Microstructure Mechanical Properties Research Articles

Comparative study of microstructural evolution and mechanical properties in friction stir processed, reinforced friction stir processed, and heat-treated reinforced friction stir processed Al composites

The development of friction stir welding (FSW) created the basic foundation for friction stir processing (FSP). This process entails refining the local microstructure and achieving the localised plastic deformation due to the stirring effect of the tool, which may involve adding additional filler material as required. The rotating tool involved in the process has a shoulder and pin responsible for heat generation for plastic deformation and localised mixing. The rotating tool is inserted and traversed on the desired surface, tailoring the material properties. The tool’s exposure to the surface causes localised plastic deformation and thermal gradient, and microstructural changes occur locally. The present investigation uses Friction Stir Processing (FSP) to fabricate an aluminium metal matrix composite. Recently, the use of aluminium alloy has been replaced by composites because of their increased mechanical and physical properties (specific properties). The experiment leads to manufacturing an aluminium metal matrix composite using aluminium oxide, boron carbide and commercially pure copper dust. Later, the effect of heat treatment on the respective metal matrix composite is studied. A comparative study among three different types of FSP techniques viz. FSP, Reinforced FSP, and Heat-treated Reinforced FSP have been performed. The tool revolution speed (RPM) and tool traverse speed of 400 RPM and 10 mm/min had been implemented, respectively. The T4 Heat-Treatment cycle was used during the current investigation. This investigative study was performed to analyse the changes in grain sizes and hardness values at the stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and on the base materials (BM) of the samples. The reinforced FSP metal matrix composite (MMC) showed an 81.26% increase in the micro-hardness value (HV) compared to the base metal. Further on analysing the microstructures, the reinforced FSP composite showed a 65.20% reduction in grain size. Moreover, the Heat-Treated sample showed an increase in the micro-hardness value by 99.8%.

Microstructural Evolution, Mechanical Property, and Strengthening in a Lightweight Mg-Y-Zn-Mn Alloy Fabricated by Multidirectional Forging and Hot Rolling

Microstructural Evolution, Mechanical Property, and Strengthening in a Lightweight Mg-Y-Zn-Mn Alloy Fabricated by Multidirectional Forging and Hot Rolling

3D-Printed high performance PEEK/CF-PEEK polymer composites—An investigation on microstructural characteristics and mechanical performance

This study investigates the microstructural characteristics and mechanical properties of 3D-printed polyether ether ketone (PEEK) and carbon fiber-reinforced PEEK (PEEK CF20) composites. Using a specifically optimized 3D printing process parametric condition, samples of pure PEEK and PEEK CF20 (containing 20% carbon fiber) were fabricated. Mechanical properties were estimated by tensile, flexural, and interlaminar shear strength (ILSS) tests, performed as per ISO and DIN standards. Results indicated that PEEK CF20 exhibits significantly enhanced mechanical properties compared to pure PEEK. The tensile strength of PEEK CF20 was 81.069 MPa, compared to 76.070 MPa for pure PEEK. Maximum load values were 1456.608 N for PEEK CF20 and 1286.137 N for pure PEEK, while ILSS values were 15.76 MPa for PEEK CF20 and 11.82 MPa for pure PEEK. Microstructural analysis through field emission scanning electron microscopy (FESEM) revealed that PEEK CF20 had better fiber-matrix bonding and fewer defects compared to pure PEEK.

Investigating the combined influence of rolling, ECAP processes, and intermediate annealing on mechanical and microstructural properties of beryllium copper alloy 25

A beryllium copper alloy 25 underwent a series of processing steps involving rolling, equal-channel angular pressing (ECAP), and subsequent annealing. This study delved into the combined effects of these processes on the microstructural evolution and mechanical properties of the deformed beryllium copper alloy 25. The investigation utilized optical microscopy, scanning electron microscopy, transmission electron microscopy, room temperature Vickers hardness testing, and tensile testing. The findings reveal a notable enhancement in the strength of the beryllium copper alloy 25 while preserving its ductility after subjecting it to six ECAP passes followed by annealing at 210 °C for 20 min, applied to the rolled sample. Initially, an increase in number of ECAP passes resulted in a gradual reduction in grain size and a weakening of the alloy's texture. This led to an increase in ultimate tensile strength up to 333.5% without reducing in percentage elongation. Notably, after six ECAP passes, the average grain size decreased from 48 µm to less than 1 µm, yielding exceptional comprehensive mechanical properties with significantly improved strength and plasticity. The resultant material exhibits promising potential for fabrication into bars and plates for a wide range of applications in aerospace and marine industries.

Co-evolution of M23C6 precipitates and cavities in a boron-free Ni-based alloy GH3617 under high-temperature He ion irradiation: Effects on cavity swelling and mechanical properties

Ni-based alloys are promising materials for advanced nuclear reactors operating at high temperatures due to their exceptional resistance to high temperatures and corrosion. Understanding the synergy of phase stability and helium effects is crucial for assessing the long-term performance and reliability of these alloys in advanced nuclear reactors. This study has investigated the co-evolution behavior of M23C6 precipitates and cavities in a boron-free solid solution strengthened Ni-based alloy GH3617 under high-temperature He ion irradiation, and its impact on alloy swelling and mechanical properties, by He ion irradiation experiments with the highest fluence of 1 × 1017 He/cm2 up to 800 °C. Transmission Electron Microscopy (TEM) and Nanoindentation are employed to investigate microstructural evolution and mechanical properties, respectively. The findings show that at room temperature and 500 °C, cavities and dislocation loops were the dominant irradiation defects, whereas at 800 °C, the density of cavities and dislocations reduced while the formation of M23C6 precipitates increased. These precipitates act as effective trapping sites for He and point defect, leading to cavity formation at the interfaces or within the precipitates. Moreover, increased irradiation fluence accelerates the co-evolution process, resulting in an increase in the density and size of both precipitates and cavities, ultimately leading to enhanced swelling. The {111} planes are favored interfaces between intragranular M23C6 precipitates and the matrix due to their minimal misfit, while the preferred interface planes between cavities with octahedral or cubo-octahedral shapes and the precipitate/matrix are also {111}, owing to their lower surface energy as well. The co-evolution of cavities and precipitates was found to influence mechanical properties, resulting in an irradiation hardening effect at lower fluences, while softening at higher fluences. This study provides novel insights into the degradation mechanisms of Ni-based alloys under coupling effect of He and high-temperature irradiation.

Microstructure and strength of cold-drawn large strain Fe35Ni35Cr20Mn10 high-entropy alloy

The Fe35Ni35Cr20Mn10 high-entropy alloy wires can achieve a large strain of 8.73 and a section reduction ratio of 99.98 %,and possess a high strength of 1868 MPa via traditional wire drawing. The microstructure evolution and mechanical properties of cold-drawn Fe35Ni35Cr20Mn10 high-entropy alloy are characterized by microstructure observation and tensile test. The results showed that The Fe35Ni35Cr20Mn10 HEA has excellent plastic forming capacity and excellent phase stability during plastic deformation. The Fe35Ni35Cr20Mn10 HEA has excellent continuous drawing ability, the main deformation mechanism is the plane slip and cross slip of the dislocation and the dynamic recovery of the sublamellar layer make the lamellar structure maintain a dynamic equilibrium state, and the lamellar thickness is basically unchanged to support the continuous plastic deformation under high strain conditions. The dynamic balance of coarsening and refining of lamellar structure in the process of plastic deformation is mainly due to the merging of HEA lamellar caused by the movement of trigeminal node induced by strain. Texture evolution showed that the <111> and <100> fiber textures were the stable texture component and the texture component content remained unchanged even under further increased strain. The Fe35Ni35Cr20Mn10 high-entropy alloy wire with high strain of 8.73 possesses excellent strength, and its tensile strength is 1868 MPa at room temperature, which has the largest strain. The dislocations proliferation, lamellar structure refinement and texture strengthening lead to high strength of the Fe35Ni35Cr20Mn10 high-entropy alloy wire.

Improved mechanical and tribological properties of (TiZrHfNbTa)C with the addition of silicon carbide whiskers

Dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with up to 10 wt % SiC whisker were prepared by spark plasma sintering. The influence of SiCw on the microstructure development, mechanical and tribological properties has been investigated. Nanohardness of HEC and SiCw phases varied between 38 GPa and 40 GPa, and indentation modulus of elasticity was ∼605 GPa. The hardness of the composites increased from 22 GPa to 27 GPa and indentation fracture resistance from 3.55 MPa m1/2 to 4.59 MPa m1/2 with increasing SiCw content. The main toughening mechanisms were crack deflection, crack branching, and crack bridging. The system HEC +5 wt% of SiCw was found to possess the highest bending strength of 623 ± 25 MPa. The composites exhibited similar coefficients of frictions with around 0.3 and wear rates approximately 1.50 × 10−6 mm3/N⋅m at 5 N and 2.66 × 10−6 mm3/N⋅m at 25 N with positive influence of SiC phase on the wear mechanisms.

Evolution of microstructure and tensile behavior in an interstitial strengthened high entropy alloy

The microstructural evolution and mechanical properties of Fe61.5Cr17.5Ni11.5Al8C1.5 high-entropy alloys (HEAs) were investigated to establish an optimal set of annealing conditions that would result in reasonable recrystallized fractions across the different temperatures and durations. The evolution of the microstructure was analyzed, tracking the transformation from the rolling texture to the recrystallization texture, as well as any phase transformations that occurred. The grain size distribution, overall microstructural features, and the effects of annealing temperature and time on the tensile properties of the HEAs were examined and discussed. The alloy was subjected to cold rolling and subsequent annealing treatments, revealing a single FCC phase after homogenization at 1260 °C. The cold-rolled samples retained the FCC structure at lower annealing temperatures (400 °C and 500 °C) but underwent a phase transformation to BCC at higher temperatures (600 °C to 900 °C). Microstructural characterization demonstrated that cold rolling introduced a high density of dislocations, while annealing facilitated recrystallization and grain growth. The tensile tests indicated that HEA samples exhibited a yield strength of 570 MPa and ductility of ∼36 % with large grain size after a long annealing at elevated temperature. In contrast, after being heat-treated at 1200 °C for 2 min, HEAs restrict FCC-to-BCC phase transformation and exhibit small grain size (3.2 µm) with M23C6-like carbide precipitation in the FCC matrix. Smaller grains provide additional boundaries, which restrict dislocations to bypass these boundaries. While carbide precipitates at grain boundaries and inside grains, it strengthens the material by pinning grain boundaries and restricting dislocation movement, resulting in a yield strength of 610 MPa and ductility of ∼41 %.

On the heterogeneous microstructure and strengthening mechanisms in a laser welding AZ80 magnesium alloy

This study investigates the microstructural characteristics and mechanical properties of a laser welded AZ80 magnesium alloy. The welding process led to the formation of coarse-grained fusion zone (FZ), where a secondary phase formed continuous network. Mg17Al12 precipitation and coarsening of grain boundaries occurred in the heat affected zone. The welded joint exhibited excellent mechanical properties with a yield strength of 202 MPa and a joint efficiency of 92%. The microstructure analysis via EPMA and EBSD in conjunction with synchrotron X-ray diffraction analysis reveals that precipitates and increased dislocation density in the fusion zone are primary strengthening mechanisms for the laser welded AZ80 Mg alloy.

Microstructural evolution and tribological behavior of HVAF sprayed FeCoNiCrMox (x=0, 0.2, 0.5, 1) coatings

High entropy alloy coatings with a unique microstructure and excellent mechanical properties show significant potential for development in friction-related applications. In this study, the microstructure, phases, hardness and tribological behavior of FeCoNiCrMox (x = 0, 0.2, 0.5, 1.0) coatings fabricated by HVAF spraying were investigated. The coating changes from a single FCC structure (x=0, 0.2) to a dual phase structure of FCC and σ (x=0.5, 1), accompanied by an expansion in the segregation regions of Cr and Mo elements. The hardness of coatings increased with higher Mo content. Tribology tests were carried out at room temperature using Si3N4 ceramic and GCr15 steel as counterfaces. The results demonstrate that, when paired with GCr15, the wear resistance of the coatings scale proportional with hardness. However, when paired with Si3N4, the coating wear rate exhibits an initial increase followed by a decrease. Notably, the FeCoNiCr and FeCoNiCrMo0.2 coatings exhibited milder friction and wear behavior when in contact with Si3N4 compared to GCr15 steel, attributed to the dominant oxidative wear. This study provides new insights and directions for the design of customized high-entropy alloy coatings based on specific friction conditions.

Optimization of microstructure and high-temperature mechanical properties of Ti4822/Ti2AlC composites through multiple solution-aging treatments

In this paper, a Ti-48Al-2Cr-2Nb (Ti4822, at%) based composite with uniformly distributed Ti2AlC nano-micro precipitates was prepared by powder metallurgy followed by a multiple solution-aging treatment. Multiple solution treatments eliminated the equiaxial γ grains in the sintered composites and refined the coarse-grained primary Ti2AlC phases, resulting in a fully lamellar microstructure with fine Ti2AlC precipitates embedded between the α2/γ lamellae. The high-temperature ultimate tensile strength of the heat-treated Ti4822/Ti2AlC composites reached 543 MPa at 800 ℃, and the elongation was 7.7 %, increased by 9.7 % and 0.8 % correspondingly compared to that of the sintered composite. The enhancement of the properties of Ti4822/Ti2AlC composite in the heat-treated state was due to the elimination of γ grains in the microstructure to transform the full lamellar microstructure on the one hand, and the refinement and dispersion of agglomerated Ti2AlC precipitates on the other hand. This study provided a valuable reference for the refinement and dispersion of the second phase in TiAl composites.

Microstructural and mechanical properties evolution for 9Cr[sbnd]Si heat resistant steel deposited metals under different heat treatment states

To develop the matched filler metal for the structural materials in Generation IV lead-cooled fast reactor (LFR), the microstructural evolution and mechanical property variation of 9CrSi heat resistant steels deposited metals were investigated both for the as-welded and as-aged (at 550 °C) weld metals. The experimental results indicate two precipitates in the as-welded deposited metals: the bigger M23C6 and the smaller MX. Si facilitates the nucleation of M23C6. The chain-like precipitates (consisting of M23C6) form at the boundaries of prior austenite and martensitic laths in high-Si specimens. They deteriorate not only the strength but also the impact energy. Meanwhile, a few δ ferrites form in high-Si deposited metal deteriorating the impact energy. Precipitates tend to nucleate at the interface between the δ ferrite and the martensite after aging. New types of precipitates (Mo-rich M6X and Laves) with rapid coarsening rate form in as-aged high-Si deposited metals as time increases. Coarse precipitates deteriorate the pinning effect, which causes the recovery of laths and dislocations. Subgrain pinned by M23C6 forms in deposited metals with post-weld heat treatment (PWHT) during aging. The structure hinders the formation of M6X and facilitates the formation of nano-sized MX. Therefore, the mechanical properties of deposited metals with PWHT are stable during long-term (up to 10,000 h) aging treatments.

Effects of microstructure and phosphorus segregation on tensile properties of friction stir welded high phosphorus weathering steel

Defect-free sound joints of high-phosphorus (0.094 wt%) weathering steel (SPA-H) were successfully fabricated using friction stir welding (FSW). This study examines the microstructural evolution and mechanical properties of joints produced at different FSW parameters. Tensile tests of the joints revealed that fractures occurred in the base metal (BM) region, indicating almost 100 % welding efficiency. Furthermore, the stir zones (SZ) demonstrated a marked improvement in tensile properties. Particularly, at the rotation rate of 80 rpm and axial load of 45 kN condition (below A1), the microstructure featured ultra-fine ferrite and cementite, resulting in high hardness (270 HV) and tensile strength (704 MPa) in steel with just 0.08 wt% C, while maintaining nearly 80 % of the total elongation of BM. However, the SZ at 80 rpm exhibited an unusual decrease in local elongation despite the fine ferrite grain size and cementite presence. Electron probe microanalysis (EPMA) and nano-hardness revealed pronounced phosphorus segregation in the ferrite region and significant localized hardness disparities induced by the segregation behavior. The strain concentration at the interfaces between these regions during the tensile process leads to crack initiation and rapid propagation. The negative factor caused by the phosphorus segregation accelerates the failure of the specimen during the necking stage and ultimately shows decreased local elongation.

Influence of laser power and scanning speed on microstructure evolutions and mechanical properties of the SLM fabricated Al-Mg-Mn-Sc-Zr alloy

The Al-Mg-Mn-Sc-Zr alloy is fabricated by selective laser melting (SLM). The influence of laser power and scanning speed on microstructure evolutions and mechanical properties is studied in this research. Results indicate that increasing laser power can refine grain structures and reduce anisotropy on the printing surface. However, the increase in laser power will enhance the residual stress inside the alloy, leading to a decrease in elongation. The scanning speed affects the molten pool energy input and cooling rate. When the scanning speed is between 750mm/s-1250mm/s, the alloy achieves a good grain refinement effect and weak texture strength. In addition, there exists a large number of nano-scaled Al3(Sc,Zr) particles precipitated during solidification and the subsequent annealing process, which can significantly enhance yield strength of the alloy. Overall, the Al-Mg-Mn-Sc-Zr alloy has a wide SLM forming window. When the laser power ranges from 200W to 250W, the scanning speed ranges from 750mm/s to 1250mm/s, and the volume energy density ranges from 80J/mm3 to 130J/mm3, the Al-Mg-Mn-Sc-Zr alloy can obtain good formability and mechanical property.

Tuning austenite stability through prior microstructure control in a low-alloy Q&P steel

Quenching and partitioning (Q&P) processing is a widely accepted heat treatment methodology for creating high strength steels consisting of ferrite, martensite, and austenite, while maintaining relatively low manufacturing costs. Though the research on effects of prior microstructure is limited, an understanding of the heat treatment response of different starting microstructures is critical to processing and creating steels with complex microstructures that contain retained austenite and may afford opportunities to further optimize properties. This study investigates the influence of starting microstructure (ferrite/pearlite versus martensite) and prior levels of cold work (38 verses 58 %) on the microstructural development and mechanical properties of a 0.2 C-2.0 Mn-1.5 Si (wt.%) steel exposed to Q&P processing. Samples with a starting martensitic microstructure resulted in higher retained austenite fractions and a more homogeneous microstructure after Q&P processing compared to a starting microstructure of ferrite-pearlite. Starting martensitic microstructures also displayed higher work hardening rates and higher uniform elongations. Larger cold reductions saw accelerated dissolution kinetics and austenite formation during intercritical annealing, resulting in more similar final microstructures from the ferrite-pearlite and martensitic starting microstructures. The results presented here indicate that varying prior processing can be a route to manipulate and control austenite stability in a Q&P processed steel.

Influence of electric pulse on microstructural characteristics and mechanical properties of cast AZ91D magnesium alloy

Influence of electric pulse on microstructural characteristics and mechanical properties of cast AZ91D magnesium alloy

A biodegradable Zn–Se alloy with potent osteogenicity, antibacterial ability, and antitumor efficacy for bone-implant applications

Biodegradable zinc-selenium (Zn-Se) alloys are expected to become a competitive material for implantation into hard tissues due to the antitumor function of Se in cancer prevention and treatment. However, adding Se to Zn to create Zn-Se alloys is a challenging task due to the high volatilization of the monomeric Zn and Se elements, and the immiscibility of Se and Zn. In this study, we have successfully prepared biodegradable Zn-xSe (x = 0, 1, 3, and 5 at. %) alloys using ultrahigh pressure sintering, which effectively suppressed the volatilization of monomeric Zn and Se elements and increased the solid solubility of Se in Zn. The microstructure characteristics, mechanical properties, degradation rate, anticoagulant, osteogenic ability and antitumor properties of the ultrahigh pressure sintered (UPS) Zn-Se alloys were systematically evaluated. The microstructure of the UPS Zn-Se alloys consisted of Zn matrix phases, Zn(Se) solid solution, and ZnSe second phases formed around the elemental Se phase. The UPS Zn-1Se showed the highest compressive yield strength of ∼205.8 ± 2.3 MPa, a fracture strain of 16.4 %, a degradation rate of 44.6 ± 0.6 μm/y, effective antibacterial ability against S. aureus, effective antitumor activity against Cal-27 carcinoma cells, dramatic osteogenic ability and excellent biocompatibility toward pre-osteoblast MC3T3-E1 cells. Overall, the addition of 1 at. % Se to Zn does not affect the growth of normal cells, but effectively inhibits the growth and reproduction of tumor cells and the Zn-1Se alloy is promising for orthopedic applications due to its unique combination of mechanical and biological properties.

Understanding low-temperature microstructure and mechanical properties of a newly designed ultra-low carbon medium manganese steel

This study examines the relationship between microstructure and low-temperature mechanical properties of newly designed medium manganese steel with ultra-low carbon, low-Ni content. The microstructural features crucial for impact toughness were identified. The study indicated that post-annealing at 650 °C for 30 min endowed the steel with superior low-temperature mechanical properties, namely tensile strength of 914 MPa, total elongation of 37.2 %, and impact energy of 187 J at −60 °C. With longer intercritical annealing durations, reverted austenite transitioned from a film-like to a blocky morphology, with an increase in both volume fraction and size, accompanied by a substantial decrease in stability. High-stability reverted austenite contributed to sustained work hardening by facilitating a continuous Transformation-Induced Plasticity (TRIP) effect during steel deformation, thereby significantly enhancing the low temperature tensile properties of the steel. Furthermore, enhanced stability of reverted austenite was identified as the pivotal microstructural factor influencing impact toughness.

Effect of various interlayers in NiTi to TC4 dissimilar joints by magnetic pulse welding

Magnetic pulse welding (MPW) has gained wide attention recently. In this paper, the connection of NiTi/TC4 dissimilar materials was achieved by adding pure Al, Cu, and Ni interlayers using MPW technology, and microstructure characterization and mechanical property tests were conducted to evaluate the joints. The results show that the atomic diffusion in the welding process plays a key role in the interface formation process. The interfacial morphology of joints consists of wavy and flat interfaces, and the mechanical interlocking of the wavy interface gives the joints excellent mechanical properties. The joints with the pure Al interlayer have the best mechanical properties, and the tensile shear force is 2.168 kN; the fracture forms of joints with different interlayers are all ductile fractures. In addition, the calculation results of the edge-to-edge crystal matching model show that the side with the high interface mismatch rate is where the joint failure problem occurs frequently.

Microstructure evolution and mechanical properties of tungsten alloy prepared by laser directed energy deposition

Tungsten heavy alloys (WHAs) are widely applied across military, medical, and other advanced industries. Laser-directed energy deposition (LDED) is an innovative approach to fabricate WHAs with intricate microstructures. This study explored the manufacturing processes and forming characteristics of three distinct tungsten alloy compositions to elucidate the microstructural formation mechanisms and performance evolution of WHAs prepared by LDED. Electron backscatter diffraction analysis revealed the occurrence of heterogeneous nucleation and dendritic precipitation in supersaturated solid phases across different alloy compositions. By applying the drag force equation derived from the two-phase flow theory, the Gaussian energy distribution inherent to the LDED process, and the low flowability of WHAs, this study reveals the microstructural layering mechanisms within LDED-produced samples. Through process optimization, 90W samples that exhibited an ultimate tensile strength of 1093MPa and elongation of 16.8% were obtained. In situ mechanical testing revealed that the reduced elongation of the WHAs produced by LDED is due to their unique fracture mechanism driven by the interconnection of cracks between fractured tungsten particles. However, by incorporating smaller W particles and optimizing the gap ratio, the stress concentration can be effectively mitigated and crack propagation can be curtailed, thereby significantly enhancing elongation.