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[March 2004]
Ceramic Cells Aid Piston Dilatometry Advance
NPL (Teddington, Middx, England) has successfully applied piston dilatometry to aluminium alloys using a boron nitride cell, and to cast iron and nickel alloys using an alumina cell. The technique has permitted the density as a function of temperature to be determined through the so-called 'mushy' zone and into the liquid state. Partial success has been obtained using a machinable glass-ceramic cell.
A report evaluating and reviewing the theory and use of double piston cells in conventional mechanical dilatometry for the determination of the melting and liquid thermal expansion characteristics of metals and alloys has recently been produced. It outlines a number of criteria that need to be satisfied for successful operation of the technique.
The technique has been shown to be particularly useful for estimating densities through the upper temperature part of the 'mushy' zone and into the liquid phase, including determination of the liquid expansion coefficient.
For a copy of the Report, please e-mail: materials@npl.co.uk
ENDS