Good Information Research Articles

Good Formability Despite High Accompanying Element Content of a Modified 20MnB4 Quenched and Tempered Steel

Abstract This article provides a comparative characterization of the mechanical and technological properties of a modified 20MnB4 quenched and tempered steel that are important for further processing. The aim of the modification was to represent the steel as a secondary steel with a significantly increased holding of accompanying elements to be assumed in the future. The aim was to check whether the increased hardening tendency due to increasing levels of accompanying elements can be compensated for by a targeted reduction in the Mn content without negatively affecting through-hardenability and tempering resistance. An industrially available steel was used as a reference condition. The results showed that the reduction of the Mn content contributed to the increase in cold formability, while a strong decrease in effective hardening depth occurred with an insignificant change in tempering behavior.

Effect of structural parameters on formability of auxetic weft-knitted fabrics based on zigzag structure

Auxetic materials are characterized by a negative Poisson’s ratio (NPR), which expands when stretched and shrinks when compressed. Due to the synclastic curvature of auxetics, they have good formability. These properties make them useful in applications requiring formability, such as composites, fashion and clothing, medical, protective, and sports fields. In this research, auxetic weft-knitted fabrics based on foldable structures were knitted. The effect of structural parameters including fabric pattern, yarn count, and loop length on the formability of auxetic weft-knitted fabrics was investigated and compared to plain weft-knitted fabric (Jersey). Auxetic fabrics with three distinct patterns and three different loop lengths were knitted using polyester yarns of varying three counts. Then, the formability experiment was conducted using the hemisphere mold, and the forming energy of fabric samples was obtained. The results demonstrated that auxetic fabrics exhibit superior formability to conventional (non-auxetic) fabrics, attributed to their synclastic curvature. Among the auxetic fabrics, those with larger zigzag angles, finer yarn counts, and larger loop lengths showed higher formability. These findings enhance the potential applications of auxetic fabrics in various industries such as medical and protective, emphasizing their ability to conform to complex shapes with minimal wrinkling.

Semi-Alicyclic Thermoplastic Polyimide Matrixes Based on Hydrogenated Pyromellitic Dianhydride and Asymmetrical 3,4′-Oxydianiline with Good Thermal Stability and Improved Optical Transparency

Thermoplastic polyimide (PI) matrixes, including PI-a (cc-34ODA) and PI-b (ct-34ODA) were prepared via the hot-pressing procedures of the resins derived from the 3,4′-oxydianiline (34ODA) and two alicyclic dianhydrides of 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride (ccHPMDA) and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride (ctHPMDA), respectively. The resins exhibited thermoplastic features with good formability at higher temperatures. The afforded semi-alicyclic PI sheets exhibited enhanced properties in comparison to commercially available, wholly aromatic thermoplastic PIs, such as PI-ref1, which are derived from 3,3′,4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-oxydianiline (44ODA), as well as PI-ref2, which is based on pyromellitic dianhydride (PMDA) and 4,4′-bis(3-aminophenoxy)biphenyl (mBAPB). In addition, the developed PI sheets exhibited high heat deflection temperatures (HDT) of 267.4 °C for PI-a and 268.6 °C for PI-b. There values were significantly higher when compared with those of PI-ref1 (Ratem® YS20, HDT: 239.0 °C), PI-ref2 (Aurum® PL450C, HDT: 238.0 °C), PI-ref3 (Ultem® 1000, HDT: 206.0 °C), PI-ref4 (Therplim® TO65, HDT: 180.0 °C), and PI-ref5 based on phthalic anhydride-terminated fluorinated PIs (HDT: 215.0 °C). In terms of mechanical properties, the current PI sheets showed superior flexural properties among the polymers with the flexural strength of 189.0 ± 11.7 MPa (PI-a) and 200.5 ± 4.2 MPa (PI-b), respectively. In addition, the PI sheets exhibited comparable compression properties, inferior impact strength, and tensile properties compared with the referenced PI counterparts. Basically, the PI-b sheet showed better comprehensive properties than those of the stereoisomeric PI-a analog.

Directed energy deposition combined with interlayer remelting for improving NiTi wear resistance by grain refinement

Directed energy deposition of NiTi coatings has received much attention, however, its performance is difficult to meet the increasing requirements in the engineering field. In order to refine the grains to improve wear resistance, a novel interlayer remelting method for fabricating NiTi alloys by directed energy deposition is proposed in this study. The influence of laser interlayer remelting parameters on lattice structure, phase transformation behavior, microstructure, crystallographic evolution, and microhardness was thoroughly analysed in comparison. Good formability is demonstrated after interlayer remelting, while the high energy density leads to microstructure refinement and eutectic regions are observed between dendrites. The grain size decreases with increasing remelting speed, which is due to the faster cooling rate having a greater degree of subcooling with more nucleation points. The faster interlayer remelting speed shows a higher microhardness (586 HV0.2) with higher wear resistance, which is attributed to its finer grain size and significant grain boundary strengthening. Reciprocating sliding wear experiments show that the wear resistance is improved after interlayer remelting, especially at a load of 30 N, the specific wear rate is 1.35 * 10−4mm3/Nm, which is only 47 % of that of the untreated sample. This study proposes a technique to achieve synergistic enhancement of microhardness and sliding wear properties of reinforced coatings, which provides a theoretical basis for the application of NiTi coatings in engineering and extends the field of additive manufacturing.

304L Austenitic Stainless Steel Corrosion Studies in Neutral Environment in Presence of Sulfite Ions

Abstract This paper examined the influence of the sulfite concentration introduced in the electrolyte added to the neutral solution (1 mol L-1 Na2SO4) on the corrosion process of 304L stainless steel material. 304L. The accelerated effect of sulfite ions under corrosion rate of 304L austenitic stainless steel was demonstrated using electrochemical techniques such as linear sweep voltammetry at a low scan rate −1 mV s−1, the Tafel slope method, chronoamperometry, and electrochemical impedance spectroscopy. Electrochemical studies were conducted using a BioLogic SP150 potentiostat/galvanostat. Stainless steels are the most varied and intricate group among all steels. Among them, 304L austenitic stainless steel is one of the most commonly utilized alloys, prized for its excellent corrosion resistance and strength, hygienic and aesthetic properties, affordability, good formability, and effective weldability. [1-3]. In modern industry, the amount of austenitic stainless steel represents only about 2% of the total steel production manufactured globally. This type of steel is commonly employed in chemical engineering, metal extraction, desalination and wastewater treatment plants, the oil and gas sector, transportation and aerospace industries, the food and beverage sector, as well as in architecture and construction engineering. [1].

Microstructures, mechanical properties and damping performance of wrought Mg–Cu–Ca alloys

Mg–Cu–Ca alloy sheets show good room temperature formability and excellent thermal conductivity; however, their strength is insufficient for load-bearing applications. In this study, Mg–Cu–Ca ternary alloys were subjected to a conventional extrusion process, and the microstructures and tensile properties were systematically evaluated. The addition of extremely small amounts of Cu and Ca to pure Mg (Mg–0.03Cu–0.05Ca, wt%) led to significant refinement of dynamically recrystallized (DRXed) grains while preserving a certain fraction of un-DRXed grains, which contributed to a substantial increase in tensile yield strength. Adjusting the extrusion parameters further increased the tensile yield strength to 329MPa, driven by the combined effects of further refined DRXed grains and an increased area fraction of un-DRXed grains. The damping performance of the Mg–0.03Cu–0.05Ca alloy sheet was superior to that of commercial AZ31(Mg–3Al–1Zn–0.3Mn in wt%) alloy sheet but lower than that of pure Mg, particularly at low frequencies. This revealed that the solute segregation at grain boundaries plays a crucial role in the damping performance of Mg alloys.

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.

Experience in common: Bataille’s Nietzsche and Shestov’s

ABSTRACT Georges Bataille made no secret of the importance Friedrich Nietzsche’s life and work held for him. But Bataille’s encounter with Nietzsche remained paradoxical: he rejected or ignored most of Nietzsche’s major concepts while nevertheless insisting on the value of Nietzsche’s thought and experience as a necessary counterpoint to the political, religious, and social currents of modernity. This paper demonstrates the extent to which Bataille owes the content and to some degree also the form of his idiosyncratic reading of Nietzsche to the influence and example of the Russian emigré philosopher Lev Shestov (1866–1938). In 1925, Georges Bataille published a translation of Shestov’s The Idea of the Good in Tolstoy and Nietzsche: Philosophy and Preaching, co-signed with Shestov’s daughter Tatiana Beresovski-Chestov. The translation was the product of a period during which Bataille also spent time with the older man and benefited from his tutelage. It was Shestov’s interpretation of the meaning of the death of God in Nietzsche’s life and thought that would have the most decisive influence on Bataille’s own life and work and make him, in his turn, a philosopher of tragedy.

Effect of scanning speeds on microstructure evolution and properties of 70Cr8Ni2Y coatings by direct laser deposition

Abstract The 70Cr8Ni2Y coatings were prepared by direct laser deposition (DLD) with different scanning speeds. The microstructure evolution and the relationship between microstructure and properties of the coatings were studied. The results demonstrated that the microstructure of DLD 70Cr8Ni2Y coatings was martensite, and the phases were α′ (Fe-Cr) and γ-Fe (Fe-Ni). With the increased of scanning speed, the martensite size decreased from 5.42 ± 0.04 μm to 4.42 ± 0.01 μm and 3.20 ± 0.02 μm. When the scanning speed was 20 mm s−1, the fabricated coating displayed the highest average microhardness (883 ± 37 HV) and the lowest mass wear rate (0.061 mg mm−1) without pores. The combined strengthening effect of fine grain strengthening and solid solution strengthening, as well as good formability, were the fundamental reasons for the high hardness and wear resistance of the coating. The results of this study can provide an experimental basis for the DLD alloy coatings with high hardness and wear resistance.

Microstructures and mechanical properties of Co-based Elgiloy fabricated by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) has emerged as a promising method for additive manufacturing due to its high efficiency and cost-effectiveness. This study aimed to fabricate Co-based Elgiloy by WAAM based on cold metal transfer technology. An 18-layers thin alloy wall was prepared. The microstructure, texture and mechanical properties of the as-deposited samples were investigated. Results indicated that the prepared alloy had good formability and was composed of a single face center cubic structure. The tensile properties of the alloy exhibited anisotropy due to the large number of columnar grains growing along the building direction in the alloy. The tensile samples along the building direction exhibited lower yield strength but better elongation due to the columnar grain growth direction and the softening effect of the remelted zone.

Highly thermally conductive BNNS/PANF dielectric composite boards prepared by a facile compression moulding process

The structural design of an efficient heat conduction channel is critical for heat dissipation in electronic packaging material. The build of oriented boron nitride nanosheet (BNNS) network inside polymers has attracted much attention due to its excellent thermal conductivity and dielectric properties. However, to fabricate a BNNS/polymer composite, complex method and low thermal conductive resin for binding BNNS network are commonly involved, which severely restrict its facile production and enhancement in thermal conductivity. Herein, by utilizing para-aramid nanofibers (PANF) as assistance to BNNS to form thermal conduction network, we obtained high performance composite boards with good formability and adjustable sizes via a simple compression moulding of the BNNS/PANF aerogels. The composite boards exhibit a remarkable in-plane thermal conductivity of 10.62 W/m K−1 at 50 wt% BNNS loading, outstanding practical thermal management capability, excellent thermal stability, low dielectric constant and loss, showing great potential for electronic packaging applications. This facile construction strategy provides a feasible way for the large-scale production and application of high-performance thermal management materials in the future.

Ultrasonic vibration-assisted single point incremental forming of hemispherical shaped component using AA3003 material

ABSTRACT Ultrasonic vibration-assisted single point incremental forming is a recent hybrid process variant of the single point incremental forming process. In this process, longitudinal ultrasonic vibration is used as an assistance in the conventional forming process. In this paper, the effect of amplitude of vibration in the ultrasonic vibration assisted single point incremental forming process have been researched. For the same, experimental work has been carried out by forming the hemispherical shaped components using multistage forming strategy. Moreover, numerical simulation work has been carried out using the LSDYNA solver and the results have been discussed in the light of depth of forming and strain distribution. The experimental fracture forming line is also developed for the AA3003 material for single point incremental forming process. High amplitude of vibration of 12 micron with 20 kHz frequency leads to poor formability; however, the lower amplitude of vibration of 8 micron with 30 kHz frequency leads to good formability.

플라톤의 ‘무시케’ 교육과 이성의 관계: ‘시가’의 내용을 중심으로

This study was designed to clarify the relation of ‘mousike’ education in the Republic of Plato and the development of Reason, focusing on the education of poetry. Mousike is composed of works of art, and is considered as the foundation of the development of reason. According to Gadamer, works of art make it possible to possess the truth, in the sense that they bring to light what is otherwise constantly hidden and withdrawn. This gives support of the argument of Plato that Mousike makes foundation of reason. However, in interpreting on the poetry of Homer, Gadamer’s theory of arts is not sufficient to explain mousike education. Plato, criticizing the poetry of Homer, insists that God isn’t the cause of all things but only of good ones. Plato’s sense of good poetry is able to arouse ‘transcendental imagination’. In virtue of it, a learner of a good poetry, instead of obsessing over the particular images in the poetry, conceive of ‘the Good’. Furthermore, a learner of Mousike is able to understand one’s life in the light of the idea of the Good. In virtue of the transcendental imagination, one is able to think of the universal beyond the particulars given by way of sensation as well as acquire the self-understanding which can recognize the ignorance of oneself. Mousike Education makes it possible for a learner to develop reason through transcendental imagination and selfunderstanding.

Role of Al content on tensile properties and stretch formability of Mg–Al–Mn alloy sheet produced by continuous hot-rolling

Continuous rolling is a novel cost-effective process to fabricate high-performance Mg alloy sheets with good room-temperature formability, and we investigated the effect of Al content on tensile properties and room-temperature formability of a recently designed Mg–Al–Mn alloy sheet. An excellent combination of tensile 0.2 % proof stress (TPS) and limiting dome height (LDH) was achieved by adding the moderate content of Al (2 % or 4 %). The sheets annealed at a low temperature of 250 °C showed the TPSs of ∼170–180 MPa and LDHs of ∼8 mm. The LDHs further increased to ∼9 mm by the annealing at 350 °C, while moderate TPSs of ∼150–160 MPa were maintained. Further, the sheets had an in-plane isotropy in which the tensile properties along the rolling direction were very similar to those along the transverse direction. The good properties were achieved by fine grain structure with the reduced intensity of the (0001) poles. Indeed, the Elasto-ViscoPlastic Self-Consistent modeling revealed the increase of the activity of the prismatic slip by adding 4 % of Al, while it had a limited effect in improving the stretch formability. Further, we found that the deformation microstructure of the as-rolled sheets became uniform by the 2 % and 4 % Al addition, which would contribute to the reduced intensity of the (0001) poles after the annealing.

Synergistic mechanism of hetero-structured Al–Mg–Si–Cu–Zn–Fe–Mn alloys with greatly enhanced strength, ductility and formability

Al–Mg–Si alloy sheets applied in automobile industry are required to possess good formability, high strength and ductility. Herein, our results show that a heterogeneous cellular microstructure, i.e., soft domains embedded in hard domains, can be readily attained via a short-flow processing route with concomitant improvement in the strength (YS: 177–184 MPa, UTS: 317–328 MPa), elongation (25.7%–27.3 %) and formability (r‾= 0.771, Δr = 0.047) of pre-aged alloy. The distribution of recrystallization grains, texture and coupled soft/hard domains in the Al–Mg–Si–Cu–Zn–Fe–Mn alloys and the effect on mechanical properties have been investigated. Moreover, the formation and synergistic action mechanisms of coupled soft/hard domains were put forward in this work.

EFFECTS OF PROCESSING AL-MG ALLOY BY SEVERE PLASTIC DEFORMATION: TENSILE PROPERTIES AT HIGH TEMPERATURES

Aluminum and wrought non age-hardenable such as Al-Mg alloys became interesting alternatives for various structural applications in spite of generally moderate strength, but relatively good formability and good corrosion resistance. Increasing overall strength while preserving or even improving ductility in special conditions without any any change in chemical composition that oppositely could alter other features of the material - such as weldability, becomes an objective worthy of research. A suitable way to increase the potential of Al-Mg alloys is the raising up the mechanical properties by structural refinement. Ultrafine grain size provides enhanced mechanical and/or physical properties such as strength and very good ductility – close to superplasticity at slightly higher strain rate and relatively lower temperatures – and better corrosion resistance. Well-known as one of the most encouraging and efficacious structure refining method amid other severe plastic deformation (SPD) techniques, equal channel angular pressing (ECAP) has been deeply investigated thanks to dramatic improvements in structure and therefore properties of bulk ultrafine grained/nanostructured materials. The aim of this study is to evaluate by tensile testing at higher temperatures the mechanical properties of an Al-3.4%Mg alloy previously processed by ECAP up to 8 passes, as a candidate for replacing AA5154 which contains different amounts of chromium. The tensile tests conducted at different temperatures using a computer-controlled testing machine with different strain rates showed in terms of engineering stress vs. engineering strain evolution that the ECAPed Al-3.4%Mg alloy have the potential to be used in technological processes at high temperatures, opening opportunities for industrial applications requiring high ductility.

A Review on Traditional Processes and Laser Powder Bed Fusion of Aluminum Alloy Microstructures, Mechanical Properties, Costs, and Applications.

Due to its lightweight, high strength, good machinability, and low cost, aluminum alloy has been widely used in fields such as aerospace, automotive, electronics, and construction. Traditional manufacturing processes for aluminum alloys often suffer from low material utilization, complex procedures, and long manufacturing cycles. Therefore, more and more scholars are turning their attention to the laser powder bed fusion (LPBF) process for aluminum alloys, which has the advantages of high material utilization, good formability for complex structures, and short manufacturing cycles. However, the widespread promotion and application of LPBF aluminum alloys still face challenges. The excellent printable ability, favorable mechanical performance, and low manufacturing cost are the main factors affecting the applicability of the LPBF process for aluminum alloys. This paper reviews the research status of traditional aluminum alloy processing and LPBF aluminum alloy and makes a comparison from various aspects such as microstructures, mechanical properties, application scenarios, and manufacturing costs. At present, the LPBF manufacturing cost for aluminum alloys is 2-120 times higher than that of traditional manufacturing methods, with the discrepancy depending on the complexity of the part. Therefore, it is necessary to promote the further development and application of aluminum alloy 3D printing technology from three aspects: the development of aluminum matrix composite materials reinforced with nanoceramic particles, the development of micro-alloyed aluminum alloy powders specially designed for LPBF, and the development of new technologies and equipment to reduce the manufacturing cost of LPBF aluminum alloy.

Investigation into the Hot-Forming Limit for 22MnB5 Hot-Forming Steel under a Stamping Process

Hot-forming technology for 22MnB5 hot-forming steel (22MnB5 HF steel) plates has been widely used in the automobile manufacturing industry in recent years. Physical simulation and numerical modeling were carried out in order to determine the forming limit of a 22MnB5 steel plate for the stamping process. The deformation experiments were performed in a temperature range of 600~900 °C and a strain rate range of 0.1~10 s−1. In the uniaxial tensile tests, it was found that at the forming temperature of 600 °C, the condition of dynamic recrystallization was not fully reached, and thus the corresponding tensile strength was much larger than that at other deformation temperatures. In the numerical simulation of bulging experiments, it was found that 22MnB5 steel had good formability when the initial deformation temperature was high and the forming speed was low by using the instability criterion, combining the maximum punch force and strain path transition. The forming limit diagram of 22MnB5 steel at a temperature of 700 °C and tool speed of 25 mm/s was obtained by means of simulation and a hot stamping experiment. The establishment of the forming limit of the 22MnB5 steel plate can provide theoretical and technical guidance for the hot-forming process.

Polyarylene ether nitrile dielectric composites with good formability and processability

High dielectric constant polymer matrix composites are widely used in the domain of dielectric energy storage and electric field regulation depending on their high energy density, easy processing and light weight. Nevertheless, high dielectric constants are often achieved by adding fillers to the polymer, which increase the viscosity of the resin and make processing difficult. In this work, a novel filler GO coated with silicone powder (GO-silicone) was designed and prepared. The silicone powder on the surface of GO acts as a lubricant and improves the dispersion of GO in the polyarylene ether nitrile (PEN) resin, thus enhancing the dielectric properties of the PEN-based composite. The dielectric constant of the PEN/GO-silicone composite film with 4 wt% filler loading reaches 15.9 at 1 kHz, which is 4.3 times greater than that of the pure PEN film and 1.1 times greater than that of PEN composite simply filled with GO and silicone powder. Besides, the incorporation of GO-silicone declines the viscosity, which is very favorable for the processing and shaping of high dielectric composites. This work provides a novel technical route for the large-scale production of high dielectric composites.

A comparative study on cryogenic formability and paint baking property of AA7075 alloy sheets tempered at fast retrogressed and pre-aged conditions

Forming at cryogenic temperatures provides a new approach to the formability improvement of 7000-series high-strength aluminum alloys. However, the cryogenic forming process based on solution-treated (W) or peak artificial aged (T6) alloys cannot meet the demands of autobody manufacturing for good formability, high post-formed strength and high efficiency simultaneously. The fast retrogression (FR) treatment of AA7075-T6 and pre-aging (PA) treatment of AA7075-W are elaborately designed to tailor a pre-hardened AA7075 alloy, which has good cryogenic formability and relatively high initial strength, and can be further strengthened by paint baking in high efficiency. The results show the optimum fast retrogression temperature for AA7075-FR is 400 °C, at which the sample can acquire a cryogenic elongation of 29.2% and obtain 90% of initial T6 sheet tensile strength by the combined effect of cryogenic pre-deformation and subsequent paint baking treatment. The optimum pre-aging temperature for AA7075-PA is 120 °C, at which the sample can acquire a cryogenic elongation of 31.0% and exceed 96% of tensile strength of AA7075-T6 after paint baking treatment. The comparative study demonstrates that the supersaturated solid solution matrix with an appropriate proportion of GP zones and η′ phases, but few Cr-containing dispersoids and precipitate free zones, is an ideal pre-hardened microstructure to get a good combination of cryogenic formability and final strength. The precipitation of GP zones and η′ phases is prior to the formation of precipitate free zones during pre-aging of AA7075-W, making the pre-aged hardening cryogenic forming process more suitable for automobile industry.