Effect of multidirectional forging and equal channel angular pressing on ultrafine grain formation in a Cu-Cr-Zr alloy

The microstructure evolution was investigated in a Cu-0.3%Cr -0.5%Zr alloy subjected to large plastic deformation at temperature of 400° C. Two methods of large plastic deformation, i.e., equal channel ang ular pressing (ECAP) and multidirectional forging (MDF) were used. The large plastic deformations resulted in the development of new ultrafine grains. The formation of new ultrafine grains occurred as a result of continuous reaction, i.e., progressive incr ease in the misorientations of deformation subboundaries. The faster kinetics of microstructure evolution was observed during MDF as compared to ECAP. The MDF to a total strain of 4 resulted in the formation of uniform ultrafine grained structure, while ECAP to the same strain led to the heterogeneous microstructure consisting of new ultrafine grains and coarse remnants of original grains . Corresponding area fractions of ultrafine grains comprised 0.23 and 0.59 in the samples subjected to ECAP and MDF, respectivel

Grain refinement in a Cu-Cr-Zr alloy during multidirectional forging

Structural changes during plastic deformation were studied in a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging up to a total strain of 4 at the temperatures of 300 K and 673 K. The deformation behavior was characterized by a rapid increase in the flow stress at an early deformation followed by a steady-state flow at large strain. The development of the new ultrafine grains resulted from the progressive increase in the misorientations of the strain-induced low-angle boundaries, which evolve into high-angle boundaries with increasing cumulative strain through a strain-induced continuous reaction that is quite similar to continuous dynamic recrystallizatio

Deformation microstructures, strengthening mechanisms, and electrical conductivity in a Cu-Cr-Zr alloy

Cr-0.06%Zr alloy subjected to multiple equal channel angular pressing (ECAP) at temperatures of 473-673 K were investigated. The new ultrafine grains resulted from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process. The development of ultrafine-grained microstructures is considered as a type of continuous dynamic recrystallizatio

Ultrafine grain evolution in a Cu-Cr-Zr alloy during warm multidirectional forging

The microstructure evolution and the deformation behavior of a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging at a temperature of 673 K under a strain rate of about 10-³ s-¹ were studied. Following a rapid increase in the flow stress during straining to about 1, the strain hardening gradually decreases, leading to a steady-state flow behavior at total strain above 2. The multidirectional forging led to the development of ultrafine grained microstructures with mean grain sizes of 0.9 μm and 0.64 μm in the solution treated and aged samples, respectively. The presence of second phase precipitates promoted the grain refinement. After processing to a total strain of 4, the fractions of ultrafine grains (D < 2 μm) comprised 0.36 and 0.59 in the solution treated and aged samples, respectivel

Development of ultrafine grained austenitic stainless steels by large strain deformation and annealing

The development of ultrafine grained structures in 316L and 304-type austenitic stainless steels subjected to large strain cold working and subsequent annealing and their effect on mechanical properties were studied. The cold rolling was accompanied by a mechanical twinning and a partial martensitic transformation and resulted in the development of elongated austenite/ferrite grains with the transverse size of about 50 nm at a strain of 4. The grain refinement by large strain cold working resulted in an increase of tensile strength above 2000 MPa in the both steels. Annealing at temperatures above 500°C resulted in ferrite-austenite reversion. However, the transverse grain/subgrain size remained on the level of about 100-150 nm after annealing at temperatures up to 700°

New model of mobile learning for the high school students preparing for the unified state exam

© 2017. In this paper we study a new model of mobile learning for the Unified State Exam (USE) preparation in Russian Federation. USE - is the test school graduates need to pass in order to obtain Russian matura. In recent years the efforts teachers put for preparation of their students to the USE diminish how well the subject is actually mastered by the students. The problem lays in the key performance indicators the teachers must reach. The KPI is not unified across the country, but often it includes, in one or another form, the USE score the students get. The main proposition of this research is to use gamification in order to transfer the USE preparation out of the classroom activities. The most natural platform for this gamification is the ecosystem of the smartphones and social media available to the students. We build the USE preparation didactical model that addresses the challenges the teachers currently have. Then we discuss the architecture and the implementation for the whole solution

Microstructure evolution in a Cu-Cr-Zr alloy during warm intense plastic straining

The effect of equal channel angular pressing at a temperature of 200°C to a total strain of 12 on microstructure evolution and mechanical properties of a Cu-0.87wt.%Cr- 0.06wt.%Zr was investigated. New ultrafine grains resulted from gradual increase in the misorientations of strain-induced low-angle boundaries with increasing number of passes. Therefore, the development of ultrafine grains is considered as a kind of dynamic recrystallization. The equal channel angular pressing to a total strain of 12 resulted in the formation of almost equiaxed ultrafine grained structure with an average grain size of 0.5 Tm and 0.7 Tm in the solution treated and aged samples, respectively. At the same time, the fraction of ultrafine grains comprises 0.77 in the solution treated samples and 0.72 in the aged samples. Significant grain refinement led to the remarkable increase of the ultimate tensile strength up to 550 MP

Grain refinement kinetics and strengthening mechanisms in Cu-0.3Cr-0.5Zr alloy subjected to intense plastic deformation

The ultrafine-grained microstructures, mechanical properties and electrical conductivity of a Cu-0.3%Cr-0.5%Zr alloy subjected to equal channel angular pressing (ECAP) at a temperature of 400°C to a total strain of 1, 2, and 4 were investigated. The ultrafine-grained microstructure resulting from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process is considered as a type of continuous dynamic recrystallizatio

Natural adaptogenes on the basis of beekeeping products in the correction of fatigue during the recovery period of the annual training cycle for athletes of winter coordination sports

Objective: to evaluate the effectiveness of the application of bee products in correction of signs of fatigue during the recovery period in athletes of complex coordination sports. Materials and methods: 40 athletes of complex winter sports 15-21 years old (mean age - 19.05±3.42 years (M±m)) were examined: the main group (24 people) received 10% aqueous-alcoholic extract of bee moth larvae during 25 days of the recovery period; rantrol group (16 persons) received dry adsorbed royal jelly. The parameters of hematopoiesis, immune and hormonal status, physical working capacity were studied. Results: a decrease in the concentration of TNF-a and IL-4, and increase in IL-1ß and IL-6 within the reference values was established after the course of beekeeping products intake in both groups of athletes. The administration of the bee moth larva extract resulted in a decrease in the CIC (p = 0.010), an increase in the CD3 +, CD 19- lymphocytes (p = 0.028), CD3 +, CD4 + lymphocytes (p = 0.016), and signs of stimulation of erythropoiesis in the form of an increase in erythrocytes (p = 0.016) and reticulocytes (p = 0.027), as well as an increase in testosterone (p = 0.038) and physical performance (p = 0.041; p = 0.034), that was more pronounced in comparison with the royal jelly intake. Conclusions: the use of bee moth larva extract in the recovery period resulted in more significant improvement in the state of the oxygen-providing blood system, correction of the immunological imbalance and hormonal parameters of adaptation, and preservation of the level of physical fitness achieved in the competitive period in comparison with royal jelly

Forecasting the development of mechanical engineering using the system dynamics method

At modern conditions of world economy tendencies, the connections between subjects of economy are becoming more difficult and closer. In particular, if in the past were spread hard forms of private ownership of enterprises at present-day world is going conversion to more flexible and mobile composition of subjects' activities. Computer simulation modeling is giving the best results at the areas were the participants of social and economic activities are spending significant efforts and sufficiently much time for visuality playing and analysis of possible variants of the development of the events. The more difficult is the situation the more objects, factors, and possible variants of events' progress is necessary to play in different combinations between together and bigger effect possible to expect from application of simulation model for analyzing of the situation and for searching and making optimized decisions. The application of system dynamics method allows executing forecasting of economic agents including the sectors of economy. © 2020 American Institute of Physics Inc.. All rights reserved