Prakt. Met. Sonderband 41 (2009) 97
well as the isothermal age hardening process (i.e. solution treatment plus ageing at 750°C for 15
min) only marginally increased the hardness state. For this reason the incorporation of the heat
. treatments within a production process chain may not be recommendable since an acceptable hard-
ve damages in ness state is already induced in the material by the casting process. A detailed discussion on the
this alloy are physical mechanisms responsible for the hardening behaviour of this alloy is beyond the scope of
> grinding and the present report. The quality of surface preparation appears to depend not significantly on the
kely to lead to hardness state of the specimens.
of the already
es reasonably Table 4. List of the porosity, grain size as well as hardness values of the AuAgCu micro specimens.
f surface qual- Specimen Porosity [%] Grain size [um] Hardness [HV 0.05]
mages of etch- As-cast «2 4a 268
ished surfaces 400 °C/15min “2 89 274
ked difference Solution treated 4 38 163
‘igure 2a-d the _Age hardened £0 x 276
cal contrast is
cimen (Figure
rgely darkened 4 Conclusion
curred at those
evealed micro- 3 a i } } i
rocedure. Seg- This study has demonstrated the viability of preparing metallographic micro-sections of a Au-Ag-
icles observed Cu ternary alloy using a combined solution of potassium cyanide and the oxidizing agent; ammo-
\icro specimen nium peroxide. The KCN etchant provides better results than a chloride based etching agent. Al-
Iso provide es- though polishing steps must be conducted in a delicate manner for this alloy, the presence of small
ight in the im- scratches on the imaged surface need not be reason for a repetition or prolongation of polishing
as the micro- steps as this will merely introduce new defects such as rounded edges. It has been shown that the
uiaxed) of the hardness in the as-cast state of this Au-Ag-Cu micro-specimen compares well with that in the age
mens (Table 4) hardened state.
) in the micro-
ng behaviour.
he elimination 5 Acknowledgements
nding at pains-
robably devel- We are grateful to Prof. Dr. Gundi Baumeister, formerly of the Institute for Materials Research
polishing cloth (IMF III) Forschungszentrum Karlsruhe, for producing the microcast specimens. The Deutsche For-
-based etchant schungsgemeinschaft is acknowledged for financial support under the project SFB499/D1.
1e micro speci-
over the speci-
3 is so however
25.0 wt.-% Ag 6 References
aque white pre-
[1] K. Obergfell, V. Schulze, K-H. Lang, D. Lohe, DVM-Tagung —Werkstoffpriifung, Bad
lity of incorpo- Nauheim, 1999, pp. 331 — 339.
sults have been [2] G. Beck, H.-H. Beyer, W. Gerhartz, J. HauBelt, U. Zimmer (Eds.), Edelmetall-Taschenbuch,
lite comparable Degussa AG, Heidelberg, Hiithig, 1995, pp. 530 — 353.
C for 15 min), [3] T. Shiraishi, M. Ohta, M. Nkagawa, R. Ouchida, J. Alloys Compounds. 1997, 257, 306.
sle phase alloy, [4] P.P. Corso, R. M. German, H. D. Simmons, J. Dent. Res. 1985, 64, 854.
* for 15 min as 51 G. Baumeister, J. Hausselt, S. Rath, R. Ruprecht, Adv. Micro- Nanosyst. 2005, 4, 357.
