Iranian Journal of Materials Science and Engineering

---

 

---

The lean duplex stainless steels (LDSS) have excellent features due to the microstructural phase
combination of austenite and ferrite grains. These steels have low Ni and Mo contents which can reduce the cost
and stabilize the austenite fraction in the microstructure. In recent years, welding is used to enhance the
microstructural behaviour of LDSS. In this paper, Gas tungsten arc welding (GTAW) was performed on LDSS
S32101 with different heat energy inputs and varying welding currents. The influence of heat inputs (0.85 and 1.3
kJ/mm) on welded samples was investigated to study the microstructural behaviour, phase balance, and mechanical
& corrosion performance. The microstructures studies were carried out using an optical microscope, scanning
electron microscope and X-ray diffraction. The effect of Heat input led to the significant microstructural evolution
in weld metals with high austenite reformation. The microstructure of weldments consisted of inter-granular
austenite (IGA), grain boundary austenite (GBA) and Widmanstatten austenite (WA). Important mechanical
properties such as tensile strength and micro-hardness were investigated to understand the performance of
weldments. The polarization method was used to understand the corrosion behaviour of weldment in a 3.5% NaCl
solution. The experimental results showed enhanced properties of welds that could be suitable for industrial
applications.

---

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.
 

---

In the present study, bulk refined-structured Al 5083 alloy with high mechanical properties was successfully fabricated by hot consolidation process of nanostructured melt- spun flakes. The influence of cooling rate and pressing conditions on the microstructure and mechanical properties of the alloy were investigated using X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), microhardness, and compression tests. Rapid solidification combined with the hot consolidation at T=753 K (480 °C) and P= 800 MPa for 20 min produced a bulk sample with the desirable bonding, good microhardness (184.2±12.4 HV), and high strength (273±8 MPa) combined with 7 pct. fracture strain. These amounts are 78.6±5.1 HV, 148 ±9 MPa and about 5 pct. for the as-cast sample. Microstructural refinement during the controlled consolidation of nanostructure rapidly- solidified flakes contributes to such high mechanical properties of the bulk sample.

 

---

---

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.

---

The Directed Energy Deposition (DED) process is very sensitive to thermal environments, tends to produce residual stresses and geometric distortion. It is important to understand the influence of processing parameters on these effects in order to enhance build quality. The objective of this study is to control residual stress and distortion in the DED process by investigating baseplate thickness, number of layers deposited before laser interruption, dwell time, and laser power by a full factorial experiment design. The numerical results were validated by experimental measurement of residual stress using the X-ray diffraction (XRD) technique. The optimized processing conditions resulted in a 43% reduction in residual stress and a 33% decrease in dimensional distortion compared to the baseline setup. Among the four factors, baseplate thickness had the most significant effect, whereas dwell time had the least impact. To the best of the authors’ knowledge, the combined effect of baseplate thickness, dwell time, number of layers deposited before laser interruption, and laser power on residual stress and distortion in DED has not been previously investigated. The findings of this study provide a mathematical basis for future research aimed at optimizing process and material parameters in DED process.
 

---

---

The present investigation delves into the friction stir welding of AA5052 and AZ31B alloys, examining the effects of three distinct parameter configurations. A face-centered central composite design, structured to incorporate full replications for comprehensive and reliable analysis, was employed. A pivotal element of this study is implementing an advanced deep neural network (DNN) model. Characterized by its varied activation functions, structural parameters, and training algorithms, this DNN model was adeptly configured to precisely predict the tensile strength and microhardness of the welded joints. This comprehensive examination also included a quantitative assessment of the parameter effects on joint microstructure and mechanical properties. Flawless welds with exemplary surface characteristics were attained through a meticulously optimized set of parameters: a tool rotation speed set at 825 rpm, a tool traverse speed of 15 mm/min, and a shoulder diameter of 18 mm. During the welding process, the formation of intermetallic compounds, specifically Al₁₂Mg₁₇ and Al₃Mg₂, was observed. An exceptionally refined grain size of 2.23 µm was observed in the stir zone, contributing to the joint's enhanced tensile strength, measured at 180 MPa. The hardness of the specimen fabricated at the high rotational speed is more elevated due to the brittle intermetallic compounds. The better mechanical properties are related to the reduction and distribution of intermetallic compounds formed in the interface zone.  

---

Acrylic resins are one of the most important thermoplastic resins used in various industries due to their significant properties. However, they are inherently brittle and addition plasticizers to them is very common. In this study, role of both Polyethylene Glycol (PEG) and Triacetin on the mechanical properties of acrylic resin have been investigated. To do so tensile test, bending and wear tests have been performed. To achieve the optimal mixture of plasticizers, a tensile test has been carried out, and the best percentage of the mixture has been determined. Subsequently, bending and wear tests were conducted, which showed a significant increase in the bending strength of the acrylic resin after the addition of plasticizers. Furthermore, it was found that the abrasion mechanism of the resin was significantly altered compared to its pure state.
 

---

The present study focuses on the phase and structural features of MnAl intermetallic compound during solid-state synthesis. In this regard, the milling process was done in differentMn_50+xAl_50-x (0<x<7.5)powder mixtures and the prepared samples were evaluated using X-ray diffractometer, scanning and transmission electron microscopy, differential thermal analysis and vibrating sample magnetometer. The results showed that the τ-MnAl magnetic phase with L1₀ structure could not be formed during the milling and low temperature annealing. During milling process, Al atoms dissolve in Mn network and a single β-Mn supersaturated solid solution (SSSS) form. The β-Mn (SSSS) phase is unstable and transforms into the icosahedral quasi-crystal as well as γ_2-Al₈Mn₅ and β-Mn stable phases during subsequent annealing.
 

---

The stability of microstructure at high temperatures is necessary for many applications. This paper presents investigations on the effect of changes in temperature on the microstructures of additively manufactured Ti6Al4V(ELI) alloy, as a prelude to high temperature fatigue testing of the material. In the present study, a Direct Metal Laser Sintering (DMLS) EOSINT M290 was used to additively manufacture test samples. Produced samples were stress relieved and half of these were then annealed at high temperatures. The samples were then heated from room temperature to various temperatures, held there for three hours and thereafter, cooled slowly in the air to room temperature. During tensile testing, the specimens was heated up to the intended test temperature and held there for 30 minutes, and then tensile loads applied to the specimens till fracture. Metallographic samples were then prepared for examination of their microstructures both at the fracture surfaces and away from them. The obtained results showed that changes in temperature do have effects on the microstructure and mechanical properties of Ti6Al4V(ELI) alloy. It is concluded in the paper that changes in temperature will affect the fatigue properties of the alloy.

---

Celestite ore, the primary mineral for producing strontium compounds, particularly strontium carbonate, is processed using the black ash method, which involves carbothermic reduction, water leaching, and carbonation. This study aims to investigate the combined effect of mechanical activation and additional graphite on the recovery rate and purity of strontium carbonate. Celestite ore with a strontium sulfate content of 79% was obtained from the Dasht-e-Kavir mine. Acid washing with 10% hydrochloric acid significantly reduced carbonate impurities, resulting in a celestite purity of 96.9%. Mixtures of celestite and graphite with varying amounts of graphite were prepared with and without milling. The mixtures were roasted at 900 °C for 1 hour to form strontium sulfide, followed by hot water leaching. After filtration, sodium carbonate was added to the leachate containing SrS, resulting in the formation and precipitation of white strontium carbonate crystals. The results showed that the addition of graphite increased the recovery rate in unmilled specimens. However, the recovery rate decreased significantly when 1 and 10 hours of milling were applied in the presence of excess graphite. Conversely, in the absence of additional graphite, milling for 1 and 10 hours increased the strontium recovery rate to over 95%. Furthermore, the analysis of strontium carbonate obtained from the sample with the highest recovery rate showed a purity of over 99.9%.

---

This study presents the manufacturing of Al 1050/Mg AZ31B bimetallic sheets using the cool roll bonding process, followed by an investigation of the effect of annealing temperature on mechanical properties and microstructural features. Annealing treatment was performed at 200, 300, and 400 degrees Celsius. Mechanical testing includes tension, micro-hardness, three-point bending, and fracture toughness. Scanning electron microscopy equipped with energy-dispersive X-Ray spectroscopy (SEM-EDX) and X-ray diffraction (XRD) were used to investigate the microstructure in the infiltration zone. Mechanical testing shows that increasing the annealing temperature decreases the tensile strength of the two-layer specimens. Micro-hardness, XRD, and SEM-EDX investigations confirm the presence of intermetallic particles in the penetration zone. The Micro- hardness test showed that with the increase of the annealing temperature, the hardness in the penetration zone of Al 1050/Mg AZ31B increases. This increase in micro-hardness result confirms the presence of harder intermetallic phases with increasing annealing temperature in the penetration zone.
 

---

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.

---

Glass ionomer cements (GICs) are widely utilized in clinical restorative dental applications, which suffer from poor mechanical strength. Recent research shows that GIC achieves optimal performance when modified with lower percentage of filler materials, particularly when using nanoparticles, due to the resultant increase in surface area and packing density of the cement. Notably, while some modifications show promise, others fail to deliver improvements in material characteristics. This study addressed a gap in the literature by investigating the impact of acidic/basic additives, such as Diopside (CaMgSi₂O₆) and Zirconia (ZrO₂), on the properties of the cement. The reactivity of zirconia and Diopside differ distinctly from traditional calcium-aluminosilicate glass when exposed to acidic conditions in GICs. Also, to clarify the impact of acidity/basicity on filler reactivity during cement setting, the potential mechanical enhancement effects by using nano-sized particles is limited to submicrons. This research incorporated Diopside at concentrations of 2, 4, and 6 wt.%, and zirconia at 8, 10, and 12 wt.% into a glass powder component. Results demonstrated that adding 8 wt.% Zirconia led to a 49% enhancement in compressive strength, also improve microhardness by 16 wt.%, attributed to its non-reactive nature, minimal dissolution, and high inherent strength of ZrO₂. In contrast, Diopside had a detrimental effect due to its basic nature compared to that of glass powder. These findings highlight the potential of zirconia as a valuable reinforcing material for the successful mechanical performance of glass ionomer cements. Conversely, basic fillers like diopside appear unsuitable for achieving improved mechanical performance in these systems.

---

The present work deals with the corrosion behavior and mechanical properties of a coted AZ31 magnesium alloy through plasma electrolyte oxidation (PEO) coating process in different alkaline electrolytes based on sodium silicate (Si-coating), sodium polyphosphate (P-coating) and sodium aluminate (Al-coating). The scanning electron microscopy (SEM) equipped with the energy dispersive x-ray spectroscopy (EDX) plus x-ray diffraction were recruited to investigate the morphology, chemical composition, and phase structure of coatings, respectively. Microscopic scrutiny revealed that the coating in the phosphate electrolyte was twice as thick and the relative porosity percentage was higher than those formed in the other electrolytes. The phase analysis indicated that the MgO was present as the prevailing phase in the Al-coating and P-coating. However, the dominant phase in the Si-coating was Mg₂SiO₄. Electrochemical testing was examined in a solution containing 3.5.wt% sodium chloride, showing improvements in corrosion resistance of coated alloys. These investigations confirmed that the corrosion resistance of Si-coating was dramatically higher than others which could be attributed to the presence of the dense and stable Mg₂SiO₄ phase as well as its relatively low porosity. According to the results of tensile tests, the coated samples had lower tensile strength and elongation than the uncoated one. The tensile strength and elongation diminished upon changing the electrolyte from Al-coating to P-coating, while the yield strength was almost similar. Further analyses indicated that the drop of tensile strength and elongation could be attributed to the presence of cracks and pores in the brittle ceramic PEO coating as stress concentration regions during deformation. Those areas are created due to thermal stress during the coating process and deformation in the elastic stage.
 

---

This study successfully synthesized the CoCrFeNiMn high-entropy alloy (HEA) using a two-step powder metallurgy approach: mechanical alloying (MA) followed by spark plasma sintering (SPS). The research investigated the effects of processing parameters, specifically MA duration and SPS temperature, on the alloy's microstructure, densification, and mechanical properties. X-ray diffraction (XRD) analysis after 25 hours of MA (ball-to-powder ratio of 10:1) confirmed the formation of a single-phase face-centered cubic (FCC) solid solution. Scanning electron microscopy (SEM) images revealed significant powder particle refinement, with average particle sizes decreasing from initial micrometers to sub-micrometer ranges. The alloyed powders were then consolidated via SPS at temperatures of 800°C, 900°C, and 1000°C (40 MPa, 10 min in argon). Detailed analysis of the sintered samples showed relative densities ranging from 95.78% to 96.77%, with the highest density (96.77%) achieved at 1000°C. Vickers microhardness measurements exhibited a peak hardness of 446 HV at 900°C, with a decrease to 420 HV at 1000°C, primarily due to grain growth. This research establishes the combined MA and SPS approach as effective for producing high-density, high-hardness HEAs, underscoring the critical role of processing parameters in tailoring their final properties.
 

---

---

There is a global need to develop engineering materials to address the increasing demands in various industries. Spark plasma sintering (SPS) is one of the most distinguished powder metallurgy techniques, offering the opportunity for the fabrication of different types of materials. This work emphasizes optimizations of the important process parameters, including temperature, pressure, and holding time, involved in the SPS of the WC, WC-Co, and WC-Cr, as well as assessing the influence of the content of the Co (6-24 wt.%) and Cr (0.2-1 wt.%) binders on the overall characteristics of the SPS-ed cermets. The results illustrate that the process parameters highly affect the physicomechanical properties of the SPS-ed WC, where the most appropriate conditions from a physicomechanical viewpoint are obtained at a sintering temperature of 1700 °C, a pressure of 80 MPa, and a holding time of 5 min. The included Co binder reduces the optimum temperature and pressure down to 1200 °C and 70 MPa, respectively. The addition of the Co improves the final properties of the WC irrespective of its content. The highest tribomechanical properties are attained when 18 wt. % of Co is added. Similar to that of Co, the incorporation of Cr into the WC increases the tribomechanical performance. In general, the use of Co and Cr metallic binders seems a useful strategy to promote the overall properties of the SPS-ed WC.