TRIP Effect Research Articles

Effects of Instructional Strategies and Gender on Junior Secondary School Students’ Achievement in Business Studies in Rivers State, Nigeria

Business Studies is offered in Junior Secondary Schools (JSS) as a subject meant to expose learners to commerce, office management, trade and book keeping. In spite of its importance, performance in the subject is below expectation in Rivers State. Previous studies revealed that brainstorming and field trip will improve learning outcomes but they are rarely used while teaching Business Studies. This study, therefore, determined the effects of brainstorming (BTM), field trip (FTTM), and conventional teaching methods (CM) and gender on secondary school students’ achievement in Business Studies. All the JSS 2 students (467) in the selected schools participated in the study. The treatment lasted for seven weeks. The instrument used was Business Studies Achievement Test (r=0.82), Data collected was analysed using Analysis of Covariance (ANCOVA) at 0.05 level of significance. There was a significant main effect of treatment on students’ achievement in Business Studies [F(2,131)=26.70, partial η2=0.29]. Participants in FTTM had the highest mean (35.79), followed by BTM (35.71) and CM (27.54). Results revealed that gender did not have a significant main effect on students’ achievement in business studies [F(1,131) =.315, P> .05]. Brainstorming and Field trip teaching methods influenced learning outcomes of students in Business studies in Rivers state but Field trip method was better. It is therefore suggested that teachers should use both methods during Business studies classes.

Effect of Forming and Heat Treatment Parameters on the Mechanical Properties of Medium Manganese Steel with 5% Mn.

Medium manganese steels fall into the category of modern third-generation high-strength steels. Thanks to their alloying, they use a number of strengthening mechanisms, such as the TRIP and TWIP effects, to achieve their mechanical properties. The excellent combination of strength and ductility also makes them suitable for safety components in car shells, such as side reinforcements. Medium manganese steel with 0.2% C, 5% Mn, and 3% Al was used for the experimental program. Sheets with a thickness of 1.8 mm without surface treatment were formed in a press hardening tool. Side reinforcements require various mechanical properties in different parts. The change in mechanical properties was tested on the produced profiles. The changes in the tested regions were produced by local heating to an intercritical region. These results were compared with classically annealed specimens in a furnace. In the case of tool hardening, strength limits were over 1450 MPa with a ductility of about 15%.

A Novel Design to Eliminate Lüders Band in Medium-Mn Steel and Its Microstructure-Property Relationship

In the current work, we design a novel medium Mn steel with a superior mechanical property and no Lüders band. For industrial applications, a “low Mn addition” chemical composition and two kinds of different annealing processes with various initial microstructures were introduced. Consequently, the sample subjected to full austenitized quenching plus intercritical annealing process exhibited an outstanding mechanical property without the Lüders band. The microstructural evolution and austenite reverted transformation behavior were discussed in detail. In addition, austenite stability was estimated by chemistry stability and mechanical stabilization. It seemed that the austenite stability was significantly influenced by the morphological component. Thus, the sample with single lath-like ferrite and austenite exhibited the most excellent mechanical property. Furthermore, the “Lüders band” phenomenon was considered to rely on the restriction of martensitic recovery and recrystallization by lath-like morphology. The occurrence of the Lüders band was attributed to the low work-hardening ability caused by dynamic recovery. The formation of lath-like morphology could prevent the occurrence and propagation of the Lüders band by increasing the dislocation density and active TRIP effect.

Study of trip card data analysis system under big data

Abstract Digital technologies such as the Internet, big data, cloud computing, mobile communication, and artificial intelligence have played an important role in the prevention and control of this new crown epidemic. Driven by big data technology, collaborative governance in the digital era has injected new dynamics for collaborative governance in the general sense, especially in this new crown epidemic prevention and control shows a different governance logic from the past, and the refinement and extraction of this governance logic is the key to enhance the ability of new crown epidemic prevention and control. Compared with the previous model in which a single governmental governance body played a role. In this paper, the necessity of building a big data analysis system is clarified by analyzing the limitations of the data analysis means of the existing trip code system. The overall epidemic prevention advantage of adopting the big data trip code policy has increased by 51.95% for regions with high crisis risk level and strong economic power, such as Guangdong, Zhejiang and Shanghai, which need to face the risk spread from domestic and imported risks under the big data trip code control, the increase of new cases compared to the previous comparison has decreased by 68.5%, which can visually see the big data trip code epidemic prevention We can visually see the effectiveness of big data trip codes in preventing the epidemic and making excellent contributions to the global fight against the epidemic.

Influence of Austenite Stability on the Machinability of Different Grades of Austempered Ductile Iron (ADI) During Dry Turning Machining

This work evaluated the machinability characteristics of three different austempered ductile irons using three machinability indicators: cutting force, tool wear, and surface roughness. Additionally, this paper addresses the interplay among the production conditions of ADIs, microstructural development, the TRIP effect arising from transformations of the retained austenite into martensite, and the machinability behavior of ADIs. Various characterization studies including hardness measurement, X-ray diffraction analysis, light and electron microscope were used. Machinability results indicated that the increase in cutting force is always associated with a corresponding increase in the martensite content when the cutting depth was increased from 0.5 to 2.0 mm. Such correlation is more evident with ADI grade austempered at high austempering temperature, 375 °C (ADI-375). It was noticed that although ADI-375 has only 0.46% martensite in the structure before machining, this ratio increases with the highest depth of cut of 2.0 mm to reach about ~ 23% martensite with a corresponding increase in the cutting force. Ferrite content and morphology have a great impact on the overall surface finish of each grade as it leads to deteriorating the surface characteristics of the investigated alloys. This could explain the highest roughness values across all processing experiments obtained in the ADI grade austenitized in the intercritical region (IADI), which mainly contains the highest ferrite content. Tool wear and chip characteristics were also studied in this work.

Enhanced mechanical property of Ti-45551 alloy due to TRIP effect

The martensitic phase transformation of nearly β titanium during deformation facilitates the increase and stabilization of strain hardening rate leading to excellent formability. In this work, a nearly β titanium (Ti-4Al-5Mo-5V-5Cr-1Nb %) was designed and exhibited a high yield stress (~760 MPa), a well rate of strain hardening (~950 MPa) up to 40% true strain. Microstructure characterization of the samples after deformation revealed that the excellent mechanical properties were induced by martensitic phase transformation without twinning.

Discontinuous transformation-induced plasticity behaviour in governing the mechanical behaviour in medium-Mn steels

ABSTRACT Here, we address the continuing challenges and scientific gaps in obtaining high strength and high elongation in medium-Mn steels. Electron microscopy and X-ray diffraction studies clearly underscored that the discontinuous transformation-induced plasticity played a determining role in impacting high strength–toughness combination in conjunction with the microstructural constituents. The discontinuous TRIP effect during deformation involved stress relaxation, which was responsible for high ductility. An excellent combination of a high tensile strength in the range of 1238–1502 MPa and a total elongation of 25–33.6% was obtained when the steels were subjected to an intercritical hardening in the temperature range of 600–750°C and low tempering at 200°C. The intercritical hardening influenced the co-existence of austenite, ferrite and martensite in a manner such that the deformation behaviour varies with the Mn-content.

Hot-rolled Al-added medium Mn steel (Fe-8Mn-2.85Al-1Si-0.2C): Microstructural evolution and tensile behavior

In this study, a low Al (<3%) added medium manganese steel has been developed through melting casting route in an open-air induction furnace. The cast steel ingot has been intercritical annealed at 720 °C after hot deformation, that includes hot forging and hot rolling treatment, respectively. Microstructure characterization coupled with X-ray diffraction (XRD) has been performed after each processing step to understand the extent of austenite formation and its subsequent transformation to ferrite/martensite. The processed steel possesses the ultimate tensile strength, yield strength and ductility of 1000±20 MPa,700±10 MPa and 18.5 ± 0.5, respectively. To understand the possible cause of enhanced strength and deformation mode rietveld analysis has been carried out. It reveals that developed (final processed) steel possesses ∼18% (volume%) of austenite that subsequently reduced to ∼6.139% after tensile testing, indicating significant transformation of austenite to martensite (continuous and enhanced TRIP effect). The morphological characteristic of martensite in developed steel has been investigated using transmission electron microscopy (TEM). It reveals lath morphology of martensite due to low carbon content. The TEM and 3D atom probe analysis reveals the precipitation of intergranular type kappa (k) carbide in intercritically annealed specimens due to probable segregation of C and Al. However, volume fraction of the same is low. The SFE of the steel has been found to be ∼16 mJ m− 2, calculated by the modified Olson and Cohen method that also concludes TRIP is the preferred deformation mechanism in the developed steel.

Deformation behaviors at cryogenic temperature of lean duplex stainless steel with heterogeneous structure prepared by a short process

In this study, a lean duplex stainless steel with a heterogeneous lamellar structure is created using a quick technique of direct cold rolling combined with severe plastic deformation and short annealing. The deformation behaviors and fracture mechanisms at cryogenic temperature are investigated. In accordance with the findings, the duplex stainless steel S32304 exhibits excellent mechanical properties at 203 K, with tensile strength reaching 1160 MPa, elongation reaching 44.1%. Nearly 44.4% more elongation exists at 203 K than at 298 K. The synergistic coupling strengthening of the TRIP and TWIP effects of the austenite, HDI strengthening, and dislocation proliferation of coarse ferrite grains stimulated by the austenite grains with various orientations can all be credited for the excellent mechanical properties at 203 K. Additionally, the prominent deformation substructures, such as nanotwin bundles, and the strong interaction between dislocations and nanotwin bundles, are also contributed to strain hardening at 203 K. However, at 573 K, dislocation slip becomes the primary deformation mechanism of the two phases, and severe dislocation accumulations in the coarse ferrite grains become a possible site for crack nucleation, leading to a higher loss of ductility than at 298 K and 203 K.

Enhancing strength-ductility combination in a novel Cu–Ni bearing Q&P steel by tailoring the characteristics of fresh martensite

The present work aims to study the effect of quenching temperature on phase transformation, microstructural characteristics and mechanical properties of a novel Cu–Ni bearing Q&P steel based on combining the experiments and modeling. In this study, a new constrained carbon equilibrium (CCE) model was proposed by considering the effect of intercritical ferrite and multi-element synergistic partitioning. The optimum quenching temperature and corresponding retained austenite (RA) fraction can be reflected in the new CCE model, which is in good agreement with XRD results. Furthermore, the significant role of fresh martensite in the tensile strength and fracture behavior were elucidated. As the volume fraction of fresh martensite increases from 9.8% to 57.8%, the strengthening contribution to the tensile strength increases from 13.7% to 68.8%. Meanwhile, the fracture mechanism transforms from ductile into quasi-cleavage fracture due to an increased amount of fresh martensite and the absence of tempered martensite. The superior mechanical properties, ultimate tensile strength of 1152 MPa, yield strength of 797 MPa, total elongation of 25%, and the product of strength and elongation (PSE) up to 28.8 GPa% were obtained in QP-200, which is largely due to the combined effect of the better deformation ability of a considerable amount of tempered martensite and the continuous TRIP effect provided by multiscale RA with different morphologies.

Strategy of complex carbides in microalloyed 4Mn steels processed by quenching and austenite reversion

This work describes a strategy to employ complex carbides for high-yield microalloyed 4Mn steels processed by quenching and reversion (Q&R). The nano/microstructural details are investigated by using electron microscopy and atom probe. It is found that complex carbides are classified into two types and contribute to yield strength in different ways. First, coarse carbides (MC1), which are retained after austenization and quenching, provide the Zener pinning effect and contribute to strengthening by microstructure refinement and precipitation hardening. Second, nanoscale carbides (MC2), which precipitate in martensite during austenite reversion, provide precipitation hardening. Furthermore, the precipitation of MC1 accelerates austenite reversion due to the finer martensite microstructure. Hence, the strengthening effects and TRIP effect can be tuned by controlling the proportion of the two types of carbide. This concept is validated in Ti-Mo 4Mn steel, which exhibits a high yield strength of about 850 MPa, a high ultimate tensile strength of about 950 MPa, and excellent elongation of over 20%. The complex carbide strategy is able to increase yield strength without sacrificing much ductility for Q&R medium-Mn steels.

Microstructure and tensile properties of metastable Fe50Mn30Co10Cr10 high-entropy alloy prepared via powder metallurgy

With the characterization of microstructure and tensile properties, the feasibility of preparing Fe50Mn30Co10Cr10 high-entropy alloys (HEAs) via powder metallurgy was explored, and the effect of sintering temperature and deformation temperature on the microstructure and tensile properties of the alloy was investigated. The alloys sintered at different temperatures possessed a dual-phase structure with face-centered cubic (FCC) and hexagonal close-packed (HCP). The average grain size, HCP phase fraction, and twinning boundary fraction increased with the sintering temperature. The best combination of strength and ductility was obtained in the alloy sintered at 1000 °C, which exhibited a strongly temperature-dependent mechanical behavior, i.e., when the deformation temperature decreased from 298 to 77 K, the yield strength and ultimate tensile strength increased from ∼287 to ∼490 MPa and from ∼745 to ∼1107 MPa, respectively, with only a tiny loss of uniform elongation; this is mainly attributed to the deformation mode of the alloy varied with deformation temperature. During tensile deformation at 298 K, dislocation slip, phase transformation, detwinning of annealing twins, and mechanical twinning were the dominant mechanisms, while no mechanical twinning was activated at 77 K. The excellent combination of strength and ductility for the alloy at 77 K relative to 298 K is mainly attributed to a more significant TRIP effect. Powder metallurgy can be used as a promising way for manufacturing metastable high entropy alloys with excellent tensile properties.

Simultaneous enhancement of strength-ductility via multiple precipitates and austenite in a novel precipitation-hardened martensitic stainless steel

In this study, the advantages of the novel precipitation-hardened martensitic stainless steel (abbreviated as novel steel) in terms of an excellent strength–ductility balance are fully elucidated utilizing various methods and tests. The novel steel increases the yield and ultimate tensile strength from 1480 ± 20 MPa and 1500 ± 18 MPa to 1530 ± 15 MPa and 1650 ± 20 MPa, respectively, and simultaneously improves the elongation from 9.7 ± 0.5% to 17.8 ± 1.1% over that of conventional PH13–8Mo steel. Specifically, the novel steel is mainly strengthened and toughened by three factors, including fine grain strengthening, precipitation strengthening of multiple precipitates (Cu, NiAl) and the TRIP effect. The contribution of fine grain strengthening is quantitatively evaluated through the Hall–Petch relationship. Meanwhile, the value of strengthening contributions by multiple precipitates are quantitatively evaluated through the shearing or Orowan mechanism. Significantly, compared with conventional PH13–8Mo steel, the addition of Cu leads to the formation of multitudinous metastable austenite in the novel steel. The TRIP effect can be generated by metastable austenite upon applied loading conditions. An accessible pathway is found to exploit high-performance stainless steel.

Effects of Cu and Nb on martensite hardening and transformation-induced plastic deformation behavior of maraging TRIP-aided steel

Martensite hardening and transformation-induced plastic deformation (TRIP) are crucial to the mechanical properties of steels. In this study, maraging TRIP-aided steel was developed. The addition of Cu and Nb can effectively promote transformation-induced plastic deformation, this is due to the characteristic of the alternating combination of soft and hard phases. In contrast, the addition of Nb has a more significant effect on martensite hardening, which can be attributed to the smaller effect of Nb on the martensite transformation start temperature (Ms). The multi-phase structure and precipitation strengthening, lead to the ultimate tensile strength and elongation of the maraging TRIP-aided steel is ∼1300 MPa and ∼24%, respectively. It was found that the prior austenite formed a continuous network surrounding bainite and martensite. The high-density dislocations in bainite and martensite increased the hardness. In addition, the metastable austenite phase was transformed into the martensite phase, and a heterostructure with the alternating distribution of bainite/austenite was formed during deformation. The refinement of grains effectively reduced the concentration of stress. Massive nanometer-scaled precipitates were formed in Nb-containing steel after peak aging, and the co-precipitation of Nb-rich and Mo-rich phases occurred in the steel. The large-sized Laves-Fe2(Nb, Mo) effectively enhanced the strength of steel, and the fine and dense Ni3Ti was beneficial to the simultaneous improvement of strength and plasticity. Therefore, the jointed mechanisms of martensite hardening, and the TRIP effect improved the strength while retaining good plasticity.

Microstructure and mechanical properties of a martensitic stainless steel (0.2%C–12%Cr) after quenching and partitioning (Q&P) process

This paper investigates microstructure and mechanical properties of a commercial martensitic stainless steel (0.2%C–12%Cr) after the quenching and partitioning process. The characterization was performed by optical microscopy, SEM, XRD, EBSD, density, dilatometry, hardness, Charpy, and tensile tests. Different retained austenite fractions were obtained by varying the quenching temperature (Qt). The results showed a decrease in the yield and ultimate tensile strength because of the increase in the retained austenite fraction for Qt ranging from 90 °C up to 165 °C. The absorbed energy was increased by 79%, probably due to the increment of mechanically stabilized retained austenite fraction. The fracture surface showed ductile characteristics for Qt ranging from 90 °C to 165 °C after tensile and Charpy tests. The best balance of strength and ductile found was Qt = 190 °C with a total elongation of 22.9 ± 2.2% and an ultimate tensile strength of 1444 ± 20 MPa owing to the retained austenite to martensite transformation that postponed occurrence of necking (TRIP effect). On the other hand, a decrease in the impact toughness occurred due to the retained austenite presence with low mechanical stability in the microstructure. Different fracture mechanism behavior was observed for tensile tests (ductile fracture) and impact tests (quasi-cleavage). For Qt = 215 °C, the presence of fresh martensite and non-mechanical stabilized retained austenite promoted an increase in ultimate tensile strength and a decrease in the yield strength, area reduction, total elongation, and absorbed energy. Finally, fracture surfaces showed brittle characteristics after tensile and Charpy tests.

Hardening behaviour, mechanical properties and wear evaluation of TRIP/TWIP manganese steels: A comprehensive review

Steel is by far the most popular structural material in the world. Due to its excellent strength and hardness, non-magnetic manganese steel provides adaptability. The effect of SFE on induced plasticity is thoroughly explored together with several hardening behaviors, including strain hardening, grain size hardening, solid solution hardening, and precipitation hardening of manganese steel, showing the TRIP/TWIP phenomena. By a thorough literature analysis, the effect of TRIP and TWIP on the mechanical and sliding wear parameters of manganese steel is well shown. Steel that has a TWIP phenomenon can be produced commercially and improves strength by providing improved plasticity. The addition of microalloying components has a significant impact on intermetallic precipitation, which imparts hardness and strength to the steel. Manganese steel with the TRIP/TWIP phenomenon demonstrates greater resistance to sliding wear under both lubricated and unlubricated situations as a result of improvements in its mechanical characteristics.

Microstructure and mechanical properties of medium manganese steel in intercritical annealing

A new type of cold-rolled medium manganese steel was investigated. The test steel was treated by Q&P process. With the increase in annealing temperature, the grain size gradually increases, the carbides dissolve progressively and the fine lath grains transform into massive or equiaxed grains. Both the volume fraction and the stability of the retained austenite are continuously decreasing, which together affect the change of mechanical properties. At the intercritical annealing temperature of 680°C, the specimens have higher retained austenite content and transformation rate. At the same time, due to the discontinuous TRIP effect caused by the retained austenite stability gradient inside the specimen, it exhibits excellent comprehensive mechanical properties, and the product of strength and elongation is 43.5GPa·%.

Effect of tempering and partitioning (T&P) treatment on microstructure and mechanical properties of a low-carbon low-alloy quenched and dynamically partitioned (Q-DP) steel

We performed a direct quenching and dynamical partitioning (Q-DP) process, following intercritical annealing, to a low-carbon low-alloy steel. Performing an additional tempering treatment on the Q-DP steel, we investigated the carbon partitioning behavior upon tempering. We emphatically analyzed the effect of tempering and partitioning (T&P) treatment on the microstructure evolution and mechanical properties of the Q-DP steel, especially on carbon partition, retained austenite stabilization, TRIP effect and work hardening. Results show that the synergetic partition of carbon and Mn from ferrite to austenite during intercritical annealing and the dynamical partition of carbon upon quenching jointly achieve the stabilization of retained austenite in the Q-DP sample. The actual volume fraction of retained austenite is larger than the theoretical calculating value, which is attributed to the dynamical partition of carbon. The T&P treatment at 300 °C for 15 min does not result in obvious decomposition of retained austenite, but leads to apparent carbon partition from martensite to retained austenite. The carbon partition upon tempering enhances the mechanical stability of retained austenite, thus weakening the TRIP effect during tensile deformation and promoting the TRIP effect to occur at higher true strain level. The much higher work hardening rate at the late deformation stage near necking, for the quenched tempered and partitioned (Q-T&P) sample, leads to a higher uniform elongation, compared with the Q-DP sample. The existence of carbon-enriched stable retained austenite after necking happens finally enhances the post necking elongation of the steel.

Cryogenic impact property of a high-strength-ductility 304L stainless steel with heterogeneous lamella structure

A high-strength-ductility 304L stainless steel with heterogeneous lamella structure (HLS) was fabricated by cold rolling and subsequent partial recrystallization. The HLS was composed of lamellar recrystallized grains (mean grain size of ∼4.1 μm) embedded in a hard matrix of ultra-fine grains (mean grain size of ∼0.65 μm) and dislocation-cell structure. It exhibited a superior cryogenic impact property compared with coarse-grained, fine-grained and cold-rolled 304L stainless steels. This was mainly attributed to the suppression of crack propagation by lamellar recrystallized grains, dislocation-cell structure and TRIP effect. In addition, the extra fracture energy was also caused by the delamination in ultra-fine grains. This work will give an important theoretical guidance for the cryogenic applications of the HLS 304L stainless steel.

Simultaneous improvement of yield strength and ductility in medium Mn steel by combining gradient structure and TRIP effect

Simultaneous improvement of yield strength and ductility in medium Mn steel by combining gradient structure and TRIP effect