FeAl Intermetallic Compound Research Articles

A novel strengthening strategy for diffusion bonded joint of AlCoCrFeNi2.1 eutectic high entropy alloy to 304 stainless steel

To explore the potential engineering applications of eutectic high entropy alloys (EHEA), the interfacial microstructure and mechanical properties of the diffusion bonded joint between AlCoCrFeNi2.1 EHEA and 304 stainless steel were investigated. The diffusion zone was composed of solid solution zone and Fe2Al5 intermetallic compound zone. Due to the difference in the element diffusion rates between the dissimilar base metals and that between the two phases of EHEA, a solid solution region composed of FCC phase and γ-Fe phase is constructed on the EHEA side near the interface, which enhances the shear strength of joint. Besides, the shear strength of joint first increases and then decreases. The maximum shear strength of 355 MPa is obtained at 980 °C, 60 min, and 30 MPa. The interlocking structure and local solid solution structure are formed in the diffusion zone, thus synergistically enhancing the shear strength of joint.

Electrospark deposition of metalloceramic Fe–Al/HfC coating on steel 1035

To improve the tribotechnical behavior and heat resistance of steel 1035, composite metalloceramic Fe–Al/HfC coatings were prepared by electrospark deposition. A non-localized anode was used as an electrode consisting of a mixture of iron and aluminum granules with a molar ratio of 3:2 and with the addition of HfC powder. The cathode gain had positive values indicating that HfC powder can be deposited on steel 1035 using the Fe60Al40 anode mixture. Moreover, the cathode gain monotonically increased with the increase in addition of HfC powder to the anode mixture. The coatings structure is represented by a matrix of FeAl intermetallic compound reinforced with HfC grains, which corresponds to the structure of a metalloceramic composite. Concentration of HfC in the coating increased with the addition of HfC powder to the anode mixture. Deposition of Fe–Al/HfC coatings according to the proposed technique allows reducing the friction coefficient of steel 1035 from 6 to 40 vol. %. Depending on the concentration of HfC in the anode mixture, the wear resistance of Fe–Al/HfC coatings varied nonmonotonically with a maximum at 8 vol. %. The use of Fe–Al/HfC coatings makes it possible to increase the wear resistance of the steel surface to 10 times. Comparison of the final weight gain of the samples after 100 h of oxidation resistance tests at a temperature of 700 °C allows us to conclude that electrospark deposition Fe–Al/HfC coatings can increase the oxidation resistance of steel 1035 by 1.7–2.2 times. Analysis of the study results shows that adhesion of Fe–Al composition to HfC is weak. This was reflected in decrease in hardness, wear resistance and oxidation resistance of coatings with an increase in the concentration of HfC in the anode mixture above 8 vol. %.

Conceptual Design of a Pilot Process for Manufacturing Aluminum-Based Intermetallic Compound Powders

The FeAl intermetallic compound is of great interest for industry due to its low density, low cost and high mechanical and corrosion resistance, so it can replace stainless steels and nickel-based alloys for some applications. In previous publications, the concept (principle) test for a novel FeAl powder manufacturing process has been shown. It consists mainly of the following stages: (a) metallic strip manufacture through rapid solidification, (b) water vapor exposure of these metallic strips for their disintegration and powder generation and (c) powder drying. Experimental tests were performed for 2 g of the FeAl intermetallic compound. However, this process can be extended to manufacture any other intermetallic compound containing aluminum, such as TiAl, NiAl, CoAl or any other that can be obtained from every element that can combine with aluminum, if the aluminum content is between 55 and 60 at.%. Nowadays, this process is at technology readiness level (TRL) 3. Therefore, in this paper, a process equipment up-scaling configuration for producing up to 15 kg powder is proposed. This manufacturing process is an industrial alternative to those commonly used to produce powders of this type of intermetallic compounds, such as mechanical alloying (MA). Moreover, several alternatives for employing renewable energy sources are given, making it even more environmentally sustainable.

A novel amorphous-nanocrystalline interface layer for bonding immiscible Mg/steel by pinless friction stir spot weld with preset nanoscale Fe2Al5 film

The absence of a bonding medium is the principal problem of immiscible Mg/Fe system. Obtaining an interface layer at the Mg/steel interface is the key to achieving a metallurgical bonding. However, the type and thickness of the interface layer has a random nature during the welding process of Mg/steel dissimilar metals, which has a large impact on the joint properties. An effective AZ31 Mg alloy/22MnB5 steel joint with 12 μm width Fe2Al5 interface layer is bonded by pinless friction stir spot welding, and obtained maximum shear strength 1.4 kN. In addition, a specific type and thickness of Fe2Al5 intermetallic compound was chosen as the interface layer in this study. Nano-scale Fe2Al5 interface layer prepared by magnetron sputtering method, which achieved a large improvement in Mg/Fe2Al5 coated steel properties with a maximum shear strength 2.4 kN. The shear strength of the Mg/Fe2Al5 coated steel joint was improved by 86.8% after the interface layer thickness was changed from the micron scale to the nanoscale. Nanoscale Fe2Al5 amorphous-nanocrystalline interface layer was contribute to its higher shear strength. The following orientation relationship exists for the Fe2Al5/steel part of the region, (110)Fe2Al5//(101)α-Fe. This study investigated the effect of the mixed structure of nanocrystalline and amorphous interface layers on the interfacial bond strength besides the analysis of nanostructured interface layers. The molecular dynamics simulation indicates that as the thickness of the η-Fe2Al5 interface layer decreases, the stress of the α-Mg/η-Fe2Al5/α-Fe model tends to increase and then decrease.

Effect of high entropy alloy as the interlayer on the interfacial microstructure and mechanical property of Al/steel bimetal by compound casting

Al/steel bimetal prepared by compound casting process exhibits an increasing application prospect in the lightweight field due to the combination of the advantages of Al alloy with steel materials. Unfortunately, a large number of hard and brittle Al–Fe intermetallic compounds (IMCs) are prone to form at the interface, resulting in insufficient interfacial bonding strength of Al/steel bimetal. Therefore, in the present work, the typical CoCrFeNiMn high entropy alloy (HEA) coating fabricated by laser cladding technique was used as the interlayer of Al/steel bimetal to suppress the Al–Fe IMCs. The results showed that the reaction layer of Al/steel bimetal with HEA interlayer first forms Al5Co2 rather than Al5Fe2 phases compared with the as-cast bimetal. More importantly, the Al5Co2 phase layer consists of nanocrystals. Besides, the elements like Cr, Ni and Mn are uniformly distributed into the reaction layer and no IMCs are detected. This contributes to a reduction in the grain size of Al5Fe2 phase. Although the characteristic of brittle with respect to Al5Co2 compound, the interfacial bonding strength of bimestal is improved by 33% compared with that of the as-cast bimetal, attributing to the fact that the nanocrystals formed at the interface make the surface energy and defect size increase in terms of Griffith's theory. In short, laser cladded CoCrFeNiMn HEA coating provides a new choice for the interlayer selection of Al/steel bimetal.

Fabrication of Fe–30Al alloy using plasma arc welding powered twin-wire directed energy deposition-arc process: Droplet transfer, microstructure, and mechanical property investigation

Intrinsic brittleness and cold cracking sensitivity of Fe–Al intermetallic compounds make their fabrication and processing difficult. In recent years, an innovative additive manufacturing (AM) technology, twin-wire directed energy deposition-arc (TW-DED-arc), has been developed to prepare defect-free Fe–Al alloys via in-situ alloying of Fe and Al elements in a gas tungsten arc welding (GTAW) generated molten pool. However, unconstrained plasma of regular tungsten arc leads to excessive heating area and residual stress during AM buildup. And relatively weak arc pressure of GTAW makes composition inhomogeneity a concern in the in-situ alloying molten pool. To solve the two potential drawbacks, plasma arc welding (PAW) possessing higher energy density and arc pressure is used to power the TW-DED-arc process and fabricate Fe–30Al alloy. In the present research, a special wire-feeding strategy for stable twin-wire feeding of Fe and Al wires is successfully developed to overcome the droplet transfer difficulty induced by constrained arc of PAW and large thermophysical properties difference of heterogeneous filler wires. And according to microscopy characterization results, the innovative PAW powered TW-DED-arc process is capable of fabricating defect-free Fe–30Al bulk sample with homogeneous Al content and epitaxial columnar grain structures. The successful application of PAW-powered TW-DED-arc technique in fabrication of iron aluminide provides stabler and more efficient route for iron aluminide component.

Friction stir welding of AA5010 aluminum alloy to St-12 carbon steel using CoCrCuFeNi high entropy alloy interlayer

Dissimilar friction stir welding (FSW) of AA5010 aluminum alloy to St-12 carbon steel using an equiatomic CoCrCuFeNi high-entropy alloy (HEA) interlayer was investigated. Mechanical properties of the joints fabricated under different plunge depths of the FSW tool were examined and correlated to microstructural evolutions. The incorporation of the HEA interlayer successfully prohibited the formation of AlFe intermetallic compounds (IMCs). Also, the interlayer was metallurgically consistent with both base metals, although quite thin complex IMC layer was formed at the aluminum/HEA interface as a result of sluggish diffusion of constituent elements of HEA towards the aluminum. The application of suitable plunge depth in the steel part, i.e. 0.2 mm, resulted in the perturbation of the HEA/steel interface and then the formation of interfacial mechanical interlocks that were beneficial to the strength of the joints. However, excessive FSW tool plunge depth caused large voids to form near hooks, acting as stress concentration areas during shear-tensile test. An appropriate plunge depth of the tool achieved an ideal joint that exhibited fracture from the aluminum side rather than the joint interfaces. It also provided a strength value as high as 80 % of the nominal strength of aluminum base metal.

Effect of Mg and Si contents on hot-dip 55Al-Zn plating: Experimental and molecular dynamics simulation

This paper combines experiments and molecular dynamics simulations to investigate the effects and mechanisms of different Mg and Si contents in hot-dip 55Al-Zn plating on the microstructure. Non-equilibrium molecular dynamics was used to simulate the diffusion process between plating and substrate. The structure and composition of the plated layers were analyzed by electron probe and transmission. Both experimental and simulation results show that Mg and Si elements tend to be enriched at the substrate interface and form the Mg2Si phase. The Fe-Al intermetallic compound layer can be divided into two parts, Fe4Al13(Si, Zn), which is far from the substrate, and Fe4Al13, which is close to the substrate, and grows along the direction perpendicular to the substrate interface. When the Mg content in the plating is 0, Si is enriched near the substrate and exists in the form of Si particles. When the Mg content in the plating is high, Si is present mainly in two forms: diffused in the Fe-Al intermetallic compound layer and formation of Mg2Si. The increase of Mg content in the plating promotes the breaking of Fe atomic bonds, but the aggregation of Mg elements hinders the diffusion of Fe. The Si dispersed in the intermetallic compound layer hinders the diffusion of Fe atoms and makes the intermetallic compound layer thinner. The above results explore the microscopic mechanism of the effect of Mg and Si elements on the plating layer at the atomic level and provide new ideas for the study of conventional hot-dip galvanized steel.

Control of various Zn-based weld seam/steel interface structures in AA5083/FH36 steel welded joint

Replacing steel with aluminum alloy is appealing to realize the lightweight of ship structure, so it is inevitable to weld these two materials in products. When joining AA5083 aluminum alloy to FH36 steel with the thickness of 6 mm by tungsten inert gas (TIG) arc welding process, the liquid Zn-based filler metal reacted with steel matrix to form Fe-Zn intermetallic compounds (IMCs) and Fe-Al IMCs. A novel interface structure composed of spinous Г-Fe3Zn10, thinner η-Fe2Al5Zn0.4 and a small number of dispersed δ-FeZn10 with a relatively high bonding strength can be obtained at the weld seam/steel interface by optimizing the backing welding current. When the backing welding current was 120 A, the maximum tensile strength of joint could reach 98 MPa. Simulation indicated that a large stress concentration developed at the weld seam/steel interface, within crack active temperature range of Fe-Zn and Fe-Al IMCs, during the backing welding process. The lattice misfit of δ-FeZn10/η-Fe2Al5Zn0.4 and Г-Fe3Zn10/η-Fe2Al5Zn0.4 interfaces were 19.9% and 9.4%, which revealed that dislocations were more likely to accumulate around δ-FeZn10, providing the location of crack initiation in aluminum alloy/steel welded joints.

Plasma-Pulsed GMAW Hybrid Welding Process of 6061 Aluminum and Zinc-Coated Steel

A novel plasma-pulsed GMAW hybrid welding (plasma-GMAW-P) process is proposed for joining 6061 aluminum and zinc-coated steel. The results show that the change in welding heat input has little effect on the microstructure of the joint and the composition of the intermetallic compounds (IMCs) but only changes the thickness of the reaction layer (increased from 5 μm to 12 μm). when the plasma arc current is 20 A and the MIG current is 80 A, the welded joint obtained has the highest tensile-shear force. With the optimal process parameters, the weld strength obtained by filling ER4043 welding wire is the highest, accounting for 65% of the tensile-shear force of the base material. The effect of the plasma arc acting on the joint properties is studied through the microstructure and a tensile-shearing test. The action position of the plasma arc plays a significant role in the Al/steel interface, which directly influences the strength of the welded joints. Regardless of the plasma-GMAW-P style used to obtain the joints, Fe-Al IMCs appear at the interface. When the plasma arc is in front of the welding direction and the GMAW-P arc is in the rear, the tensile-shear force reaches the maximum of 3322 N.

Effect of shielding gas on surface formation during laser welding of Al-Si coated press-hardened steels

The Al-Si coating was negative to the laser welding of press-hardened steel (PHS). This study carried out the comparative analysis of the shielding gas (Pure Ar and CO2 shielding gas) on the surface formation of welded seam. The results showed that the intermittent umbrella-shaped Fe-Al intermetallic compounds (IMCs) on both sides of the weld were presented for the Ar shielding gas, but it was disappeared for CO2 shielding gas. The adjacent Al-Si coating on the humps of the molten pool was melted by the heat conduction of the liquid metal, and flowed into the molten pool at the gap of two humps. The reaction between Fe and Al occurred to form Fe-Al IMCs as umbrella-shaped. The CO2 shielding gas provided a reaction opportunity with liquid Al to form the floated film on the surface of molten pool due to low Gibbs free energy, which presented particles oxides on the weld surface after solidification.

Investigation of microstructure related to corrosion evolution, mechanical and electrochemical properties on doped Si of binary Zn–Al coating

The cycling corrosion test is the first evaluation for silicon doped of 55 wt% Al–Zn coated (GL) steel and microstructure related to corrosion evolution, mechanical and electrochemical properties on the GL steel is investigated. Native oxides grown on the GL surface were hydrolyzed to form the hydroxide, followed by the formation of the hydrozincite and layered double hydroxides products. Galvanic corrosion selectively occurred at the boundary Zn-rich phase to form simonkolleite. These corrosion products played a role in GL protection. We clearly expressed images that the pitting morphology began to occur at the boundary Zn-rich region and stopped corroding on the Fe–Al intermetallic compound layer. Following this, the primary Al-rich region started to be corroded until GL corrosion finish, then red rust of steel corrosion occurred. Moreover, we were the first to study that the tensile surface by bending could accelerate the GL corrosion at the intersection of the boundary phase; in contrast, the compressive surface inhibited corrosion slightly. Electrochemical impedance measurements combined with an equivalent circuit model were developed to support specific corrosion evolution.

Interfacial microstructure and strength of magnetic pulse welded A5052 aluminum alloy/SPCC steel lap joint

A5052 aluminum alloy and SPCC steel plates were welded using magnetic pulse welding, and interfacial microstructure and strength of the lap joint were examined. The A5052 aluminum alloy and the SPCC steel plates were used for a flyer plate and a parent plate, respectively. Charging energy stored in capacitor and gap between the A5052 aluminum alloy and the SPCC steel plates were changed. Microstructure was examined by using an optical microscope, a scanning electron microscope and a scanning transmission electron microscope. Tensile-shear test was used for evaluating the strength of the joint. The magnetic pulse welding of A5052 aluminum alloy and SPCC steel was achieved at the charging energy above 6.0 kJ and at the gap between the plates above 1.0 mm. The range of charging energy in which the strong welding is accomplished was different at each gap and the range increased with decreasing the gap. The lap joint was not fractured at the welding interface by the tensile-shear test whereas the fracture occurred at a part of the aluminum base metal. The welding interface exhibited characteristic wavy morphology. An intermediate layer was produced along the wavy interface. Scanning transmission electron microscope observation revealed that the intermediate layer is composed of fine Al-Mg grains and dispersed dendritic Al-Fe intermetallic compound particles.

Study of the brittleness mechanism of aluminum/steel laser welded joints with copper and vanadium interlayers

Intermetallic compounds (IMCs) generated by direct laser welding of aluminum and steel decrease the strength of the joint. To evaluate the effect of alloying elements on the weldability of aluminum/steel dissimilar materials, the copper (Cu) and vanadium (V) were introduced into the interlayer to inhibit the generation of Fe-Al IMCs. Comparing with direct welding, Cu promotes the generation of Al2Cu and V transforms the disordered Fe/Al interface into a continuous Al/V interface to promote the generation of Al3V and Al21V2. In addition, the first-principles calculations were carried out to study the elastic properties and electronic properties of intermetallic compounds. The results show that high brittleness of FeAl, Fe2Al5 and FeAl3 results from strong covalent bonding and antibonding. The Fe(d) orbit hybridizes with Al(s) and Al(p) orbits while resonant peaks and wide pseudogap appear in the density of states. The low brittleness of Al2Cu results from the less count of covalent bonds with 76.2% of weaker antibonding; the low brittleness of Al21V2 results from the lower covalent bond strength with a maximum overlap bond population of 0.265. With the addition of Cu, the strength of the joint was increased to 63 MPa from 31 MPa. Furthermore, the addition of V completely prevents the formation of Fe-Al IMCs, which results in the highest joint strength (93 MPa). The results of the first-principles calculations and experiments are in good agreement.

Design of shock wave attenuation effects on multi-impedance-matched laminated composites

To improve the protective performance of composite armor materials, three types of laminated composites with different arrangements were designed by the principle of impedance matching. The impedance combination schemes used in this work were high impedance→low impedance (type I), low impedance→high impedance (type II), and high and low impedance (type III). The microstructures and properties of the test samples prepared in a vacuum hot-pressing furnace were investigated by micro-indentation and dynamic impact experiments. According to the propagation theory of one-dimensional elastic waves in multilayered media, the propagation law of shock waves in the as-prepared laminated composites was examined. Micro-indentation test results revealed that the hardness of the Fe2Al5 intermetallic compound formed by the reaction of Al and 304 SS was the highest and ranged from 917.5 HV to 1026.3 HV. The type II layered composite had the highest compressive strength (1139 MPa) followed by the type I composite and the type III composite. The type III composite manifested the highest energy absorption efficiency (73%) followed by the type II layered composite and the type I composite.

Fe–Al intermetallic suppression of dissimilar RSW joints using stainless-steel interlayers

Austenitic and ferritic stainless-steel interlayers for resistance spot welding of an AlSi-coated 2000MPa UTS press-hardened boron steel and a 6022-T4 aluminium alloy were investigated to improve joint performance. CALPHAD and kinetic-based simulations were explored to determine the effects of Cr on the formation of Fe–Al intermetallic compounds. Selected area diffraction reveals the formation of FeCrAl9 along the interlayer-Al interface and suppresses the formation of FeAl3. The implementation of stainless-steel interlayers significantly improved the mechanical performance of the joint, with the 430 foil condition experiencing a substantial decrease in the Fe–Al intermetallic.

Effects of the adjustable ring-mode laser on intermetallic formation and mechanical properties of steel to aluminium laser welded lap joints

Research has confirmed a positive effect of laser beam shaping on controlling weld profiles and keyhole stabilisation, with significant reductions of porosity in weldments. However, few attempts with scattered results have studied the impact of laser beam shaping on intermetallicphase formation. This paper implements the adjustable-ring mode (ARM) laser and studies the impact of the core/ring power ratio to explore the impact on intermetallic phase formation and mechanical properties during remote laser welding of IF steel to 1050 aluminium. It was found that in conduction mode, the core/ring power ratio of 0.2 provided a larger surface area for bonding at the weld interface, and this was translated through the maximum lap-shear strength of 97.6 N/mm2 (joint efficiency 71%). Furthermore, this significantly reduced the Fe2Al5 intermetallic compound (IMC) thickness by 62% and total IMC thickness by 40% in contrast to a core-dominant beam (power ratio greater than one). In keyhole mode, cracking and lower lap-shear strengths were observed compared to the conduction mode. Notably, with a core/ring power ratio of 0.5 a significant grain refinement in the steel side of the weld was observed.

Controlling interfacial composition and improvement in bonding strength of compound casted Al/steel bimetal via Cr interlayer

The fabrication of Al/steel bimetal with a good metallurgical interface is always a great challenge, particularly for the improvement of bonding strength due to the inevitably extensive formation of brittle Al–Fe intermetallic compounds (IMCs) at the interface. Therefore, in this work, the electroplated Cr coating with thickness of 5 μm was firstly used as the interlayer of Al/steel bimetal to suppress Al–Fe IMCs and further improve the interfacial bonding strength. Al/steel bimetal was prepared by compound casting combined with a hot-dip aluminizing process. The results showed that the interface of Al/steel bimetal with Cr interlayer contained an unmolten Cr coating and a reaction layer, in which the latter consisted mainly of Al13Cr4Si4, Al5Cr, Al-rich solid solution and CrSi2 phases. Besides, the morphology of these new Al–Cr–Si and Al–Cr phases was granular rather than the tongue-shaped of Al–Fe phase and the polygonal blocky of Al–Fe–Si phase. Both the microstructure characterization and kinetics calculation results revealed that the application of Cr interlayer could avoid the contact between Fe atoms from steel side and Al atoms from Al alloy side, thereby suppressing the formation of brittle Al–Fe phases at the interface. Moreover, the reaction layer showed a lower nano-hardness than that of without Cr interlayer. With assistance of Cr interlayer, Al/steel bimetal with maximum shear strength of 115.5 MPa was obtained and the interface failed through the Al alloy side. The morphology characteristic and lower nano-hardness of these new phases, the composite structure consisting of Al–Cr–Si and Al–Cr layer together with the Al-rich solid solution layer greatly contributed to the enhancement of the interfacial strength for the Al/steel bimetal.

Effect of Ni Coating on Microstructure and Property of Al Alloy/Steel CMT Welding-Brazing Joints

The cold metal transfer (CMT) welding-brazing process was chosen to join Al alloy and Ni-coated steel using AlSi12 as the filler wire. The macrostructure and microstructure of the joints were tested by using an optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). The tensile properties and corrosion properties of the joints were also tested. The results showed that Ni coating could improve the wettability and spreadability of molten AlSi12 filler metal on the steel surface, resulting in a good appearance for the Al alloy/steel joint. Ni coating could hinder the chemical metallurgical reaction between Al atom and Fe atoms to inhibit the formation of brittle Fe-Al intermetallic compounds (IMCs) and reduce the thickness of the IMCs layer. Meanwhile, the Ni atom reacted with the Fe and Al atoms to form Al3Ni2, (Fe, Ni) Al3 and (Fe, Ni)2Al3, which improved the tensile strength of the joints. All joints with Ni coating cracked near the Al alloy. When the Ni-coating thickness was 5 μm, the tensile strength of the joint reached a maximum of 202.5 MPa. The addition of Ni could also improve the corrosion resistance of the joints. Significantly, when the Ni-coating thickness was 10 μm, most of the Ni coating was still solid, and the interface reaction layer was mainly composed of α-Ni solid solution and some (Fe, Ni)2Al3.

The Al-Fe Intermetallic Compounds and the Atomic Diffusion Behavior at the Interface of Aluminum-Steel Welded Joint

The formation of intermetallic compounds (IMC) at the Al/Fe interface determined the mechanical property of steel-aluminum welded joint. To understand the interfacial microstructure evolution and relate diffusion mechanism of atoms cross the Al/Fe interface, the effect of welding parameters on the interfacial IMC was studied, and the molecular dynamics method (MD) was used to simulate the diffusion process of Al and Fe atoms. Four temperatures (950 K, 1000 K, 1050 K, and 1100 K) were selected in the simulation model. The interfacial IMC are distributed in a laminar pattern, and their physical phases are mainly composed of Fe2Al5, controlling the Al/Fe atomic ratio of 5:2 in the IMC configuration, the Embedded Atom Method (EAM) potential is used to describe the interactions between Al and Fe atoms. In the Al-Fe system IMC conformation, the mean square displacement and diffusion (MSD) coefficient of Al atoms at different temperatures were small, and the main diffusion path is the Al atoms across the IMC conformation into the Fe crystal structure. The diffusion in the IMC conformation was mainly along the direction perpendicular to the interface. The diffusion mechanisms were mainly vacancy diffusion and interstitial diffusion mechanisms.