Study by Differential Thermal Analysis of Reverse Spinodal Transformation in 15-5 PH Alloy.

Alloy 15-5 PH is a stainless steel with 15 wt.% Cr and 5 wt.% Ni that is precipitation hardened by addition of Cu. In its semi-finished state, this alloy consists in Cu-supersaturated soft martensite; its high specific properties come from a final tempering consisting in a heating to 550-600°C, holding for 4 hours, and then air cooling. This treatment leads to nanometric Cu precipitation that hardens the material and to transformation of some martensite to reverted austenite which is then stable and provides ductility. While a' embrittlement of such steels is known to occur at temperature in the range 450-520°C, it has been reported that they can be sensitive to the same phenomenon after long term ageing at temperature as low as 300°C, with a significant loss of ductility and an increase of the ductile-to-brittle transition temperature. Atom probe studies showed that this degradation is related to demixtion of martensite into Fe-rich and Cr-rich phases. Depending on the ageing temperature, demixtion can proceed through a nucleation and growth precipitation or by spinodal decomposition of the martensitic matrix. The present study reports differential thermal analyses (DTA) performed upon heating samples of material held at various temperatures (290-525°C) for various times (410 h to 8500 h) that have been characterized by atom probe. A clear DTA signal is obtained upon the reverse spinodal transformation that is further found to depend on ageing conditions.

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Field ion microscope investigations of atomic processes at surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153117 ◽

1989 ◽

Vol 47 ◽

pp. 228-229

Author(s):

G. L. Kellogg ◽

P. R. Schwoebel

Keyword(s):

Single Crystal ◽

Crystal Surface ◽

Linear Chain ◽

Atom Probe ◽

Nucleation And Growth ◽

Single Atom ◽

Initial Structure ◽

Atomic Processes ◽

Single Crystal Surfaces ◽

Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

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Reports From the Field: “Vini Ansanm” Come Together for Inclusive Community Music Development in Port-au-Prince, Haiti

The Oxford Handbook of Social Media and Music Learning ◽

10.1093/oxfordhb/9780190660772.013.17 ◽

2020 ◽

pp. 273-289

Author(s):

Donald DeVito ◽

Gertrude Bien-Aime ◽

Hannah Ehrli ◽

Jamie Schumacher

Keyword(s):

Social Media ◽

Inclusive Education ◽

Children With Disabilities ◽

Small Population ◽

Significant Loss ◽

Community Music ◽

Music Learning ◽

Loss Of Life

Haiti has experienced a series of catastrophic natural disasters in recent decades, resulting in significant loss of life and long-term damage to infrastructure. One critical outcome of these disasters is that there are approximately 400,000 orphans in the small population of just over 10 million. Throughout Haiti, children with disabilities are often considered cursed, and thus are rejected by the community in which they live. Haitian children with disabilities need creative and educational activities that will help them grow, develop, enjoy their lives, and become accepted members of the community. This chapter on the Haitian Center for Inclusive Education presents a case study of social media engagement and music learning, with an emphasis on social justice that has contributed to sustainable efforts.

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The ductile-to-brittle transition and ductile failure envelopes of orthotropic ice under biaxial compression

Acta Metallurgica et Materialia ◽

10.1016/0956-7151(95)90149-3 ◽

1995 ◽

Vol 43 (10) ◽

pp. 3661-3668 ◽

Cited By ~ 37

Author(s):

E.M. Schulson ◽

S.E. Buck

Keyword(s):

Ductile Failure ◽

Biaxial Compression ◽

Brittle Transition ◽

Failure Envelopes ◽

Ductile To Brittle Transition

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Size dependence of ductile to brittle transition of Zr-based metallic glasses under multiaxial loading

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2021.07.002 ◽

2021 ◽

Author(s):

Xiangkui Liu ◽

Jian Kong ◽

Xinxiang Song ◽

Shuai Feng ◽

Qipeng Wang ◽

...

Keyword(s):

Metallic Glasses ◽

Size Dependence ◽

Multiaxial Loading ◽

Brittle Transition ◽

Ductile To Brittle Transition

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Nutrient retention behind a tropical mega-dam: a case study of the Sardar Sarovar Dam, India

SN Applied Sciences ◽

10.1007/s42452-020-04118-7 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Harish Gupta ◽

S. Kiran Kumar Reddy ◽

Mounika Chiluka ◽

Vamshikrishna Gandla

Keyword(s):

Arabian Sea ◽

Inorganic Nitrogen ◽

Nutrient Retention ◽

Significant Loss ◽

N Removal ◽

Narmada River ◽

Sardar Sarovar ◽

The Impact

AbstractIn this study, we demonstrate the impact of the construction of a mega-dam on the nutrient export regime of a large tropical river into the Arabian Sea. Long-term (11 years) fortnight nutrient parameters, upstream and downstream to Sardar Sarovar (SS) Dam, were examined to determine the periodical change in nutrient fluxes from the Narmada River, India. During this 11-year period, the average discharge of the Narmada River upstream to Rajghat (35.3 km3 year−1) was higher than that of downstream at Garudeshwar (33.9 km3 year−1). However, during the same period, the suspended sediment load was reduced by 21 million tons (MT) from 37.9 MT at Rajghat to 16.7 MT at Garudeshwar. Similarly, mean concentrations of dissolved silica (DSi) reduced from 470 (upstream) to 214 µM (downstream), dissolved inorganic phosphate (DIP) from 0.84 to 0.38 µM, and dissolved inorganic nitrogen (DIN) from 43 to 1.5 µM. It means that about 54%, 55%, and 96% flux of DSi, DIP, and DIN retained behind the dam, respectively. The estimated denitrification rate (80,000 kg N km−2 year−1) for the reservoir is significantly higher than N removal by lentic systems, globally. We hypothesize that processes such as biological uptake and denitrification under anoxic conditions could be a key reason for the significant loss of nutrients, particularly of DIN. Finally, we anticipated that a decline in DIN fluxes (by 1.13 × 109 mol year−1) from the Narmada River to the Arabian Sea might reduce the atmospheric CO2 fixation by 7.46 × 109 mol year−1.

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The nucleation of the Izmit and Düzce earthquakes: Some mechanical logic on where and how ruptures began

Geophysical Journal International ◽

10.1093/gji/ggab040 ◽

2021 ◽

Author(s):

Michel Bouchon ◽

Hayrullah Karabulut ◽

Mustafa Aktar ◽

Serdar Özalaybey ◽

Jean Schmittbuhl ◽

...

Keyword(s):

Strike Slip ◽

Seismic Events ◽

Fault Geometry ◽

Brittle Transition ◽

The North ◽

Impending Rupture ◽

Natural Tendency ◽

Ductile To Brittle Transition ◽

Mechanical Logic ◽

Rupture Speed

Summary In spite of growing evidence that many earthquakes are preceded by increased seismic activity, the nature of this activity is still poorly understood. Is it the result of a mostly random process related to the natural tendency of seismic events to cluster in time and space, in which case there is little hope to ever predict earthquakes? Or is it the sign that a physical process that will lead to the impending rupture has begun, in which case we should attempt to identify this process. With this aim we take a further look at the nucleation of two of the best recorded and documented strike-slip earthquakes to date, the 1999 Izmit and Düzce earthquakes which ruptured the North Anatolian Fault over ∼200 km. We show the existence of a remarkable mechanical logic linking together nucleation characteristics, stress loading, fault geometry and rupture speed. In both earthquakes the observations point to slow aseismic slip occurring near the ductile-to-brittle transition zone as the motor of their nucleation.

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