Multi-objective Optimization of Electrodeposition of Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano Composite Coating on Al6061 Substrate

Response surface methodology based Grey relation analysis has been used to optimize the coating parameters of composite coating on aluminium based alloys. This approach gives the best combination of coating parameters to get maximum coating thickness, adhesive strength, microhardness, and minimum wear rate. For each response, the effect of coating parameters at different levels have been discussed. From Grey relation grade, the optimum parameters for better composite coating performance are found to be: temperature, 34 °C; current density, 1 A/dm²; and percentage of particle loading, 1.2 g/L. At 95% significance level, the Current density shows statistical significance on overall composite coating performance.     

Joint effect of scandium and zirconium on the recrystallization of aluminum Al–Mg<Subscript>2</Subscript>Si alloys

Metallographic analysis and hardness measurements are used to study the recrystallization processes in aluminum Al–Mg₂Si alloys with scandium and combined scandium and zirconium additions that occur during annealing of the cold-deformed alloys at 100–600°C. The temperature of the onset of recrystallization of the Al–Mg₂Si alloys with scandium and combined zirconium and scandium additions is shown to be 50°C higher than that of the alloys free from scandium and zirconium. It was noted that the small grain sizes of the alloyed compositions lead to weaker disordering during recovery and recrystallization.     

The Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiB<Subscript>2</Subscript>/Fe Complex Reinforcement on Wear and Mechanical Properties of Al-Matrix Composites

In this study, the effect of Al₂O₃–TiB₂/Fe complex ceramic–metal reinforcement (CCMR) on wear and mechanical properties of Al-(Al₂O₃–TiB₂/Fe) composites were investigated. For this purpose, Al₂O₃–TiB₂/Fe CCMR was synthesized by mechanochemical process. The produced reinforcement powders were added to Al matrix, milled for 10 h and then hot extruded. The results showed that the metallic component (Fe rich phase) in this reinforcement acted as a pin, sticking the ceramic parts (Al₂O₃–TiB₂) to Al matrix. The best volume percentage of CCMR in Al matrix was recognized to be about 2.5 %. This composite showed a combination of wear resistance (0.005 mg/m), strength (500 MPa) and ductility (of about 6 %).     

Observations of Facet Formation in Near-<Emphasis Type="Italic">α</Emphasis> Titanium and Comments on the Role of Hydrogen

Faceted features are frequently observed on the fracture surfaces of titanium alloys that have failed by static loading, continuous cycling, dwell fatigue loading, and stress corrosion cracking (SCC). Although the facets formed under different loading conditions seem qualitatively similar, there are significant differences in the spatial and crystallographic orientations of the facets as well as subtle differences in facet surface topography. The current study compares and contrasts facets for various loading conditions (cyclic, creep, SCC, and dwell) in the Ti-8Al-1Mo-1V alloy with the primary motivation being to understand the mechanisms of crack initiation and faceted growth during dwell fatigue. The spatial and crystallographic orientations of the facets were determined using quantitative tilt fractography and electron backscatter diffraction, whereas facet topography was examined using ultra-high-resolution scanning electron microscopy. Collectively, the experimental observations suggest that hydrogen may play an important role in facet formation and accelerating small crack growth rates during dwell fatigue loading.     

Effect of ZnS Content on Pb–Sb Separation of PbS–Sb<Subscript>2</Subscript>S<Subscript>3</Subscript>–ZnS Ternary System Under Water Vapor Atmosphere

Effect of ZnS on volatilization of Sb₂S₃ from PbS–Sb₂S₃–ZnS ternary system under water vapor atmosphere has not been reported in the literature. The mechanism of roasting process with steam in PbS–Sb₂S₃–ZnS system has been investigated in this paper. According to the fact that the calcine only consists of PbS and ZnS, it is indicated that the existence of ZnS can elevate the melting point of the PbS–Sb₂S₃–ZnS sample and make PbS and Sb₂S₃ more difficult to combine each other. As a result, the activity of Sb₂S₃ is increased and hence Sb₂S₃ will be easily volatilized into the vapor phase from the calcine. In conclusion, the ZnS in the sample can improve the Pb–Sb separation result.     

Effect of the milling time on the magnetic properties of powder compositions of the Sm<Subscript>2</Subscript>Fe<Subscript>17</Subscript>N<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> intermetallic compound and an Nd–Fe–B alloy

The effect of the wet milling time on the magnetic properties of powder compositions consisting of the hard magnetic Sm₂Fe₁₇N _x (x = 2.9–3.0) nitride and a rapidly quenched Nd_9.6Fe_76.3Co_4.3Zr_3.4B_6.4 (at %) alloy, which are taken in different mass proportions, is studied. The compositions containing no more than 20 wt % alloy are found to exhibit a substantial increase in the magnetic characteristics as compared to those of the nitride. It is shown that the determining effect on the coercivity is related to the degree of structural imperfection of Nd–Fe–B powders, whereas the specific remanent magnetization and the specific magnetization in a field of 2 T are determined by the corresponding characteristics of the alloy. The optimum composition and efficient treatment conditions for powder mixtures are determined.     

Formation of ZrO<Subscript>2</Subscript>–SiC Composite Coating on Zirconium by Plasma Electrolytic Oxidation in Different Electrolyte Systems Comprising of SiC Nanoparticles

Plasma electrolytic oxidation (PEO) coupled with electrophoretic deposition (EPD) was used to fabricate ZrO₂/SiC composite coating on the zirconium metal. The PEO–EPD process was carried out in three different electrolyte systems consisting of 5 g/l sodium aluminate or trisodium orthophosphate or sodium metasilicate with 4 g/l SiC nanoparticles. The X-ray diffraction results indicate monoclinic zirconia is the major phase in phosphate and silicate electrolyte while the coating produced in aluminate electrolyte is composed of tetragonal zirconia. The potentiodynamic polarization studies (PDP) indicate that composite coating produced in phosphate?+?SiC nanoparticle containing electrolyte exhibit superior resistance to corrosion, which can be attributed to the pore-free morphology of the coating. All the PEO–EPD coatings show exceptionally good adhesion strength (L_c ?> 40 N). The coating fabricated in phosphate?+?SiC nanoparticles is found to be the best coating because of its superior resistance to corrosion and reasonably good adhesion strength.     

Effect of Hypoeutectic Boron Addition on the <Emphasis Type="Italic">β</Emphasis> Transus of Ti-6Al-4V Alloy

In the present study, the β transus of boron-modified Ti-6Al-4V alloy was found to be almost equivalent to that of the normal alloy, although there is a difference in interstitial element content large enough to produce significant change. Compositional analysis confirms the scavenging ability of the boride particles that are present in the microstructure toward the interstitial elements. This factor can successfully retard the α → β phase transformation locally and increase the overall β transus of boron-added material.     

The effect of the aging period on the martensitic transformation and kinetic characteristic of at % Cu<Subscript>68.09</Subscript>Al<Subscript>26.1</Subscript>Ni<Subscript>1.54</Subscript>Мn<Subscript>4.27</Subscript> shape memory alloy

In this work, the effect of aging period on the characteristic transformation temperatures, thermodynamic parameters and structural variations of CuAlNiMn shape memory alloys were investigated. Aging was performed at above the austenite finish temperature of the un-aged specimen (120°C) for six different retention times, namely 1h, 2h, 3h, 4h, 5h and 6h. The changes in the transformation temperatures were examined by differential scanning calorimetry at different heating/cooling rates. The aging period was found to have an effect on the characteristic austenite and martensite transformation temperatures and thermodynamic parameters such as the enthalpy and entropy of alloys. High-temperature order-disorder phase transitions were determined using a differential thermal analysis, which showed that all the un-aged and aged specimens had an A2 → B2, B2 → L2₁ and an L2₁ → 9R, 18R transition. The structural analysis of the un-aged and aged specimens was performed through X-ray diffraction measurements at room temperature. The intensities of the diffraction peaks varied according to the aging time.     

Effect of Cerium on Microstructures of Hard Alloys

Microstructures and crack extending characteristic of the YG8R,YT5R and YT14R hard alloysadding a trace cerium were studied by AEM and HVEM with a tensile holder.In the hard alloys addingcerium,the compounds of Ce_2O_3 or Ce_2O_2S could be formed,extending of stacking faults and transforma-tion from fcc Co to hcp Co were suppressed,volume fraction of fcc Co in the alloys was increased,andstrength of Co and(TiW)C phases and grain boundaries were raised.Plastic deformation in Co phase nearedges of the tensile cracks was more strong,and the tensile cracks could pass through some smaller WCgrains.     

Effect of Cerium on Morphology of Phosphide Eutectic

At present, in cast iron fine melting, lowering phosphorus concentration with no loss ofother favorable elements at the same timeseems to be a problem, which still has notbeen solved thoroughly. Therefore, looking foran appropriate nodulizer to modify the morphology of phosphide eutectic, especially inhigh strength cast iron, is necessary. On theother hand, phosphorous can also exhibit itsfaVorable effect on mechanical properties aswell as processing behaviors. For instance,gray cast iron cont…     

Effects of the Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Content on the Viscosity of CaO-SiO<Subscript>2</Subscript>-10 Pct Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> Quaternary Slag

The present study experimentally investigates the effect of Cr₂O₃ on the viscosity of molten slags. The viscosities of CaO-SiO₂-10 pct Al₂O₃-Cr₂O₃ quaternary slags with two different binary basicities (R, basic slag with R = 1.2 and acidic slag with R = 0.8) were measured by the rotating cylindrical method from 1813 K to 1953 K (1540 °C to 1680 °C). The results showed that the viscosity of both types of slag decreased as the Cr₂O₃ content increased, but the viscosity of acidic slags exhibited a greater decrease. The slags showed good Newtonian behavior at such high temperatures. Cr₂O₃ could act as a network modifier to simplify the Si-O-Si tetrahedral structure, as verified by the Raman spectral analysis, which was consistent with the decreasing trend of viscosity. The activation energy of viscous flow decreased slightly with increasing Cr₂O₃, but increasing the basicity seemed to be more effective in decreasing the viscosity than adding Cr₂O₃.     

Influence of alloying the TiC<Subscript>0.5</Subscript>N<Subscript>0.5</Subscript> carbonitride with zirconium on an interaction mechanism with the Ni–Mo melt

The influence of alloying the TiC_0.5N_0.5 titanium carbonitride with zirconium on the mechanism and kinetic features of the contact interaction with the Ni–25%Mo melt (t = 1450°C, rarefaction 5 × 10^–2 Pa) is investigated for the first time by electron probe microanalysis and scanning electron microscopy. The main effects of the modifying influence of zirconium on the dissolution, phase formation, and structure formation processes which occur during the interaction of the Ti_1–n Zr _n C_0.5N_0.5 carbonitride (n = 0.05 and 0.20) with the Ni–Mo melt are revealed and the factors promoting their manifestation are analyzed. The practical absence of zirconium and nitrogen in the composition of the K-phase (the Ti_{1 – n} Mo _n C _x metastable solid solution, where n ≤ 0.65 and x = 0.7 ± 0.1) is confirmed experimentally. It is shown that the zirconiumenriched Ti_0.80Zr_0.20C_0.5N_0.5 carbonitride cannot be recommended as a refractory component of cermet because of the limitations of the chemical character.     

Fabrication of aluminum–ceramic skeleton composites based on the Ti<Subscript>2</Subscript>AlC MAX phase by SHS compaction

A one-stage manufacturing technology of aluminum–ceramic skeleton composites by combining the processes of self-propagating high-temperature synthesis (SHS) of a porous skeleton formed by the MAX phase of the Ti₂AlC composition and its impregnation by the aluminum melt under pressure (SHS compaction) is considered. A composition of the exothermic charge 2Ti + C + 22.5 wt % Al + 10 wt % TiH₂, which provides the formation of a porous skeleton of the Ti₂AlC phase without impurity phases by the SHS technology, is selected. It is shown that, when impregnating the hot SHS skeleton with aluminum, new phases are formed such as the MAX phase (Ti₃AlC₂), titanium carbide (TiC), and titanium aluminide (Al₃Ti). However, the content of the basic MAX phase remains high, and the ceramic component of the material consists of Ti₂AlC by 76%. When analyzing the microstructure, it is revealed that the composite has certain residual porosity after impregnation and cooling. The influence of the impregnation pressure (q = 22, 28, and 35 MPa) on the distribution of the aluminum content over the height and radius of the diametral sample section is investigated experimentally. It is shown that the nonuniform Al distribution over the sample bulk is caused by the nonuniform pressure and temperature fields, as well as the different compactibility of hot inner and colder outer sample parts. The degree of compaction of characteristic zones is leveled as the impregnation pressure increases, and the composition inhomogeneity over the sample bulk decreases. The difference in aluminum concentration over the sample bulk at q = 35 MPa does not exceed 5%. The SHS-compacted aluminum–ceramic skeleton composite based on the Ti₂AlC MAX phase corresponds to high-strength Al-Zn–Mg–Cu aluminum alloys by the hardness level (HB ≈ 150 kg/mm²).     

Evolution of the Spectral Emissivity and Phase Transformations of the Al-Si Coating on Usibor<Superscript>®</Superscript> 1500P Steel During Austenitization

Usibor^® 1500P coupons are austenitized in a Gleeble 3500 thermomechanical simulator using a two-step heating procedure in an argon atmosphere. Variations in spectral emissivity are measured in-situ using a near infrared spectrometer and ex situ with a Fourier transform infrared reflectometer. Microstructural evolution and surface roughness are investigated using optical microscopy, FE-scanning electron microscopy, and a surface profilometer. A series of phase transformations of Al-Fe-Si intermetallic phases at the coating/steel substrate interface cause the surface phase and surface roughness to change, which in turn influences the spectral emissivity. At the beginning of the first heating step, the coupons have very low spectral emissivity, due to the molten Al-Si coating. Spectral emissivity increases significantly with increasing soak time from 5 to 12 minutes, associated with the surface phase transformation of the coating into Al₇Fe₂Si intermetallic phase and an increase in surface roughness. Through the second step heating at 1173 K (900 °C), the spectral emissivity shows a gradually decreasing trend with increasing soak time, caused by the surface phase transformation from Al₅Fe₂ into AlFe intermetallic phase with a decrease in surface roughness.     

Revisiting the structure of SiC–B<Subscript>4</Subscript>C–Me<Superscript><Emphasis Type="Italic">d</Emphasis></Superscript>B<Subscript>2</Subscript> systems and prospects for the development of composite ceramic materials based on them

The liquidus surface in SiC–B₄C–Me ^d B₂ quasi-ternary eutectic systems (where Me ^d B₂ is CrB₂, VB₂, NbB₂, TaB₂, ZrB₂, HfB₂, and W₂B₅) is modeled in the approximation of the regular solution model based on the experimental data on bordering systems and individual compounds. The calculated and experimental data are compared. Regularities of the structure of phase diagrams of SiC–B₄C–Me ^d B₂ systems are analyzed. It is noted that the diboride concentration appropriately decreases in the triple eutectic with an increase in its melting point. Correlation dependences between the eutectic temperature and melting point \({t_{eut}} = f\left( {t_m^{M{e^d}{B_2}}} \right)\) and formation enthalpy of diboride \({t_{eut}} = f\left( {\vartriangle H_f^{M{e^d}{B_2}}} \right)\) are constructed. The character of dependences is close to previously observed similar dependences in SiC–Me ^d B₂ and B₄C–Me ^d B₂ bordering quasi-binary systems. It is concluded based on the analysis of the structure and parameters of analyzed systems that it is promising to develop a broad series of construction and functional ceramic materials and coatings fabricated by “free” sintering and by pulsed methods of heating and consolidation based on the considered systems.     

Effect of Rhenium on Formation of the Structure of Eutectic Alloys Based on β-NiAl + γ-Re

We have studied phase equilibria and plotted the partial phase equilibria diagram for Ni Al Re in the region of compositions ranging from 0.2 to 14 at.% rhenium. We have established the dependence of the structure and the phase composition of the alloys in the Ni Al Re system on the rhenium concentration. We have determined the optimal ratio of the components at which the alloys have the maximum melting point. We have shown that the structure of the alloys is a composite consisting of a NiAl-based matrix and -Re fibers.