The Research on Hot Compression Mechanism of Light Alloy

2012 ◽  
Vol 204-208 ◽  
pp. 4079-4082
Author(s):  
Jun Wei Liu ◽  
Shi Qiang Lu ◽  
Xian Juan Dong ◽  
Xuan Xiao ◽  
Gui Fa Li
Keyword(s):  
Mechanical Property ◽  
Microstructure Evolution ◽  
Main Mechanism ◽  
Second Phase ◽  
Light Alloy ◽  
Two Stage ◽  
Second Stage ◽  
Second Phase Particles ◽  
Before And After ◽  
Compression Mechanism

In this research, in order to explore the main mechanism of direct and two-stage compression in as-cast light alloy, the mechanical property, microstructure evolution and the flowing of second phase particles were studied, before and after deformation. Then, the influence of the strain volume in first stage on flowing stress of the second stage deformation also was researched.

scholarly journals Effects of Second-Phase Particles on Microstructure Evolution in Mg-2Zn Based Magnesium Alloys during Annealing Treatment

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 777
Author(s):  
Yun Zhang ◽  
Haitao Jiang ◽  
Yujiao Wang ◽  
Zhe Xu
Keyword(s):  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
Annealing Treatment ◽  
Salt Bath ◽  
Annealing Process ◽  
Second Phase ◽  
Recrystallization Behavior ◽  
Basal Texture ◽  
Static Recovery ◽  
Second Phase Particles

As an important fabrication process, annealing treatment is conducted to eliminate distortion in magnesium alloy sheets. Second-phase particles can provide nucleation sites for recrystallization grains, and the basal texture is related to the recrystallization behavior. Three experimental Mg-2Zn-based magnesium alloy sheets were investigated by the salt bath annealing process. Combined with variations in hardness softening, evolution of microstructure and basal texture, the effect of second-phase particles on microstructure evolution was analyzed. The results showed that the significant influence of size and distribution of second-phase particles on static recrystallization in magnesium alloy sheets was exhibited, which lead to the formation of two stages in the annealing process, combined with static recovery behavior. Second phase particles with coarse size were beneficial to recrystallization grains’ nucleation and increased recrystallization behavior in the initial stage of annealing. Second-phase particles with fine size inhibited recrystallization behavior and weakened the softening of hardness. The basal texture was weakened by second phase particles at the stage of recrystallization nucleation. The change in basal texture at the stage of grain growth was related to the size of second-phase particles. The regulation of basal texture enhancement can be envisioned by modifying second-phase particles.

Mechanical property evaluation of second phase particles in a Mg–8Al-0.5Zn alloy using micropillar compression

2020 ◽  
Vol 775 ◽  
pp. 138973 ◽  
Author(s):  
R. Sarvesha ◽  
Ubaid-ur-Rehman Ghori ◽  
Yu Lung Chiu ◽  
Ian P. Jones ◽  
S.S. Singh ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Second Phase ◽  
Property Evaluation ◽  
Second Phase Particles ◽  
Micropillar Compression

Two-stage ignitions during rapid compression: spontaneous combustion in lean fuel-air mixtures

1984 ◽  
Vol 393 (1805) ◽  
pp. 371-395 ◽  
Keyword(s):  
Heat Output ◽  
Second Phase ◽  
Gas Temperature ◽  
Total Delay ◽  
Two Stage ◽  
Second Stage ◽  
Compressed Gas ◽  
Rapid Compression ◽  
Lean Mixtures ◽  
Lean Fuel

The two-stage ignition of acetaldehyde + oxygen-nitrogen (‘air’) mixtureis investigated under rapid compression. The conditions are parallel to those brought about during the compression stroke in spark ignition and diesel engines. An approximately tenfold compression of pre-mixed gases is brought about mechanically. The time for rapid motion of the piston is 22 ms, and gases are ultimately compressed into a cylindrical volume, length 2.10 cm and diameter 4.50 cm. When air is used the temperature of the gases at the end of compression but before reaction is about 580 K. Heat losses are important in the stages following rapid compression. In a novel development, a miniature turbine is fitted to the combustion chamber. It is used to en­hance cooling rates. Two-stage combustion occurs in the post-compression period. There is a delay before the first stage is perceptible. The first stage itself is only mildly exothermic ( ca . 100 W cm -3 ) and the temperature rises associated with it are not large (∆ T < 150 K). These properties are not greatly affected by initial composition or by the temperature reached during compression. The second stage, however, is very strongly affected in intensity by such changes. Increases of mixture strength and of compressed gas temperature enhance both the extent and the rate of temperature change. For example, the second stage of combustion is weak in very lean mixtures ( ϕ < 0.25) and the approach to the maximum tem­perature is sufficiently slow for reaction to be markedly non-adiabatic; however, with mixtures for which ϕ > 0.5, very vigorous reaction occurs, and flame temperatures achieve adiabatic values. The total delay time before second-stage ignition is least for a mixture with ϕ = 0.6. This minimum reflects differing responses to mixture strength of its two constituent times. The duration of the first phase (ז 1 ) in which there is no measurable heat output, does not vary much in very lean mixtures, but it lengthens in the range 0.5 < ϕ < 1.0. The effect may be attributed to a small diminution in compressed gas temperature due to a decrease in γ . The duration of the second phase (ז 2 ) in which two-stage heat release is observed falls very sharply as the mixture strength is increased, and for ϕ > 0.5 it is negligible. However, the second phase is lengthened substantially when heat-transfer rates are artificially enhanced; the second stage of two-stage ignition may even be quenched in consequence. This is a most important and novel conclusion of the present study.

scholarly journals Anaerobic two stage degradation pattern of fermentable components of municipal solid waste

2018 ◽  
Vol 19 (4) ◽  
pp. 706-715
Keyword(s):  
Solid Waste ◽  
Biogas Production ◽  
Degradation Kinetics ◽  
Gas Production ◽  
Second Phase ◽  
Two Stage ◽  
Second Stage ◽  
Degradation Pattern ◽  
Urban Solid Waste ◽  
Linear Fit

With increased contribution of household and kitchen wastes in overall MSW and its preferred conversion by biomethanation there is a need to study decomposition rates and kinetics, ‘leachate potential’ and related issues– especially to promote decentralized treatment. Anaerobic digestion characteristics of ten predominant types of the fermentable components (fruits, vegetables and their mixture) commonly found in urban solid waste in Bangalore were examined under lab conditions by monitoring biogas production in micro-digesters at room temperatures (25±3°C). The rate of decomposition, the pattern of fit and extent and rate of biogas production from these potential feedstocks are analyzed to understand the degradation kinetics. All feedstocks showed a two stage linear fit for gas production comprising of a rapid initial phase lasting 10-20days accounting for >70% gas production followed by a slower second phase. Degradation could be predicted using a two stage linear fit transiting from initial to a second stage at an appropriate unique transition point, yet similar amongst fruits or vegetables. The need for large aceticlastic capability (rapid initial degradation) thus becomes a criteria for biomethanation process of such feedstocks.

scholarly journals Flipping the classroom for information literacy instruction

2018 ◽  
Vol 12 (1) ◽  
pp. 48
Author(s):  
Jing Shen
Keyword(s):  
Collaborative Learning ◽  
Information Literacy ◽  
Flipped Classroom ◽  
Pilot Project ◽  
Full Potential ◽  
Two Stage ◽  
Personalised Learning ◽  
Second Stage ◽  
Before And After ◽  
Phenomenological Perspective

This study examined the possibility of enabling personalised, collaborative information literacy (IL) instruction through a flipped class model. Two-stage interviews were conducted before and after a pilot project was given to participants, which was designed according to guiding principles of personalised learning and online collaborative learning (OCL) theory. The study used a qualitative framework to gauge learners’ perceptions regarding the effectiveness and feasibility of the design. Samples were taken from learners who had previously been involved in a flipped classroom. The data collected from the two-stage interviews were compared and further discussed in light of Giorgi’s (1999) understanding of learning through a phenomenological perspective. Five participants were involved in the study. For the first-stage interviews, the five participants all responded positively towards the prospectus of a flipped, personalised and collaborative IL instruction. For the second-stage interviews, three participants offered feedback regarding an interactive PowerPoint specifically designed for a flipped IL instruction, which had incorporated elements of personalisation and group activities. All three participants in the second stage interviews spoke favourably of the content of the interactive PowerPoint, but they also all exhibited a degree of hesitation when multiple options were presented to them. They were still expecting clear instructions instead of taking control of the process. This study discovered a gap between learners’ positivity towards a flipped, personalised and collaborative learning model, and the fact that learners are fundamentally accustomed to traditional learning paths. This implies there are hurdles to overcome before the flipped model can deliver results, especially when learners are expected to take more control over their own learning. Further research is needed to explore ways of altering learner mind sets in order to enable learners to embrace the full potential of flipped learning.

scholarly journals Flipping the classroom for information literacy instruction

2018 ◽  
Vol 12 (1) ◽  
pp. 48 ◽  
Author(s):  
Jing Shen
Keyword(s):  
Collaborative Learning ◽  
Information Literacy ◽  
Flipped Classroom ◽  
Pilot Project ◽  
Full Potential ◽  
Two Stage ◽  
Personalised Learning ◽  
Second Stage ◽  
Before And After ◽  
Phenomenological Perspective

This study examined the possibility of enabling personalised, collaborative information literacy (IL) instruction through a flipped class model. Two-stage interviews were conducted before and after a pilot project was given to participants, which was designed according to guiding principles of personalised learning and online collaborative learning (OCL) theory. The study used a qualitative framework to gauge learners’ perceptions regarding the effectiveness and feasibility of the design. Samples were taken from learners who had previously been involved in a flipped classroom. The data collected from the two-stage interviews were compared and further discussed in light of Giorgi’s (1999) understanding of learning through a phenomenological perspective. Five participants were involved in the study. For the first-stage interviews, the five participants all responded positively towards the prospectus of a flipped, personalised and collaborative IL instruction. For the second-stage interviews, three participants offered feedback regarding an interactive PowerPoint specifically designed for a flipped IL instruction, which had incorporated elements of personalisation and group activities. All three participants in the second stage interviews spoke favourably of the content of the interactive PowerPoint, but they also all exhibited a degree of hesitation when multiple options were presented to them. They were still expecting clear instructions instead of taking control of the process. This study discovered a gap between learners’ positivity towards a flipped, personalised and collaborative learning model, and the fact that learners are fundamentally accustomed to traditional learning paths. This implies there are hurdles to overcome before the flipped model can deliver results, especially when learners are expected to take more control over their own learning. Further research is needed to explore ways of altering learner mind sets in order to enable learners to embrace the full potential of flipped learning.

Microstructural evolution and corrosion behaviour of friction stir-processed QE22 magnesium alloy

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ankur Kumar ◽  
F. Khan MD ◽  
Sushanta Kumar Panigrahi ◽  
Gajanan P. Chaudhari
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behaviour ◽  
Galvanic Corrosion ◽  
Point Of View ◽  
Second Phase ◽  
Friction Stir ◽  
Ultrafine Grained ◽  
Second Phase Particles ◽  
Before And After ◽  
The Matrix

Abstract Effect of microstructural changes after friction stir processing (FSP) on the corrosion behaviour of rare earth containing QE22 magnesium alloy is studied. FSP produced ultrafine-grained α-Mg matrix and refined the Mg12Nd precipitates whereas Mg12Nd2Ag precipitates got dissolved in the matrix. Although its hardness increased from 76 to 90 VHN, the FSPed alloy displayed inferior corrosion resistance in 3.5 wt% NaCl solution. This is attributed mainly to the iron contamination from FSP and presence of refined second phase particles which work as active cathodic sites. The role of distributed Mg12Nd precipitates before and after FSP is analysed from micro galvanic corrosion point of view.

Extraction replicas for the analysis of second phases in nonferrous alloys using Analytical Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 874-875
Author(s):  
G. J. C. Carpenter ◽  
J. Ng-Yelim
Keyword(s):  
Carbon Film ◽  
Analytical Electron Microscopy ◽  
Carbon Support ◽  
Single Stage ◽  
Chemical Information ◽  
Second Phase ◽  
Ferrous Alloys ◽  
Two Stage ◽  
Second Phase Particles ◽  
Thin Carbon

The technique for extracting second-phase particles from steels onto a carbon support film for analysis in the transmission electron microscope (TEM) has been in continuous use since its development by Bradley, nearly 30 years ago. However, the availability of EDX and EELS accessories, capable of giving chemical information, has provided an incentive for the technique to be used with other alloys.The purpose of this presentation is to review some applications of extraction replication to non-ferrous alloys.Briefly, extraction involves chemically etching only the matrix phase of an alloysothat second-phase particles stand proud and can be extracted onto a carbon film. The most straightforward procedure is to make a single-stage direct-carbon replica, where carbon is evapourated onto the etchedsurface of a mctallographic specimen and subsequently stripped by further etching.An alternative approach is the two-stage technique, where the particles are first stripped from an etched specimen using a plastic film, e.g. cellulose acetate, such as "Bioden". The plastic surface containing theparticles is then coated with a layer of carbon, typically 10˜20nm thick, and the plastic is dissolved, leaving the particles attached to the carbon film. Although the two-stage technique involves anextra operation, it has some advantages. In particular, it is possible to strip films after differentdegrees of etching, without the necessity to re-polish the specimen. Also, with the single-stage technique, an etchant suitable for removing the replica may react so strongly that the thin carbon film breaks up during stripping.

scholarly journals The Two-Stage Model of Entrepreneurs Financing Based on the Entry/Exit Decision

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Kaihong Wang ◽  
Yin Mingyang ◽  
Zuo Jiani
Keyword(s):  
Investment Decision ◽  
Fund Raising ◽  
Second Phase ◽  
Two Stage ◽  
Preferred Stock ◽  
Second Stage ◽  
Angel Investor ◽  
Dividend Distribution ◽  
Angel Investment ◽  
Negative Relationships

Normally entrepreneur would raise fund from angel investors during the initial round. If the venture program was by then successful, the entrepreneur would then continue the fund-raising process from venture capitalist. By adopting the convertible preferred stock, we managed to construct the two-stage angel investment decision process. This research reveals the following: (1) The probability of the first stage’s success has negative relationships with levels of priority dividend in both first and second stages, as well as with the venture capitalist’s proportion of shares. (2) The probability of the second stage’s success has negative relationships with the venture capitalist’s proportion of shares and the dividend level of both first and second stage funding. (3) There has been a threshold of dividend distribution, which belongs to angel investor. While the level of angel investor’s shares is higher than the threshold, AN would decide to join the second phase of the program; otherwise, AN would exit the project at the end of the first stage.

Microstructure Evolution in a P911 Steel under Creep Conditions

2011 ◽  
Vol 409 ◽  
pp. 223-227
Author(s):  
Alla Kipelova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Microstructure Evolution ◽  
Second Phase ◽  
Tempered Martensite ◽  
Laves Phases ◽  
Heat Resistant Steel ◽  
Second Phase Particles ◽  
Austenite Grains ◽  
The Stability ◽  
Lath Structure ◽  
Carbide Particles

Microstructure evolution in a P911 heat resistant steel was examined under conditions of aging and creep at a temperature of 600°C and an applied stress of 200 MPa. The tempered martensite lath structure (TMLS) evolved after heat treatment consisted of prior austenite grains (PAG), packets, blocks and laths. The mean transverse lath size and the interior dislocation density were about 345 nm and 3.5 × 1014 m-2, respectively. Various second phase particles precipitated upon tempering. Fine MX carbonitrides were homogeneously distributed throughout the tempered martensite laths, while relatively coarse M23C6 carbide particles were located on high-and low-angle boundaries. Upon creep test, precipitation of Laves phases was found. The stability of TMLS during creep is discussed in detail.

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