Amount Of Deformation Research Articles

Microstructural Evolution and Mechanical Properties of Cu–Ag Alloy via Different Severe Plastic Deformation Processes

The field of artificial intelligence and integrated circuits is experiencing rapid development, particularly in the area of highly integrated and miniaturized components, in which Cu-Ag alloys, as a typical lead frame material, play a crucial role. However, current research is primarily focused on low Ag content alloys, and there are few studies on the regulation of the microstructure and mechanical properties of high Ag content Cu-Ag alloys. This limitation hindered the development and utilization of the high Ag content Cu-Ag alloys. In this study, the microstructure and mechanical properties of Cu-28Ag (wt. %) alloy after room temperature and cryogenic rolling were investigated. It was demonstrated that the cryogenic rolling yielded better surface quality, an enhanced dendrite refinement effect, and a more distinct layer structure compared to room temperature rolling. The conductivity of the alloy decreased after cryogenic rolling due to increased electron scattering within the Cu matrix. The tensile strength improved, but the elongation decreased. Specifically, at a deformation amount of 95%, the alloy exhibited an ultimate tensile strength, yield strength, and elongation of 640 MPa, 631 MPa, and 1.9%, respectively. This strengthening was mainly attributed to the refinement of grains, the presence of dislocations, and precipitation. Furthermore, the samples subjected to liquid nitrogen rolling at a deformation amount of 95% exhibited improved homogeneous deformation capacity, which was attributed to grain size refinement, uniform distribution of high-density dislocations, deformation structure, and heterogeneity-induced deformation enhancement.

Investigating the effect of ceramic fiber on the mechanical properties of glassphalt

Glassphalt suffers from performance defects, especially against moisture damage and fatigue cracking. In this research, the performance of glassphalt modified with CF has been evaluated against moisture damage, fatigue cracking and rutting. Based on this, Modified Lottman, Wilhelmy Plate (WP), Indirect Tensile Stiffness Modulus (ITSM), Indirect Tensile Fatigue (ITF), and Repeated Load Axial (RLA) tests have been performed on glassphalt modified with CF. The results of the WP test revealed that CF reduced the acid properties and increased the basic properties of the base bitumen. This increased the adhesion of bitumen and glass cullet, which have acidic properties, and enhanced the glassphalt’s performance against adhesive failure. CF also increased the strength of bitumen cohesion, which reduced the possibility of cohesion failure. CF enhanced the stiffness modulus of the glassphalt by forming physical bonds in the base bitumen. The fatigue life of samples containing 1, 3, and 5% CF at 15 ℃ increased by 79%, 114%, and 65%, respectively, compared to the control sample, with the 3% fiber sample showing the greatest improvement in fatigue life among the modified samples. Similar trends were observed at 25 ℃. At 30 ℃, the amount of permanent deformation at the end of loading in samples containing 1, 3, and 5% CF decreased by 32%, 58%, and 74%, respectively. A similar trend was observed at 50 ℃. These findings indicate that the inclusion of additives significantly reduces the permanent deformation of the samples under higher temperatures, thereby enhancing their overall performance and stability.

Assembly Accuracy Analysis Method Based on Multi‐Stage Linearized Contact

ABSTRACTPrecision improvement in mechanical manufacturing faces challenges due to nonlinear effects impacting assembly accuracy analysis models. An assembly accuracy analysis method based on multi‐stage linearized contact is proposed to address this issue. A model of part surface asperities considering morphological errors is established using the linear superposition of discrete cosine transform (DCT) kernel functions and the assembly interface is simplified. By employing homogeneous coordinate transformation (HCT), the prediction of the part's pose during the assembly process with the rigid body assumption is achieved. The elastic contact process is divided into multiple stages according to the order of the asperity participating in the contact and further subdivided into several linear processes by adding nodes at each stage. The relationship between the assembly load and the deformation amount is established based on the related theories of contact mechanics and the geometric relationship between the assembly interfaces, thus enabling the prediction of the part's pose during the assembly process. Taking a multi‐way hydraulic valve as an object, by comparing the accuracy of pose prediction of the algorithm before and after adding nodes, it is proved that the proposed method can significantly improve the precision of assembly accuracy analysis.

Effect of deformation amount on microstructure and properties of spray formed Al-12.3Zn-2.2Mg-1.5Cu alloy with secondary aging

Effect of deformation amount on microstructure and properties of spray formed Al-12.3Zn-2.2Mg-1.5Cu alloy with secondary aging

Enhanced mechanical properties of Sr-modified Al–Mg–Si alloy by thermo-mechanical treatment

Abstract In this study, the effect of thermomechanical treatments applied to strontium-modified A360 alloy on the microstructure and mechanical properties of the alloy was investigated. Optical microscopy, XRD, and SEM were employed to examine the microstructural properties, while tensile and hardness tests were conducted on the samples to evaluate the mechanical properties. It was observed that the strength values increased as the deformation amount increased, and subsequently, optimum conditions (tensile strength and ductility) were determined after the subsequent aging treatment. Following cold deformation, dendritic structure shifted towards the direction of deformation along with the eutectic silicon structure. After aging, it was found that the dendritic structure transformed into equiaxed grains at certain temperature. The highest tensile strength of 383 MPa was achieved in the sample with a deformation amount of 70 %. In this case, the ductility value was 2.85 %. Subsequently, the optimum conditions after aging were determined as 160 °C & 4 h, resulting in a tensile strength of 341 MPa and ductility of 3.62 %.

Effects of Hot Rolling on the Microstructure, Mechanical, and Damping Properties of High‐Nitrogen Stainless Steel

In this study, the mechanical and damping properties of high‐nitrogen stainless steel, containing 0.65 wt% nitrogen, after being subjected to hot rolling to deformation ratios 19%–85% are investigated. Mechanical properties are assessed using tensile testing and Vickers hardness testing while damping properties are analyzed using a dynamic mechanical analyzer. A significant improvement in tensile strength is observed in samples deformed to an 85% reduction, showing an ultimate tensile strength of 1227 MPa compared to the initial 810 MPa of the annealed sample. Both the frequency and temperature damping capacities increase with the amount of deformation, peaking at 66% reduction, before slightly declining at 85% reduction. In the study, Finkelshtain–Rosin internal friction peaks, characteristic of austenitic steels, are identified in the temperature range of 100–250 °C. Deformation up to a 66% thickness reduction results in deformed grains with a continuous increase in dislocation density, accounting for trends in the mechanical and damping properties. However, the 85% reduction leads to a finer microstructure with a high fraction of low‐angle grain boundaries formed through continuous dynamic recrystallization during hot rolling. This creates immobile dislocation networks, which adversely affect the damping properties.

Dynamic response characteristics of coal/rock during water injection and freezing process under gas atmosphere and its control effect on gas outburst

The freezing method compensates for the defect of sacrificing coal integrity to reduce gas content, which is the case with traditional methods, achieving the improvement of coal body strength while reducing coal seam gas energy storage, improving the safety of coal and gas outburst accidents in deep coal seams during the process of rock cross-cut coal uncovering. This study conducted water injection and low-temperature freezing experiments on coal/rock samples under the gas atmosphere, analyzing the effects of water and temperature on sample temperature, deformation, and gas adsorption and desorption characteristics. The results indicate that water can displace adsorbed gas in coal/rock samples, and the relationship between the gas displacement and the water content of the sample satisfies an improved exponential function. The center temperature Tm of low water content coal/rock samples decreases with time and gradually tends to stabilize, while the Tm of high water content samples experiences a short-term deceleration or stagnation due to the phase transition heat release of water when it drops to around 0 °C. The cooling rate of samples with low water content and no gas is higher and that of rocks is higher than that of coal samples. Coal/rock samples with high water content experience frost heave during the freezing process, but the overall deformation is still dominated by cold shrinkage, and the amount of deformation is negatively correlated with temperature and water. The gas adsorption capacity of coal decreases linearly with the temperature. At the same time, an increase in water content and a decrease in freezing temperature will significantly reduce the gas desorption capacity of coal samples, effectively reducing the gas expansion energy of coal samples, especially the desorption gas expansion energy. In engineering implementation of this method, the ice phase network can fill the coal pores and cracks and improve the mechanical properties of the coal/rock mass, and the gas pressure in the coal seam and stress concentration near the coal rock interface can be reduced by low temperature and cold shrinkage, thereby achieving safe exposure of the coal seam and preventing accidents from occurring.

Review of Patents on Small Grinding Wheel Polishing Technology

Abstract: Grinding disc polishing is an important polishing method that can be used to manufacture various high-precision and high-quality optical components. The smoothing effect of grinding discs is a simple and effective method widely used to suppress MSF errors. Grinding disc technology has good polishing effects on flat, spherical, aspherical, and free form surfaces. The polishing mechanism is to generate chips through the small plastic cutting of abrasive particles, but it only uses a very small amount of abrasive particles to exert force and uses the flow friction between the abrasive particles and the grinding disc and the workpiece to flatten the surface roughness of the workpiece. It can be seen from the relevant literature that the floating tool holder maintains a constant pressure to solve the problem of uneven pressure distribution between optical components. The adjustable tool holder can adjust the amount of spring deformation to adapt to local surface changes of optical parts, ensuring consistent material removal. The force-adaptive tool holder can be adjusted in real time during the machining process to reduce errors generated during machining. The jointed tool holder improves the fit between the grinding wheel and optical components, ensuring a tight fit between the grinding wheel and optical components. This patent paper aims to introduce grinding wheel polishing technology as an essential method for manufacturing high-precision, high-quality optical components. It explores the optimization of abrasive tool design and the improvement of processing efficiency and proposes suggestions and prospects for future research, applications, and development. Through querying literature and patent databases, patent documents related to grinding disc polishing technology were collected and analyzed. The design characteristics of the device structure, technological innovations, as well as the effectiveness and improvements in practical applications were focused. Grinding disc polishing technology effectively removes surface defects and enhances the optical performance of optical components, particularly in suppressing MSF errors. This technology is suitable for flat, spherical, non-spherical, and freeform surfaces, with broad potential applications. Despite the numerous advantages of grinding disc polishing technology, such as simplicity, effectiveness, and wide applicability, critical issues still need to be addressed, including surface morphology control, improving polishing efficiency, and enhancing consistency. Future research should focus on optimizing tool design and developing new polishing materials and processes to improve the manufacturing quality and efficiency of optical components.

Increasing the operating time of pumping units of water-reducing wells through the use of self-cleaning filters

Relevance. At enterprises engaged in open-pit mining, water-reducing wells equipped with submersible installations of electric submersible pumps are widely used in drainage systems. A significant content of particles of mechanical impurities in the pumped-out well fluid causes intense hydro-abrasive wear of the working stages of the electric submersible pumps. Among the existing methods of combating hydro-abrasive wear of submersible pumps in water-reducing wells, the simplest, most economical and effective is the use of filters of various designs. An urgent task is to increase the operating time of submersible electric submersible pumps while reducing the time and costs for cleaning or replacing filters. Aim. Justification of the designs and operating parameters of a self-cleaning filter and tubing string extension included in the electric submersible pump assembly of a dewatering well. Methods. Static calculations of deformation of the tubing column and the tubing column extension under the influence of overpressure. Results and conclusions. The authors have carried out the analysis of an electric submersible pump functioning in the dewatering wells of quarries during the development of mineral deposits by the open method. It was revealed that the main reason for the failure of the electric submersible pumps is the hydro-abrasive wear of the working stages of the submersible pump. The authors propose a method to increase the operating time of the electric submersible pumps in dewatering wells complicated by intensive removal of particles of mechanical impurities by using a self-cleaning filter of the original design. It is noted that a promising direction of development of the drive for self-cleaning filters is the use of deformation of the tubing column. Based on the calculations carried out, it was concluded that the small depths of dewatering wells cause an insufficient amount of deformation of the tubing string to clean the filter element. To increase the length of the reciprocating movement of the electric submersible pumps relative to the production string of a dewatering well, it is proposed to use a tubing string extension of an original design. The operating parameters of the tubing string extension were calculated, which showed the possibility of providing the required amount of controlled reciprocating movement of the electric submersible pumps in the well to restore the throughput of a self-cleaning filter.

Strength and plasticity coordination improvement mechanism in network structure TiBw/TA15 composite via multi-DOF forming

TiBw/TA15 composite with network TiB whisker (TiBw) reinforcement architecture, exhibits high strength but limited plasticity, presenting a significant challenge in enhancing the plasticity of TiBw/TA15 composites. In the current work, strength and plasticity coordination improvement of TiBw/TA15 composite is achieved through the application of multi-degrees of freedom forming (multi-DOF forming) technology. The α phase spheroidization behaviour and strength-plasticity coordination improvement mechanisms are investigated. The results elucidate that increasing deformation amount through multi-DOF forming leads to more pronounced α phase spheroidization and refinement. This effect is attributed to the generation of substantial strain along the deformation path, particularly in the regions where hard TiBw particles rotate (i.e., the tips of TiBw). Additionally, the impediment of dislocation movement by TiBw causes dislocations to accumulate along these rotation regions via single slip and cross slip mechanisms, thereby accelerating the α phase spheroidization process. Furthermore, with increasing deformation amount, the strength and plasticity are coordinately improved. The tensile strength and elongation increase linearly from 972 MPa to 1239 MPa (increased by 27.5 %) and from 5.6 % to 7.9 % (increased by 41.1 %) as the deformation condition advanced from the sintered state to the 40 % deformation condition, respectively. Improved plasticity can be attributed to the refinement of grains and TiBw, promoting more uniform plastic deformation and reducing stress concentrations during tensile testing. The strengthening mechanisms encompass load transfer strengthening facilitated by TiBw, grain refinement strengthening and dislocation pinning effect caused by TiBw.

Reverse deformation design for bending control in welding of ring stiffeners

After Double Side Arc Welding (DSAW), the ring stiffener undergoes significant radial bending deformation due to the release of residual plastic stress, which severely impacts the dimensional quality of the welded component. This type of stress release-induced deformation is difficult to control through the application of external constraints. In this paper, a method for designing reverse deformation to compensate for bending deformation is proposed, based on the Distribution Function based Inherent Strain Method (DFISM). By leveraging the rapid calculations from DFISM and parametric modeling, welding deformation samples of ring stiffeners of different sizes were obtained in sample, and the optimal reverse deformation amount for the ring stiffener was determined using parameter evaluation criteria. The compensation effect of the designed reverse deformation was tested through DSAW experiments, where the calculation and experimental error were less than 1.0 mm (7.8 % of the total deformation), and the maximum error between the welded ring stiffener and the theoretical profile after reverse deformation design was within 1.2 mm (0.03 % of the theoretical radius). The Reverse Deformation Design Method (RDDM), based on rapid calculations and parametric modeling, effectively compensates for the bending deformation of the ring stiffener.

The Influence of Various Deformation Amounts on the Microstructure and Deformation Mechanism of Mg-Y-Nd-Gd-Zr Alloy under Dynamic Compression

The Influence of Various Deformation Amounts on the Microstructure and Deformation Mechanism of Mg-Y-Nd-Gd-Zr Alloy under Dynamic Compression

Evaluation and Prediction of Mechanical Properties According to Welding Methods of Ni 825/A516-70N Clad Plates

In this study, the microstructures and mechanical properties of different methods of FCAW (Flux-cored arc welding) + FCAW or FCAW + GTAW (Gas tungsten arc welding) welding on Ni825/A516-70N clad plate were investigated, using a double U groove angle on a laboratory scale. The amount of specimen deformation with FCAW + FCAW welding was ~1.5 mm, and that with FCAW + GTAW welding was ~3.6 mm. In the Vickers hardness tests, the average hardness value of the FCAW + GTAW welding specimens tended to be higher, and the hardness of the steel showed the same value. Also, in the tensile tests, the maximum strength and elongation of the FCAW + GTAW specimens were found to be higher. The SEM analysis of the welding boundaries of each specimen revealed the phenomenon of grain refinement in the specimens with FCAW + GTAW welding. This was due to the slow welding speed of this welding process and the rapid cooling rate caused by the relatively low layer thickness despite the relatively high number of weld passes. The computer simulation of the amounts of deformation were similar, with a value of 1.5 mm for FCAW + FCAW and 3.6 mm for the computer simulation, indicating the credibility of the simulation. In the computational simulation of butt welding, FCAW + GTAW showed high values for both residual stress and angular strain. The L-seam and C-seam of the demo vessel size were welded under the same conditions as the actual welding. The residual stress and angular deformation in the L-seam were 849 MPa and 2.3 mm for the FCAW + FCAW and 852 MPa and 2.9 mm for FCAW + GTAW. The residual stress and angular deformation in the C-seam were 920 MPa and 0.7 mm for FCAW + FCAW and 930 MPa and 0.9 mm for FCAW + GTAW, respectively.

Precursory crater contraction associated with the 2017 eruption of Shinmoe-dake volcano (Japan) detected by PALSAR-2 and Sentinel-1 InSAR

The time series of PALSAR-2 and Sentinel-1 images reveal inflation at the volcanic flank and contraction at the crater for approximately 5 months before the 2017 eruption of Shinmoe-dake volcano, Japan. While the observation of inflation at the volcano’s flank is ubiquitous, few studies have reported crater contraction preceding an eruption. The flank inflation stopped after the 2017 eruption, while the contraction at the crater continued until the 2018 eruption. We found that a pipe-shaped deformation source above sea level best fits the observation preceding the 2017 eruption. Suppose the flux of ejected materials constrains the conduit radius during the previous 2011 eruption. In that case, the amount of deformation of the pipe-shaped deformation source, whether open or closed at its top, is too large to be realistic. Although constraining the conduit radius from the eruption flux overestimates the pressure change of the pipe-shaped deformation source, water-saturated fractures along the volcanic conduit could extend the effective conduit radius of the pressure source. We propose one potential scenario for the mechanism of the crater contraction preceding volcanic eruptions based on the combination of compaction due to cooling by ambient groundwater and material withdrawal within the conduit. The groundwater inflows from the ambient aquifer through cracks in the porous conduit wall, which are generated by conduit expansion during the magma ascent. Decoupling from the conduit wall due to a decrease in volume of the material promotes material instability and crater contraction. The interaction between the groundwater and the magma triggers the 2017 eruption of Shinmoe-dake volcano, as previous studies have reported.Graphical

Uncovering the influence of deformation amount on microstructure evolution and mechanical behavior of the multi-DoF formed WE43 magnesium alloy

The urgent need of improving energy efficiency accelerates the development of lightweight magnesium alloy, especially for high-performance wrought magnesium alloy. In this research, multi-degrees of freedom (multi-DoF) forming process as a novel severe plastic deformation technique was applied to the forged-annealed WE43 magnesium alloy plates. The effect of deformation amounts ranging from 10% to 40% on microstructure and mechanical property of the experimental material was investigated in detail. Initially forged-annealed WE43 magnesium alloy is composed of rodlike-shaped Mg12Nd and cuboid-shaped Mg24Y5 at the grain boundaries as well as globular-shaped Mg41Nd5 inside the grains. Multi-DoF forming process results in remarkable microstructure change, which is characterized by increasing dissolution of these second phases, grain refinement, formation of twins and disappearance of basal texture in WE43 magnesium alloy with deformation amounts increasing. Compared with the initial forged-annealed one, the multi-DoF formed WE43 magnesium alloy displays an increasing tensile strength but a decreasing plasticity with deformation amounts increasing. The increasingly improved strength is mainly attributed to the joint contribution of increasing solution strengthening, fine-grained strengthening and work hardening, while the increasingly decreased plasticity is mainly attributed to the increasing dislocation despite the basal texture disappearing. This research will provide a novel method of fabricating high-performance wrought magnesium alloy.

Influence of different rolling passes and deformation amounts on the microstructure evolution and strengthening mechanism of Cu-Ni-Si alloy

Under the condition of controlling the total rolling deformation to 80.0%, the effects of multi-pass rolling, the ratio of deformation between the first and second stages in two-stage rolling, and aging parameters on the microstructural evolution and property enhancement of Cu-Ni-Si alloy were investigated. The results showed that the second-stage rolling promotes the formation of high-density dislocations, significantly enhancing dislocation strengthening. Simultaneously, the high-density dislocations facilitate the precipitation of the second phase during aging, and concurrently improving the strength and electrical conductivity of the alloy. In the two-stage rolling and aging process, a ratio of first-stage to second-stage rolling deformation less than 1 yields superior comprehensive properties. Specifically, when the first-stage rolling deformation is 35.0% and the second-stage deformation is 68.8%, the alloy achieves an optimal electrical conductivity of 49.53% IACS, hardness of 272.9 HV0.1, tensile strength of 773.0 MPa, and yield strength of 723.3 MPa. This is because a rolling ratio less than 1 results in higher dislocation density; the δ-Ni2Si precipitates have a coherent relationship with the Cu matrix, the interparticle spacing of precipitates is smaller. The average grain size is refined from 1.29 μm to 1.08 μm, significantly enhancing grain boundary strengthening. Dislocation strengthening and second-phase strengthening are the primary strengthening mechanisms of the alloy, and the calculated alloy strength agrees well with the experimental values, with errors less than 3.4%. Additionally, the Avrami equation in phase transformation kinetics was utilized to study the variation law of the volume fraction of the δ-Ni2Si phase with aging time.

Can Large Strains Be Accommodated by Small Faults: “Brittle Flow of Rocks” Revised

AbstractBrittle deformation in the upper crust is thought to occur primarily via faulting. The fault length‐frequency distribution determines how much deformation is accommodated by numerous small faults versus a few large ones. To evaluate the amount of deformation due to small faults, we analyze the fault length distribution using high‐quality fault maps spanning a wide range of spatial scales from a laboratory sample to an outcrop to a tectonic domain. We find that the cumulative fault length distribution is well approximated by a power law with a negative exponent close to 2. This is in agreement with the earthquake magnitude‐frequency distribution (the Gutenberg‐Richter law with b‐value of 1), at least for faults smaller than the thickness of the seismogenic zone. It follows that faulting is a self‐similar process, and a substantial fraction of tectonic strain can be accommodated by faults that don't cut through the entire seismogenic zone, consistent with inferences of “hidden strain” from natural and laboratory observations. A continued accumulation of tectonic strain may eventually result in a transition from distributed fault networks to localized mature faults.

Strengthening Study on Microsphere Particle Peening for Flexspline Surface of Harmonic Reducer

Abstract The service stability of the flexspline directly affects the service life of the harmonic reducer. Its main failure modes are fatigue fracture of the flexspline, damage of the flexible bearing, tooth wear or transmission slip, the above problems are often sprouted and developed from the surface. Researches show the novel surface treatment technology-Microsphere Particle Peening can significantly enhance the surface performance of the flexspline of the harmonic reducer, and thus improve its fatigue resistance. Therefore, studying this novel shot peening technology has significant scientific significance and practical value. In this paper, Microsphere Particle Peening is adopted to strength the flexspline surface and the effects of three different Microsphere Particle Peening conditions on the surface performance of the flexspline is analyzed. The research results indicate that Microsphere Particle Peening technology can introduce larger residual compressive stress, reduce the surface roughness, increase the surface hardness, improve the microstructure morphology, and effectively control the deformation amount of the flexspline by controlling the processing parameters of Microsphere Particle Peening. Therefore, Microsphere Particle Peening technology has broad engineering application prospects in the surface strengthening of precision components.

Study on the warm deformation behavior and microstructure evolution of the MDIFed Ti–6Al–4V titanium alloy

The Gleeble-3500 thermal simulator was utilized to perform warm compression experiments on multi-directional isothermal forged (MDIFed) mixed microstructure Ti–6Al–4V titanium alloy with partial ultra-fine grains at the conditions of deformation temperatures ranging from 550 °C to 700 °C, strain rates ranging from 0.001 s−1 to 0.1 s−1, with the maximum deformation amount at 50%. The results show that the true stress-strain curve exhibits typical dynamic recrystallization (DRX) characteristics at different deformation conditions. Based on the Arrhenius Model, the constitutive equation of the MDIFedTi-6Al–4V titanium alloy was successfully constructed. The correlation coefficient (R) and average absolute relative error (AARE) values are 0.98341 and 7.01%, respectively, indicating that the Arrhenius Model can well describe the warm deformation behavior of the alloy. Through activation energy spectrum analysis, the average activation energy is approximately 308 kJ/mol. Further, utilizing the dynamic material model (DMM), power dissipation diagrams, instability diagrams, and processing maps were drawn, and the optimal warm processing ranges were determined to be 630 °C–700 °C, 0.001s−1∼0.002s−1 and 650 °C–700 °C, 0.06s−1∼0.1s−1. At the same time, the unstable domains were identified to be concentrated in the range of 550 °C–640 °C, 0.03s−1∼0.1s−1. Through the analysis of local misorientation and Schmidt factor in EBSD technology, The results indicate that the deformation mechanism of the MDIFed Ti–6Al–4V titanium alloys is primarily governed by dislocation slip and DRX. The activation of multiple slip systems contributes to the coordination and homogeneity of deformation, thereby enhancing the overall plastic deformation ability of the MDIFed Ti–6Al–4V titanium alloys.

Continuous and discontinuous dynamic recrystallization in the superplastic deformation of moderately cold-deformed Cr4Mo4Ni4V martensitic steel

This study employs lath martensite as the starting structure to achieve superplasticity through limited cold deformation, revealing how the dynamic recrystallization mechanism during superplastic deformation changes with the amount of prior cold deformation. Results show that an elongation close to 700 % can be achieved with 25 % cold deformation, and the peak stress is significantly reduced. The amount of deformation required to achieve superplasticity with martensite as the initial processing structure is much lower than with ferrite as the initial processing structure. However, when the deformation increased from 25 % to 50 %, the elongation increased only slightly, from 696 % to 756 %, while the peak stress increased from 90.1 MPa to 96.4 MPa. The reason is that continuous dynamic recrystallization (CDRX) is suppressed, and softening occurs only through discontinuous recrystallization (DDRX), thus weakening the softening effect. The superplastic deformation mechanism for samples with high cold deformation mainly involves grain boundary sliding (GBS) associated with DDRX, while for samples with moderate cold deformation, it involves GBS accompanied by both CDRX and DDRX. Strain rate jump (SRJ) tests reveal that even 5 % cold deformation can accelerate the growth of the m-value during deformation. Interestingly, the m-value of the 25 % deformed sample is slightly higher than that of the 50 % deformed sample. This research offers a promising route for achieving superplasticity in high-alloy low-carbon steel, revealing continuous and discontinuous dynamic recrystallization accompanied by grain boundary sliding in superplastic cold-deformed martensitic Cr4Mo4Ni4V steel.