprising the step consisting in carrying out a heat treatment of the part (20), the heat treatment preferably being chosen from the group consisting of solution treatment followed by quenching or annealing, natural ripening or tempering, annealing, T6 full heat treatment, preferably full heat treatment, and a mixture thereof.