Evolution of Annealing Twins in a Hot Deformed Nickel-Based Superalloy

The hot deformation characteristics of a GH4169 superalloy are investigated at the temperature and strain rate ranges of 1193–1313 K and 0.01–1 s−1, respectively, through Gleeble-3500 simulator. The hot deformed microstructures are analyzed by optical microscopy (OM), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) technology. The effects of deformation parameters on the features of flow curves and annealing twins are discussed in detail. It is found that the shapes of flow curves are greatly affected by the deformation temperature. Broad peaks appear at low deformation temperatures or high strain rates. In addition, the evolution of annealing twins is significantly sensitive to the deformation degree, temperature, and strain rate. The fraction of annealing twins first decreases and then rises with the added deformation degree. This is because the initial annealing twin characters disappear at the relatively small strains, while the annealing twins rapidly generate with the growth of dynamic recrystallized grains during the subsequent hot deformation. The fraction of annealing twins is relatively high when the deformation temperature is high or the strain rate is low. In addition, the important role of annealing twins on dynamic recrystallization (DRX) behaviors are elucidated. The obvious bulging at initial twin boundaries, and the coherency of annealing twin boundaries with dynamic recrystallized grain boundaries, indicates that annealing twins can motivate the DRX nucleation during the hot deformation.

Research on Three-point Bending Mechanical Performance of Square Tube Structure Filled with Foam Aluminum

In this paper, the quasi-static three-point bending experiments are carried out to study the deformation behavior of square tube and square tube filled with foam aluminum. The difference of bending deformation mode, loading characteristics and energy absorption efficiency between tube and foam aluminum filled tube is compared. And the influence of adhesive between the foam aluminum core and the tube wall on the bending deformation of square tube filled with foam aluminum is analyzed. Based on the bending super beam element model of tube structure, the relationship between the moment and rotation of square tube filled with foam aluminum under transverse static loading is analyzed. And the formula for calculating the moment and rotation angle of square tube filled with foam aluminum at three-point bending is obtained. In order to compare the simulation results, theoretical calculation results and experimental results of quasi-static bending, the three-point bending deformation of square tube and filled with foam aluminum under quasi-static and impact loading is simulated by finite element method. The results show that the filling of foam aluminum can improve the bearing capacity and energy absorption performance of the square tube structure. Under the bending load, the deformation degree of the bearing section is greatly reduced, which increases the bearing capacity of the structure and increases the stability of its bending resistance.

Research on Multi-Stage Composite Loading Process Control Method for Roller Staking of Self-Lubricating Spherical Plain Bearings

The staking quality of Self-lubricating Spherical Plain Bearings (SSPBs) directly affects the safety of aircraft and the service life of bearings. Reliable loading process control methods and precise process parameter indexes will come into the creation of efficacious staking quality. Therefore, this paper aims to analyze the mechanical state of the roller staking process and give a load control method and corresponding parameter indexes for the high-quality roller staking process. First, based on the analysis of quality inspection requirements, five states of the deformation degree of the flanging lip of the V groove during the roller staking process were proposed, and their relationship with the requirements was studied. Then, the mechanical states corresponding to the five deformation states of the flanging lip deformation were obtained by numerical simulation, and the feeding displacement was determined. Meanwhile, a Multi-Stage Composite Loading (MSCL) process control method was first proposed to control the material damage of the flanging lip, i.e., the rotate speed of the roller tool was constant during the roller staking process, and the displacement–time control was adopted first; when the staking load reaches a staking value, the force–time control was used to make the staking quality meet the requirements. Finally, the staking quality of the MSCL method was verified though the test. The research shows that the feeding displacement needs to be added to the requirements, and the recommended value is 0.5–0.6 times of the V groove depth. A good surface quality and non-material-damage of the flanging lip is more likely to be obtained by the MSCL process control method. The research reveals the formation mechanism of process deformation, and gives more precise process control indexes. At the same time, it provides a theoretical reference for more reliable technical standards.

Influence of Cold Rolled Deformation Degree and Heating Rates on Crystallite Dimension and Recrystallization Fraction of Aluminum Plates

In order to study the microstructure evolution rule of pure aluminum plates during different cold-rolled (CR) deformation degrees and annealing processes, samples with aCR deformation of 50~85%, heating rates of 60~100 °C/min and annealing at the target temperature of 350~500 °C were investigated. The microstructure, crystallite dimension and grain boundary characteristics were characterized by the methods of polarizing microscope (PM) and electron backscattered diffraction (EBSD). The results showed that the crystallite dimension of the initial state was 102 μm and ends up completely broken with an increase in the CR deformation degree. When the CR deformation increases to 85%, the deformed micro-bands were very small, with a band spacing of 5~10 μm. At this time, the grain distortion is more serious, there are more high-density grain defects, such as dislocations, and there is a high deformation of the storage energy, which is the energy preparation for the subsequent finished products to withstand the annealing process. The recrystallization fraction was higher with an increase in annealing temperature. After completed recrystallization, the grains showed an equiaxed shape. Orientation imaging and misorientation angle analysis showed that the red-oriented grains of the (001) plane, which had preferred nucleation, recrystallization and rapid grain growth. Final grains of the completed recrystallization are relatively coarse. Under the same deformation, the average crystallite dimension of the recrystallized grains decreases with an increase in annealing heating rate.

Performance Comparison of Zn-Based and Al–Si Based Coating on Boron Steel in Hot Stamping

The coatings of boron steels play an important role in affecting the quality of hot stamping parts, so it is important to evaluate the hot stamping performance of coatings before designing processes. Taking the U-type hot stamping part of boron steel as research objects, the surface quality, microstructure and temperature variation of samples with GA (galvannealed), GI (galvanized) and Al–Si coatings were observed and analyzed to evaluate the anti-oxidation, forming and quenching performances of different coatings. The results show that all the GA, GI and Al–Si coatings could provide good oxidation protection and also act as the lubricants for avoiding the friction damage of sample substrates and die-surface. But the different compositions of GA, GI and Al–Si coatings will contribute the different colors. Under the same deformation degree, the Al–Si coating can provide the best substrate protection and the GI coating will induce cracks in the substrate because of the liquid metal-induced embrittlement phenomenon. There is no significant difference between the quenching performances of GA, GI and Al–Si coatings, and the thermal conductivity of the GI coating is slightly better than Al–Si and GA coatings.

Complex Structural Effects in Deformed High-Manganese Steel

The research presented in this paper is part of a larger project concerning deformation behavior, microstructure and mechanical properties of high-manganese steels with different chemical compositions and processed under various conditions. The current investigation deals with the development of microstructure and crystallographic texture of Fe-21.2Mn-2.73Al-2.99Si steel deformed in tension until fracture at ambient temperature. The deformation process of the examined steel turned out to be complex and included not only dislocation slip and twinning but also strain induced phase transformations (g ® e) and (g ® a′). The formation of e-martensite with hexagonal structure was observed within the microstructure of the steel starting from the range of lower strains. With increasing deformation degree, the a′-martensite showing a cubic structure gradually began to form. Attempts have been made to explain the circumstances or conditions for the occurrence of the deformation mechanisms mentioned above and their impact on the mechanical properties. The obtained results indicate that the strength and plastic properties of the steel substantially exceed those of plain carbon steels. Since both, mechanical twinning and the strain-induced phase transformations took place during deformation, it seems that both types of deformation mechanisms contributed to an increase in the mechanical properties of the examined manganese steel.

Microstructure and crystallographic texture of Cu-Zn alloys subjected to ECAP and flat rolling

This paper presents the results of the microstructure and crystallographic texture investigations of the Cu-Zn alloys system with different stacking fault energies (SFE) subjected to severe plastic deformation (SPD) by equal channel angular pressing (ECAP) and subsequent flat rolling. It is shown that ECAP leads to the formation of an ultrafine-grained (UFG) structure. Further flat rolling is accompanied by a decrease in the size of structural elements and the formation of nanoscale twins, which are more likely to be detected in an alloy with a lower SFE. As the deformation degree increases, the main crystallographic textures components of the investigated alloys become Brass and Goss components.

Research of deformation compensation method in laser metal deposition process of 316L stainless steel product

It is exists the problem of big product manufacturing with minimal dimensions tolerances. To solve this problem it is necessary to compensate the deformations influence. In researching of method, it became clear that deformation degree has changed and depended on size and form of part. However, the amount of deformation degree to dimension of part is still independent of size. This fact has observed after production of axis-symmetrical parts. The simple axis-symmetrical part was built up. The dimensions of part was measured, and the compensation coefficient was calculated. The dimensions of part was scaled on this coefficient for compensation of shrinkage effect. After that the experiment was repeated.

Assessment of the degree of violations of hemostasis parameters, rheology, markers of inflammation in patients with arterial hypertension and different risks of venous thromboembolic complications

The aim of the work is to investigate the parameters of hemostasis, electrical and viscoelastic parameters of red blood cells and markers of inflammation in persons suffering from arterial hypertension to determine the possibility of assessing the severity of hemorheological disorders.Material and methods. The study included 203 patients (156 patients with arterial hypertension and 47 patients without hypertension). The parameters of hemostasis, markers of inflammation and red blood cells were studied.Results. The possibilities of assessing the severity of hemorheological disorders in patients with arterial hypertension, based on the study of parameters: hemostasis, erythrocytes (by dielectrophoresis). In patients with hypertension, as the risk of venous thromboembolic complications increased, acceleration of leukocyte-platelet aggregation, increased fibrinogen level and decreased activity of XII-dependent fibrinolysis, which creates prerequisites for rheological disturbances, were revealed. The most accurate prediction of result according to severity of hemorheological disorders (differentiation moderate and expressed disorders from the lungs) is provided by such indicators of electric and viscoelastic parameters of erythrocytes, as the polarizability of red blood cells at a frequency of 106 Hz (AUC = 0,750 in), the speed of movement of cells to the electrodes (AUC = 0,746), deformation degree at a frequency of 5 × 105 Hz (AUC = 0,733), conductivity cell (AUC = 0,730), the generalized viscosity (AUC = 0,729), the index of aggregation of erythrocytes (AUC = 0,716), graduation according to the degree of strain at all frequencies (AUC = 0,716), generalized stiffness (AUC = 0,714), the deformation amplitude at frequency of 106 Hz (AUC = 0,711), the capacity of the cells (AUC = 0,693). The measure of specificity for different indices of erythrocytes is 75.4–99,3 % and a sensitivity of 84.1–98.6 %.Conclusions. The study of the parameters of hemostasis, markers of inflammation, red blood cells allowed us to determine the key indicators for assessing the severity of hemorheological disorders in patients with arterial hypertension. The work was carried out within the framework of the budgetary theme under the State Assignment No. 121090800102-4.