Cr Alloy Research Articles

Influence of laser powder bed fusion parameters on microstructure and mechanical properties of Co–Cr dental alloy

This research investigates the impact of three process parameters of Laser Powder Bed Fusion (LPBF) - laser power, scanning speed, and base plate preheating temperature on the structure and mechanical properties of the EOS CoCr SP2 dental alloy. The LPBF process was used to fabricate dental Co–Cr alloy specimens for microstructural analysis and mechanical properties testing. Light and electron microscopy were used to determine microstructural parameters, including porosity, inclusions, and cracks. The material's chemical composition was analysed by EDS, while XRD and EBSD methods were used to determine the presence of microstructural phases and the crystallographic orientation of individual grains. The mechanical properties were evaluated through a static tensile test (Rp0.2, ε), a toughness test (KVa), and a three-point bending test to determine the flexural strength (Rms). In the microstructure, differences were observed that reflected statistically significant differences in mechanical properties (one-way analysis of variance (ANOVA) and Scheffé post hoc test (α = 0.05)) Using the base plate preheating temperature ϑp = 310 °C with a constant scanning speed v = 900 mm/s in combination with increasing laser power P from 160 W to 250 W the proportion of porosity decreased while the mechanical properties of toughness (KVa) and flexural strength (Rms) increase to maximum values.

Good strength-ductility synergy achieved in a Fe62Ni16Co9Mn9Ti3Si1 Fe-high-entropy alloy with heterogeneous structures

Developing metal structural materials with a good combination of strength-ductility is of great significance for the rapid development of the aerospace industry and the energy industry. High-entropy alloys (HEAs) have attracted widespread attention due to their excellent mechanical properties, especially the excellent ductility and toughness of face-centered cubic (FCC) high-entropy alloys. However, similar to traditional alloys, there is a trade-off between strength and ductility in HEAs. In this paper, we report the successful preparation of Fe-HEA (Fe62Ni16Co9Mn9Ti3Si1 (atomic percentage, %)) with high strength-ductility synergy at room temperature by cryo-rolling and annealing at 600 °C for 10 min (CR600), which increases the yield strength by 59% compared to room temperature rolling (RR600), while the uniform elongation decreases by only 20%. The ultra-high yield strength and the not significant reduction in uniform elongation are mainly attributed to the formation of high-density dislocations, dual-phase bimodal ultra-fine grain heterostructures, (NiMn)3-xTix and (Fe, Ni)2SiTi composite nanoprecipitates, precipitation-induced chemical composition heterogeneity, and BCC→HCP phase transformation during tensile deformation during CR and subsequent annealing at a reduced temperature (600 °C). In addition, by increasing the annealing temperature of the alloy after CR to 800 °C, its uniform elongation can be increased to 53%, which is mainly due to the excellent strain hardening ability induced by changes in heterogeneous structures, nanoprecipitates, and martensitic phase transformation. Compared with other similar alloys, our CR alloy exhibits higher strength-ductility synergy. The results of this study provide a new perspective for developing HEAs with higher strength-ductility synergy.

Effect of Anisotropy on Residual Stress Measurement of 316L Stainless Steel by Ultrasonic Surface Wave

Fe–Cr alloys are widely used in power, petroleum, and manufacturing industries for their good resistance to corrosion and oxidation at high temperatures. Ultrasound is the only nondestructive method so far to measure the residual stress of in-service components. However, for parts with material anisotropy, such as materials processed by rolling, the measurement accuracy is highly restrained. In this paper, a rolled 316L stainless steel sample is used to study the influence of texture on the measurement of residual stress by ultrasonic surface wave. The experimental results show that the propagation velocity of surface waves in the sample has anisotropic characteristics. The wave velocity parallel to the rolling direction (0°) is the maximum, and the wave velocity perpendicular to the rolling direction (90°) is the minimum, thereby affecting the measurement accuracy. It is found that reducing the frequency of surface waves can reduce the influence of anisotropy. Therefore, a low-frequency method and modified formula are used to improve the measurement accuracy. The maximum error in the rolling direction is reduced from 21.3 to 3.6 MPa, and the maximum relative error is also reduced from 45.4 to 9.0%. The modified formula can further reduce the influence of anisotropy, with the maximum error value further reduced to 2.3 MPa, the maximum relative error reduced to 4.9%, and the surface wave detection accuracy effectively improved.

Controlling the Fe-intermetallic phases and mechanical properties of secondary Al-9Si-1Fe alloy with Cr and Mn additions

In secondary Al-Si based alloys, microalloying with Mn and Cr can modify harmful platelet-type AlxFeySiz intermetallic phases to less detrimental α-Alx(Fe, Mn, Cr)ySiz phase (script or polygonal morphologies). However, the α-Alx(Fe, Mn, Cr)ySiz phase morphology, phase composition and the addition of Fe-correcting elements can be influenced by solidification conditions. Therefore, this research is aimed to highlight the morphological evolution and mechanisms of α-Alx(Fe, Mn, Cr)ySiz phase in a Cr added Al-9 %Si-1 %Fe-0.2 %Cr (all weight percentage thereafter, unless otherwise stated) alloy with varying Mn concentrations (0.25 %, 0.5 %, and 0.8 %). Microstructure evolution of Fe intermetallic phases is investigated under different casting conditions using a wedge-shaped die, Cu-chill block and melt quenching experiments. Thermodynamic simulations have been performed using CALculation of PHAse Diagrams (CALPHAD) method and compared with the experimental results for phase composition and formation temperatures of α-Alx(Fe, Mn, Cr)ySiz phase. The results indicated that for 0.25Mn-0.2Cr addition to Al-9Si-1Fe alloy, compact morphology containing polygonal phases are formed in Cu-chill casting, while the wedge castings predominantly show a mixed structure with platelets and script type morphologies. Tensile tests revealed a higher elongation value of 6.6 % for mixed structure with platelet and script phases, which is decreased to 4.2 % for polygonal phases in Al-9Si-1Fe-0.2Cr-0.25Mn alloy. This study highlights the importance of solidification conditions on morphologies of Fe-intermetallic phases and the mechanical properties by comparing selected literature relevant to high pressure die-casting process.

Molecular dynamics study of tribological properties of Ni–Cr alloy coatings with different pore shapes

The presence of nanopores with different shapes cannot be avoided during the coating preparation process, and the pore shape is an important factor affecting the coating friction mechanism. This paper applies molecular dynamics to study the tribological properties of Ni–Cr alloy coatings containing spherical, rectangular and ellipsoid-shaped pores. It is found that the coating with spherical pores has the smallest fluctuation of friction coefficient and the shallowest depth of wear scar. The atoms near the rectangular pores are more likely to move towards the corners of the pores due to shear strain, and the stress concentration in the spherical pores is less than that in the rectangular and ellipsoidal pores. The spherical pore has the least effect on the potential energy inside the coating, and the interatomic bond strength is optimal. The ellipsoidal pore is also more effective in insulating the heat transfer to the bottom of the coating, protecting the substrate underneath the coating and prolonging the coating life. Coatings with rectangular pores generate more interstitial atoms during friction, producing Frank dislocation loop and prismatic dislocation loops.

Preparation of high strength and electrical conductivity copper-chromium pseudobinary alloy by cold-rolling of a billet produced by laser additive manufacturing

A new method to prepare large Cu–Cr alloy with both high strength and high conductivity has been developed. Cu–Cr billets are produced efficiently by laser additive manufacturing, and the microstructure of the alloy is changed by severe plastic deformation caused by large cold rolling ratio. The strength of the alloy can be significantly increased to 677 MPa by eliminating pores, introducing texture and refining grain. The deformation twins caused by plastic deformation processing make up for the plasticity loss caused by grain refinement. With the increase of density and the deformation of Cr particles, the electrical conductivity of the alloy is increased to 28.7 MS/m. Our findings not only deepen the understanding of laser additive manufacturing of highly reflective metals, but also provide a new idea for the preparation of high-strength and high-conductivity Cu alloy workpieces.

Effect of Cr content on thermally activated deformation in single-crystal micropillars of Fe–Cr binary alloys

This study identifies the role of solute Cr in the thermal activation process in the plastic deformation of α-(Fe, Cr) ferrite (BCC solid solutions) using micropillar compression tests for micron-sized single-crystals fabricated on various Fe–Cr binary alloys that were solution-treated at 1573 K. Fe–18%Cr single-crystal micropillars with a mean diameter d of ∼2 μm exhibited a relatively higher strain rate sensitivity (m) of 0.12 for the stress required for slip initiation. Larger Fe–18%Cr micropillars (d = 5 μm) exhibited a lower m value of 0.04. The corresponding activation volume of 50 b3 was equivalent to the millimeter-sized pure Fe and Fe–18%Cr alloy specimens (60–70 b3), indicating the prevalence of a general mechanism involving dislocation motion (kink-pair nucleation of screw dislocations). This mechanism controls the thermal activation process of plastic deformation in the Fe–18%Cr alloy, which has sufficient sources for dislocation multiplication. In the Fe–25%Cr and Fe–40%Cr single crystal micropillars, a less pronounced size-dependent m value (0.01–0.03) was determined, almost independent of specimen size. The corresponding activation volumes of large micropillars (74–77 b3) were similar to those of millimeter-sized specimens, which indicates a mild effect of solute Cr atoms on the thermal activation process of dislocation motion in Fe–Cr binary alloys at ambient temperature. Initial dislocations, rather than Cr content in Fe–Cr binary alloys, led to the low changes in size-dependent activation volume of Fe–Cr alloys with higher Cr content. Planar faults (Cr-enriched regions) were observed in Fe–40%Cr alloys, which may become sufficient sources for dislocation nucleation. However, the influence of Cr-enriched regions on dislocation motion remains unclear.

Tribological Study of Fe–Cr Alloys for Mechanical Refinement in a Corn Stover Biomass Environment

The tribological behavior of three Fe–Cr alloys with Cr contents ranging from ~12 to 16 wt.% as well as low-alloy high-carbon 52100 steel were investigated using pin-on-disk wear testing. Wear tests were performed in both open atmospheric (dry) and biomass environments (wet). Delamination and abrasion were observed to be the dominant wear regimes following dry wear tests. For wet testing, adhesion and pitting corrosion were determined to be the primary wear mechanisms in the Fe–Cr alloys while adhesion and delamination/cracking were identified as the primary wear mechanisms in the 52100 steel. The 440C stainless steel and 52100 steel specimens exhibited the lowest wear volume following dry (7.58 ± 0.52 mm3 and 0.78 ± 0.05 mm3, respectively) and wet wear testing (0.11 ± 0.06 mm3 and 0.12 ± 0.09 mm3, respectively); however, these specimens exhibited the most significant corrosion damage. The 410 stainless steel specimen exhibited the best resistance to corrosion after wear testing in the deacetylated and disc-refined corn stover slurry and had measured wear volumes after dry and wet wear testing of 6.84 ± 0.88 mm3 and 0.33 ± 0.12 mm3, respectively. The worst wear resistance was observed by the 420 stainless steel specimen after both dry and wet wear testing.

Alloying on the high-temperature oxidation behavior of Nb-Ti-Si-based alloy additively manufactured by laser directed energy deposition

Nb-Si-based alloys have important application prospects in the new generation of high-thrust-to-weight ratio aero-engines hot-end components. Understanding how alloying affects the microstructure and oxidation resistance of Nb-Si-based alloys is crucial for their applications. In this work, the effects of Zr, Cr and Mo on the microstructure and high-temperature oxidation resistance of Nb-23Ti-14Si-based alloys prepared by laser directed energy deposition (LDED) were investigated. Results showed that the oxidation resistance at 1250 °C of as-deposited Nb-23Ti-14Si-based alloys enhanced by Zr, Cr and Mo alloying, of these, Cr is the most significant, followed by Zr and Mo. The oxide film of Nb-23Ti-14Si-based alloys have three distinct oxide layer: the inner, middle, and outer oxide layer. The formation of SiO2 layer in the Nb-23Ti-14Si-based alloys' outer oxide layer when Zr and Cr alloying, respectively. Furthermore, following oxidation at 1250 °C for 20 h, and the weight gain per unit area is around 32.52 mg/cm2, and the creation of CrNbO4 layer when Cr content is up to 10 at.%.

Competitive segregation to grain boundaries between Cr and Co in FeNiCrCo alloy

Alloying elements segregating to grain boundaries (GBs) is vital in determining structural stability and mechanical properties of alloys, especially in high‐entropy alloys (HEAs) that consist of multiple elements. However, some details remain unclear, such as the process of varied atoms (Cr and Co) cosegregation to GBs in FeNiCrCo alloy. Therefore, the competition and cooperation between Fe, Ni, Cr, and Co atoms segregating to GBs of FeNiCrCo alloy were investigated via molecular dynamic (MD) simulation. Five [110] symmetric tilt GBs of FeNiCrCo were applied to study the relation between the tendency of atomic segregation especially Cr and Co and GB characters including GB energy and GB excess free volume (GB excess volume). A competitive segregation phenomenon between Cr and Co atoms was discovered, which could be dominated by GB excess volume and different atomic radii among components.

Thermal fatigue performance enhancement of new high-Cr martensitic die steels based on overall microstructure manipulation by trace TiC–TiB2 nanoparticles

Thermal fatigue failure is one of the main factors affecting the service life of hot work die steel. Achieving excellent thermal fatigue resistance for hot working die steels can benefit the industry economically. In this work, (TiC + TiB2)/Al master alloys were used to add TiC–TiB2 nanoparticles into high-Cr die steels, which achieves microstructure manipulation and obtains excellent thermal fatigue resistance and strength-plastic combination. The results showed that after being manipulated by 0.02 wt% TiC–TiB2 nanoparticles, the surface oxidation zone of the high-Cr die steel after different thermal fatigue cycles is reduced than high-Cr die steel without manipulation. TiC–TiB2 nanoparticles effectively refined the heat-treated microstructure of high-Cr die steel, promoting the Cr element and alloy carbides being more uniformly distributed in the matrix, which prevents the occurrence of oxidative pitting and conducive to the formation of a dense and uniform Cr2O3 oxide layer, and further preventing the initiation of thermal fatigue cracks. Moreover, these finer and more uniformly distributed precipitates in TiC–TiB2 nanoparticles manipulated high-Cr die steels will promote stress dispersion and hinder thermal fatigue crack propagation. This work provides a promising avenue for the design of low-cost, high-performance, and long-life die steels for industrial applications.

Prediction of Macrosegregation in Fe–C–Cr Alloy Casting through Coupling with Thermodynamic Phase Transformation Path

The continuum macroscopic transport approach combined with a tabulated thermodynamic phase transformation path is established to predict the macrosegregation in Fe‐1.05 wt% C‐1.65 wt% Cr hypereutectoid steel castings. A combined partial‐equilibrium (PE) and para‐equilibrium (PA) thermodynamic approximation is developed to retrieve the phase transformation path in steels. PA routine is performed on both austenite to stoichiometric cementite transition and austenite to α‐ferrite transition in eutectoid transformation. The approach is also applied to a hypoeutectoid alloy to predict austenite to α‐ferrite transition as well as δ‐ferrite to austenite transition in mushy zone. Thermodynamic properties in macroscopic transport approach are updated by group interpolation from tabulated phase transformation path. Results show that the interaction between substitutional solute Cr and interstitial C weakens the segregation of C and the amount of cementite in the center of casting, making the C distribution more consistent with that obtained by original position statistical distribution analysis in GCr15SiMn alloy castings. This implies that including the contribution of more components can make the estimate more reasonable. The results indicate the potential of macroscopic transport prediction coupled with tabulated phase transformation path through PE + PA approximation.

The effect of ceramic bonder on shear bond strength at the metal-ceramic interface in casted and direct metal laser sintering cobalt-chromium alloy - An in vitro study.

Aim: (1) The aim of this study was to evaluate the effect of a ceramic bonder at the metal ceramic interface in sintered and casted cobalt–chromium (Co–Cr) alloy. (2) To compare the shear bond strength between the different manufacturing techniques: Casting and direct metal laser sintering (DMLS). Setting and Design: In vitro comparative study. Materials and Methods: For the casting group, 40 clear acrylic patterns with dimensions of 20 mm × 10 mm × 2.5 mm were designed in a software and casted with Co–Cr alloy. For DMLS samples, a standard tessellation language file with the abovementioned dimensions was created through a software to fabricate 40 samples. All the samples were equally distributed into the following four groups: Group A – Casted samples with the application of Cerambond (n = 20)Group B – Casted samples without application of Cerambond (n = 20)Group C – DMLS samples with application of Cerambond (n = 20)Group D – DMLS without application of Cerambond (n = 20). Ceramic buildup was done on all 80 samples, followed by firing up to a temperature of 920°C in a ceramic furnace. SBS was evaluated using a universal testing machine and failure modes were examined under the electron microscope. Statistical Analysis Used: ANOVA test and Tukey’s honestly significance difference post hoc test for multiple comparisons. Results: One-way analysis of variance test revealed that the shear load and bond strength values of all four groups were statistically different with P < 0.001. Post hoc Tukey’s test showed statistically significant difference among the four groups. The mean shear strength of Group C was significantly greater when compared to other groups, respectively. Conclusions: Within the limitations of this study, the application of Cerambond to both casted and sintered samples showed significantly increased SBS values and it was also observed that sintered samples had higher strength than casted samples. Altogether, the results indicate that the use of Cerambond increased the shear strength between cobalt Cr alloy and ceramics, thereby prolonging the longevity of the restorations.

Investigation of the thermodynamic, structural, electronic, mechanical and phonon properties of D0c Ru-based intermetallic alloys: an ab-initio study

Abstract We present the structural, elastic, electronic, magnetic, and phonon properties of D0c X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) alloys in their respective ground-states at zero pressure using first-principles density functional theory (DFT). The calculated heat of formation for Sc3Ru, Ti3Ru, V3Ru, Mn3Ru, and Zn3Ru are negative, signifying their thermodynamic stability. Meanwhile, we find that Sc3Ru, V3Ru, Mn3Ru, Co3Ru, Ni3Ru, Cu3Ru and Zn3Ru alloys are mechanically stable. The electronic properties indicate a metallic nature in all the X3Ru alloys due to valence-conduction band overlap at the Fermi energy. Additionally, the phonon dispersion curves suggest that Cr3Ru, Fe3Ru, Ni3Ru, Cu3Ru, and Zn3Ru are dynamically stable. These results provide a comprehensive overview of the stability, electronic, and mechanical properties of D0c Zn3Ru structures, suggesting their suitability for engineering novel alloys in high-temperature structural applications.

Synergic investigation of microstructure, precipitation, and micro-segregation on Inconel 825 weldments: A comparative study between GTAW and EBW

Inconel 825, a Ni–Fe–Cr alloy highly regarded for its exceptional corrosion resistance and high-temperature strength. This investigation studies the effect of heat input, precipitation, and micro segregation of Inconel 825 weldments and compares the effectiveness of two welding techniques: gas tungsten arc welding (GTAW) and electron beam welding (EBW). The findings indicate that increasing heat input generally enhances weldment quality by reducing the lack of penetration. However excessive heat input in GTAW leads to root cracking and solidification cracking; while EBW demonstrates better control over undercut and maintains consistent weld quality even at higher heat inputs. Both GTAW and EBW samples exhibit dendritic grain morphologies with distinctive grain boundaries. Precipitates, such as Al4C3 and TiN, are observed in both processes, contributing to improved mechanical properties. While GTAW weldments show some degree of segregation for Mo, Cu, Ti, and Al, EBW weldments demonstrate negligible segregation for major alloying elements but micro-segregation of Ti and Al. EBW weldments additionally showcase higher average hardness, superior tensile strength, and ductility compared to GTAW weldments. This can be attributed to lower heat input, faster cooling rates, and a reduced rate of elemental segregation. Fractographic analysis reveals the presence of voids and micro-voids, indicating a ductile mode of failure for both GTAW and EBW samples. These void characteristics vary based on the heat input and microstructural features.

Effect of Cr and Ni on mechanical response and microstructural evolution of nanocrystalline ferrite: A molecular dynamics study

Microalloying plays a critical role in improving the mechanical properties of steel. To offer a better theoretical guide for experimental research at the atomic level, this paper investigated the synergistic mechanism of adding trace amounts of alloy Cr and Ni and the microstructure evolution of nanocrystalline ferrite during the mechanical response process. First-principles calculations were implemented to investigate electronic properties. Hybrid molecular dynamics and Monte Carlo simulations were employed to explore the deformation mechanism under uniaxial tension and scratching. Specifically, comprehensive differences between doped and pure nanocrystalline ferrites were explored regarding local stress-strain state, dislocation evolution, twin expansion, and grain boundary activity. The results show that Cr- and Ni-doped nanocrystalline ferrite has higher strength and better wear resistance. The potential mechanism is that the addition of Cr and Ni enhances the atomic bonding strength with Fe atoms, hinders the movement of dislocations caused by lattice distortion, and suppresses grain boundary slip and migration, thereby improving the resistance to plastic deformation and grain boundary stability. Theoretical calculations based on microstructure indicate that compared to solid solution strengthening, Ni-induced grain boundary strengthening plays a dominant role in improving yield strength. Under large deformation, the trend of mechanical response is reversed. The suppression of dislocation motion by Cr reduces the dislocation density and dislocation entanglement, resulting in flow stress and local scratch force being smaller than that of pure samples. However, the formation of more nanoscale twins and twin-dislocation interactions enhances strain-hardening ability during tensile. Finer nanostructured subgrains are formed under scratching. These results provide valuable insights into the understanding of the strengthening mechanism and plastic deformation mechanism of Cr-Ni system low alloy steel under dynamic loading.

Study of nano-broaching properties on nickel-based high-temperature alloys based on molecular dynamics simulation

Broaching technology, as the preferred high-volume machining process for nickel-based high-temperature alloy turbine disk tongue and groove machining, directly determines the reliability and stability of the turbine disk during its service. Although a host of scholars have carried out extensive experimental studies on the broaching process, there are few reports on the exploration of the atomic scale response in the broaching process. In this paper, the plastic deformation, defect evolution and distribution, surface formation, and stress changes during nano broaching of nickel-based single-crystal alloys are analyzed based on the molecular dynamics simulation (MD) method to reveal their broaching properties. The results show that the thermal softening effect induced by the accumulation of cutting temperature is the main reason for the violent plastic deformation within the matrix. The phase transition of the matrix structure, the depth of the subsurface damage layer, and the dislocation density increase with the increase of the cutting distance at the initial stage of the broaching process, and then slow down the upward trend at the stable broaching stage, and fluctuate in a certain range gradually. Meanwhile, the sources of atoms in chips produced by different broaching teeth in the broaching process alternates with the cutting distance. In addition, the diffusion depth of hydrostatic pressure and von Mises stress increases significantly with the increase of broaching distance. The simulation results can provide atomic-scale details for the broaching process of single-crystal Ni Fe Cr alloys and help to optimize the nano-broaching process of nickel-based high-temperature alloys.

High-throughput pseudo-binary diffusion couple approach for alloy design in cobalt-based superalloys

The paper describes a high-throughput method for alloy design in in Co-based superalloy. The approach is an extension of the diffusion couple method used for the determination of diffusion coefficients. We present the use of such a method in low-density cobalt-based superalloys Co-30Ni-10Al-5Mo-2Ta-2Ti-xCr (x = 0–14 at. %) exploring the effect of Cr content on the microstructural evolution, mechanical, and oxidation properties. The composition profile is developed at relatively high temperature with Co-30Ni-10Al-5Mo-2Ta-2Ti and Co-30Ni-10Al-5Mo-2Ta-2Ti-14Cr as end members in which only the solid solution γ phase grows in the interdiffusion zone. This is subsequently subjected to heat treatment for the evolution of g and γ՛ phases. The composition-dependent microstructure and respective mechanical properties were probed using FE-SEM and nano-indentation respectively. The following composition-dependent properties were successfully probed from the high-throughput diffusion couple: 1) The morphological transition of γ՛ precipitates, 2) The solubility limit of Cr in the alloy for TCP formation, 3) Hardness and average elastic modulus, and 4) The nature and topology of oxidized layers as a function of chromium concentration. Therefore, this method facilitates the optimization of multiple properties in a single experiment, identifying the optimal composition range typically between 5 and 8 at. % of Cr in the present alloy.

Evaluation of the effects of an Iraqi phosphate bonded investment and two commercial types on the marginal fitness of porcelain- fused- to- metal copings .

The effect of different phosphate- bonded investments on the marginal fitnessof porcelain- fused—to-metal copings cast by one type of noble alloy and one type ofbase metal alloy was studied. Three types of phosphate—bonded investments (Castorit -Super C, Norvest, and Iraqivest) were used for investing the thirty copings of eachgroup. The marginal fitness of each coping was determined by measuring the verticalmarginal discrepancies between the gingival margin of the coping and the margin ofthe preparation at four reference points on the labial, mesial, palatal and distal aspectsof the die by the aid of light traveling microscope .The statistical analysis of the results showed that there were significantdifferences in marginal fitness among different investments for both Pd- Ag& Ni-Cralloys. The Castorit- Super C and Norvest investments produced comparable resultswith both alloys, while the Iraqivest appeared less compatible with Pd-Ag alloy thanthe other two investments and it had comparable compatibility to Norvest investmentwhen used with Ni- Cr alloy. The Ni- Cr alloy (Heraenium NA) copings revealedsignificantly greater marginal discrepancy than the Pd-Ag alloy (QD) eopingsspecially when using Castorit- Super C and Norvest investments .

Enhanced ferroelectric photovoltaic performance of Bi2FeCrO6 thin films for neuromorphic computing applications

Nowadays, ferroelectric photovoltaic synapses have attracted great attention due to its polarization controllable and self-powered features. However, the large bandgaps of ferroelectric oxide materials limit its application. This study focuses on the enhancement of ferroelectric photovoltaic properties and the synaptic application of Bi2FeCrO6 (BFCO) device. It is found that the bandgap of BFCO can be modulated by Cr alloying, which causes its photovoltaic effect in the visible region to exceed that of BiFeO3 (BFO) significantly. The short-circuit current density (JSC) of BFCO device in the visible region increases by about 100 times than that of BFO. Furthermore, the polarization modulation and multi-states response are demonstrated by an external electric field. For BFCO ferroelectric photovoltaic synapse, long-term potentiation/depression (LTP/LTD) measurements show an excellent synaptic plasticity of the polarization modulation. The simulated image recognition rate using the MNIST dataset reaches a high accuracy of 96.06%. This work has expanded the potential application of ferroelectric photovoltaic synapse in the visible region.