Impact Toughness Behavior Research Articles

Microstructural Dependence of the Impact Toughness of TP316H Stainless Steel Exposed to Thermal Aging and Room-Temperature Electrolytic Hydrogenation.

This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

Lignin-polylactic acid biopolymer blends for advanced applications – Effect of impact modifier

In this study, lignin underwent chemical modification via acetylation of hydroxyl groups to enhance its interfacial connection with poly (lactic acid) (PLA). Further enhancement of the blend was attained by adding an impact modifier, Biomax Strong. Incorporating Biomax Strong into PLA-lignin blends resulted in improvements in material characteristics, particularly in impact strength and thermal stability. This blend exhibited a unique set of mechanical properties, characterized by a reduction in tensile modulus as well as an increase in ductility. This will allow a more versatile use of PLA in various applications. The observed improved impact strength highlights the synergistic effect of stress redistribution within the PLA matrix contributing to widespread applications of PLA based composites. This can clearly be observed for the compound containing PLA and 15 wt.% lignin, where the impact strength was approximately 15 kJ/m2. With the addition of 5 wt.% impact modifier, the impact strength increased by 60 %, reaching approximately 25 kJ/m2. This synergy effect reinforces the overall structure, improving the impact toughness behavior. The combination of Biomax Strong and lignin not only address the limitations of PLA but also introduces new opportunities for applications requiring a balance of impact strength, ductility, and thermal stability. These advancements indicate a promising future for composite materials in various applications.

Effect of equal-channel angular pressing on microstructure, aging kinetics and impact behavior in a 7075 aluminum alloy

Among the precipitation hardenable 7xxx series aluminum alloys, AA7075 alloys (one of the most important engineering alloys) due to their low density (lightweight), high toughness and strength, and enhanced fatigue behavior have been used over the years in aerospace, aircraft, automotive, construction and marine applications. In the present study, the influence of the artificial aging through conventional heat treatment (i.e., precipitation hardening) and the thermomechanical treatment (equal-channel angular pressing (ECAP) + post-ECAP aging) on the quasi-static tensile, impact toughness and precipitation behavior as well as on the microstructure of an AA7075 alloy is investigated systematically. The results indicate that the ECAP process as well as post-ECAP aging result in considerably increased strength and hardness of the AA7075 alloys because of the superimposed effects of grain boundary strengthening (Hall-Petch relation), strain hardening (by means of the increased dislocation density) and precipitation hardening (due to the fine precipitates formed in Al matrix). Multi-pass ECAP processing has been found to result in a considerable decrease of the impact toughness (from 15.3 J·cm−2 to 7.6 J·cm−2) associated with the failure mode (i.e., ductile-to-brittle transition) of the AA7075 alloys, whereas the artificial peak aging leads to a marked improvement (∼67 %) in the impact toughness in ECAPed conditions. Moreover, the ECAP process noticeably accelerates the precipitation kinetics of AA7075 alloys: The peak aging time in the ECAPed alloy is reduced significantly – from 30 h to 4 h. The results of the present study provide a deeper understanding of the combination of ECAP and heat treatment, and their effect on the fracture mode and toughness under impact loading, the aging kinetics and the microstructural evolution of an AA7075 alloy.

Investigations of microstructure, impact toughness, and fatigue failure behavior of bulk UFG Al–Li 8090 alloy processed by multi-axial forging

Investigations of microstructure, impact toughness, and fatigue failure behavior of bulk UFG Al–Li 8090 alloy processed by multi-axial forging

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions.

Effect of Aging on Impact Toughness and Fracture Behavior of Three Wrought Aluminum Alloys

Herein, the effect of the aging state on the impact toughness of three typical wrought Al alloys (7075, 2024, and 6A01) is investigated. At room temperature, the fracture mode of the three aluminum alloys at different aging states is a ductile transgranular fracture. At low temperatures, high‐strength aluminum alloys exhibit a mixture fracture of transgranular and intergranular, while medium‐strength aluminum alloys are still dominated by transgranular fractures. The effect of the aging state on the impact toughness of aluminum alloys was analyzed based on the deformation mechanism and morphology near grain boundaries. The underaged state with planar slip dislocations exhibits good plasticity and work‐hardening ability, which reduces the strain localization caused by dislocation plugging and thus improves the impact toughness of the alloy. Furthermore, the fine grain boundary precipitates and the narrow precipitation‐free zone of the underaged increase the uniform deformation capacity near the grain boundaries and inhibit the initiation and propagation of cracks. Compared with high‐strength aluminum alloys, medium‐strength aluminum alloys exhibit higher impact toughness due to the formation of a larger plastic zone and shear lip area during impact.

Study on impact toughness and fracture behaviour of an Al–Mg-Sc alloy

The impact toughness and fracture behavior of an Al–Mg-Sc alloy at two different temperatures were investigated. The results reveal that the maximum load at room temperature is slightly higher than that at 120 °C. The total impact displacement for complete fracture of the alloy at room temperature is shorter than that at 120 °C. For fracture, the shear lip area of the room temperature sample is smaller than that of the 120 °C sample. Also, the percentage of intergranular fracture at room temperature is higher than that at 120 °C and the degree of plastic deformation was more severe for the 120 °C sample.

Application of ceramic nanoparticles in microstructure manipulation and simultaneously strengthening toughness and wear resistance of tool and die steels

Simultaneously improving the wear resistance and toughness can extend the service life of steel. In this study, nano-TiC-H13 steel was successfully fabricated by pre-dispersion nano-TiC/Al master alloy in conventional casting to simultaneously improve the wear resistance and toughness. The influence of nano-TiC ceramic particles on the microstructure, tensile properties, impact toughness, and wear behavior under the synergistic effect of high load and temperature was explored. Results indicated that nano-TiC ceramic particles can effectively refine the microstructure and promote the precipitation of the finer carbides, which significantly improved the properties of steel. The no-notch impact toughness (380.2 J/cm2), U-shaped notch impact toughness (36.6 J/cm2), and yield strength (1440 MPa) of nano-TiC-H13 increased by 12.7%, 31.2%, and 8.2%, respectively, compared with that of H13. Furthermore, the volumetric wear rate (8.2 × 10−10 m3/m) of nano-TiC-H13 under 450 °C and 30 N is decreased by 28.6% in contrast with H13. The high strength and plasticity in nano-TiC-H13 can resist the intrusion of debris and reduce plastic deformation. This work provides an innovative approach for the simultaneous improvement of the wear resistance and toughness of steel.

Effect of Ni additions on microstructure, interfacial diffusion behavior and properties of Fe-based/B4C composite coating by vacuum cladding

In order to improve the hardenability and toughness of Fe-based/B 4 C composite coatings, which were bonded on ASTM 1045 steel by vacuum cladding, nNi ( n = 0, 1, 3, 5, weight %) were added into the coatings. The influences of Ni additions on the microstructures, interfacial diffusion behavior, impact toughness and three-body abrasive wear behavior of composite coatings were investigated systematically. The results indicated that coatings were completely fused with steel substrate without micro-defects. When the amount of Ni was increased, the activity of the C atom on the coating side was enhanced, the decarburization zone near the interface disappeared, and the metallurgical bonding state of interface was strengthened. Furthermore, the increment of Ni improved the hardenability of coating and promoted the transformation from pearlite to martensite in the matrix structure of the coating. The impact toughness of the coating samples also increased with the increment of Ni additions, and reached the maximum of 4.8 J/cm 2 at 5Ni sample. The three-body abrasive wear test implied that when 3 wt% Ni was added to the coating, the mass loss was 0.14 g, which was much lower than that of other samples and exhibited the best wear resistance. The wear mechanism of coatings changed from partial plastic cutting and fatigue spalling to single fatigue spalling. • Ni addition strengthens the metallurgical bonding state of the coating interface. • The increase of Ni addition improves the hardenability of the coating matrix. • Ni addition improves the impact toughness and wear resistance of the coating.

Charpy impact toughness of Cu–Fe–Mn-based immiscible medium-entropy alloys

Impact toughness at ambient and cryogenic temperatures was investigated with systematic fracture analyses for CuFeMn and Al15(CuFeMn)85 (at%) immiscible medium-entropy alloys. These two types of alloys exhibited different impact toughness behavior at different temperatures, while exhibiting higher impact toughness values than those of dual-phase steels with a similar strength level.

Joint-design effect on the metallurgical and mechanical behavior of duplex stainless steel welds

In the present investigation, the influence of joint design on the microstructure and the mechanical properties of SAF 2205 duplex stainless steel welds are reported. Plates with two different joint designs were welded using the gas tungsten arc welding process. To investigate the sole effect of joint design, the joints were designed in such a way that both joints have similar groove volumes. The weldments were investigated for microstructural characterization, ferrite content, and microhardness study; later, they were subjected to Charpy V-notch impact test, transverse tensile test, and fatigue testing in order to investigate the mechanical performance. Both the weld joints were able to achieve 100% joint efficiency in view of the transverse tensile test. Different weld joint configurations demonstrated the influence of the differential heat dissipation characteristics of the joints, evident from different morphological features revealed through optical microscopy of the weldment. The welding affected the ferrite(α)-austenite(γ) ratio of the weld metals and differed the welds in terms of ferrite content in the root and weld pass. The weld zone of the U-joint showed a 65.8% ferrite fraction and thus showed 18% more hardness as compared to the V-joint, while the V-joint had the highest yield stress of 617 MPa. The study revealed that the U-joint performed better in comparison to the V-joint in terms of microhardness, impact toughness, and fatigue behavior. The U-joint could resist around 15% more fatigue cycles than the V-joint under high cycle fatigue.

Influence of SiC particles and post-heat treatment on the properties of Ti-6Al-4V-based surface nanocomposite fabricated by friction stir processing

Friction stir processing was used to successfully fabricate a Ti-6Al-4V-based surface nanocomposite with a uniform dispersion of SiC reinforcement particles (FSP). Reinforced SiC particles showed good interfacial bonding with the matrix material. Microstructural modification after FSP and post-FSP heat treatment in terms of grain refinement and reinforcement behavior of SiC particles was investigated using an optical microscope (OM), scanning electron microscope (SEM), and electron back-scattered diffraction (EBSD). Microhardness test, Charpy impact test, and pin-on-disc wear test were carried out to measure the hardness, impact toughness, and tribological behavior of fabricated surface composites, respectively. Fully β-transformed microstructure comprising a mixture of fine basket-weave lamellar α/β and ultrafine martensite α′ was evident in the FSPed stir zone. The incorporation of SiC reinforcement resulted in additional microstructure refinement during FSP due to Zener pinning and particle-stimulated nucleation (PSN) caused by SiC particles. Nearly two-fold improvements in microhardness and wear resistance, whereas a slight but noteworthy improvement in impact toughness was observed. Enhancements in mechanical and wear properties were primarily ascribed to the combined effect of microstructural refinement, formation of martensite (α′), and dispersion strengthening (Orowan Mechanism).

A critical review on the effects of process-induced porosity on the mechanical properties of alloys fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is an emerging additive manufacturing technique that is currently adopted by a number of industries for its ability to directly fabricate complex near-net-shaped components with minimal material wastage. Two major limitations of LPBF, however, are that the process inherently produces components containing some amount of porosity and that fabricated components tend to suffer from poor repeatability. While recent advances have allowed the porosity level to be reduced to a minimum, consistent porosity-free fabrication remains elusive. Therefore, it is important to understand how porosity affects mechanical properties in alloys fabricated this way in order to inform the safe design and application of components. To this aim, this article will review recent literature on the effects of porosity on tensile properties, fatigue life, impact and fracture toughness, creep response, and wear behavior. As the number of alloys that can be fabricated by this technology continues to grow, this overview will mainly focus on four alloys that are commonly fabricated by LPBF—Ti-6Al-4 V, Inconel 718, AISI 316L, and AlSi10Mg.

Influence of Fly Ash and Emery based particulate reinforced AA7075 surface composite processed through friction stir processing

The novel friction stir technology is adopted in modern automotive industries to meet the desired properties like hardness, impact toughness and tribological behaviour over the conventional techniques like stir casting, compo casting, squeeze casting, electroplating and infiltration methods. AA7075 surface composites fabricated with different volume fractions of fly ash and emery particles is said to enhance the aforementioned properties. The composites are processed through friction stir process (rotational speed −1200 rpm, transverse speed – 56 mm/min, tool tilt angle – 2 °). During characterization, the Microstructural examination of surface composites depicts fine and homogenous distribution of reinforcements in the friction stir process region owing to severe plastic deformation and dynamic recrystallization process. Substantially, good interface is formed between the reinforcement particulates and base substrate. Inclusion of Fe3O4, Al2O3 and SiO2 constituents through fly ash and emery reinforcements associated with the homogenous dispersion strengthening mechanism favours for the superior hardness of surface hybrid composite specimen 50E50FA. Decremented grain size and load bearing capacity of the reinforcements is beneficial for the crack propagation resistance that enhances the impact toughness behaviour (17.4 J/cm2) of the same specimen. Wear rate of the specimens are evaluated through pin on disc tribometer. The decrease in the wear rate of hard specimen 50E50FA is observed due to the reduced contact area between its surface and counter disc. The morphology of worn specimens using SEM analysis shows the combined abrasive and adhesive wear as the worn mechanism.

Effect of filler metal combination and post weld heat treatment on pitting corrosion and impact toughness of GTA welded AISI 410 SS joints

The Experimental work was done to investigate the role of pitting corrosion resistance as well as impact toughness behavior of gas tungsten arc welded martensitic stainless steel (AISI 410SS) joints. In this study 6 mm thick cold rolled AISI 410 stainless steel plates were utilized as a base plate. The welding was accomplished by using three different filler materials (Inconel 625, AISI 316 SS, and AISI 410 SS). The effect of post weld heat treatment (PWHT) and different filler materials on the pitting corrosion resistance, impact strength, and metallurgical performance of the GTA welded plates was investigated. The analysis for pitting and impact was studied in two circumstances first in as-received situation and second in PWHT situation.The outcomes formulated from research work indicates that the filler material composition induces the significant variation in the impact toughness along with pitting corrosion resistance of the experimental specimens. The minimum mass loss (1.3818 mg) of Inconel 625 filler welded joint indicates that the maximum resistance of the tested samples against the pitting corrosion. Furthermore, the PWHT helps to enhance the pitting resistance. The maximum impact toughness (average CVN 121.5 J) shown by (WJ-2P) in PWHT condition. The experimental study indicates that the Inconel 625 filler material helps to improve the pitting resistance and impact toughness of the welded specimens in as-received along with PWHT condition.

Effect of retained austenite on impact toughness and fracture behavior of medium carbon submicron-structured bainitic steel

The effects of retained austenite on the crack propagation behavior of a submicron-structured bainitic steel under impact fracture were studied. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron back-scattering diffraction (EBSD) were employed to characterize the size, distribution, and quantity of the matrix structure, and the microstructure of the impact fracture samples under conditions of two different bainitic processes. The retained austenite content at 280 °C was higher than that at 320 °C, and the microstructure appeared more uniform and refined, resulting in better impact toughness. The martensite + retained austenite constituents took part in the initiation of the fracture process and the crack ended at film of retained austenite. During fracture, a mixture of brittle, hard block martensite + retained austenite was easy to induced a crack opening. The effect of the transformation-induced plasticity of the retained austenite with a small block and film can effectively cause passivity and even inhibit crack growth.

Tailored ductility and strength for enhanced impact toughness of laser powder fusion built Alloy 718

Impact toughness of Alloy 718 built via laser powder bed fusion (LPBF) in as-built and thermally post-treated conditions were investigated. The effect of various stages in the thermal post-treatment, including stress relief, hot isostatic pressing, solution treatment, and aging on the microstructure, texture, ductility, hardness, and impact toughness were studied. The greatest impact toughness was found in the as-built Alloy 718 material, associated with the high ductility of the material. The ductility results were also inversely related to the hardness of the investigated materials. Where the material with the highest ductility had the lowest hardness etc. Anisotropy in the impact toughness behavior was present in the as-built and post-heat treated specimens, which was explained by the presence of texture in all of the investigated material. With the applied heat treatments, recrystallization occurred and the preferential crystal orientations were randomized, decreasing the texture. The thermal post-treating conditions rendered different types of microstructures, with various grain sizes. The carbide content remained the same for the three investigated thermal post-treating conditions.

Experimental studies on effect of post weld heat treatments on the pitting corrosion and impact toughness of GTA welded martensitic stainless steel joints

Objectives: The present experimental work investigates the effect of post weld heat treatments on the pitting, impact toughness and metallurgical properties of gas tungsten arc welded martensitic stainless steel joints. Methods/Statistical analysis: Martensitic stainless steel (AISI410 SS) cold rolled plates used as a base materials and welded using GTAW process with two filler materials (ER 304LSS and ER 410 SS for root pass and cover passes respectively). Three heat treatments namely annealing, quenching and plasma nitriding were given to the specimens. After the heat treatments the specimens were subjected to pitting corrosion test, impact toughness test, microhardness testing and microstructural examination. Findings: Pitting corrosion results under different heat treatments of the welds showed that the post weld heat treatment induces the significant variations in the pitting resistance. The maximum pitting resistance (minimum mass loss of 0.5108mg) was possessed by the weld with plasma nitriding treatment. The maximum energy absorption capacity of the welds of 62 Joules was obtained in the annealing treatment. The average microhardness values of 474VHN, 372 VHN, 492VHN and 559VHN was obtained in as welded condition, under annealing treatment, under quenching treatment and under plasma nitriding treatment respectively of the welded joints. Based on the micro-structural studies of the welded joint in as received and post weld heat treated conditions, the significant microstructural changes were observed in weld metal zones. Novelty/Applications: The present experimental study can beneficially be adopted for welding of martensitic stainless steel (AISI 410 SS) as it suggests the processing conditions to forecast the adequate pitting resistance, impact toughness and microhardness behaviour in similar service conditions. Keywords Pitting corrosion, impact toughness, post weld heat treatments, microhardness, microstructure, GTAW

Glass/Caryota urens hybridized fibre-reinforced nanoclay/SiC toughened epoxy hybrid composite: mechanical, drop load impact, hydrophobicity and fatigue behaviour

Glass/Caryota urens hybridized fibre-reinforced nanoclay/SiC toughened epoxy hybrid composites were prepared and characterized for its mechanical, drop load impact toughness, hydrophobicity, and fatigue behaviour. The rapidly increasing demand in polymer matrix composites proportionally increasing the environmental pollution and now this factor is a prime concern for all researchers worldwide. Thus, this research study is aimed to prepare and investigate the natural fibre-based polymer matrix composites by keeping the environmental factors in consideration. Replacing the synthetic fibres completely by natural fibre also not a great development since, the natural fibres are inferior in useful properties. Thus, in this present investigation, a hybrid form of glass-Caryota urens fibre was introduce as primary reinforcement for nanoclay-SiC toughened epoxy resin matrix. The mechanical and drop load impact results revealed that the addition of nanoclay and SiC into the epoxy resin improved the toughness together with glass-Caryota urens hybrid fibre. Moreover the addition of nanoclay and Caryota urens fibre in epoxy resin matrix improved the fatigue life cycle up to 55,182 for 50% of ultimate tensile stress. The hydrophobicity of silane-treated reinforcements gives marginal loss in water absorption compared to bare epoxy resin. These properties improved hybrid fibre epoxy composites could be used in many engineering applications.

Impact and Flexural Strength Prediction of Plain Concrete with Hybrid Fibres

An experimental study on effect of fibres in impact resistance and toughness behaviour of concrete is outlined in this paper. The investigation is carried out with steel, glass and polypropylene fibre in suitable combination. Hybrid Fibre Reinforced Concrete (HFRC) means advanced concrete form manufacturedby a specific fibre mix. The main motive for adding fibres in the composite is to control cracks, enhances the impact resistance and increases the toughness characteristics of the concrete. The impact test conducted using drop weight type test apparatus and the toughness value predicted using flexural testing machine as per the standards JSCE-SF 4 and ACI respectively. Experimental findings showed that the introduction of hybrid fibers into concrete can regulate the formation and propagation of cracks due to stress competently and increase concrete strength and impact strength.