Phase transformations and mechanical strength of OPC/Slag pastes submitted to high temperatures

2007 ◽  
Vol 41 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Alessandra Mendes ◽  
Jay Sanjayan ◽  
Frank Collins
Keyword(s):  
Mechanical Strength ◽  
Phase Transformations ◽  
High Temperatures

scholarly journals Study of the Turning Nickel Base Alloy Pyromet® 31V (SAE HEV8)

2011 ◽  
Vol 278 ◽  
pp. 312-320 ◽  
Author(s):  
Marcos Valério Ribeiro ◽  
André Luís Habib Bahia
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
High Temperatures ◽  
Base Alloy ◽  
Production Costs ◽  
Machining Parameters ◽  
Nickel Base Alloy ◽  
Low Thermal Conductivity ◽  
Nickel Base ◽  
Coated Carbide

Considering the constant technological developments in the aeronautical, space, automotive, shipbuilding, nuclear and petrochemical fields, among others, the use of materials with high strength mechanical capabilities at high temperatures has been increasingly used. Among the materials that meet the mechanical strength and corrosion properties at temperatures around 815 °C one can find the nickel base alloy Pyromet® 31V (SAE HEV8). This alloy is commonly applied in the manufacturing of high power diesel engines exhaust valves where it is required high resistance to sulphide, corrosion and good resistance to creep. However, due to its high mechanical strength and low thermal conductivity its machinability is made difficult, creating major challenges in the analysis of the best combinations among machining parameters and cutting tools to be used. Its low thermal conductivity results in a concentration of heat at high temperatures in the interfaces of workpiece-tool and tool-chip, consequently accelerating the tools wearing and increasing production costs. This work aimed to study the machinability, using the carbide coated and uncoated tools, of the hot-rolled Pyromet® 31V alloy with hardness between 41.5 and 42.5 HRC. The nickel base alloy used consists essentially of the following components: 56.5% Ni, 22.5% Cr, 2,2% Ti, 0,04% C, 1,2% Al, 0.85% Nb and the rest of iron. Through the turning of this alloy we able to analyze the working mechanisms of wear on tools and evaluate the roughness provided on the cutting parameters used. The tests were performed on a CNC lathe machine using the coated carbide tool TNMG 160408-23 Class 1005 (ISO S15) and uncoated tools TNMG 160408-23 Class H13A (ISO S15). Cutting fluid was used so abundantly and cutting speeds were fixed in 75 and 90 m/min. to feed rates that ranged from 0.12, 0.15, 0.18 and 0.21 mm/rev. and cutting depth of 0.8mm. The results of the comparison between uncoated tools and coated ones presented a machined length of just 30% to the first in relation to the performance of the second. The coated tools has obtained its best result for both 75 and 90 m/min. with feed rate of 0.15 mm/rev. unlike the uncoated tool which obtained its better results to 0.12 mm/rev.

The Complex Oxidation Behavior of Pd Combustion Catalysts

2001 ◽  
Vol 7 (S2) ◽  
pp. 1064-1065
Author(s):  
K. Lester ◽  
A.K. Datye
Keyword(s):  
Phase Transformations ◽  
High Temperatures ◽  
Catalytic Combustion ◽  
Catalyst Activity ◽  
Combustion Process ◽  
Reaction Rates ◽  
Stable Operation ◽  
Temperature Combustion ◽  
High Temperature Combustion ◽  
Complex Oxidation

Combustion of natural gas for power generation leads to NOx formation due to the high temperatures encountered. Catalytic combustion allows the entire combustion process to be completed at temperatures where NOx formation can be avoided. The catalyst of choice is supported PdO. As temperature is increased, PdO decomposes to Pd metal with profound effects on catalyst reactivity. Persistent hysteresis in reaction rates have been related to the decomposition of PdO into Pd and its reformation.Understanding and controlling the phase transformations, and the resulting activity variations, is of enormous importance for high temperature combustion catalysts where predictable catalyst activity is necessary for stable operation. Farrauto et al. studied the phase transformations of PdO to Pd using thermogravimetric analysis (TGA). They concluded that while PdO decomposes to Pd at high temperatures during the heating cycle, upon cooling the Pd does not transform to PdO till the temperature drops by several hundred degrees.

The structural stabilities of the intermetallics and the solid-state phase transformations induced by lattice vibration effects in the Al–Zr system by first-principles calculations

2010 ◽  
Vol 25 (9) ◽  
pp. 1689-1694 ◽  
Author(s):  
Hui Zhang ◽  
Shaoqing Wang
Keyword(s):  
Solid State ◽  
Phase Transformations ◽  
High Temperatures ◽  
First Principles ◽  
Lattice Vibration ◽  
Enthalpies Of Formation ◽  
Phase Transformation Temperature ◽  
First Principles Calculations ◽  
Experimental Phase Diagram ◽  
Good Agreement

We investigated the structural stabilities of the intermetallics and the solid-state phase transformations induced by lattice vibration effects in the Al–Zr system by first-principles calculations. The calculated lattice parameters of all the phases and the phonon dispersion relations for pure Al and Zr are in good agreement with the experimental data. AlZr(oC8), Al4Zr5 (hP18), and Al3Zr5 (tI32) are predicted to be the high-temperature phases. To study the structural stabilities at high temperatures, the thermodynamic properties of the intermetallics are calculated via the linear response approach within the harmonic approximation. Thanks to the calculated enthalpies of formation at high temperatures, Al3Zr5 is predicted to be stabilized above 1163 K with respect to AlZr2 and Al2Zr3, in good agreement with the phase transformation temperature (1273 K) in the experimental phase diagram.

Phase Equilibria and Phase Transformations at High Temperatures in Ternary Alloys of the Ni–Ti–Zr System at 50–100 Ni at.%

2019 ◽  
Vol 58 (3-4) ◽  
pp. 210-221
Author(s):  
A. M. Storchak ◽  
T. Ya. Velikanova ◽  
L. V. Artyukh ◽  
A. V. Grytsiv ◽  
M. A. Turchanin ◽  
...  
Keyword(s):  
Phase Equilibria ◽  
Phase Transformations ◽  
High Temperatures ◽  
Ternary Alloys

Effect of deuterium on phase transformations in fullerenes at high temperatures and high pressures

2017 ◽  
Vol 81 (11) ◽  
pp. 1330-1335
Author(s):  
P. A. Borisova ◽  
M. S. Blanter ◽  
V. V. Brazhkin ◽  
M. M. Murashev ◽  
V. A. Somenkov ◽  
...  
Keyword(s):  
Phase Transformations ◽  
High Temperatures ◽  
High Pressures

scholarly journals Effect of high temperatures on the mechanical behaviour of hybrid cement

2020 ◽  
Vol 70 (337) ◽  
pp. 213 ◽  
Author(s):  
B. Qu ◽  
A. Fernández Jiménez ◽  
A. Palomo ◽  
A. Martin ◽  
J. Y. Pastor
Keyword(s):  
Fracture Toughness ◽  
Mechanical Strength ◽  
High Temperatures ◽  
Mechanical Behaviour ◽  
Ordinary Portland Cement ◽  
Bending Strength ◽  
Hydrated Cement ◽  
Hydrated Cement Paste ◽  
Physical Chemical ◽  
Innovative Methodology

The high-temperature mechanical behaviour of a pre-industrial hybrid alkaline cement (HYC) was studied. The HYC in question contained 30 % Portland clinker and 70 % of a blend of slag, fly ash and a solid activator (mix of alkaline salts with a predominance of Na2SO4). The material was tested during exposure to high temperatures to establish its compressive and bending strength and elastic modulus, as well as fracture toughness, analysed using an innovative methodology to notch the hydrated cement paste specimens. Post-thermal treatment tests were also run to assess residual mechanical strength after 2 h of exposure to temperatures ranging from 400 °C to 1000 °C. TG/DTA, MIP and SEM were deployed to ascertain heat-induced physical-chemical changes in the structure. The higher mechanical strength during and after treatment exhibited by the hardened hybrid alkaline cement than the CEM I 42.5R ordinary portland cement (OPC) paste used as a reference was associated with the lower water and portlandite content found in HYC. Pseudo-plastic behaviour was observed at high temperatures in the loaded HYC in the tests conducted during exposure.

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