Composition Segregation Research Articles

Revealing complex microstructure formation mechanisms in the Al[formula omitted]Cr[formula omitted]Fe[formula omitted]Ni[formula omitted]Ti[formula omitted] compositionally complex alloy

The complex phase evolution sequence of a promising new high temperature structural alloy with composition Al20Cr20Fe35Ni20Ti5 (at.%) has been studied in situ using an electromagnetic levitation (EML) setup combined with time-resolved high energy X-ray diffraction (XRD), as well by scanning transmission electron microscopy (STEM) observations during in situ heating. These experiments were supplemented by both scanning electron microscopy (SEM) and high resolution STEM observations of the as-cast alloy microstructure, as well as by energy dispersive X-ray spectroscopy (EDS) composition measurements. Differential scanning calorimetry (DSC) was used to identify liquidus, solidus, A2 ↔ B2, and B2 ↔ L21 transition temperatures. The results obtained by these complementary techniques indicate that the alloy forms primary dendrites of A2-structured body-centered cubic (bcc) phase initially from the melt, followed by ordered bcc of B2-structure in interdendritic regions once compositional segregation has sufficiently enriched the remaining liquid. Ordered B2 precipitates form within the primary A2-structured dendrites and the interdendritic B2 regions undergo a continuous decomposition reaction into a maze-like arrangement of A2 and B2/L21 phases below the solidus. Below approximately 1380 K, the B2 domains in both dendritic and interdendritic regions likely undergo a continuous ordering transition to the L21 phase. The experimental observations of Al20Cr20Fe35Ni20Ti5 are found to be in good agreement with CALPHAD predictions but suggest that the solubility limits of the L21-Heusler phase in the database should be relaxed to include greater Fe solubility for the Ni sublattice and to consider deviations in order parameter from stoichiometric ordering.

Re-Examination of the Microstructural Evolution in Undercooled Co-18.5at.%B Eutectic Alloy.

The undercooling (∆T) dependencies of the solidification pathways, microstructural evolution, and recalescence behaviors of undercooled Co-18.5at.%B eutectic alloys were systematically explored. Up to four possible solidification pathways were identified: (1) A lamellar eutectic structure consisting of the FCC–Co and Co3B phase forms, with extremely low ΔT; (2) The FCC–Co phase primarily forms, followed by the eutectic growth of the FCC–Co and Co2B phases when ΔT < 100 K; (3) As the ΔT increases further, the FCC–Co phase primarily forms, followed by the metastable Co23B6 phase with the trace of an FCC–Co and Co23B6 eutectic; (4) When the ΔT increases to 277 K, the FCC–Co phase primarily forms, followed by an FCC–Co and Co3B eutectic, which is similar in composition to the microstructure formed with low ΔT. The mechanisms of the microstructural evolution and the phase selection are interpreted on the basis of the composition segregation, the skewed coupled zone, the strain-induced transformation, and the solute trapping. Moreover, the prenucleation of the primary FCC–Co phase was also detected from an analysis of the different recalescence behaviors. The present work not only enriches our knowledge about the phase selection behavior in the undercooled Co–B system, but also provides us with guidance for controlling the microstructures and properties practically.

Effects of Composition Segregation in PMN-PT Crystals on Ultrasound Transducer Performance.

This study investigates the relationship between the composition segregation in lead magnesium niobate-lead titanate (PMN-PT; PMN-29%PT, PMN-29.5%PT, PMN-30%PT, PMN-30.5%PT, and PMN-31%PT) single crystals within morphotropic phase boundary (MPB) and the corresponding ultrasonic transducer performance through PiezoCAD modeling and real transducer testing. For five crystals with compositions distributed across the main body of a crystal ingot, the piezoelectric coefficient and free relative permittivity values were measured to vary by over 30%, whereas the transducer bandwidth and center frequency values were modeled to change by less than 10%. For the single-element ultrasonic transducers fabricated using those crystals without matching layers, the variations of -6-dB bandwidth, insertion loss, receiver-free field voltage response, and center frequency were measured to be 9.61%, -15.23%, 9.76%, and 1.41%, respectively, confirming the modeling results. Using the Mason and Krimholtz, Leedom, and Matthaei (KLM) models, it is found that the relatively stable transducer performance can be attributed to the relatively consistent electromechanical coupling coefficient, acoustic impedance, and clamped relative permittivity originated from the stable elastic compliance properties among the crystals of various compositions. It is expected that the relatively stable performance could be extended to multielement transducers with matching layers for the same contributing mechanisms. Our results suggest that it is possible to use crystal plates of different compositions within the MPB region, obtained from one and the same ingot, to fabricate a batch of ultrasonic transducers that will exhibit a similar performance, significantly reducing the cost of materials.

Microstructure and properties of CoCrNiFeMnAl0.5 high-entropy alloys prepared by gas atomization combined with oscillatory pressure sintering

In order to improve the mechanical strength of Cantor alloy and obtain the uniform microstructure, about 9.1 at.% of Al element was introduced and a new CoCrNiFeMnAl0.5 HEAs was prepared by gas atomization combined with oscillatory pressure sintering. The effects of powder sizes on the microstructure and mechanical properties of the as-sintered alloys were investigated and the corresponding strengthening mechanism was discussed. The results show that the CoCrNiFeMnAl0.5 HEAs were composed of FCC phase with good plasticity and BCC phase with high strength. The as-sintered alloys have higher relative density and uniform microstructure without the defects of composition segregation and coarse structure like the as-cast alloy. The yield strength and microhardness of the as-sintered alloys increased to 775 MPa and 369.3 HV, which were 173% and 104% higher than that of the as-cast alloy, respectively. It is indicated that the strength and microhardness of the as-sintered alloys depend on the powder sizes. The strengthening mechanisms of the as-sintered alloys were mainly attributed to the second phase strengthening and the grain boundary strengthening.

Role of Strain-Induced Microscale Compositional Pulling on Optical Properties of High Al Content AlGaN Quantum Wells for Deep-Ultraviolet LED

A systematic study was carried out for strain-induced microscale compositional pulling effect on the structural and optical properties of high Al content AlGaN multiple quantum wells (MQWs). Investigations reveal that a large tensile strain is introduced during the epitaxial growth of AlGaN MQWs, due to the grain boundary formation, coalescence and growth. The presence of this tensile strain results in the microscale inhomogeneous compositional pulling and Ga segregation, which is further confirmed by the lower formation enthalpy of Ga atom than Al atom on AlGaN slab using first principle simulations. The strain-induced microscale compositional pulling leads to an asymmetrical feature of emission spectra and local variation in emission energy of AlGaN MQWs. Because of a stronger three-dimensional carrier localization, the area of Ga segregation shows a higher emission efficiency compared with the intrinsic area of MQWs, which is benefit for fabricating efficient AlGaN-based deep-ultraviolet light-emitting diode.

Substrate depended chemical composition segregation and electrical property of perovskite films

Morphology and chemical composition of the CH3NH3PbI3 films on bare glass and indium tin oxide (ITO) are investigated. The film on bare glass is smoother with a narrow grain size distribution, while the one on ITO is rougher with a large grain size distribution. Energy-dispersive X-ray and X-ray photoelectron spectra reveal that there is a superstoichiometric ratio of CH3NH3+ cations in the upper part of the CH3NH3PbI3 film deposited on ITO. Such a chemical composition segregation originates from the higher affinity of PbI2 to ITO. It is demonstrated that the CH3NH3+ cations can migrate to cathode under applied positive bias, which forms an ionic conductivity and increases the current of the device. Thus the device is in a high conductivity state. A large number of CH3NH3+ cations accumulated near the cathode forms a build-in electric field with a direction opposite to the external field. This restricts further migration of the CH3NH3+ cations and the device turns to a low conductivity state. The migration and accumulation of the CH3NH3+ cations manipulate the device to switch between the high and low conductivity states, endowing the device working as a memristor.

Graphene Oxide-Induced Substantial Strengthening of High-Entropy Alloy Revealed by Micropillar Compression and Molecular Dynamics Simulation.

Plastic deformation mechanisms at micro/nanoscale of graphene oxide-reinforced high-entropy alloy composites (HEA/GO) remain unclear. In this study, small-scale mechanical behaviors were evaluated for HEA/GO composites with 0.0 wt.%, 0.3 wt.%, 0.6 wt.%, and 1.0 wt.% GO, consisting of compression testing on micropillar and molecular dynamics (MD) simulations on nanopillars. The experimental results uncovered that the composites exhibited a higher yield strength and flow stress compared with pure HEA micropillar, resulting from the GO reinforcement and grain refinement strengthening. This was also confirmed by the MD simulations of pure HEA and HEA/GO composite nanopillars. The immobile <100> interstitial dislocations also participated in the plastic deformation of composites, in contrast to pure HEA counterpart where only mobile 1/2 <111> perfect dislocations dominated deformation, leading to a higher yield strength for composite. Meanwhile, the MD simulations also revealed that the flow stress of composite nanopillar was significantly improved due to GO sheet effectively impeded dislocation movement. Furthermore, the mechanical properties of HEA/1.0 wt.% GO composite showed a slight reduction compared with HEA/0.6 wt.% GO composite. This correlated with the compositional segregation of Cr carbide and aggregation of GO sheets, indicative of lower work hardening rate in stress-strain curves of micropillar compression.

Amorphous magnesium alloy with high corrosion resistance fabricated by laser powder bed fusion

Mg alloy suffers from poor corrosion resistance due to the corrosive microdefects including grain boundary, precipitates, and composition segregation, which lead to interfacial corrosion and galvanic corrosion, limiting the orthopedic application. In this work, an amorphous Mg-Zn-Ca alloy is fabricated by laser powder bed fusion (LPBF). LPBF provides a large degree of undercooling to achieve rapid solidification, which inhibits the nucleation and growth of the alloy and obtains the amorphous structure. Moreover, LPBF can prepare Mg alloy with complex porous internal structures and personalized shapes according to implant requirements. The results show the Mg-Zn-Ca alloy fabricated by LPBF is mainly composed of amorphous phases with chemical homogeneity. The amorphous alloy has excellent corrosion resistance, and its corrosion rate is 0.35 mm•y−1, which is within the ideal range of degradation rates for human bone implants. The corrosion product film is dense and uniform due to the formation of ZnO and Ca3(PO4)2 and uniform corrosion, preventing further corrosion and protecting the alloy matrix, thus reducing the degradation rate of the amorphous alloy. The amorphous alloy prepared by LPBF is expected to promote the application of Mg alloy in orthopedics.

Thermodynamic modelling to predict phase stability in BCC + B2 Al–Ti–Co–Ni–Fe–Cr high entropy alloys

This paper examines the potential of thermodynamic modelling as a simple and inexpensive means for assessing phase stability in a series of non-equiatomic high entropy alloys and compares with CALPHAD calculations to demonstrate an appropriate level of simplifying assumptions. The modelling was motivated by alloys from the Al–Ti–Co–Ni–Fe–Cr system, which were produced by iteratively following the natural compositional segregation of the two-phase BCC + B2 microstructure present in a Al2TiCoNiFeCr alloy after casting and heat treatment. This produced a range of multicomponent B2-type alloys with different volume fractions of a BCC secondary phase. The solubility limits and traditional empirical thermodynamic driving forces for phase stability were investigated to explain the formation of the two phases. Limitations of prior semi-empirical models are highlighted, with advancements demonstrated by accounting for contributions from the effect of ordering on configurational entropy, the difference in enthalpy from intermetallic compounds, and thermal influences on both entropy and enthalpy. The new models are compared against the current leading thermodynamic modelling approach, CALPHAD, with excellent correlation. This work outlines a methodology to predict and design phase constitution in future high-performance BCC + B2 alloys and, more generally, it demonstrates the value of models with temperature-dependent thermodynamic quantities for exploring new, complex compositional regions.

Preparation of IC21 Spherical Powders by PREP Process

The IC21 spherical powders with main content of Ni3Al were successfully manufactured by the high speed plasma rotating electrode process (HS-PREP). The powders particle size distribution fitted the mixed spraying model well. The chemical contents changes after melting were detected. The microstructure of the IC21 powders was formed by cellular crystal on the surface and dendrite inside, which was a typical PREP powder. The morphologies and properties of the irregular powders were also analyzed which indicated that the composition segregation and oxides inclusion of the electrode were the main reason for the formation. However, its proportion was less than 0.5%, which would not affect the additive manufacturing. The fundamental powder particle size distribution data for different rotating speeds was measured. The morphology and properties result show that the PREP could support qualified IC21 spherical powders with significant powder yields.

Compositional control and high-temperature phase stability of plasma-sprayed Ba(Mg1/3Ta2/3)O3 coatings

The Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) ceramic is considered a promising material for high-performance thermal barrier coating (TBC), due to the ultra-high melting point and excellent thermophysical properties . However, the preferential evaporation of Mg from BMT during plasma spraying causes the composition in deposited coatings to deviate from the standard stoichiometry , resulting in the formation of undesirable barium tantalite. These impurities would accelerate the cracking and failure of BMT with low fracture toughness during thermal shock , which greatly limits the application of BMT coatings. In this study, the evaporation of Mg, and the evolutionary characteristics of the composition and microstructure of BMT particle in the plasma spray process were investigated. The relationship between the melting conditions of BMT particles and the composition and microstructure of the coatings was analyzed. The compositional controls, and the high-temperature phase stability of plasma-sprayed BMT coatings were studied and characterized. The results indicate that the evaporation intensity of Mg was strongly affected by the melting conditions of the BMT particles in the plasma jet . The particles with a higher degree of melting had a greater evaporation intensity of Mg, owing to the higher heat transfer and element diffusion rate, and more impurity phases formed in the deposited coating. The nonuniformity of Mg evaporation in BMT particle could lead to composition segregation, promoting the formation of the impurity phases during particle solidification, and ultimately affect the composition uniformity of the coating. By employing the powder with large particle sizes and adjusting the spray parameters to reduce the energy of plasma jet under the premise of ensuring the coating deposition quality, the evaporation intensity of Mg and the content of impurity phase could be significantly restrained, and the high-temperature phase stability of the coatings could be greatly improved compared to the original unmodified BMT coatings. • Evaporation behavior of Mg in plasma sprayed Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) was investigated. • Relationship between the melting conditions of BMT particles and the characteristics of the coating was analyzed. • The composition of BMT coating was controlled by adjusting the powder size and spraying parameters. • Significant improvement in high-temperature phase stability of the BMT coatings was achieved.

Reaction products of Sm2Zr2O7 with calcium-magnesium-aluminum-silicate (CMAS) and their evolution

During flight, many silicates (sand, dust, debris, fly ash, etc.) are ingested by an engine. They melt at high operating temperatures on the surface of thermal barrier coatings (TBCs) to form calcium-magnesium-aluminum-silicate (CMAS) amorphous settling. CMAS corrodes TBCs and causes many problems, such as composition segregation, degradation, cracking, and disbanding. As a new generation of TBC candidate materials, rare-earth zirconates (such as Sm2Zr2O7) have good CMAS resistance properties. The reaction products of Sm2Zr2O7 and CMAS and their subsequent changes were studied by the reaction of Sm2Zr2O7 and excess CMAS at 1350 °C. After 1 h of reaction, Sm2Zr2O7 powders were not completely corroded. The reaction products were Sm-apatite and c-ZrO2 solid solution. After 4 h of reaction, all Sm2Zr2O7 powders were completely corroded. After 24 h of reaction, Sm-apatite disappeared, and the c-ZrO2 solid solution remained.

Crystallization kinetics of monatomic antimony

Elemental antimony (Sb) has been carried out recently as a phase-change material to overcome composition segregation in a heavily cycled memory cell. Explosive crystal growth of Sb is desirable for fast operation speed in memory; however, poor thermal stability, i.e., fast spontaneous crystallization at room temperature, significantly impedes its applications. In this work, we designed a thermal stability enhanced “monatomic” Sb in a specific confined structure of [Sb(3 nm)/SiO2(5 nm)]32 and investigated its crystallization kinetics by using the ultrafast differential scanning calorimetry method. It was found that this nanoscale Sb exhibits appealing amorphous thermal stability with a crystallization activation energy of 2.68 eV and the temperature for 10-year data retention more than 361 K. Moreover, strong non-Arrhenius crystallization behavior with a high fragility index of 90 was unrevealed in Sb supercooled liquids, which has the maximum crystal growth rate of 2.17 m s−1 at 785 K. Thanks to the fast crystal growth rate and attractive thermal stability of this monatomic Sb, it could be one of the most important candidates for high-integrated on-chip memory without any composition segregation.

Effect of post-weld heat treatment (PWHT) on microstructure and corrosion behavior in ENiCrFe-7 weld overlay cladding materials

Effect of post-weld heat treatment(as-weld, 615℃/16 h and 615℃/48 h) on microstructure and corrosion behavior in ENiCrFe-7 weld overlay cladding materials had been investigated, the results showed that the heat treatment had an obvious influence on microstructure and corrosion properties. As-weld Alloy ENiCrFe-7 exhibited to be compressive residual stress, and it had a lot of homogeneously distributed microstructure defects(e.g. composition segregation), the pits were evenly distributed on the surface of the sample after polarization, its passive current density was the least due to formation of the densest passive film. With increasing heat treatment time to 16 h, the compressive residual stress was rapidly decreased, the degree of Cr-depletion in the dendrites was obviously increased, and a large number of pits were concentrated in the Cr-depletion area. With increasing heat treatment time to 48 h, the compressive residual stress was slightly increased compared with that at heat treatment time of 16 h, both the degree of Cr-depletion in the dendrites and microstructure defects were improved, the looser passive film was formed, general corrosion was mainly performed during polarization.

Comparison of the rusting behaviors of S450EW weathering steel under continuous spray and wet/dry cycling

The rusting behaviors of S450EW weathering steel under exposure conditions of continuous spray and wet/dry cycling were comparatively studied through electrochemical tests and characterizations on rust layers. Wet/dry cycling promotes the formation of γ-FeOOH and its transformation to α-FeOOH rather than to Fe3O4, inducing a lower content of Fe3O4/γ-Fe2O3 than that under continuous spray. The rust layer formed under wet/dry cycling presents less compositional segregation and structural stratification. Wet/dry cycles promote the diffusion of oxygen and ions and make rust formation and evolution proceed more equally at any thickness of the rust layer through the migration of the air/electrolyte interface.

Effect of the as-built microstructure on the martensite to austenite transformation in a 18Ni maraging steel after laser-based powder bed fusion

During laser-based powder bed fusion, the non-equilibrium solidification conditions promote local elemental segregation, leading to a characteristic microstructure composed of cellular walls. These walls can display either low carbon BCC martensite or FCC retained austenite crystal structures, thus affecting the subsequent isochronal or isothermal martensite to austenite phase transformation mechanisms. In the present study, the effect of the non-homogeneous as-built microstructure on the martensite-to-austenite reversion phenomena was studied for a 18Ni maraging steel fabricated by laser-based powder bed fusion. In-situ synchrotron X-ray diffraction was used to retrieve the austenite volume fraction and lattice parameter evolution during the physical simulation of continuous heating cycles to the austenitic field; and during isothermal tempering cycles throughout the inter-critical tempered martensite + austenite (α’ + γ) field. The as-built microstructure resulted in the expansion of the inter-critical α’ + γ field during very slow heating rates. This was associated to the synergic effects of compositional segregations (anticipating reversion) and pre-existing retained austenite (delaying solubilization). During conventional inter-critical tempering, the as-built microstructure did not fundamentally alter the austenite reversion kinetics, resulting in similar high temperature microstructures at the end of the isothermal stage relative to the solution treated state.

Element Distribution and Its Induced Peritectic Reaction during Solidification of Ti-Al-Nb Alloys

The element distribution and the microstructures of directionally solidified ingots of Ti-45Al-8Nb and Ti-46Al-8Nb alloys were studied by scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) equipped with wavelength-dispersive X-ray spectroscope (WDS). At high solidification rates, e.g., more than 50 μm/s, the ingot solidified in columnar β dendrites, while at low solidification rates, e.g., less than 30 μm/s, the solidification path changed from initial β solidification to L + β→α peritectic solidification, forming cellular dendrites with the β phase matrix surrounded by the α phase. The difference of Ti content in dendritic arms and interdendritic regions was not pronounced. The composition segregation was mainly caused by the mutual conversion of Al and Nb contents. Therefore, it was difficult to distinguish the variation of Ti in microstructure by EPMA-WDS map and line profiles. The composition of the peritectic α phase was different from that of the α phase transformed directly from the β phase. The Al content of the former was about 1 at% higher than that of the latter, while the Nb content was about 1 at% lower. The change of solidification path in the final solidified part resulted from the more severe segregation caused by slow solidification.

The impact of neighborhood racial/ethnic residential segregation on tobacco use in the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND AND AIM: In the US, race/ethnicity is highly correlated with residential location, with Whites and racial/ethnic minorities often living segregated from one another. This differential residential location may contribute to important disparities in health behaviors, such as tobacco use. We examined associations of neighborhood racial/ethnic residential segregation with tobacco smoking. METHODS: We studied 14,107 White and Black adults aged 45-64 who participated in the Atherosclerosis Risk in Communities (ARIC) study from 4 US communities: Forsyth Co., NC; Jackson, MS; Minneapolis, MN; and Washington Co., MD. Neighborhood racial/ethnic composition and residential segregation (G statistic) were estimated using 2000 US census tract data. We estimated odds ratios (OR) and 95% confidence intervals (CI) for current tobacco smoking using mixed-effects logistic regression models. RESULTS:Overall 29% of participants were current tobacco smokers (27% of White participants and 32% of Black participants). After adjustment for age, sex, education, neighborhood population size and neighborhood income, a 10% increase in Non-Hispanic Black residents in a neighborhood was associated with a higher odds of current tobacco smoking among Black participants (OR: 1.07 [95% CI: 1.01, 1.14]) but not White participants (OR: 1.00 [95% CI: 0.94, 1.07]). Black participants living in a cluster of neighborhoods where minority populations (race/ethnicity other than non-Hispanic White) were overrepresented had a 54% (95% CI: 1.09, 2.16) higher odds of tobacco use compared to their counterparts in non-clustered neighborhoods. Among White participants, living in a cluster of neighborhoods where minority populations were underrepresented was associated with a lower odds of tobacco smoking (OR: 0.87 [95% CI: 0.75, 1.00]). CONCLUSIONS:Neighborhood factors, in particular, living in predominantly minority and segregated neighborhoods contributed to tobacco use among Black adults. These findings support the need for neighborhood-level tobacco control interventions to reduce tobacco use in the US. KEYWORDS: Socio-economic factors, Epidemiology, Environmental disparities, Spatial statistics

Modelling evaporation in electron-beam physical vapour deposition of thermal barrier coatings

This work presents computational models of ingot evaporation for electron-beam physical vapour deposition (EB-PVD) that can be applied to the deposition and development of thermal barrier coatings (TBCs). TBCs are insulating coatings that protect aero-engine components from high temperatures, which can be above the component’s melting point. The development of advanced TBCs is fuelled by the need to improve engine efficiency by increasing the engine operating temperature. Rare-earth zirconates (REZ) have been proposed as the next-generation TBCs due to their low coefficient of thermal conductivity and resistance to molten calcium-magnesium alumina-silicates (CMAS). However, the evaporation of REZ has proven to be challenging, with some coatings displaying compositional segregation across their thickness. The computational models form part of a larger analytical model that spans the whole EB-PVD process. The computational models focus on ingot evaporation, have been implemented in MATLAB and include data from 6 oxides: ZrO2, Y2O3, Gd2O3, Er2O3, La2O3 and Yb2O3. Two models (2D and 3D) successfully evaluate the evaporation rates of constituent oxides from multiple-REZ ingots, which can be used to highlight incompatibilities and preferential evaporation of some of these oxides. A third model (local composition activated, LCA) successfully predicts the evaporation rate of the whole ingot and replicates the cyclic change in composition of the evaporated plume, which is manifested as changes in compositional segregation across the coating’s thickness. The models have been validated with experimental data from Cranfield University’s EB-PVD coaters, published vapour pressure calculations and evaporation rate formulas described in the literature.

Corrosion Damage Behavior of X65/Incoloy 825 Welded Bimetallic Composite Pipe in H2S Environment

For the long-term service of X65/Incoloy 825 bimetallic composite pipe girth welds in the H2S environment, the corrosion damage behavior was investigated. Characterizations of welded joints were conducted by OM, SEM, XRD, and EDS. The pitting corrosion’s 3D surface morphology of welded joints in NACE-B solution saturated with H2S was investigated. The results show that composition segregation occurs in the welding process, and the Laves phase appears between dendrites, which lead to the decrease in corrosion resistance. The maximum depth of the corrosion pit is 2.46 μm after 30 days, 4.54 μm after 60 days, and 10.94 μm after 180 days. The cell automata (CA) model of corrosion damage was established based on the MATLAB program, and the basic elements of the cell automata model were determined. Through the simulation of the electrochemical reaction and diffusion process, the influence of different parameters of the pitting corrosion morphology was determined. The simulation results were compared with experimental data, which are available for the prediction of the morphology and size of the corrosion pits on the sample surface after 300 days. The results will be beneficial for the long-term service of the bimetallic composite pipe.