Al Intermetallic Compounds Research Articles

Study the Effects of Dielectric Type on the Machining Characteristics of γ-Ti Al in Electrical Discharge Machining

The current study surveys the results of using deionized water and kerosene as dielectrics in the machining outputs of γ-TiAl intermetallic compound obtained in electric discharge machining. Influences of these different dielectrics properties on machining speed, tool wear, surface cracks and roughness were compared. Scanning electron microscopy micrographs were prepared to investigate influences of dielectrics on the surface characteristics of electrically discharged samples. Results indicate which by kerosene dielectric; the material removal rate (MRR) is further compared to another one. But deionized water as dielectric causes higher tool wear ratio than kerosene dielectric. Electrical discharged samples in deionized water have higher surface roughness, in addition it contains surface cracks, whereas kerosene dielectric results better surface finish in low pulse current. According to XRD spectra electric discharge machining in deionized water and kerosene dielectrics produces Ti3 Al intermetallic compound on the produced surface.

The investigation on a universal local structural feature in Mg–Al alloys

In an effort to reveal the common local structural feature associated with the off-stoichiometry in Mg–Al intermetallic compounds, the occupation mechanism of anti-site defects in Mg17Al12 and MgAl2-C36 are investigated via the first-principles method concentrated on both energetics and electronic structures. Combined the energetic effect of anti-site defects on the structural stability with bonding characteristics in the off-stoichiometric compositions, the common local structural feature is exhibited by the structural motif that Al bonded skeleton perpendicular to the Mg hexagon. Further, such structural motif is embedded into both fcc-Al and hcp-Mg to construct Mg–Al supersaturated solid solution system, and the obtained formation energies in these cases are favored over the corresponding special quasi-random structures. Thus, we suggest that the local structural feature shared by the two off-stoichiometric compounds might be universal in Mg–Al alloys, from the intermetallic compounds to supersaturated solid solutions.

A corrosion study of Ag–Al intermetallic compounds in chlorine-containing epoxy molding compounds

Typical epoxy molding compounds (EMC) contain chlorine ions that cause silver wire-bond failures under highly accelerated temperature/humidity stress test (HAST). To understand the corrosion mechanisms, experiments were designed to emulate the HAST environment and conditions and performed. Specifically, Ag–Al joints, Ag, Al, Ag3Al, and Ag2Al samples were encapsulated in chlorine-containing EMC, respectively, and went through HAST. EMC with high chlorine content (1000 ppm) was chosen to accelerate the corrosion rate and shorten experiment time. The experimental results show that chlorine-induced corrosion occurs only on Ag3Al and Ag2Al compounds. It does not occur on Ag or Al samples. The corrosion rates of bulk Ag3Al and Ag2Al disks were measured under HAST up to 125 h. The corrosion rate of Ag3Al is twice of that of Ag2Al, meaning that Ag2Al is more resistant to corrosion. Careful evaluations reveal that the corrosion is caused by both moisture and Cl− ions. Microstructures, compositions, and phases of corroded regions were examined in details. In the corroded regions, Ag3Al and Ag2Al compounds disintegrate into aluminum oxide pieces and dispersed Ag precipitates with voids and cracks. The chlorines detected near voids and cracks suggest formation of aluminum chloride as an intermediate product that is hydrolyzed into aluminum oxide. A corrosion chemical model is proposed to establish the reactions of Ag3Al and Ag2Al compounds with chlorine-containing EMC. New information obtained in this research can help the search of new processes and techniques to counter or reduce the chlorine-induced corrosion of devices and packages. The corrosion test method presented may possibly become an acceptable test standard to consider.

Morphology of Intermetallic Compound and Interface Bonding State in Pure Al/Steel Clad Plates after 645°C/1h Diffusion Annealing

The correlation between intermetallic compound (IMC) and interface bonding state of the pure Al/08Al steel clad plate after 645°C/1h diffusion annealing was studied using the SEM. The results indicated that after 645°C/1h diffusion annealing for the pure Al/08Al steel clad plate, the IMC grew continuously along the interface with the thickness of 2-6 μm, while, at some regions grew abnormally with the thickness up to 10-30 μm. Moreover, some intrinsic defects at the interface, such as voids in the abnormally grown IMC and micro cracks along the interface were observed. The voids were possibly caused by huge difference of Al and Fe in diffusion coefficient, which is known as Kirkendall effect. On the other hand, the micro cracks could be attributed to the thermal stress during the cooling process because of larger difference of thermal expansion rate between Al and Al-Fe IMC. The intrinsic defects at the interface of Al/Steel could supply a novel way to correlate the morphology of IMC and interface bonding strength.

The effect of amorphous nanocrystalline inoculants on structures and properties of high speed steel

High speed steel (HSS) is widely used in the production of high-speed cutting tools and roll etc, and the modification method is an effective approach for improving the microstructure and properties of HSS. Fe–Al–Cr–Nb–C–N amorphous nanocrystalline inoculants were fabricated using the method of in situ reaction and rapid solidification. The phase compositions of Fe–Al–Cr–Nb–C–N inoculants were analyzed. And the effect of inoculants on structures and properties of AISI T1 HSS was studied. The results show that the inoculant is a mixture of amorphous and nanometer crystal, and Fe–Al(–Cr) intermetallic compounds are the matrix phases of inoculant, while particulate nitride, carbide and oxide are the important precipitation. After modification, the quenching and tempering microstructure of HSS has been refined significantly. The carbides contents increase and the sizes of carbides decrease in HSS. The hardness, red-hardness, wear resistance and impact toughness of T1 HSS were also improved obviously after modification.

Synthesis of $$\hbox {Fe}_{3}$$ Fe 3 Al Intermetallic Compound by Mechanical Alloying

In the present work, nanostructured $$\hbox {Fe}_{3}\hbox {Al}$$ intermetallic compound has been synthesized by mechanical alloying (MA) of $$\hbox {Fe}_{75}\hbox {Al}_{25}$$ powder milled for 40 h followed by heat treatment at $$1100\,{^{\circ}}\hbox {C}$$ for 2 h in Ar atmosphere. The structural evolution of the $$\hbox {Fe}_{75}\hbox {Al}_{25}$$ powder during MA and subsequent isothermal annealing was analyzed using X-ray diffraction (XRD). After 40 h of milling, a disordered Fe(Al) solid solution is formed. On annealing, the Fe(Al) solid solution undergoes an ordering transformation resulting in the formation of ordered $$\hbox {D0}_{3}$$ - $$\hbox {Fe}_{3}\hbox {Al}$$ . The presence of the (111) superlattice peak in the XRD plot of the annealed powder is a direct evidence of the ordered arrangements in the alloy. A shallow exothermic peak below $$600\,{^{\circ}}\hbox {C}$$ in the DSC plot of the 40-h milled powder also confirms the formation of ordered $$\hbox {D0}_{3}$$ - $$\hbox {Fe}_{3}\hbox {Al}$$ . The EDX analysis of the $$\hbox {Fe}_{75}\hbox {Al}_{25}$$ powder milled for various periods of time confirmed the gradual increase in Al diffusion in the Fe particles. The diffusion process of Al in Fe was analyzed using the elemental maps of Fe and Al in the $$\hbox {Fe}_{75}\hbox {Al}_{25}$$ powder milled for various periods of time. HRTEM images confirmed that the $$\hbox {Fe}_{3}\hbox {Al}$$ synthesized by MA is <15 nm in size.

Microstructure and mechanical behaviour of cold metal transfer welded Mg/Al dissimilar joint using wire AZ31 as filler metal

ABSTRACTMg/Al dissimilar butt joint was produced by modified cold metal transfer process using wire AZ31 as filler metal. The energy input characteristics and the microstructure and mechanical behaviour of the joint were investigated. Microstructural analysis shows that a diffusion Mg–Al intermetallic compounds interface layer formed along the weld boundary near Al substrate. The interface layer consisted of three intermediate layers from Al substrate to weld metal: Mg2Al3 layer, Mg17Al12 layer and Mg17Al12 + α-Mg solid solution eutectic layer. The tensile strength of the welded joint was 38.4 MPa, which was fairly dependent on the lowest strength of the three intermediate layers. The brittle fracture occurred primarily within the thinnest Mg2Al3 intermediate layer adjacent to Al substrate.

Weldability and Fracture Behaviour of Low Carbon Steel/Aluminium/Stainless Steel Clad Sheet with Resistance Spot Welding

This paper focuses on the resistance spot welding of low carbon steel/aluminium/stainless steel 3-ply clad sheet. Weldability, microstructure, tensile properties and fracture behaviour of the clad sheet with resistance spot welding were evaluated. A “squeeze-out pulse” was used to melt and squeeze out the core aluminium completely from the vicinity of the weld zone before the application of actual welding current. This enabled the clad sheet to be welded without the formation of any Fe–Al intermetallic compound layer in the weld zone. The fracture mode associated with the peel test of the spot weld was used as the criterion for resistance spot weldability evaluation of the clad sheet. A weldability lobe diagram in the welding current–welding time space based on the fracture mode was constructed and it revealed a wide weldable window especially at a welding time of 18 cy. A tensile shear test with a cross head speed of 1 mm/min was conducted to study the tensile strength and fracture behaviour. It revealed four different fracture modes namely button pull, clad-bond fracture, partial thickness-partial clad-bond fracture and interfacial fracture. The nugget size and melting of clad interface and stainless steel layer were the dominant factors in determining the fracture mode.

Investigation of formation the Ti – Al intermetallic compounds on the surface of TiAl(γ) alloy

Investigation of formation the Ti – Al intermetallic compounds on the surface of TiAl(γ) alloy

Scalable Nanoporous (Pt1-xNix)3Al Intermetallic Compounds as Highly Active and Stable Catalysts for Oxygen Electroreduction.

Author: Bimetallic platinum-nickel (Pt-Ni) alloys as oxygen reduction reaction (ORR) electrocatalysts show genuine potential to boost widespread use of low-temperature fuel cells in vehicles by virtue of their high catalytic activity. However, their practical implementation encounters primary challenges in structural and catalytic durability caused by the low formation heat of Pt-Ni alloys. Here, we report nanoporous (NP) (Pt1-xNix)3Al intermetallic nanoparticles as oxygen electroreduction catalyst NP (Pt1-xNix)3Al, which circumvents this problem by making use of the extraordinarily negative formation heats of Pt-Al and Ni-Al bonds. The NP (Pt1-xNix)3Al nanocatalyst, which is mass-produced by alloying/dealloying and mechanical crushing technologies, exhibits specific activity of 3.6 mA cm-2Pt and mass activity of 2.4 A mg-1Pt at 0.90 V as a result of both ligand and compressive strain effects, while strong Ni-Al and Pt-Al bonds ensure their exceptional durability by alleviating evolution of Pt, Ni, and Al components and dissolutions of Ni and Al atoms.

Ti-Al Membranes for Microfiltration

Porous membranes made of Ti – 48 at. % Al intermetallic compound was obtained by elemental powder synthesis. These disks can be used as microfiltration membranes due to their low pores size and interconnected porosity. During this study titanium (purity 99.5%) and aluminum (purity 99 %) with low particle size range were mixed in corresponding ratios. The powder mixture was pressed at 500 MPa and the samples were heat treated in two stages. In the first step is the forming of Al3Ti compound by a solid state reaction at a temperature of 640 °C, slightly below the melting point of aluminum. In the second step the Ti-Al compound was formed at the temperature of 1300 °C and the sintering the porous structure was accomplished too. The obtained membranes were characterized by X-ray diffraction and scanning electron microscopy (SEM).

Technology of the deposition of composite coatings based on Ti–Al intermetallic compounds by vacuum-arc plasma discharge

A technique for the deposition of composite coatings based on Ti–Al intermetallic compounds by vacuum-arc plasma discharge is developed. X-ray diffraction data on the obtained coatings are reported. The effect of deposition modes on the intermetallic-compound contents in the coatings is established.

In-situ reactive fabrication and effect of phosphorus on microstructure evolution of Ni/Ni–Al intermetallic composite coating by laser cladding

The objective of the study was in-situ reactive fabrication of Ni/Ni–Al intermetallic composite coating by laser cladding with preplaced nickel and aluminum mixed powder on nickel alloy substrate. The phase composition and improvement of microstructure evolution of Ni/Ni–Al intermetallic composite coating were investigated by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometer. It was shown that the Ni/Ni–Al intermetallic composite coating was composed of γ-Ni, Ni3Al, and NiAl and the addition of phosphorus had a crucial influence on microstructure evolution of coating. Interfacial cellular microstructure was refined by introducing phosphorus element and the preferred growth was weakened by the fine Ni3Al+Ni3P dual-phase microstructure. The exothermic effect of forming Ni–Al intermetallic compounds (IMCs) improved the fluidity of liquid pool and homogenized the composition of molten pool. The synchronous formation of Ni3Al and Ni3P led to forming skeletal microstructure. Microhardness of coating is about 6 times higher than that of substrate. The addition of phosphorus element has a contribution to improving microhardness (up to 750HV0.2) while the microhardness is not increased but homogenized by addition of Y2O3.

Effect of intermetallic compounds on the bonding state of kinetic sprayed Al deposit on Cu after heat-treatment

Abstract Post heat-treatment has generally been applied to products in the spray coating field as a method of improving mechanical properties. For kinetic spray process, the heat-treatment condition of dissimilar material pair (coating and substrate) should be controlled carefully, since brittle intermetallic compounds can be created at the interface. In this study, Al was kinetic sprayed onto a Cu substrate and was heat-treated under various heat-treatment conditions to investigate the effect of Cu Al intermetallic compounds on bond strength. When adhesive bond strength was tested, fracture was induced at the lower interface of the CuAl 2 layer in all heat-treated specimens. The bond strength was enhanced at relatively lower temperature heat-treatment (300 and 350 °C) assisted by diffusion bonding between the Al deposit and Cu substrate. However, the bond strength was weakened sharply after heat-treatment at 400 °C due to decreased interaction between the Cu substrate and the diffused Cu elements, which resulted from the formation of a CuAl 2 layer on the side of Al deposit. The bond strength recovered at 450 and 500 °C, since intimate bonding was achieved between the CuAl 2 layer and the lower layer (Cu 4 Al 3 or CuAl), which was chemically grown between the CuAl 2 and Cu 9 Al 4 layers.

Interfacial evolution and bond reliability in thermosonic Pd coated Cu wire bonding on aluminum metallization: Effect of palladium distribution

In this paper, the growth kinetics of Cu–Al intermetallic compounds formed during isothermal annealing of Pd–Cu wire bonds with different palladium distribution at 175°C are investigated by electron microscopy and compared to bare Cu wire bonds. Transmission electron microscopy (TEM) was used to provide high resolution imaging of the Cu–Al IMCs in the as-bonded state and TEM-EDX used to analyze the concentrations of Pd at the bond interface in the as-bonded state. Cu–Al IMCs were found to grow thicker with increasing annealing duration. The growth kinetics of the Cu–Al IMCs were correlated with the diffusion process during thermal annealing. The IMC thickness for Pd–Cu wire bonds with Pd at the bond interface was found to be thinner as compared to that for Pd–Cu wire bonds with no Pd at the bond interface. Thus, the presence of palladium at the bond interface has slowed down the IMC growth. Nano-voids were found in the Pd–Cu wire bonds with Pd at the bond interface, but not in the Pd–Cu wire bonds with no Pd at the bond interface. The IMC growth rate for the Pd–Cu bonds with no Pd was found to be close to that for bare Cu for the initial annealing durations. Corresponding bond pull testing showed that Pd–Cu wire bonds containing Pd have best preserved the bond strength after 168h aging at 175°C due to the beneficial presence of Pd.

Interface formation in magnesium/aluminium bimetallic castings with a nickel interlayer

The natural oxide layer is an inherent barrier in interfacial bonding between aluminium (Al) and magnesium (Mg) alloys in Mg/Al bimetallic casting, resulting in insufficient wettability between the molten Mg and solid Al substrate during bimetallic casting processes. In this investigation, a ‘zincate + nickelling’ surface treatment has been developed for Al alloy 6061 substrate, replacing the oxide layer with a nickel coating. This procedure comprises a combined pickling/redox-reaction and nickelling process, which drastically improves the substrate’s wettability with molten Mg. The bimetallic experiments conducted on a self-designed high-vacuum test apparatus provide valuable understanding of the interfacial phenomena of Mg/Al bimetallic castings. The test results show that the shear strength of bimetallic castings is significantly improved due to the fact that the formation of Mg–Al intermetallic compounds is impeded by a nickel coating. The potential corrosion problem associated with nickel additions could be addressed by an organic top coating for the bimetallic system.

WEAR RESISTANCE AND WEAR MECHANISM OF A HOT DIP ALUMINIZED STEEL IN SLIDING WEAR TEST

Sliding wear experiments were conducted on a hot dip aluminized steel to investigate its wear resistance and wear mechanism. The wear tests were also carried out on a hot dip galvanized steel and the base material (steel Q345) as a comparison. Results show that the wear resistance and hardness of the hot dip aluminized steel are significantly higher than that of the hot dip galvanized steel and the steel Q345 at room temperature. The better wear resistance of the hot dip aluminized steel attributes mainly to the formation of a transition layer containing abundant Fe–Al intermetallic compounds and the transformation of wear-resisting oxides during the friction process. The main phase in the transition layer is [Formula: see text]. The thickness of the transition layer is about 90–120 [Formula: see text]. When the wear load increases from 3 N to 19 N, the wear type of the aluminized layer transform from adhesive wear (3 N) into abrasive wear (7 N) and finally into slight wear mixed with oxidation (higher than 11 N).

Reinforcement mechanism and wear resistance of Al2O3/Fe-Cr-Mo steel composite coating produced by laser cladding

Abstract The nanometer Al 2 O 3 dispersion strengthened Fe–Cr–Mo composite coatings by crosscurrent CO 2 laser on 316L steel were produced. The microstructure and phase composition of the coatings were examined through optical microscopy and X-ray diffraction analyses. Hardness distribution, tensile properties and wear resistance of the coatings were determined to analyse the mechanical properties and the strengthening mechanism of the cladding layer. Results showed that Al 2 O 3 was partly dissolved, and produced Fe 3 Al intermetallic compound; this new phase and Al 2 O 3 feature fine grain, high hardness, high tensile strength, and excellent wear resistance. Fe–Cr–Mo steel with 8 wt.% Al 2 O 3 was considered appropriate for uniformity of the microstructure. Under the same proportion with micro-Al 2 O 3 , the nano-Al 2 O 3 was easily melted and generated Fe 3 Al. Improved hardness and wear resistance could be ascribed to the high bonding strength of Al 2 O 3 reinforced phase to the matrix through the transition of Fe 3 Al intermetallic compound.

Nanoporous (Pt1−xFex)3Al intermetallic compounds for greatly enhanced oxygen electroreduction catalysis

Here we report a nanoporous (Pt1−xFex)3Al intermetallic compound exhibiting impressive electroreduction catalytic activity and durability for the oxygen reduction reaction.

Importance of Bonding Atmosphere for Mechanical Reliability of Reactively Bonded Solder Joints

Self-propagating exothermic reaction bonding (SERB) technique with Al/Ni multilayer film is fascinating in the viewpoint of lots of outstanding features, such as atmosphere-independent exothermic reaction and its self-propagation. The reactively bonded solder joints with high bonded strength are required for practical use in semiconductor devices. We have investigated the fracture strength of rectangular-solid specimens with reactively bonded solder joint (Sn–3.5Ag solder/reacted NiAl/Sn–3.5Ag solder) sandwiched by single crystal silicon (SCS). In this paper, the influence of bonding atmosphere on the fracture behavior is discussed by means of four-point bending testing and fracture surface observation. The fracture strength increases with increasing pressure load during bonding. The strength of the vacuum-bonded specimens is found to be higher than that of the air-bonded specimens. The fracture surface observation results suggest that Al oxide and intermetallic compounds (IMCs) formed at the reacted NiAl layer and the SnAg solder layer, respectively, would have affected the strength of the Al/Ni SERB joints.