Materials—Metallic and Non-Metallic

1961 ◽  
Vol 65 (602) ◽  
pp. 83-85
Author(s):  
N. J. L. Megson
Keyword(s):  
High Temperature ◽  
Titanium Alloys ◽  
Aluminium Alloys ◽  
Elevated Temperatures ◽  
Maximum Temperature ◽  
Considerable Time ◽  
Heating Effects ◽  
Rain Erosion

With increasing speeds of aircraft, problems arise over materials of construction, partly through kinetic heating effects which cause temperature rises and partly through rain erosion effects. Additionally, account has to be taken of a required life of 30,000 hours which is much longer than that over which most materials are normally evaluated.For speeds of Mach 2.2, the maximum temperature attained will be of the order of 130°C, while for Mach 2.7 the corresponding temperature will be 200°C or higher. For the lower speed, it is probable that aluminium alloys will be satisfactory, although it must be emphasised that no information is yet available on the long-term behaviour of materials at the elevated temperatures likely to be experienced. Test programmes are in hand, but these will necessarily take considerable time for their completion. For speeds of Mach 2.7 or above, steel or titanium alloys will be required, but here again the necessary evaluation for long periods at high temperature has yet to be completed.

scholarly journals CO Detection Investigation at High Temperature by SiC MISFET Metal/Oxide Gas Sensors

Proceedings ◽  
2021 ◽  
Vol 56 (1) ◽  
pp. 41
Author(s):  
Lida Khajavizadeh ◽  
Anita Lloyd Spetz ◽  
Mike Andersson
Keyword(s):  
High Temperature ◽  
Gas Sensors ◽  
Elevated Temperatures ◽  
Long Term Stability ◽  
Stability Performance ◽  
Catalytic Metal ◽  
Co Detection ◽  
Effect Transistor ◽  
Metal Oxide Gas Sensors

In order to investigate the necessary device improvements for high-temperature CO sensing with SiC metal insulator semiconductor field effect transistor (MISFET)-based chemical gas sensors, devices employing, as the gas-sensitive gate contact, a film of co-deposited Pt/Al2O3 instead of the commonly used catalytic metal-based contacts were fabricated and characterized for CO detection at elevated temperatures and different CO and O2 levels. It can be concluded that the sensing mechanism at elevated temperatures correlates with oxygen removal from the sensor surface rather than the surface CO coverage as observed at lower temperatures. The long-term stability performance was also shown to be improved compared to that of previously studied devices.

Martensite decomposition during post-heat treatments and the aging response of near-α Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) titanium alloy processed by selective laser melting (SLM)

2021 ◽  
pp. 2050018
Author(s):  
Haiyang Fan ◽  
Yahui Liu ◽  
Shoufeng Yang
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Titanium Alloys ◽  
Selective Laser Melting ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Aging Treatment ◽  
Water Quenching ◽  
Laser Melting ◽  
Aging Response

Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-[Formula: see text] titanium alloy explicitly designed for high-temperature applications, consists of a martensitic structure after selective laser melting (SLM). However, martensite is thermally unstable and thus adverse to the long-term service at high temperatures. Hence, understanding martensite decomposition is a high priority for seeking post-heat treatment for SLMed Ti-6242. Besides, compared to the room-temperature titanium alloys like Ti–6Al–4V, aging treatment is indispensable to high-temperature near-[Formula: see text] titanium alloys so that their microstructures and mechanical properties are pre-stabilized before working at elevated temperatures. Therefore, the aging response of the material is another concern of this study. To elaborate the two concerns, SLMed Ti-6242 was first isothermally annealed at 650[Formula: see text]C and then water-quenched to room temperature, followed by standard aging at 595[Formula: see text]C. The microstructure analysis revealed a temperature-dependent martensite decomposition, which proceeded sluggishly at [Formula: see text]C despite a long duration but rapidly transformed into lamellar [Formula: see text] above the martensite transition zone (770[Formula: see text]C). As heating to [Formula: see text]C), it produced a coarse microstructure containing new martensites formed in water quenching. The subsequent mechanical testing indicated that SLM-built Ti-6242 is excellent in terms of both room- and high-temperature tensile properties, with around 1400 MPa (UTS)[Formula: see text]5% elongation and 1150 MPa (UTS)[Formula: see text]10% elongation, respectively. However, the combination of water quenching and aging embrittled the as-built material severely.

scholarly journals Brazing Strategies for High Temperature Ultrasonic Transducers Based on LiNbO3 Piezoelectric Elements

Instruments ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 2 ◽  
Author(s):  
Christopher Bosyj ◽  
Neelesh Bhadwal ◽  
Thomas Coyle ◽  
Anthony Sinclair
Keyword(s):  
High Temperature ◽  
Lithium Niobate ◽  
Elevated Temperatures ◽  
Piezoelectric Element ◽  
Low Noise ◽  
Ultrasonic Transducers ◽  
Acoustic Coupling ◽  
Industrial Operations ◽  
Critical Components

Long-term installation of ultrasonic transducers in high temperature environments allows for continuous monitoring of critical components and processes without the need to halt industrial operations. Transducer designs based on the high-Curie-point piezoelectric material lithium niobate have been shown to both be effective and stable at extreme temperatures for long-term installation. In this study, several brazing techniques are evaluated, all of which aim to provide both mechanical bonding and acoustic coupling directly to a bare lithium niobate piezoelectric element. Two brazing materials—a novel silver-copper braze applied in a reactive air environment and an aluminum-based braze applied in a vacuum environment—are found to be suitable for ultrasound transmission at elevated temperatures. Reliable wide-bandwidth and low-noise ultrasound transmission is achieved between room temperature and 800 °C.

High Temperature Oxidation and Corrosion of Silicon-Based Non-Oxide Ceramics

1999 ◽  
Vol 122 (1) ◽  
pp. 13-18 ◽  
Author(s):  
H. Klemm ◽  
M. Herrmann ◽  
C. Schubert
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Temperature Stability ◽  
Ambient Air ◽  
High Temperature Stability ◽  
Temperature Oxidation ◽  
Sic Ceramics ◽  
Silicon Based

The present study is focussed on the oxidation behavior of nonoxide silicon-based ceramics. Various Si3N4 and SiC ceramics were examined after long term oxidation tests (up to 5000 h) at 1500°C in ambient air. The damage mechanisms were discussed on the basis of a comprehensive chemical and microstructural analysis of the materials after the oxidation tests. The diffusion of oxygen into the material and its further reaction in the bulk of the material were found to be the most critical factors during long term oxidation treatment at elevated temperatures. However, the resulting damage in the microstructure of the materials can be significantly reduced by purposeful microstructural engineering. Using Si3N4/SiC and Si3N4/MoSi2 composite materials provides the possibility to improve the high temperature stability. [S0742-4795(00)00301-X]

scholarly journals HIGH TEMPERATURE OXIDATION OF TI-6AL-4V ALLOY FABRICATED BY ADDITIVE MANUFACTURING. INFLUENCE ON MECHANICAL PROPERTIES

2020 ◽  
Vol 321 ◽  
pp. 03006
Author(s):  
Antoine CASADEBAIGT ◽  
Daniel MONCEAU ◽  
Jonathan HUGUES
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Additive Manufacturing ◽  
Titanium Alloys ◽  
Oxidation Kinetics ◽  
High Temperature Oxidation ◽  
Effect Of Temperature ◽  
Premature Failure ◽  
Temperature Oxidation

Titanium alloys, such as Ti-6Al-4V alloy, fabricated by additive manufacturing processes is a winning combination in the aeronautic field. Indeed, the high specific mechanical properties of titanium alloys with the optimized design of parts allowed by additive manufacturing should allow aircraft weight reduction. But, the long term use of Ti-6Al-4V alloy is limited to 315 °C due to high oxidation kinetics above this temperature [1]. The formation of an oxygen diffusion zone in the metal and an oxide layer above it may reduce the durability of titanium parts leading to premature failure [2, 3]. In this study, Ti-6Al-4V alloy was fabricated by Electron Beam Melting (EBM). As built microstructure evolutions after Hot Isostatic Pressure (HIP) treatment at 920 °C and 1000 bar for 2h were investigated. As built microstructure of Ti-6Al-4V fabricated by EBM was composed of Ti-α laths in a Ti-β matrix. High temperature oxidation of Ti-6Al-4V alloy at 600 °C of as-built and HIP-ed microstructures was studied. This temperature was chosen to increase oxidation kinetics and to study the influence of oxidation on tensile mechanical properties. In parallel, two other oxidation temperatures, i.e. 500 °C and 550°C allowed to access to the effect of temperature on long-term oxidation.

Castable Aluminium Alloys for High Temperature Applications

2013 ◽  
Vol 765 ◽  
pp. 8-12 ◽  
Author(s):  
Yang Yang Fan ◽  
Makhlouf M. Makhlouf
Keyword(s):  
High Temperature ◽  
Aluminium Alloys ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Eutectic System ◽  
Casting Alloys ◽  
Elevated Temperature Tensile ◽  
Nickel Base ◽  
Room Temperature Strength ◽  
Temperature Applications

Most traditional aluminium casting alloys are based on the aluminium-silicon eutectic system because of its excellent casting characteristics. However, the solidus in this system does not exceed 577 °C and the major alloying elements used with silicon in these alloys have high diffusivity in aluminium. Therefore, while these elements enhance the room temperature strength of the alloy, they are not useful at elevated temperatures. Considering nickel-base superalloys, whose mechanical properties are retained up to temperatures that approach 75% of their melting point, it is conceivable that castable aluminium alloys can be developed on the same basis so that they are useful at temperatures approaching 300 °C. In this publication, we present the thought process behind developing a new castable aluminum alloy that is designed specifically for such high temperature applications and we present the alloy’s measured castability characteristics and its elevated temperature tensile properties.

scholarly journals Investigation of low-temperature cofired ceramics packages for high-temperature SAW sensors

2016 ◽  
Vol 5 (1) ◽  
pp. 85-93
Author(s):  
Jochen Bardong ◽  
Alfred Binder ◽  
Sasa Toskov ◽  
Goran Miskovic ◽  
Goran Radosavljevic
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Acoustic Wave ◽  
Temperature Sensor ◽  
Elevated Temperatures ◽  
Failure Mechanisms ◽  
Maximum Temperature ◽  
Sensor Devices ◽  
Production Cycles ◽  
Cofired Ceramics

Abstract. Surface acoustic wave (SAW) temperature sensor devices have been developed for operating temperatures up to and above 1000 °C. A challenging task to make these devices available on the market is to develop an appropriate housing concept. A concept based on low-temperature cofired ceramics (LTCC) has been investigated and tested under elevated temperatures up to 600 °C. The devices showed promising results up to 450 °C. Thorough analysis of the possible failure mechanisms was done to increase the maximum temperature above this limit in further production cycles.

Packaging Technology for High Temperature Capacitive Pressure Sensors

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000367-000372 ◽  
Author(s):  
Liang-Yu Chen ◽  
Glenn M. Beheim ◽  
Roger D. Meredith
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Pressure Sensors ◽  
Differential Pressure ◽  
Capacitive Pressure Sensor ◽  
Packaging Technology ◽  
Parasitic Parameters ◽  
Term Performance

High temperature pressure sensors are critical sensing elements for the next generation of intelligent aerospace engine technology, as well as long-term exploration missions to Venus, where the surface temperature is 485°C. Various high temperature pressure sensors based on different sensing mechanisms are under development at the NASA Glenn Research Center. In order to test long-term performance and reliability of these sensors in a high temperature environment, and eventually commercialize these sensors, high temperature durable and long-term reliable packaging is essential. A prototype packaging technology for micro-sensors designated for applications in high temperature and high differential pressure environments has been developed and reported previously. Packaged high temperature silicon carbide pressure sensors have been successfully tested between room temperature and 500°C. This paper reports an improved version of this packaging technology and testing results of a packaged commercial Si capacitive pressure sensor at elevated temperatures. The parasitic parameters of the packaging are electrically characterized from room temperature to 500°C at 120Hz, 1kHz, 10kHz, and 100kHz. This packaging is primarily designed for high temperature capacitive pressure sensors, but it also applies to other high temperature sensors, especially those for high differential pressure environments.

Effect of Temperature Dropping during Solution Treatment in Rejuvenation Heat Treatment and its Long-Term Heating Simulation on Microstructures of Nickel Base Alloy, Udimet 520

2017 ◽  
Vol 891 ◽  
pp. 25-32
Author(s):  
Kritsayanee Saelor ◽  
Panyawat Wangyao
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Turbine Blades ◽  
Solution Treatment ◽  
Effect Of Temperature ◽  
Solution Temperature ◽  
Nickel Base ◽  
Low Precipitation

Udimet 520 is a low precipitation strengthened nickel-based superalloy, which was designed and developed to be gas turbine blades at elevated temperatures. However, after long-term service under high stresses and temperatures, the microstructure of the turbine blades could be continually degraded. Therefore, the mechanical properties could be worse than the new ones. The rejuvenation heat treatment of degraded turbine blades, which were made of cast Udimet 520, was following by solution treatment at 1,121oC / 4 hours and then double aging processes including primary aging at 843 oC / 24 hours and secondary aging at 760oC / 16 hours, respectively. However, in practical reheat treatment processes, the temperature during solution treatment could be dropped by error or malfunction of high temperature heating furnace because the furnace has to be operated continually at very high temperature for very long time resulting in final reheat treated microstructures in many nickel base superalloys. To simulate this effect, the droppings of temperature during solution treatment are chosen and performed for 3 levels; 840oC, 800oC and 760oC, which could happen in practical working then heated up again immediately to solution temperature level. The maximum number of temperature dropping during the single solution treatment is up to 3 times. Received results show that the effect of temperature dropping during solution treatment has influenced on the final rejuvenated microstructures slightly due to the low precipitation behavior of the alloy. The long term heating at 800oC and 900oC / 1000 hours provided much effect in gamma prime particle coarsening.

scholarly journals Inelastic behavior and destruction of materials under isothermal and non-isothermal, simple and complex loads

2020 ◽  
pp. 107-119
Author(s):  
V. S Bondar ◽  
D. R Abashev
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Cyclic Loading ◽  
Inelastic Deformation ◽  
Elevated Temperatures ◽  
Complex Loading ◽  
Applied Theory ◽  
Inelastic Behavior ◽  
Significant Difference

The paper deals with mathematical modeling of inelastic behavior and destruction of structural materials (steels and alloys) under simple, complex, isothermal and non-isothermal loads in repeated and long-term exposures to thermomechanical loads. The modeling is carried out on the basis of the applied theory of inelasticity, which belongs to the class of flow theories in combined hardening. The main provisions are formulated and a summary of the main equations of the applied theory of inelasticity is given. The material functions closing the applied theory of inelasticity are determined, and the connection of the defining functions with the material ones is given. Further, the results of some original experimental studies are considered, which are compared with the results of calculations based on the applied theory of inelasticity. In all studies, inelastic deformation is performed under conditions repeated and long-term exposures to thermomechanical loads. Inelastic deformation of AL-25 aluminum alloy samples under uniaxial tension-compression under both isothermal and non-isothermal cyclic loading is considered. Inelastic deformation under complex loading along the two-link polyline deformation paths with different deformation rates under high temperature conditions is studied on tubular 30HGSA alloy samples. Inelastic deformation of tubular stainless steel 304 samples under complex loading at elevated temperatures is considered. Soft cyclic loading is performed along two-link stress trajectories with different fracture angles. At the end of the links of the stress trajectory, exposure is carried out for 8 hours. The results of the calculations based on various theories used in the calculations are analyzed. Inelastic deformation and destruction of samples made of 12X18N9 stainless steel under rigid cyclic deformation under both isothermal and non-isothermal loads is considered. The duration of the loading cycle is 4 minutes, which allowed the effects of healing and embrittlement to appear at a high temperature. There is a significant difference (much higher) in the number of cycles to failure in common-phase and anti-phase modes of changes in force strain and temperature.

Sign in / Sign up

Export Citation Format

Share Document