Iranian Journal of Materials Science and Engineering

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In this research, the effect of RSW parameters including current intensity, welding time and welding force (coded by A, B and C) on the radius, thickness and area of ​​the nugget and the radius of the HAZ of TRIP steel joints was investigated by DOE and RSM. A 3D coupled thermal-electrical-structural FEM was used to model RSW. To validate the FE model, two TRIP steel sheets were welded experimentally. During welding, the temperature was measured and the results were compared with the FE results and a good agreement was obtained. The boundaries of the welding zones were determined according to the critical temperatures and the responses in all samples were calculated. Using analysis of variance, direct, quadratic and interaction effects of parameters on the responses were studied and a mathematical model was obtained for each response. The direct linear effects of all parameters on all responses were significant. But among the interaction effects, the effect of B×C on the nugget radius, the effect of A×B on the nugget thickness, the effect of A×B on the nugget area and the effects of A×B and B×C on the HAZ radius were significant.  Also, current intensity had the greatest effect on all responses.
 

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The aims of this research were to evaluate the effects of different thermomechanical treatments on the microstructure and investigate some of the mechanical properties of a TWIP steel rich in Mn & Al. So, a block of a TWIP steel with nominal composition Fe-17.5Mn-1.36Al-0.8C was cast and then subjected to hot rolling followed by cold rolling and heat treatment. Cold rolling was performed before heat treatment in order to reduce the grain size and improve the tensile and fatigue properties. X-ray diffraction technique was used before and after the heat treatment to evaluate the possibility of any phase formation. No sign of martensitic transformation after cold deformation was observed. However, by increasing the amount of cold deformation, the number of mechanical twins and slip band increased resulted to an increase in hardness and strength. The best tensile and fatigue result were obtained after 47% thickness reduction and annealing at 715˚C for 10 min. Under these conditions, the mean grain size reduced from 138 to 9 μm resulted to an increase in yield strength from 395 to 510 MPa, and the fatigue life improvement from the mean life of 10200 for the cast sample to 21500 cycles for the treated sample, when these samples underwent fatigue tests at a stress range of 650 MPa and R=0. In addition, the diameter and depth of dimples in fracture surfaces decreased by reducing the grain size but the fracture mode was remained ductile and adequate plastic deformation occurred before failure.
 

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The effect of Strain-Induced Melt-Activated (SIMA) Process, ultrasonic treatment (UST) and Al-5Ti-1B refiner on the microstructure and globularity of Al–15%Mg2Si composite was studied. Deformation of 25% were used. After deformation the samples were heated at 560, 580 and 595 °C for 5, 10, 20 and 40 min. The composite was treated with different amounts of the Ti concentrations and ultrasonic treatment with different power. Microstructural study was carried out on the alloy. It was observed that SIMA process, ultrasonic treatment and Al-5Ti-1B refiner has caused the globular morphology of Mg2Si particles. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 595 °C and 20 min respectively. Optimum amount of Ti refiner is 1 wt.% and power for UST is 1800W. After applying the SIMA process, Al-5Ti-1B master alloy and ultrasonic treatment, the strength and engagement have increased. This means that tensile strength increases from 251 MPa to 303 MPa and elongation percentage improves from 2.1 to 3.4, respectively.
 

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Amorphous calcium phosphate (ACP) which is a transient phase in natural bio-mineralization process has recently gained the spotlight. This study aimed to assess the effect of incorporation of nano-ACP (NACP) in a dental adhesive with/without surface treatment with silane coupling agent on bond strength. NACP was synthesized by the wet chemical precipitation technique. To characterize the structure of NACP, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used. Forty molars were randomized into 4 groups of 10. The teeth were restored with composite resin and the bonding agent (one of the four groups). Adper Single Bond 2 was used as the control group. In 4wt% NACP group, NACP fillers were added to the bonding agent. In 0.4wt% and 4wt% SNACP groups, silanized NACP fillers were added to the bonding agent. Finally, the mode of failure of specimens was determined. Data were analyzed by one-way ANOVA and Tukey's post-hoc tests. P<0.05 was considered statistically significant. Addition of 4wt% non-silanized NACP decreased the bond strength compared with the control group (P<0.05). The bond strength of the groups with silanized fillers was not significantly different from that of the control group. Addition of silanized NACP to dental adhesive had no significant adverse effect on bond strength, which is a promising finding to pave the way for the synthesis of bonding agents containing bioactive fillers.

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Several extensive researches are being carried out in the field of 3D printing. Polymer matrices, such as High-Density Polyethylene (HDPE), are less explored in particular on the microstructure and mechanical properties of HDPE composites developed via Fused Deposition Modelling (FDM) process. Very scarce amount of works is devoted to study HDPE’s reinforced with carbon nano-tubes (CNT’s) . In the present work, we report on the mechanical properties of  HDPE composites prepared via FDM process. Varying proportions of CNTs ( 0.5, 1, 1.5 and 2%) are used as reinforcements. It is found that increasing CNT content enhances impact and tensile strength, with HDPE/2.0%CNT outperforming pure HDPE by approximately 71.6% and 25.4%, respectively. HDPE/2.0%CNT composite also showed Young's modulus approximately 49.2% higher than pure HDPE. According to fracture analysis, pure HDPE failed near ductile, whereas composites failed brittle. CNTs occupy the free positions in the polymeric chains, and their tendency to restrict chain mobility causes HDPE to lose ductility and begin to behave brittle. The use of CNTs as reinforcement successfully improved the mechanical properties of HDPE.

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In this study, the potential of calcined montmorillonite as a primary precursor for one-part alkali-activated cement incorporated with high percentage of limestone, is evaluated. Comparative studies on the properties of the sodium silicate activated metakaolin-limestone and metamontmorillonite-limestone fresh and hardened cement pastes depending on several formulation and processing parameters (precursor nature, dosages of limestone and alkali reactant, curing conditions) showed that metamontmorillonite exhibits reactivity comparable to that of metakaolin in the studied cement systems. The mechanical performance of optimal alkali-activated cement formulations consisted of 20-30% of metamontmorillonite and 70-80% of limestone is provided by both reactivity of metamontmorillomite under sodium silicate activation and the filler, nucleation, and chemical effects of the raw limestone. The reaction products and microstructures of alkali-activated metamontmorillonite-limestone cement-based hardened pastes were investigated using thermal, XRD, and SEM/EDS analyses.   
 

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Phase transformations and the evolution of hardness during elevated-temperature annealing of Inconel 718 superalloy manufactured by the laser powder bed fusion (L-PBF) were investigated. The microstructural evolution, elemental analysis, phase formation, and hardening were characterized by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Vickers indentation test, respectively. It was observed that the effect of annealing treatments is directly governed by the annealing parameters (i.e. time and temperature), for which the hardness measurement as a fruitful and convenient tool can reveal this effect. The increase of the hardness, which was obtained by the annealing (aging) treatments at the temperature range of 800-900 °C, indicated precipitation of the Ni₃Nb γ˝ strengthening phase; while owing to the coarsening of precipitates as a results of overaging at this temperature range, the hardness decreased. For instance the length and aspect ratio of precipitates in the aged sample at 800 °C for 1 h is 67.14 nm and 0.32, respectively; while these values in the aged sample at 800 °C for 8 h is 78.34 nm and 0.44, respectively. On the other hand, the decrease of the hardness at temperatures of 950 and 1000 °C was attributed to the decrease of dislocation density in conjunction with the Ni₂Nb Laves phase dissolution. Hence, it is crucial to determine the annealing parameters according to the required microstructure and properties.

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In the present investigation, an attempt was made to evaluate the dissolution behavior of Ti in molten KCl-LiCl. The X-ray diffraction (XRD) pattern of heated Ti plate at 800 oC for 4 h without carbon black in molten salt revealed that TiCl3 formation was feasible. For more assurance, Ti plate was heated at 950 oC for 4 h in the presence of carbon black to identify synthesized TiC. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images from precursors and the final product showed that nano-crystalline TiC formation from coarse Ti particles was almost impossible without Ti dissolution. Thermodynamics calculations using Factsage software proved that it was possible to form various TiClx compounds. The TiC formation mechanism can be discussed in two possible ways: a reaction between Ti ion and carbon black for synthesizing TiC (direct) and a reaction between TiCl4 and carbon black led to indirect TiC synthesis. Elemental mapping using energy dispersive X-ray spectroscope (EDS) indicated that up to 815 oC, chlorine existed in the map. 

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Deformation-induced α΄-martensite generally forms at shear bands in the coarse-grained austenite, while it nucleates at grain boundaries in the ultrafine-grained (UFG) austenite. The available kinetics models are related to the nucleation on the shear band intersections, and hence, their application to investigating the kinetics of α΄-martensite formation for the UFG regime cannot be justified. Accordingly, in the present work, the general Johnson–Mehl–Avrami–Kolmogorov (JMAK-type) model was implemented for comparing the kinetics of α΄-martensite formation in the UFG and coarse-grained regimes using an AISI 304L stainless steel. On the experimental front, the X-ray diffraction (XRD) patterns and the electron backscattered diffraction (EBSD) maps were used for phase and microstructural analyses, respectively. It was revealed that the simple JMAK-type model, by considering the dependency of the volume fraction of α΄-martensite on the strain, is useful for modeling the experimental data, predicting the nucleation sites based on the theoretical Avrami exponents, and characterizing the transformation kinetics at low and high strains.

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Two-dimensional molybdenum disulfide (MoS₂) is used as a promising flame retardant and smoke suppressant nano additive in polymer composites due to its high thermal stability and layered structure. In this study, thermoplastic polyurethane (TPU) was melt-blended with MoS2 (1wt. %) and a halogen-free intumescent flame retardant (IFR) system. The IFR system consisted of ammonium polyphosphate (APP), Melamine polyphosphate (MPP), and pentaerythritol (PER), with a total amount of 25 wt. %. The TPU/IFR/MoS2 composite exhibited outstanding flame-retardant properties, achieving a UL-94 V-0 rating and a limiting oxygen index (LOI) value of 34%. Reaction-to-fire performance of the TPU/IFR/MoS2 composite was evaluated by cone calorimeter test (CCT). The CCT results indicated high flame-retardant efficiency and considerable smoke suppression performance, along with a significant decrease in the peak heat release rate (PHRR: 65.9%), peak smoke production rate (PSPR: 65.6%), and peak CO production (PCOP: 60.7%) compared to the neat TPU. The significant improvement in fire performance of TPU composite was mainly attributed to the effects of the physical barrier of MoS2 and catalytic carbonization of the IFR system. These resulted in forming an intumescent compact carbonized layer during the combustion, effectively restricting dripping. The continuous structure of the residual char was revealed by FESEM. Thermogravimetric analysis (TGA) indicated improved thermal behavior of the TPU composite in high temperatures. This work provides an effective method to improve the reaction to fire of TPU composites by incorporating traditional IFRs and MoS2, resulting in enhanced fire safety.

 
 

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The coated β-tricalcium phosphate (β-TCP) with dicalcium phosphate dihydrate (DCPD) has attracted much attention in the biomaterials field due to the increase in its osteoconductivity. Besides, the porous bioceramic scaffolds with controlled pore sizes are significant in stimulating bone-like cell activity. In this study, the effect of the setting-time process and acidic-calcium phosphate (CaP) concentrations on the fabrication and properties of porous DCPD/ β-TCP scaffolds were studied. Subsequently, the specimens were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), compression strength and Fourier transforms infrared (FTIR). The study results revealed that the porous DCPD/ β-TCP scaffolds with macro- and micropore sizes were successfully obtained after the 300-600 µm of porous β-TCP granules were exposed to an acidic-CaP solution. Furthermore, the setting-time process and acidic-CaP concentrations increased the DCPD interlocking between granules, and the mechanical strengths of scaffolds increased up to 0.5 MPa. Meanwhile, the porosity levels were changed based on the formation of DCPD crystals. This study was expected to provide novel insights to researchers in the field of bioceramics through its investigation on the creation of porous DCPD/ β-TCP scaffolds.

 

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The lindgrenite compounds [Cu₃(MoO₄)₂(OH)₂] with various architectures and high crystallinity were prepared by a simple surfactant-assisted hydrothermal method. Then, the Cu₃Mo₂O₉ samples were prepared by calcination of the as-synthesized Cu₃(MoO₄)₂(OH)₂. The resulting samples had high crystallinity, colloidal properties, high-yield, large-scale production capability with using of nontoxic and inexpensive reagents and water as an environmentally solvent. The scanning electron microscope studies showed that the as-prepared lindgrenite nanostructures were well crystallized with rod, sheet and hollow sphere morphologies. These products were content of the Cu₃(MoO₄)₂(OH)₂ rods with diameters of about 100 nm, the Cu₃(MoO₄)₂(OH)₂ nanosheets with thickness of 30–100 nm and the Cu₃(MoO₄)₂(OH)₂ hallow spheres, consisting of a large number of nanosheets with thickness of about 40-70 nm. The Cu₃Mo₂O₉ samples that obtained by thermal treatment of lindgrenite retained the original morphologies. Meanwhile, the photoluminescence and magnetic properties of the nanosheet samples showed super paramagnetic behavior at room temperature and in comparison with previous works, Cu₃(MoO₄)₂(OH)₂ and Cu₃Mo₂O₉ samples synthesized by the surfactant-assisted hydrothermal method had a very obvious red-shifted PL emission and high intensity.
 

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The Nickel tungsten (Ni-W) alloy was electrodeposited on stainless steel (SS) substrate using potentiostatic mode at room temperature. Potentiostatic electrodeposition was carried out by varying the deposition time. The physicochemical properties of Ni-W alloys were studied using X-Ray diffraction (XRD), Electron Microscopy and micro-Raman spectroscopy. Recorded XRD spectra was compared with standard JCPDS card and the presence of Ni was confirmed, no such peaks for W were observed. Further study was extended for micro-Raman analysis. From Raman spectroscopy study the appearance of Ni-O and W⁶⁺=O bonds confirms that the Ni-W present in amorphous phase. Several cracks were observed in SEM images along with nanoparticles distributed over the electrode surface. The appearance of cracks may be correlated with the in-plane tensile stresses, lattice strains and stacking faults and may be related to the substrate confinements.
 

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Heterostructure photocatalyst of CuWO₄ modified SnO₂ (CuWO₄/SnO₂) was fabricated by in simple wet-impregnation process and evaluated via degradation of rose Bengal (RB) under visible light irradiation. The samples had been completely characterized by Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis-DRS), X-ray diffraction (XRD), Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), High-resolution TEM (HR-TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett and Teller surface analysis (BET). The result divulged that amongst the catalysts, CuWO₄/SnO₂ displayed higher photocatalytic activity than CuWO₄ or SnO₂. The enhanced photocatalytic efficiencies are attributed to the charge transfer from SnO₂ to CuWO₄ nanoparticles, which efficiently decrease electron-hole recombination energy level. The time required for maximum degradation of rosebengal (RB) under visible light over CuWO₄/SnO₂ was 180 min. The other parameters such as pH (pH=8), photocatalyst dosage (0.2 g/L) and dye concentration (20 µM) were optimized to achieve high degradation efficiency (98.5%). The excellent photocatalytic activity of CuWO₄/SnO₂ is due to efficient separation of photogenerated electron-hole pairs. The holes (h⁺) and superoxide radicals (O₂^•-) are the reactive species involved in photocatalytic mechanism for gdegradation of RB.

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In this study, the hot deformation and dynamic recrystallization behavior of low carbon steel containing 21 ppm boron was investigated. After homogenizing the samples at 1250 ℃ for 1-hour, hot compression tests were conducted at temperatures ranging from 850 ℃ to 1150 ℃ and strain rates from 0.01 to 10 s⁻¹, resulting in strain-stress flow curves. Following corrections, calculations and modeling were performed based on Arrhenius equations. Among them, the hyperbolic sine relationship provided the most accurate estimate and was selected as the valid model for the applied strain range. According to this model, the deformation activation energy (Q), was determined to be 293.37 KJ/mol. Additionally, critical and peak stress and strain values were obtained for each temperature and strain rate, and power relationships were established to describe their variation with respect to the Zener-Hollomon parameter (Z). Recrystallization fractions were derived by comparing the hypothetical recovery curves with the material flow curves, and the results were successfully modeled using the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponent was measured at approximately 2, indicating that nucleation predominantly occurred at grain boundaries. Microstructural analysis revealed that at higher Z values, recrystallization occurred along with a fraction of elongated grains, while lower Z values resulted in a greater fraction of equiaxed dynamic recrystallization (DRX) grains. The average grain sizes after compression tests at 950 ℃, 1050 ℃, and 1150 ℃ were measured as 21.9 µm, 30.4 µm, and 33.6 µm respectively at a strain rate of 0.1 s⁻¹, and 17.7 µm, 28.7 µm, and 31.3 µm at 1 s⁻¹. The overall microstructure displayed a more uniform grain size distribution with increasing deformation temperature.

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ZrO₂ is commonly incorporated into ceramic glass substrates to enhance radiopacity, mechanical strength, and chemical durability. Experience has shown that the crystallization of tetragonal zirconia in glass will have a greater effect on the mechanical properties of ceramic glass. To achieve optimal properties in zirconia, stabilizing oxides are often added to enhance its structural and mechanical qualities. In this research, in order to stabilize the tetragonal phase of zirconia, MgO and CeO₂ were added to the glass ceramic composition of the Li₂O-SiO₂-ZrO₂ system and the desired dental substrate was synthesized through the sinter process. The behavior of sintering and crystallization of basic and optimized glass was investigated using HSM and DTA thermal analysis, respectively. The results showed that the optimal sinter temperature, heat press and heat treatment are equal to 730°C, 900°C and 825°C, respectively. Then, in order to determine the crystallization behavior of the prepared samples, X-ray diffraction and microstructure images were used. The results also showed that the presence of the main Li₂ZrSi₆O₁₅ phase crystallizes at a temperature of 825°C in the base sample and the sample containing ceria. Also, due to early formation of MgSiO₃ crystals, magnesia prevents sintering and formation of Li₂ZrSi₆O₁₅ phase and stability of tetragonal zirconia phase. In the sample containing ceria, during crystallization, ZrO₂ entered its crystal structure and led to the stability of the tetragonal zirconia phase at room temperature.

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This study investigates the microstructural evolution and variations in the mechanical properties of pre-cold worked Nimonic 80A superalloy, subjected to two levels of deformation (25% and 50%) and welded via Gas Tungsten Arc Welding (GTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) techniques using ER309L filler wire. The objective is to evaluate the effect of the initial microstructure on the welding behavior of Nimonic 80A and compare the weldments produced using GTAW and PCGTAW. Microstructural characterization was conducted using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). XRD analysis demonstrated that the welding pulsed current mode, compared to the continuous current mode and at equal heat input, led to a refined microstructure, suggesting improved welded mechanical properties of the weld. It also showed a potential reduction in grain refinement with a higher level of cold work. Tensile testing demonstrated that fractures consistently occurred within the weld zone (WZ), with the PCGTAW sample achieving the highest tensile strength (766 MPa). Microhardness analysis indicated a notable reduction in hardness within the heat-affected zone (HAZ) and WZ, particularly in the 50% pre-cold worked sample. However, PCGTAW retained higher hardness due to its refined microstructure. The weld metal primarily consisted of an austenitic microstructure characterized by dendrites and interdendritic precipitates. Microstructural analysis revealed that welding induced significant changes in the weldment, with the PCGTAW sample exhibiting a more uniform microstructure and smoother transitions at the weld interface. Fractography confirmed ductile fracture in all specimens, with smoother and more uniformly distributed dimples in the PCGTAW sample. These findings highlight the advantages of pulsed current welding in optimizing the mechanical performance of Nimonic 80A welds and suggest its potential application in industries requiring superior weld quality.

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Dissimilar joints of AA2219 and Ti-6Al-4V alloys are obtained using the vacuum diffusion bonding method. The bonding pressure is controlled in the range of 1-4 MPa by keeping the bonding temperature and holding time constant. The influence of the bonding pressure on the microstructure and mechanical properties of the bonding joints is investigated. The diffusion behaviour across the interface of the bonding joints is increased with the increase in bonding pressure. The interface morphology of the specimen bonded at lower bonding pressures exhibits scraggly voids and cracks. The irregular voids and cracks are squeezed and gradually closed due to the significant increase in the diffusion between Al and Ti. The maximum shear strength of 81 MPa is obtained for the joint made at the bonding pressure of 4 MPa, and a diffusion layer of 0.76 µm is formed at the Ti side interface. The fracture morphology inferred the brittle failure of the bonding joints due to the formation of intermetallic compounds like TiAl, TiAl₂, and TiAl₃ at the interface of Al and Ti.

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This study investigates the effect of SnO₂ as an additive on the structural, electrical, optical, and gas sensing properties of LaCrO₃ nanoparticles.  SnO₂ is added into the LaCrO₃ by weight percentage (1 wt. %, 3 wt. %, 5 wt. %, 7 wt. %, 9 wt. % and 11 wt. %) employing screen printing method. Initially, the nanoparticles of SnO₂ and LaCrO₃ separately synthesis by sol-gel method and then used for the development of thick films. LaCrO₃ is used as host material while SnO₂ is additive material. The structural characterizations like FESEM, EDX and XRD were carried out to investigate the morphology, elements and crystallite size respectively. The inclusion of SnO₂ modifies the crystalline structure and surface morphology of LaCrO_3, as revealed by structural analyses. The optical characterizations like FTIR and UV were used for the study of impact of SnO₂ additive on functional group and band gap of the host material respectively. Optical studies indicate a modification in the bandgap, affecting light absorption properties and indicating changes in electronic transitions. The electrical characterizations were conducted by using half bridge method. Electrical resistivity measurements show enhanced performance, likely due to variation in charge carrier mobility induced by the SnO₂ additive. Among other selected wt. % SnO₂ additives, 9 wt. % SnO₂ added LaCrO₃ thick films shows maximum sensitivity to CH₄ gas at 120^oC operating temperature. The gas sensing characteristics demonstrate enhanced sensitivity, selectivity, and response time to target gases, suggesting that SnO₂ doping improves the sensing capabilities of LaCrO₃ nanoparticles, making them more efficient as a gas sensor. Obtained findings suggest that, SnO₂ as an additive enhances the multifunctional properties of LaCrO₃ nanoparticles, making them promising candidates for advanced gas sensing applications.
 

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This work reports the influence of Cu dopant and annealing temperature on CdO_x thin films deposited on glass substrates by spray-pyrolysis method. The Cu doping concentrations were 0, 0.46, and 1.51 at% with respect to the CdO_x undoped material. Then, the fabricated films were subjected to annealing process at temperature of 450°C. X-ray diffraction (XRD) examination confirms that the as-deposited films show a cubic crystallographic structure with high purity of CdO in the annealed films. It was found that the (111) peak is the most predominant diffraction orientation in the surveyed samples. At the microscopic scale, AFM machine was operated to quantify the three important parameters of the mean roughness (Ra), rms value (Rq), and z scale. These parameters hold highest values for the sample with 0.46 at% of Cu. Finally, reflectance, absorbance, transmittance and other optical parameters dielectric measurements were comprehensively analyzed. Our evaluation of optical band gaps for the studied samples reveals that the synthesized films have direct band gap character with the fact that the rise in the Cu contents in the as-deposited films lead to lessen the band gap values. In contrast, annealing process results in raising the band gap.