Phase Transition Seen at Alloy Grain Boundary: Cornell researchers have evidence for the proposition that gold in an iron alloy bicrystal preferentially collects at the grain boundary and triggers a change in its structure

This paper investigates the evolution of microstructures and precipitations of an ultra-low iron alloy 625 subjected to long term aging treatment by scanning electron microscope (SEM) and X-ray diffraction(XRD). Use ASTM G28A acid Fe3(SO4)2 erosion to represent intergranular corrosion weightlessness and corrosive morphology. The result shows that alloy at 750C by aging treatment for 40h, precipitated γ'' phase in the grain boundary. In high density area of γ'' phase, occurs γ'' phase to δ phase degeneration transformation by aging treatment for 200h and the needle-like δ phase becomes more with time prolonged. And γ'' phase degenerated to δ phase completely until treated for 1000h. The sample which has aging treatment tends to have intergranular corrosion and mainly because alloy element spreading leads to dilution area and grain boundary precipitated phase, plus interlaced δ phase’s dissolving, which makes sample grain particle fall off and this results in apparent weightlessness. The weightlessness rate(WLR) is related with precipitated volume score. With aging sensitization time change, can be described by Johnson-Mehl-Avrami equation, i.e.: WLR=44.32[ 1−exp( − t 10.99 ) ]+44.62[ 1−exp( − t 327.8 ) ]+1.267 ( mm/a ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbWexLMBbXgBd9gzLbvyNv2CaeHbl7mZLdGeaGqiVCI8FfYJH8 YrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfeaY=biLkVcLq=J Hqpepeea0=as0Fb9pgeaYRXxe9vr0=vr0=vqpWqaaeaabiGaciaaca qabeaadaqaaqaafaGcbaaeaaaaaaaaa8qacaWGxbGaamitaiaadkfa cqGH9aqpcaaI0aGaaGinaiaac6cacaaIZaGaaGOmamaadmaapaqaa8 qacaaIXaGaeyOeI0IaaeyzaiaabIhacaqGWbWaaeWaa8aabaWdbiab gkHiTmaalaaapaqaa8qacaWG0baapaqaa8qacaaIXaGaaGimaiaac6 cacaaI5aGaaGyoaaaaaiaawIcacaGLPaaaaiaawUfacaGLDbaacqGH RaWkcaaI0aGaaGinaiaac6cacaaI2aGaaGOmamaadmaapaqaa8qaca aIXaGaeyOeI0IaaeyzaiaabIhacaqGWbWaaeWaa8aabaWdbiabgkHi Tmaalaaapaqaa8qacaWG0baapaqaa8qacaaIZaGaaGOmaiaaiEdaca GGUaGaaGioaaaaaiaawIcacaGLPaaaaiaawUfacaGLDbaacqGHRaWk caaIXaGaaiOlaiaaikdacaaI2aGaaG4naiaacckadaqadaWdaeaape GaamyBaiaad2gacaGGVaGaamyyaaGaayjkaiaawMcaaaaa@71FA@

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Electrical conduction properties of the BZT–BST ceramics

Journal of Advanced Dielectrics ◽

10.1142/s2010135x20500265 ◽

2020 ◽

Vol 10 (06) ◽

pp. 2050026

Author(s):

Satyanarayan Patel ◽

Harekrishna Yadav

Keyword(s):

Phase Transition ◽

Energy Harvesting ◽

Grain Boundary ◽

Negative Temperature ◽

Relaxation Mechanism ◽

Point Of View ◽

Relaxation Processes ◽

Potential Applications ◽

Bst Ceramics ◽

Grain Bulk

0.5Ba([Formula: see text][Formula: see text]O3-0.5([Formula: see text][Formula: see text]TiO3 (BZT–BST) has been explored in recent times for potential applications in energy harvesting, electrocaloric and energy storage. To this end, energy harvesting/conversion and storage applications require an understanding of the conduction and loss mechanisms. The conduction mechanism in BZT–BST ceramics is studied using impedance spectroscopy (IS) at 0.1 Hz−3 MHz and 100−600[Formula: see text]C. Impedance study reveals the presence of two types of relaxation processes due to grain and grain boundary contributions. The relaxation time and dc conductivity activation energies are obtained as 1.12/1.3 eV and 1.05/1.2eV for bulk/grain boundary, respectively, and found that oxygen vacancies dominated electrical behavior. The relaxation mechanism follows non-Debye-type behavior. The high resistance of the grain (bulk) in the ferroelectric region does not contribute to the high losses; the losses probably result from the phase transition. Also, BZT–BST ceramics exhibit a negative temperature coefficient of resistance (NTCR) behaviour. From a practical application point of view in the temperature regime of 25–65[Formula: see text]C, the loss’s contribution is low. The significant contributions of loss result from the response of phase-transition in this temperature range (25–65[Formula: see text]C).

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Effects of grinding-induced grain boundary and interfaces on electrical transportation and structure phase transition in ZnSe under high pressure

Chinese Physics B ◽

10.1088/1674-1056/25/6/066802 ◽

2016 ◽

Vol 25 (6) ◽

pp. 066802

Author(s):

Jie Yang ◽

Pei Wang ◽

Guo-Zhao Zhang ◽

Xiao-Xue Zhou ◽

Jing Li ◽

...

Keyword(s):

Phase Transition ◽

High Pressure ◽

Grain Boundary ◽

Structure Phase ◽

Structure Phase Transition

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The Grain Boundary Wetting in the Sn– 25 at% In Alloys

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.258-260.491 ◽

2006 ◽

Vol 258-260 ◽

pp. 491-496 ◽

Cited By ~ 3

Author(s):

C.H. Yeh ◽

L.S. Chang ◽

Boris B. Straumal

Keyword(s):

Phase Transition ◽

Phase Diagram ◽

Grain Boundary ◽

Annealing Temperature ◽

Bulk Phase ◽

Bulk Phase Diagram ◽

Tie Lines ◽

Grain Boundary Wetting ◽

Increasing Temperature

The grain boundary (GB) wetting was investigated in the Sn – 25 at.% In alloy. It was found that the portion of GBs wetted by the melt depends on the annealing temperature. No GB completely wetted by melt was observed at 140°C, while all GBs were fully wetted after annealing at 180°C. Between 140°C and 180°C the portion of wetted GBs increases with increasing temperature. The tie-lines of GB wetting phase transition were constructed in the Sn–In bulk phase diagram.

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