KINETICS OF HOT PRESSING

Technical Report · Sun Jan 01 04:00:00 EST 1961

OSTI ID:4075371

McClelland, J D

Hot pressing of powdered materials can be described adequately by using a plastic flow theory proposed by Mackenzie and Shuttlewonth for sintering. The present derivation assumes that the principal driving force for the closing of pores is the applied hydrostatic pressure instead of the surface tension of the pores. This pressure term, when corrected for the density of the compact, can be substituted for the surface tension term in the original derivation. The resultant equations give the material densification rate in terms of a yield point and a viscosity. The equations predict that an end-point density dependent upon the applied pressure and the yield point of the material will be reached. The effect of temperature and pressure on the rate of beryllia powder compacts was obtained experimentally. The pressures ranged from 1000 to 2000 psi, the temperatures from 1200 to 1700' deg and the time from 15 to 240 min. The curves show a steep initial rate of densification followed by a gradual approach to a nearly asymptotic end-point density. The theoretical equations are found to describe successfully the densification rates observed in beryllia when reasonable values of the yield point and viscosity are assumed. (auth)

• Research Organization: Atomics International. Div. of North American Aviation, Inc., Canoga Park, Calif.
• DOE Contract Number: AT(11-1)-GEN-8
• NSA Number: NSA-15-006357
• OSTI ID: 4075371
• Report Number(s): NAA-SR-5591
• Country of Publication: United States
• Language: English

Related Subjects

BERYLLIUM OXIDES
COMPACTING
DENSITY
DISTRIBUTION
EQUATIONS
FLUID FLOW
HOT WORKING
METALS, CERAMICS, AND OTHER MATERIALS
POROSITY
POWDERS
PRESSURE
SINTERING
SURFACE TENSION
TEMPERATURE
TENSILE PROPERTIES
VISCOSITY