Niobium
Eskin 2nd edition - Dmitry G. Eskin, Georgy I. Eskin
BCAST, Brunel University London, Uxbridge, Middlesex, UB8 3PH, UK (https://www.taylorfrancis.com/books/9781466577992)
1st edition - https://www.researchgate.net/publication/255266147_Ultrasonic_Treatment_of_Light_Alloy_Melts
11/14/2017 - above requested through researchgate.net (Eskin not on researchgate.net)
Niobium's Young's modulus is constant in the range of 20-1200 °C. (Eskin[1], p. 299) Thus, unlike other acoustic materials, the resonator's frequency remains relatively constant within this temperature range. This makes it suitable for processing liquid metals. (Although other materials can be pretuned to the required operating temperature, they then can't be run on typical narrow-band power supplies at ambient temperatures.)
Eskin preview (1st edition?) - https://books.google.com/books?id=OsPHJ1lGfn0C&pg=PA299&lpg=PA299&dq=Nb+Niobium+ultrasonic+ultrasound&source=bl&ots=4QYuj5J33C&sig=0exaFW8tBxXokqlKR1etdFpqXQE&hl=en&sa=X&ved=0ahUKEwiOoIKl2bzXAhUI5mMKHWEHCqcQ6AEIYjAK#v=onepage&q=Nb%20Niobium%20ultrasonic%20ultrasound&f=false
Eskin -
In molten A7 (1070) aluminum - "These data [Table 10.1] show how easily radiators of iron alloys can be destroyed and show the superiority of the cavitation resistance of titanium, molybdenum, and especially niobium based systems. Radiators of tantalum exhibit an exceptionally high resistance; however, the use of this metal is prohibitively expensive." (p. 301) --> effects of cavitation + chem reaction to liquid metal.
"Analysis of this experimental evidence helps us make a meaningful choice of radiator material depending on the type of ultrasonic treatment and financial constraints. For example, in shape casting where the ultrasonic degassing process lasts at most thirty minutes, wide use is made of radiators of titanium and its alloys, which are readily repairable by building up the eroded face. For prolonged continuous pruification and grain refining of cast aluminum, the optimum material for radiators is niobium alloys which afford hundreds of hours of continuous ultrasonic treatment. In continuous casting of magnesium alloys, low alloy tool steels can be a reasonable choice." (p. 301)
Molten metal horn requirements (p. 298) -
- Wetted by liquid aluminum
- High density - why?
- High melting point
- High endurance
- f insensitive to temperature
- Endure large number of heating cycles
- Release an insignificant number of fine particles into the melt
Ceramic radiators have a low endurance limit and low cavitation resistance in liquid aluminum, therefore can operate at displacement amplitudes under 10 micro-meters." (p. 298)
-------------------
"Erosion resistance and performance characteristics of niobium ultrasonic sonotrodes in molten aluminum" --> Nb with 4% Mo has much better cavitation resistance than pure Nb possibly because Nb has a "much lower value of tensile stress and hardness compared to that of the Nb–Mo alloy tip".
https://www.researchgate.net/publication/257094320_Erosion_resistance_and_performance_characteristics_of_niobium_ultrasonic_sonotrodes_in_molten_aluminum
11/14/2017 - requested through researchgate.net
-------------------
Nb has low fatigue but operating ampls in molten metals is relatively low. (Eskin, table 10.1 --> 20 microns, unspecified f)
Wave speed is low so tunes shorter than usual acoustic mats.
-------------------
weiss1 --
20 kHz
"Again, no difference between the experimental results of specimens tesed in pure water or in the Ringer's solution could be detected." (p. 395)
Figure 6 (p. 401) & Table 4 (p. 405) - fatigue stress @ 5e7 cycles = 250 MPa (36 ksi) @ 50% failures (room temperature, water or Ringer's solution)
-------------------
Dave Hunicke - what is stud mat? pure Nb or alloyed?
-------------------
11/14/2017 Google search - nothing good down to level 6
-------------------
Dmitry G. Eskin -
https://www.researchgate.net/publication/257094320_Erosion_resistance_and_performance_characteristics_of_niobium_ultrasonic_sonotrodes_in_molten_aluminum
https://www.researchgate.net/publication/281873931_Review_on_corrosion-wear_resistance_performance_of_materials_in_molten_aluminum_and_its_alloys
|
|
|
|
||||
|