Pure Al Wires Research Articles

Electrodeposition Behavior of Al-Au Alloys in AlCl3-NaCl-KCl-Aucl Molten Salt

Quartz Crystal Microbalance (QCM) has been used as a highly sensitive mass sensor. This study aims to form porous gold thin films on QCM elements and apply them to highly sensitive gas sensors by attaching selective media. Physical vapor deposition and chemical etching are known methods for forming porous Au thin films. In this study, the electrochemical formation of porous gold films in AlCl3-NaCl-KCl molten salts containing AuCl was investigated. There are few reports about electrodeposition and dissolution potentials of Au in the molten salt electrolyte. As a first step in this study, voltammogram measurements and constant potential electrolysis were performed in the electrolyte, and electrodeposition potentials of Au and Al-Au alloys were discussed.An electrolyte in this study is a mixture of 61 mol% AlCl3- 26 mol% NaCl- 13 mol% KCl molten salt. The mixture salt was melted at 443 K and AuCl was added to the molten salt. A glassy carbon plate (GC) and a pure Al wire were used as the working electrode and reference electrode, respectively. The GC plate and Au mesh were used as the counter electrode for voltammogram measurement and constant potential electrolysis, respectively. Voltammogram measurements were carried out at potential range from -0.1 to 2.4 V vs. Al/Al(Ⅲ). Constant potential electrolysis was performed in the range from -0.2 to 0.3 V with an electric charge density of 40 C cm-2. The electrodeposits were observed by scanning electron microscopy (SEM) and determined the composition of Al and Au by energy dispersive X-ray spectroscopy (EDS).Au ions concentration in the electrolyte was 2.5 mmol dm-3. In voltammogram measurements, a small cathodic current was observed at about 0.8 V, then gradually increased from 0.2 V. In the potential lower than 0 V, a drastical increase of cathodic current was observed, which was attributed to Al electrodeposition. When the potential was reversed, large anodic current flowed from 0 V and a small current peak was also observed at 0.2 V. These were considered to correspond to the dissolution of Al and Al-Au alloys, respectively. Furthermore, a relatively large anodic current peak was observed at about 2 V, which was expected to be due to the dissolution of Au. From the results of constant potential electrolysis, the Au concentration in the electrodeposits at -0.1 V and -0.2 V was less than 1 at%. At 0 V, the Au concentration in the electrodeposit increased sharply to 84 at%, and at 0.3 V it increased moderately to 89 at%. From SEM observation, the morphology of the electrodeposits at -0.1 V and -0.2 V was dense, while that at potentials more than 0 V was sponge-like.AcknowledgementsThis work was supported by JST SICORP and JPMJSC2108.

Grain design in ultra-fine Al wire with remarkable combination of strength and conductivity: Ultra-fine-long grains with super strong 〈111〉 texture

The trade-off relation between the strength and electrical conductivity (EC) limits the further application of Al wires in the automotive electronic wiring harnesses. In this work, an ultra-fine pure Al wire (UFPAW) with a diameter of around 0.2 mm was successfully prepared by the process of cold drawing → intermediate annealing → cold drawing. It was quantitatively revealed that the ultra-fine grains in the radial section together with the super strong 〈111〉 texture could provide remarkable grain boundary strengthening and texture strengthening, resulting in an ultra-high strength of the UFPAW (228.3 MPa). Besides, the axial long grains could weaken the electron scattering due to the reduction of transverse grain boundaries, leading to a high EC of the UFPAW (63.14 %IACS). Consequently, the ultra-fine-long grains with super strong 〈111〉 texture were proved to be the dominant factors in achieving ultra-high strength and high EC of the UFPAW.

Influence of interlayer temperature on microstructure and mechanical properties of TiAl alloys in wire and arc additive manufacturing

TiAl intermetallics have attracted widespread attention in the aerospace and automotive fields. This study focuses on the in-situ fabrication of TiAl alloys by auxiliary wire gas metal arc (GMA) additive manufacturing in which pure Ti and Al wires are melted to form a eutectic molten pool. The effects of interlayer temperature on forming characteristics, microstructure, and mechanical properties of TiAl alloys were studied, i.e., 30, 170, 330, and 500 °C. As the interlayer temperature increases, the macro-cracks gradually disappear, the layer width increases, and the layer height decreases. The center and lower parts of the homogeneous zone in the middle region present dendritic and interdendritic γ phases. However, these parts exhibit equiaxed α2/γ nearly-lamellar colonies and massive γm phase at an interlayer temperature of 500 °C. The thicknesses of α2/γ fully-lamellar colonies in the homogeneous zone increase as the interlayer temperature increases. With the increasing interlayer temperature, the total average microhardness first decreases and then increases, the compressive strength mainly presents a decreasing trend, and the compression rate increases first and then decreases. The maximal compressive strengths in the vertical and horizontal directions are 1802.5 and 1814.3 MPa, respectively. By changing the interlayer temperature from 30 to 330 °C, the compression rates in both directions increase by 11.8 % and 13.4 %, respectively.

Investigation of failure mechanism of aluminum-scandium wire bond contact under active power cycle test

The failure mechanism of aluminum-scandium (Al-Sc) wire bond in comparison with pure Al wire bond under active power cycle (APC) test was investigated. To monitor the degradation of the bond quality, bond shear forces (shear force) were measured over the testing cycles at different level of temperature swing (ΔT). The results show that the Al-Sc wire bond was much more robust than the pure Al wire bond when the ΔT (Tmax) was mild. On the other hand, as the ΔT was increased, the shear force reduction in the Al-Sc wire bond became more and more remarkable. In the cross-sectional analysis of bond contact after the APC tests, a significant crack propagation was observed even for low ΔT conditions for the pure Al wire, and the crack progressed primarily on the wire side of the bond area. As for the Al-Sc wire, while the bond crack was efficiently suppressed for low ΔT conditions, a significant progress of crack was observed at high ΔT conditions, and the crack grew mainly through the Al pad side of the bond area. A detailed analysis at the bond interface after the APC test at high ΔT condition revealed three phenomena at the Al pad side of the bond area: grain coarsening, precipitation of Cu particles, and large void formation. As the material strength is compromised by these effects, the crack grew more easily through the Al pad side of the contact area, resulting in a rapid reduction of shear force at high ΔT. The bond failure mechanism obtained in this study will provide a valuable insight for the future development of high reliability power semiconductor device.

Manipulating molten pool in in-situ additive manufacturing of Ti-22Al-25 Nb through alternating dual-electron beams

Wired-based in-situ additive manufacturing (AM) technology couples in-situ metallurgy for material-synthesis and near net-shaping for part-fabrication. However, the manipulation and control of the in-situ metallurgy quality is one of the most critical challenges it faced now, as insufficient metallurgy not only causes inherent defects but also leads to fatal damages to the deposited component. Till now, there is almost no effective way to manipulate it. In this study, we proposed to use the alternating dual-electron beam to flexibly control the molten pool, thereby, achieving the purpose of manipulating the in-situ metallurgical process. Ti-22Al-25Nb (at.%) alloy was taken as the target alloy and fabricated in-situ with the raw materials of pre-alloyed TiNb wire and pure-Al wire. Results show that this technology not only exhibits powerful control ability to the molten pool characteristics but also brings additional in-situ co-frequency forced vibration behavior to the molten pool. The regulated elongated molten pool, as well as its vibration behavior further promotes composition homogenization, porosity reduction(densification as high as 99.999%), and grain refinement(about 32%). As a result, the tensile strength of the in-situ deposited components is as high as 993.6±32.4 MPa on average. In addition, employing an alternating heat source model, numerical simulation was also carried out for revealing the unique temperature evolution and molten pool flow mechanism of the alternating dual-beam AM technology. This work not only provides valuable guidance for the regulation of the in-situ metallurgy quality in the wired-based in-situ AM field but also supplies an unprecedented processing method for the Ti-22Al-25Nb alloy. • Ti-22Al-25Nb (at%) alloy was in-situ manufactured through twin-wire dual-electron beam AM technology. • The alternating dual-electron beam was employed to manipulate the in-situ metallurgical inside the molten pool. • The microstructure and mechanical properties of the dual-beam as-deposited sample were revealed. • The temperature evolution and molten pool flow mechanism during the alternating dual-beam AM process were studied. • The relationship between molten pool vibration behavior and grain refinement was explored.

Effect of heat input on auxiliary wire GMA-AM TiAl alloys

ABSTRACT In-situ γ-Ti48Al alloys are fabricated using auxiliary wire gas metal arc additive manufacturing in which pure Ti plus Al wires are fused in the arc. This study focuses on the influence of heat input on microstructure and mechanical properties of γ-Ti48Al alloys. As the heat input decreases, the upper part of the homogeneous zone in the middle region always shows α2/γ fully lamellar colonies with the decreased grain size, the dual-phase microstructures in the centric and lower parts gradually transform into fully lamellar colonies, and the volume fraction of α2 phase increases. The average microhardness mainly distributes in the range of 310–490 HV. With a decrease in heat input, the compressive strength in the vertical orientation reduces, and the compression rates in both orientations first decrease and then increase. The fracture morphologies always show a mixed-mode of inter-lamellar and trans-lamellar cleavage fractures.

Effect of twin-wire feeding methods on the in-situ synthesis of electron beam fabricated Ti-Al-Nb intermetallics

As a challenging but promising technology, wire-based in-situ additive manufacturing shows great advantages in material preparation and part manufacturing integration. However, compared with single-wire AM technology, it faces a more complex droplet transition pattern, which is closely related to the feeding modes of the elemental wires. In the current work, the effect of wire feeding methods on the droplet transition mode, the morphology, composition, and mechanical properties is for the first time systematically studied. Three wire feeding methods, including double-side-feeding, single-side-feeding, and parallel-feeding, were adopted to fabricate the Ti-Al-Nb intermetallics in-situ. The results show that the TiNb wire and pure-Al wire enter the molten pool separately and with a totally inconsistent droplet transition mode in the double-side-feeding and single-side-feeding methods. This droplet transition results in poor morphology, macro-segregation, and inconsistent mechanical properties. While in the parallel-feeding method, the TiNb and Al droplet transfer to the molten pool after forming a common droplet, which provides a better guarantee for the morphology and performance of the deposited parts. As a research oriented to the deposition process, the current work is of great significance for enriching the fundamental theory and promoting the development of the wire-based in-situ AM technology.

Comparative study of laser swelding-brazing of aluminum alloy to galvanized steel butted joints using five different filler wires

The purpose of this paper is to provide the gist for the selection of filler wire during the laser welding-brazing of Al to steel. A comprehensive comparison of laser welding-brazing 5052 aluminum alloy to unbeveled galvanized steel using pure Al, AlSi5, AlMg5, AlCu6, and ZnAl2 filler wires were conducted with varied laser beam offset. The comparison was carried out in terms of weld formation, interfacial microstructures, and mechanical properties. The results show that the fluidity of liquid filler is Pure Al < AlSi5 < AlMg5 < AlCu6 < ZnAl2. Too small or too large fluidity will lead to poor weld formation. The interfacial intermetallic compound consisted of layered Fe2Al5 and scattered FeAl3 when pure Al, AlMg5, and AlCu6 filler wires were used. When pure Al filler wire was used, cracks were most likely to occur in the reaction layer. The other four filler wire all improved the crack resistance. The thickness of the reaction layer significantly decreased when AlSi5 filler wire was used. Si element was found as a solid solution in the reaction layer to form Fe2(Al, Si)5 and Fe(Al, Si)3. A large amount of FeZn10 was mixed between Fe2(Al, Zn)5 when using ZnAl2 filler wire. The order of maximum tensile strength of the joints using different filler wires was AlSi5 > AlMg5 > AlCu6 > ZnAl2 > pure Al. The fracture of the joints all occurred at the brittle intermetallic layers when five different filler wires were used.

In-situ fabrication of Ti2AlNb-based alloy through double-wire arc additive manufacturing

For the reason of high temperature strength, high oxidation resistance and low density, Ti2AlNb-based alloy is expected to replace nickel-based alloy in the range of working temperature 600–800 °C and become a new generation of high-temperature structural alloys in the aerospace industry. However, Ti2AlNb-based alloys have great high-temperature deformation resistance and high brittleness, which greatly restricts its preparation and processing using traditional technology. In this research, an innovation method named double-wire arc additive manufacturing technology was adopted to in-situ manufacture Ti-22Al-24Nb (at%) alloy, and the TiNb and pure Al wire with designed feeding speed were taken as raw materials. The deposited component was investigated systematically. Results show that the composition error between the average testing value and designed value are under 1.1%, but there are also existing local segregation of composition and microstructure. The segregation phenomenon further deteriorates its mechanical properties, which means the ultimate tensile properties and elongation under room temperature and high temperature (650 °C) are 504 ± 38.59 MPa, 0.41 ± 0.03% and 375 ± 32.60 MPa, 0.76 ± 0.05% respectively on average. At the same time, the prepared alloy exhibits fully lamellar structure and XRD results show that the basic composition phases B2, O and α2 of the Ti2AlNb-based alloy successfully appeared. The in-situ manufacturing method demonstrated in this work is expected to significantly promote the wider application of AM due to its low cost advantage and high flexibility.

Microstructure and mechanical properties of Ti-52 at% Al alloy synthesized in-situ via dual-wires electron beam freeform fabrication

The in-situ synthesized Ti-52 at% Al alloy was additively manufactured for the first time by electron beam freeform fabrication (EBF3) with pure Ti and Al wires. The chemical compositions, microstructure, crystal orientation and mechanical properties of the Ti-52 at% Al walls were investigated. The results show that the actual Al content was lower than that the designed content due to the evaporation of elements. The microstructure of the as-fabricated walls was composed of γ dendrite which was oriented along the <111> direction. The solidification path was L→ γ phase due to the high cooling rate during EBF3 process. The primary dendrite spacing and the width of the secondary dendrite increased with the building height indicating that the cooling rate decreased. The dendrite disappeared in layer bands due to the repeating thermal cycles. Based on the orientation analysis, the epitaxial growth of the γ phase was found between the dendritic and interdendritice regions and between layers. The microhardness of the dendrite was higher than that of the interdendritic regions. The compressive tests at ambient temperature indicated anisotropic mechanical properties due to the dendrite structure. The compressive strength along the building direction was higher than that along the deposited direction.

Microstructure and Tribocorrosion Behavior of Al2O3/Al Composite Coatings: Role of Al2O3 Addition

Pure Al coating and Al2O3 particles reinforced Al composite coatings were prepared by arc-spraying. The feedstocks were pure Al wires and Al-based cored wires containing 10, 20, 30 vol.% Al2O3, respectively. The evolutions of microstructure, porosity and microhardness of the coatings with different Al2O3 contents were investigated. Microstructural analysis shows that the addition of Al2O3 particles improves density and decreases the porosity of the coating. The average hardness of the composite coatings varies from 39 to 416.5 HV0.1 as Al2O3 content increases from 0 to 30 vol.%. However, the microhardness of the Al matrix in the coatings increases first and then decreases as a function of Al2O3 contents. The tribocorrosion tests were performed under potentiodynamic polarization conditions in 3.5 wt.% NaCl solution. The cathodic shift of open circuit potential and the increase in current density are induced by sliding wear. Compared with pure Al coating, the Al2O3 particles reinforced composite coatings display a lower wear rate and coefficient of friction. The Al-20 vol.%Al2O3 composite coating shows superior resistance to tribocorrosion. The tribocorrosion mechanism of the composite coatings is delamination coupling of corrosion wear.

Wire arc additive manufacturing of titanium aluminide alloys using two-wire TOP-TIG welding: Processing, microstructures, and mechanical properties

Titanium aluminide (TiAl) alloys are promising high-temperature structural materials in the aerospace field. Additive manufacturing is a desirable process for fabricating TiAl alloys. In the process of wire arc additive manufacturing of TiAl alloys, Al-based and Ti-based wires were used as the feedstocks. However, it is hard to ensure the two different wires melt synchronously under the heat of one single arc, so the desired microstructures with γ (TiAl) phase and α2 (Ti3Al) phase are hard to obtain. A two-wire TOP-TIG-based additive manufacturing process for TiAl alloys is proposed in this paper. The Ti6Al4V wire and pure Al wire are used as the feedstocks. The Al wire is fed in TOP-TIG mode behind the molten pool, while the Ti6Al4V wire is fed in conventional TIG mode in front of the molten pool. The two wires melt synchronously in a broad range of parameters. The compositions of the component can be controlled by adjusting the two-wire feeding speeds. The main microstructures of the as-fabricated component contain α2/γ lamellae colonies, equiaxed γ grains, and α2 grains. In the top and middle regions, when the Al content is 45 at.%, the structures are full α2/γ lamellae; as the Al content increases to 50 at.%, some equiaxed γ grains distribute at the grain boundaries; the component with 55 at.% Al content exhibits the structures consists of equiaxed γ grains with snowflake-shaped α2/γ lamellae colonies. In the bottom region, all components exhibit the coarse equiaxed α2 grains with γ laths. As the Al content increases, the α2 phase decreases, but the γ phase increases, and from the top region to the bottom region, the volume fraction of the α2 increases by about 19.4 %. The hardness value of the top and bottom regions is higher, and the middle region exhibits the lowest hardness. As the Al content increases, the hardness decreases. The component with 50 at.% Al exhibits the highest compressive strength with 1762 MPa and the largest compressive ratio with 26.1%.

Role of Multi-Scale Microstructure in the Degradation of Al Wire for Power Transmission

As common conductive materials, Al wires are used on overhead transmission lines under long-term heating conditions. In this study, the strength degradation behavior and the strength-electrical conductivity relation of the commercially pure Al wires (CPAWs) and the Al-Fe wires (AFWs) annealed at various temperatures were investigated based on the microstructure evolution. The strength degradation rate of the AFW is always higher than that of the CPAW. A linear trade-off relation between strength and electrical conductivity for the annealed Al wires are clarified. The results reveal that the mechanisms behind the trade-off relation between the strength and the electrical conductivity for the annealed CPAWs and the annealed AFWs are the recovery of dislocations and the obvious increase of grain width, which leads to the decrease of strength and the increase of electrical conductivity. The coalescence of precipitate in the AFW leads to the obvious decrease of strength, which results in the higher strength degradation rate for the AFW as compared with that for the CPAW. Consequently, the principle of microstructure design for anti-degradation of Al wire is presented.

Samarium influence on current induced atomic displacement in Aluminium and Copper combinatorial thin film alloys

Combinatorial thin film deposition from vapor phase combined with photolithography was involved in preparation of bidimensional wires for electromigration testing along Al-Cu, Al-Sm and Cu-Sm thin film libraries. Samarium was chosen as alloying element due to its larger atomic radius, directly impacting the crystallographic properties of the conducting alloy and decreasing the total grain boundary surface through amorphisation. As reference, pure Al and Cu wires were additionally deposited and studied. Empirical estimation of the experimental errors obtained during electromigration testing was performed by high throughput measurements and a value around 2% was found for pure Al and Cu metals. The resistance against electromigration of test wires was increased by electrochemical passivation (leading to void pinning), while the empirically evaluated experimental errors increased to 30%. Electrical screening of Al and Cu-based thin film combinatorial libraries was performed at extremely high current densities (MA cm−2). In the Al-Cu system, Al–14 at.% Cu was identified as the alloy able to withstand the highest power density of 2.10 MW cm−2 before failure. The Al-Sm and Cu-Sm thin film libraries showed compositional regions of total or partial amorphization likely impacting the electromigration resistance of the alloys. Electrical screening indicated that Al-6 at.% Sm is the alloy withstanding the highest power density before failure with a value of 2.48 MW cm−2. The highest current densities before electrical failure in conducting lines were measured on pure Al at 1.39 MA cm−2, with a value of maximum power density below 2.62 MW cm−2. Careful discrimination between these two variables is necessary before choosing one of the studied materials as ideal for specific applications.

Cyclic robustness of heavy wire bonds: Al, AlMg, Cu and CucorAl

Development of advanced electronic packages can be drastically affected by implementation of new materials. The ever increasing demands for high performance and reliable power electronics, raise the need for rapid robustness evaluation of interconnects. In this study the lifetime of heavy wire bonded interconnects, fabricated with different wire material types Al, AlMg, Cu and Al coated Cu (CucorAl) bonded onto direct copper bonded ceramic substrates was investigated. The tests were performed using an accelerated mechanical fatigue testing system, which allows to determine the lifetime of the interconnects with regard to wire bond lift-off failure in a short period of time. Thus, the influence of ultrasonic power variation and the impact of aging on the performance of wire bonds with different material combinations was studied. Cu wire bonds showed clearly the best fatigue performance as well as static shear strength followed by AlMg and Al bonds. Increasing the ultrasonic power results in a higher fatigue resistance of CucorAl in comparison to pure Al wires. In certain cases, the results of the fatigue experiments and static shear tests were found to be contradictory. The presented results suggest that accelerated mechanical fatigue testing can be used as an additional fast method for qualification of interconnects and assessment of the influence of wire material, bond parameter and aging.

Breaking the trade-off relation of strength and electrical conductivity in pure Al wire by controlling texture and grain boundary

The trade-off relation between the strength and electrical conductivity in the Al conductor is a significant scientific issue. Breaking such trade-off relation is an interesting challenge for preparing the Al conductor with high strength and good electrical conductivity. In this study, an abnormal strength-electrical conductivity relation was achieved during the deformation of the cold-drawn Al wires. In particular, the interesting finding is that both the grain boundary and texture obviously influence the strength-electrical conductivity relation, i.e., the elongated grains with the strong 〈111〉 texture does not only promote the strength (74.2 MPa), but also improve the electrical conductivity (0.31 %IACS). This new finding proves that the elongated grains and the strong 〈111〉 texture can be designed and applied to prepare the Al conductor with high strength and high electrical conductivity. Furthermore, an experiment was designed to verify the mechanism, and the results show that the newly prepared commercially pure Al wire (CPAW) owns a higher electrical conductivity (∼63.0 %IACS) in comparison with the traditional CPAW (∼62.0 %IACS).

The Kirkendall void formation in Al/Ti interface during solid-state reactive diffusion between Al and Ti

In the current study, the formation of Kirkendall voids in Al/Ti interface during solid-state reactive diffusion between Al and Ti was investigated. In this regards, pure Al wire (grade 1100) was deposited on commercially pure Ti surface by means of GTAW processing and the prepared samples were annealed at 625 °C for different periods of time. The achieved results indicated that, during cladding process, a continuous layer of Al3Ti intermetallic compound with average thickness of about 2 µm, can be formed in Al/Ti interface. During annealing process, both Ti and Al diffused into each other and the growth of the Al3Ti layer occurred mainly towards the Ti side. At this condition, Kirkendall voids are formed and accumulated near to Al/Al3Ti interface. These voids started to connect to one another, coalesce into large gaps and resembling a line crack at the interface. The formed crack acts as a barrier in Al/Ti diffusing couple and inhibits the growth of Al3Ti phase.

Fabrication of Copper-Rich Cu-Al Alloy Using the Wire-Arc Additive Manufacturing Process

An innovative wire-arc additive manufacturing (WAAM) process is used to fabricate Cu-9 at. pct Al on pure copper plates in situ, through separate feeding of pure Cu and Al wires into a molten pool, which is generated by the gas tungsten arc welding (GTAW) process. After overcoming several processing problems, such as opening the deposition molten pool on the extremely high-thermal conductive copper plate and conducting the Al wire into the molten pool with low feed speed, the copper-rich Cu-Al alloy was successfully produced with constant predesigned Al content above the dilution-affected area. Also, in order to homogenize the as-fabricated material and improve the mechanical properties, two further homogenization heat treatments at 1073 K (800 °C) and 1173 K (900 °C) were applied. The material and mechanical properties of as-fabricated and heat-treated samples were compared and analyzed in detail. With increased annealing temperatures, the content of precipitate phases decreased and the samples showed gradual improvements in both strength and ductility with little variation in microstructures. The present research opened a gate for in-situ fabrication of Cu-Al alloy with target chemical composition and full density using the additive manufacturing process.

Enhancing mechanical properties of wires by a novel continuous severe plastic deformation method

Abstract Commercially pure Al wires are severely plastic deformed by a novel method called equal channel angular torsion drawing (ECATD) up to four passes. Initial wires are drawn through an equal channel angular die and simultaneously torsion deformed by turning the ECATD die. The wires are deformed up to an equivalent strain of 1 to 4 (based on FE result) at room temperature. The microstructural evolution of the wires is investigated using optical microscopy of both longitudinal and transverse cross-sections. A grain refinement from 100 μm to a mean grain size of 1–10 μm is achieved mainly at the areas near the surface of the wires. A decreasing trend of grain refinement is observed from the edge area to the wire center due to the non-uniform strain distribution, resulting in an inhomogeneous hardness. A significant increase in hardness is obtained from ∼22 HV to ∼43 HV at the wire center and to ∼60 HV at the wire edge, this confirms simulated equivalent plastic strain. The most important advantage of this process is the ability to impose continuous large plastic deformation on wires. It can be used as an industrial method for continuous strain hardening and grain refinement of wires.

In situ formation of Al/Al3Ti composite coating on pure Ti surface by TIG surfacing process

In the current study, the in-situ formation of Al/Al3Ti composite coating on Ti surface during aluminium TIG cladding was investigated. In this regards, pure Al wire (graid 1100) was deposited on commercially pure Ti surface by means of TIG process and the produced coatings were annealed at 823K (550°C) for different periods of time. The coatings were characterized by X-ray diffraction (XRD), optical and scanning electron microscopy (OM & SEM). The corrosion behaviour of the coatings was also examined in NaCl 3.5% electrolyte by potansiostate analysis. The results indicated that, Al/Al3Ti composite coating with average hardness value of about 250HV can successfully form on Ti surface during TIG cladding process. By annealing the produced coatings, the percentages of Al3Ti phase was increased and one adhesive and uniform Al3Ti layer was formed on clad/substrate interface. By increasing the annealing times, the thickness of Al3Ti phase has increased and reached to a value of about 2µm after 20h of annealing. The hardness and corrosion resistance of Al/Al3Ti composite coating was also enhanced by increasing the annealing time.