Selection Of Process Parameters Research Articles

INVESTIGATION ON PERFORMANCE OF EXTRUSION HONING PROCESS ON QUALITY OF SURFACE TEXTURE

The EH approach overcomes this limitation of conventional finishing method. The present study focus on the impact of number of passes at the specimen's entry and exit sides of the carrier media. The improvements in surface finish (Ra) on both side i.e entry and exit are evaluated as well. A dimensionless expression for Ra is also developed. The relation is implemented using Buckingham’s π theorem and comparison of developed model is performed with experimental results. SEM analysis is made to portray surface texture produced by selected process parameters such as number of passes, volume fraction and grit size of abrasive grains.

RSM design-based hybrid approach to multi-response optimization in milling Ti-6Al-4 V alloy: A comparative study

The Selection of appropriate process parameters in milling Ti-6Al-4 V alloy to reduce energy and power consumption while maintaining product quality and process stability is challenging. This study aims to optimize process parameters in milling Ti-6Al-4 V alloy with five primary criteria i.e., average cutting force, shear stress, specific cutting energy, power consumption, and average surface roughness. A total of 26 experimental tests was carried out with the variation of process parameters such as cutting speed (m/min), feed rate (mm/min), and depth of cut (mm) based on the Box-Behnken design (BBD) matrix of response surface method (RSM) under dry and high-pressure cooling (HPC). The criteria importance through the inter-criteria correlation (CRITIC) method was used to determine the relative weights of each response. At the same time, the evaluation of optimum process parameters was done by hybrid multi-response optimization (MRO) techniques such as complex proportional assessment (CRITIC-COPRAS), additive ratio assessment (CRITIC-ARAS), combined compromise solution (CRITIC-COCOSO) and technique for order of preference by similarity to ideal solutions (CRITIC-TOPSIS). After the evaluation, a cutting speed of 32 m/min, feed rate of 22 mm/min, and 0.75 mm depth of cut with HPC were selected as the optimum process parameters. Due to the lack of an identical solution, the sensitivity of the used MRO methods was checked out with the weight variation of the selected criteria. TOPSIS was noticed as the most robust MRO method with less sensitivity. Spearman’s Correlation coefficient was used to assess the correlation among the used hybrid MRO methods.

EXPERIMENTAL INVESTIGATION ON MECHANICAL PROPERTIES OF FDM-BASED NYLON CARBON PARTS USING ANN APPROACH

The implementation of the fused deposition modeling (FDM) technique in the production system is mainly due to its flexibility and ability to fabricate complex 3D prototypes and geometries. However, the mechanical strength of the printed parts needs to be investigated which was influenced by the process parameters such as layer thickness (LT), raster angle (RA), and Infill Density (ID). Therefore, these process parameters need to be optimized to attain better mechanical strength from the FDM printed parts. In this research, ePA-CF filament material was used to fabricate the specimens based on the selected process parameters such as LT (0.07, 0.14, and 0.20[Formula: see text]mm), RA (0∘, 45∘, and 90∘) and ID (50%, 75%, and 100%). The artificial neural network (ANN) method was implemented to determine the influential printing process parameters. Tensile, flexural, and impact tests were considered as the response parameters based on the various combination of the input parameters. It was concluded that the printing of nylon carbon parts using [Formula: see text][Formula: see text]mm, [Formula: see text], [Formula: see text] retains improved tensile strength of 66 MPa, flexural strength of 87[Formula: see text]MPa and impact strength of 12.5[Formula: see text]KJ/m2. Further, the propagation of cracks and the mode of failure were examined using SEM fractography. These observations substantiate that the selection of an optimal combination of FDM parameters assists in enhancing the mechanical strength of the printed nylon carbon parts.

Profile prediction for ultrasonic vibration polishing of alumina ceramics

Ultrasonic-assisted polishing methods are widely used for the precision processing of hard and brittle materials such as glass and ceramics due to their excellent polishing performance. Most research has been focused on basic removal mechanisms of ultrasonic-assisted polished materials. Some investigators have studied the profile of surfaces after conventional mechanical polishing, but less research has been done on the profile of faces after axial ultrasonically assisted polishing. This paper has established a novel force prediction model for the ultrasonically assisted polishing, which is critical for geometrical accuracy and surface finish. Also a material removal model has been developed for this process using a spherical polishing head at different tilt angles. Pressure and velocity distributions have been calculated for multi-position contact areas. The experimental study of multiple trajectory polishing of alumina ceramics showed a good correlation between the experimental and simulated surface profiles. The ultrasonic polishing process parameters were optimized by applying the gray correlation analysis. The obtained results can be used not only select ultrasonic assisted polishing process parameters but also provide theoretical underpinning for surface polishing trajectory planning.

Active and Passive Thermal Management in Wire Arc Additive Manufacturing

This article presents innovative approaches for managing residual stresses and distortion in additive manufacturing (AM) of metal components (baseplate material: EN8; filler wire material: ER70S-6). The experiments are conducted with two approaches for thermal management—passive and active. The passive approach of experiments is performed by varying the selected process parameters to study their effect on residual stresses and distortion. The chosen parameters are current, torch speed, geometry, continuous or a delay in the deposition, and cooling arrangement. Based on the understanding gained from the passive approach, the active approach of thermal management was implemented by insulating the substrate with and without adaptive current and heating the substrate. The experimental results were corroborated with the simulation to understand the process better. A comparative study for hardness was made based on the T8/5 extracted from the simulation. These experiments and simulations endorse passive and active thermal management as effective tools that can alter the distortion and residual stress pattern and the mechanical properties of an AM component. The investigation concludes that the process parameters that lead to higher heat input vis-à-vis an increase in current or a decrease in speed increase the distortion. On the other hand, the parameters that affect the rate of heat distribution vis-à-vis torch speed and geometry affect the residual stresses. When current, traverse speed and a/b ratio were kept the same, active thermal management with a heated base reduced distortion from 1.226 mm to 0.431 mm, a 65% reduction compared to passive thermal management. Additionally, the maximum residual stress was reduced from 492.31 MPa to 250.68 MPa, with residual stresses decreasing from 418.57 MPa to 372 MPa. Overall, active thermal management resulted in a 63% reduction in distortion, lowering it from 1.35 mm to 0.50 mm using external heating. The components that are difficult to complete because of the in-process distortion are expected to be manufactured with thermal management, e.g., heating the substrate is an effective measure to manage the in-process distortion. Thermal management techniques depend on geometry; for instance, a concave surface, because of self-heating, reduces the cooling rate and has relatively less variation in hardness.

The Influence of the Tool Concave Shoulder Angle on Heat Generation in the Stir Friction Welding Process with AA6061-T651 Materials

This study aims to determine the effect of the concave shoulder angle of the FSW tool on heat generation rate and temperature simulation results. The FSW tool used in this study is the FSW tool with straight cylindrical geometry, tapered cylinder, hexagonal, and tapered square. Calculation of heat generation rate is carried out for all FSW tools, then the optimal one is selected and then simulated. The process of calculating heat generation rate and simulation using the Taguchi method has 4 factors, each of which has 4 levels. The factors used in this study are tool rotation speed, welding speed, concave shoulder angle, and tool tilt angle with temperature response. on the weld joint. The results of this study indicate that the influence of the concave shoulder angle on the heat generation rate and temperature simulation is very influential. Based on the results of the heat generation rate calculation, the FSW tool with hexagonal pin geometry was chosen to be simulated. The simulation results show that the selected process parameters are tool rotation speed of 1208 rpm, welding speed of 90 mm/s, concave shoulder angle of 5°, and tool tilt angle of 3°. From the selected parameters, it was experimented with to produce a fairly good connection even though there were still surface defects.

Role of Surface-Active Element Sulfur on Thermal Behavior, Driving Forces, Fluid Flow and Solute Dilution in Laser Linear Welding of Dissimilar Metals

Understanding heat and mass transfer and fluid flow in the molten pool is very helpful in the selection and optimization of processing parameters, and the surface-active element has an important effect on the heat and mass transfer in laser welding of dissimilar metals. A three-dimensional (3D) numerical model coupled with a sub-model of surface tension, which considers the influence of local temperature and the concentration of surface-active element sulfur at the gas/liquid surface, is used to analyze the thermal behavior, driving forces, fluid flow, and solute dilution during laser linear welding of 304SS and Ni. The relationship between surface tension, driving forces, and the temperature coefficient of surface tension with the spatial distribution of temperature and the surface-active element sulfur is quantitatively analyzed. The simulation results show that the molten pool is fully developed at 45 ms, and the collision of inward and outward convection, with the maximum velocity reaching 1.7 m/s, occurs at the isotherm with a temperature between 2200 K and 2500 K. The temperature-gradient term and concentration-gradient term of surface shear stress play different roles in different positions of the free surface. The local sulfur concentration changes the temperature sensitivity of the surface tension at different sides of the free surface and further determines the transition of convection. Complex fluid flow promotes solute dilution, and the distribution of solute becomes uniform from the front to the rear of the molten pool. The Ni element is transferred to 304SS mainly at the rear side. The work provides theoretical support for the control of joint quality by changing the content of surface-active elements in dissimilar welding.

Investigation of temperature field for the in-situ fabrication of particle-reinforced alumina ceramics coating via laser induction

Laser-induced aluminum thermal reaction was used to prepare a new iron particle reinforced alumina ceramic coating on the surface of TC4 titanium alloy. The aluminum thermal reaction heat generation in the on-line laser melting and coating process is fast and not easy to control, and its effect on the coating quality is unknown and usually neglected in the preparation process. In this paper, a numerical simulation model of a dual heat source containing the reaction heat is established. The temperature field of the new Al2O3-Fe composite coating and the thermal stress distribution pattern of the components were investigated. The effects of different laser parameters on the maximum molten pool temperature, thermal deformation and coating morphology of TC4 titanium alloy substrates were also discussed. The accuracy of the model is verified by the joint temperature acquisition experiment, which provides a reference for the selection of laser cladding process parameters. The simulation results show that the maximum temperature and volume of the melt pool increase significantly due to the coupling of the induced reaction heat, and the maximum temperature is not inversely proportional to the laser scanning speed, but directly proportional. The residual stress analysis shows that the residual stress on the coating is mainly the tensile stress along the laser cladding direction, which is the main reason for the transverse crack of the single layer coating after laser cladding.

Sensitivity Analysis of Gas Tungsten Arc Welding Process Variables for Angular Distortion in Chromium Manganese Stainless Steel Using Design Thinking Approach

An approach to problem solving that is solution-based is provided by the design methodology known as Design Thinking (DT). To address complicated problems, the five stages of design thinking can be applied. This research article focuses on using the DT method, which includes empathising, defining, and coming up with ideas, to produce high-quality weld joints. The selection of welding process parameters plays a vital role in determining the quality of weld. The weld should be free from weld defects to ensure good performance. One of the major defects that affect the weld quality is angular distortion. During welding the rapid heating and cooling of the work piece results in uneven expansion and contraction in all directions. This results in the work piece getting distorted. It becomes imperative to predict distortion in the work piece so that it can be reduced by providing initial angular distortion in the negative direction. Through empathy, it has been found that the welding process parameters such as welding current (I), welding gun angle (θ), shielding gas flow rate (Q), plate length (L), and welding speed (V), significantly contribute to angular distortion of the weld joint. From the ideation process the following suggestions were arrived to predict angular distortion and identify the factor that has significant effect on angular distortion. A statistical prediction model was developed correlating the welding process parameters with angular distortion. Central Composite Rotatable Design with five factor and five levels was used to develop mathematical models. The experiments were conducted on Chromium Manganese Stainless Steel Grade AISI 202 in GTAW process. Optimization of process parameters was done using Simulated Annealing algorithm. From the sensitivity analysis it was found that the lower values of welding current, welding gun angle and higher values of welding speed, shielding gas flow rate and plate length resulted in minimum angular distortion.

Effect of solution heat treatment on microstructure, mechanical and electrochemical properties of hastelloy X fabricated by laser powder bed fusion

Laser Powder Bed Fusion (LPBF) technology provides a new way for integral forming and rapid manufacturing of complex components of Hastelloy X, but the parts fabricated by LPBF (LPBFed) inevitably have defects such as micropores, micro-cracks, and residual stress. To eliminate the above defects and further enhance the material properties of the Hastelloy X, solution heat treatment (SHT) was performed on the LPBFed parts. Although SHT can improve material properties, there are many limitations in using traditional machining because of the high hardness of Hastelloy X. So, electrochemical machining (ECM) is used to process LPBFed Hastelloy X parts and has a wide range of applications. Firstly, the optimal SHT process parameters with good comprehensive mechanical properties were obtained by orthogonal experiment, and the influence of the selection of SHT process parameters on the properties of LPBFed samples was discussed. Then, after SHT with optimized process parameters, the elongation after fracture (EAF) increases from 30.0% to 51.3%, and the ultimate tensile strength (UTS) reduces from 798.7 MPa to 732.6 MPa merely. Next, its micro-morphology was observed and analyzed. It can be seen that After the SHT, the grain size increases, and the low-angle grain boundary decreases in the XOY direction, resulting in the decrease of the intergranular area and dislocation densities to reduce the tensile strength. After the SHT, the molten pool boundary disappears in any direction, which greatly improves the plasticity of the part. and the microstructure explains the results of tensile tests. The experimental results show that the material properties of Hastelloy X can be greatly improved by this SHT process, which has great development potential and broad application prospects. Finally, to apply Hastelloy X to the Electrochemical machining (ECM) process, an experimental analysis of the electrochemical passivation performance of LPBFed samples after SHT with optimal parameters was carried out. The experimental results show that after SHT the denseness of the passivation film is improved, the corrosion resistance is enhanced, and the anisotropy of corrosion resistance is reduced. By observing the microscopic morphology of the passivation film, it can be seen that the corrosion products reduced and the number of corrosion pits decreased. This means LPBFed Hastelloy X parts after SHT is significantly improved and meets the ECM processing requirements.

A Novel Approach for Determining the Critical Quality Attributes of Mesenchymal Stem Cells by Specifying Cell Population With Replication Potential

We introduce a novel approach to determine the critical quality attributes (CQAs) of mesenchymal stem cells (MSCs) expected to exert immunosuppressive effects. MSCs retained homeostatic replication potentials, such as sustainable growth and consistent cell morphology as a population, in early passages, but lost them in late passages. Characteristic surface markers of MSCs (ie, CD73, CD90, and CD105) were no longer expressed at 2 weeks after subcutaneous transplantation into NOG mice when MSCs from late passages were transplanted, but not when MSCs from early passages were transplanted, suggesting that the biological effects of the MSCs differed according to the timing of cell harvesting and highlighting the importance of specifying MSCs that retained homeostatic features to define the CQAs. The homeostatic features of MSCs related to the balance of the redox system, nutrient requirements, and mitochondrial function were also observed until a certain passage. Therefore, we could define the CQAs of MSCs related to manufacturing by selecting process parameters (PPs) underlying the homeostatic features of MSCs and measuring these PPs quantitatively to specify the cell population with homeostatic features by limiting the passage number. The validity of the PPs stipulated in our pilot study was verified using an SKG murine arthritis model, and critical PPs (CPPs) were then selected among the PPs. Thus, CQAs related to manufacturing in the developmental phase could be defined by the CPPs in this manner, and the concept of CQAs could be refined continuously toward commercial manufacturing.

In-situ workpiece perception: A key to zero-defect manufacturing in Industry 4.0 compliant job shops

Job shop manufacturing is characterized by excellent job flexibility and highly customizable products. The dynamic nature of jobs in this manufacturing segment poses a relatively high challenge to actualizing zero-defect manufacturing (ZDM). The continuous emergence of new engineering materials and improved consumer’s contributions to product development driven by IIoT further complicates the uphill task. This study develops a methodological framework that positions in-situ workpiece perception and industrial recommender system as tools to trivialize the challenge of ZDM in job shops. In-situ workpiece perception was experimented using a case study of friction stir welding (FSW), a thermomechanical manufacturing process where existing algorithms for online quality assessment are material-specific. The novelty in this study is deciphering unique applications for the hitherto jettisoned sensor data acquired prior to the FSW tool traverse (the actual welding stage), ensuring that the material perception process does not induce defects in the products. This study presents two major contributions towards attaining first-time-right ZDM in job shops. First, a novel interlink for IIoT-driven production planning to aid the selection of optimal process parameters; second, the selection of appropriate quality assessment algorithms during the welding process.

On the correlation between processing parameters, plastic deformation, and mechanical property in hard machining of H13 steel

Hard machining, as one of the sustainable manufacturing technologies, tends to introduce highly coupled thermomechanical loads into the machined surface layer, which causes materials to suffer from severe plastic deformation underneath and, thus, the alteration of the mechanical properties. In this paper, a systemic investigation was performed on the correlation of processing parameters, plastic deformation, and mechanical properties of machined surface layer for hardened H13 steel, where the cutting parameters and tool micro-geometry are varied. The plastic deformation layer was composed of an amorphous structure and plastically deformed grain. Compared to cutting parameters, edge micro-geometry significantly influences the depth of the plastic deformation layer. The automated ball indentation (ABI) technique was utilized to evaluate the mechanical properties of the machined surface layers. Finally, the relationship between processing parameters, depth of plastic deformation, and mechanical properties was revealed. The experimental findings provide a solid foundation for processing parameter selection to improve the functional performance of manufactured components.

A continuous mashing system controlled by mean residence time

Continuous processes offer more environmentally friendlier beer production compared to the batch production. However, the continuous production of mashing has not become state-of-the-art in the brewing industry. The controllability and flexibility of this process still has hurdles for practical implementation, but which are necessary to react to changing raw materials. Once overcome, a continuous mashing can be efficiently adapted to the raw materials. Both mean residence time and temperature were investigated as key parameters to influence the extract and fermentable sugar content of the wort. The continuous mashing process was implemented as continuous stirred tank reactor (CSTR) cascade consisting of mashing in (20°C), protein rest (50°C), β-amylase rest (62-64°C), saccharification rest (72°C) and mashing out (78°C). Two different temperature settings for the β-amylase rest were investigated with particular emphasis on fermentable sugars. Analysis of Variance (ANOVA) and a post-hoc analysis showed that the mean residence time and temperature settings were suitable control parameters for the fermentable sugars. In the experimental conditions, the most pronounced effect was with the β-amylase rest. These results broaden the understanding of heterogenous CSTR mashing systems about assembly and selection of process parameters

Additive Manufacturing of Titanium-Based Materials Using Electron Beam Wire 3D Printing Approach: Peculiarities, Advantages, and Prospects

Potential of additive manufacturing technologies, namely, xBeam 3D Metal Printing for the fabrication of uniform Ti–6Al–4V (Ti-6-4, mas.%) material as well as layered titanium-based structures, with mechanical properties sufficient for wide practical application is demonstrated. The key distinctive features of this process are titanium alloy wire as a feedstock material and hollow conical electron beam for heating and melting of the wire. 3D printed with special ‘shift strategy’ Ti-6-4 alloy meets requirements to mechanical characteristics of corresponding conventional cast and wrought products, if microstructure features, material anisotropy and crystallographic texture are controlled with proper selection of processing parameters. Production of multilayered materials consisting of combined layers of different titanium materials, viz. commercially pure titanium (CP-Ti), Ti-6-4 and high-strength T110 alloys, as well as metal matrix composites (MMC) based on Ti-6-4 matrix reinforced by fine TiC particles is considered. Microstructural features and mechanical properties of all 3D printed materials are investigated. Terminal ballistic tests are performed with different ammunition. Described results show the promising potential of 3D printing technologies, xBeam 3D Metal Printing as an example, for manufacturing of titanium-based multilayered armour materials with reduced thickness and weight, and at the same time, sufficient protection characteristics.

Study on the secondary structure and hydration effect of human serum albumin under acidic pH and ethanol perturbation with IR/NIR spectroscopy

Human serum albumin (HSA) is the most abundant protein in plasma and plays an essential physiological role in the human body. Ethanol precipitation is the most widely used way to obtain HSA, and pH and ethanol are crucial factors affecting the process. In this study, infrared (IR) spectroscopy and near-infrared (NIR) spectroscopy in combination with chemometrics were used to investigate the changes in the secondary structure and hydration of HSA at acidic pH (5.6–3.2) and isoelectric pH when ethanol concentration was varied from 0% to 40% as a perturbation. IR spectroscopy combined with the two-dimensional correlation spectroscopy (2DCOS) analysis for acid pH system proved that the secondary structure of HSA changed significantly when pH was around 4.5. What’s more, the IR spectroscopy and 2DCOS analysis showed different secondary structure forms under different ethanol concentrations at the isoelectric pH. For the hydration effect analysis, NIR spectroscopy combined with the McCabe–Fisher method and aquaphotomics showed that the free hydrogen-bonded water fluctuates dynamically, with ethanol at 0–20% enhancing the hydrogen-bonded water clusters, while weak hydrogen-bonded water clusters were formed when the ethanol concentration increased continuously from 20% to 30%. These measurements provide new insights into the structural changes and changes in the hydration behavior of HSA, revealing the dynamic process of protein purification, and providing a theoretical basis for the selection of HSA alcoholic precipitation process parameters, as well as for further studies of complex biological systems.

Microstructure and mechanical properties of additively manufactured AlSi10Mg lattice structures from single contour exposure

Metal-based additive manufacturing techniques offer the ability to produce complex, near net shape parts that would be impossible or prohibitively expensive to manufacture via traditional casting and machining methods. Low density lattice structures for lightweight construction are one such example. However, there currently are no well-developed guidelines for designing and reliably manufacturing these structures. Literature on the topic is fragmented and usually only covers a limited aspect of the complex relations between process parameters, microstructure, lattice geometry and mechanical properties. This work covers the edge case of small diameter struts manufactured from AlSi10Mg via Laser Powder Bed Fusion (L-PBF) using the single contour exposure strategy, which is necessary to ensure sufficient geometric accuracy. Various cubic strut-based lattice geometries are manufactured using four laser parameter combinations corresponding to different area energy densities and beam offsets. The influence of process parameters and heat treatment on the microstructure and mechanical properties is investigated. Results show that the microstructure of filigree lattice struts can be tailored by the selection of process parameters, resulting in either uniform or core–shell structures depending on the laser power, while the macroscopic mechanical properties are mainly determined by the lattice geometry and relative density.

Corrosion Resistance of Nickel-Aluminum Sinters Produced by High-Pressure HPHT/SPS Method

As part of extensive research on the properties of nickel-aluminum alloys, corrosion tests of sintered materials produced by the innovative HPHT/SPS (high pressure, high temperature/spark plasma sintering) method were performed in 0.1 molar H2SO4 acid. The hybrid, unique device used for this purpose (one of only two such devices operating in the world) is equipped with a Bridgman chamber, which allows heating with high-frequency pulsed current and sintering of powders under high pressure in the range of 4-8 GPa and at temperatures up to 2400 °C. Using this device for the production of materials contributes to the generation of new phases not obtainable by classical methods. In this article, the first test results obtained for the nickel-aluminum alloys never before produced by this method are discussed. Alloys containing 25 at.% Al, 37 at.% Al and 50 at.% Al were produced. The alloys were obtained by the combined effect of the pressure of 7 GPa and the temperature of 1200 °C generated by the pulsed current. The time of the sintering process was 60 s. The electrochemical tests, such as OCP (open circuit potential), polarization tests and EIS (electrochemical impedance spectroscopy), were carried out for the newly produced sinters and the results were compared with the reference materials, i.e., nickel and aluminum. The corrosion tests showed good corrosion resistance of the produced sinters, with corrosion rates of 0.091, 0.073 and 0.127 mm per year, respectively. It leaves no doubt that the good resistance of materials synthesized by powder metallurgy is due to the proper selection of the manufacturing process parameters, ensuring a high degree of material consolidation. This was further confirmed by the examinations of microstructure (optical microscopy and scanning electron microscopy) and the results of density tests (hydrostatic method). It has been shown that the obtained sinters were characterized by a compact, homogeneous and pore-free structure, though at the same time differentiated and multi-phase, while the densities of individual alloys reached a level close to the theoretical values. The Vickers hardness of the alloys was 334, 399 and 486 HV10, respectively.

Process Parameter Investigation and Torsional Strength Analysis of the Additively Manufactured 3D Structures Made of 20MnCr5 Steel

An ongoing growth of the available materials dedicated to additive manufacturing (AM) significantly extends the possibilities of their usage in many applications. A very good example is 20MnCr5 steel which is very popular in conventional manufacturing technologies and shows good processability in AM processes. This research takes into account the process parameter selection and torsional strength analysis of AM cellular structures. The conducted research revealed a significant tendency for between-layer cracking which is strictly dependent on the layered structure of the material. Additionally, the highest torsional strength was registered for specimens with a honeycomb structure. To determine the best-obtained properties, in the case of the samples with cellular structures, a torque-to-mass coefficient was introduced. It indicated the best properties of honeycomb structures, which have about 10% smaller torque-to-mass coefficient values than monolithic structures (PM samples).

Dynamic recrystallization and constitutive equation of 15Cr-10Mn-Ni-N steel under hot deformation

Hot working as one of the indispensable processes for all metal materials can effectively refine the grain to improve the material properties. However, the study on the hot-deformation process of low-Ni austenitic stainless steel is scarce. In this study, we conducted single-pass compression tests to explore the dynamic recrystallization process of a low-Ni austenitic stainless steel with the chemical compositions of 15Cr-10Mn-Ni-N during deformation at various temperatures and strain rates. According to the experimental data, the true stress-strain curves are drawn and constitutive equation is established to predict the variations of stress and strain, accompanied with high accuracy. The microstructural characterizations show that the increase of deformation temperature leads to the occurrence of recrystallization in spite of the enhanced softening effect. In particular, the increase of strain rate promotes the refinement of grain size, and the average grain size significantly decreases from 200 µm to 20 µm under the compression condition of 1100 ℃ and 10 s−1. The decreasing grain size can compensate the sacrificing strength due to the reduction of Ni addition. The peak stress of 15Cr-10Mn-Ni-N austenitic stainless steel is 186 MPa at 1000 °C and 0.1 s−1, which is basically similar with the conventional austenitic stainless steel. Evidently, the austenitic stainless steel in this study has a cost-effective advantage because of its low Ni addition, i.e., we have the advantage of reducing material costs while maintaining the identical mechanical properties. Here the recrystallization process of 15Cr-10Mn-Ni-N austenitic stainless steel provides a basis for the selection of thermal processing parameters and a general understanding of the microstructure evolution.