Skip to main content Accessibility help

Microstructural changes in grain interior and grain boundary by formation of metastable and stable phases related to age-hardening in an Au-Cu-Ag-Pd alloy

  • Su-Yoen Cho (a1), Gwang-Young Lee (a1), Ji-In Jeong (a1), Yong Hoon Kwon (a1), Hyung-Il Kim (a1) and Hyo-Joung Seol (a1)...


The hardness changes caused by formation of the metastable and stable phases were examined and correlated with the microstructural changes in grain interior and grain boundary during aging at 350 °C to clarify the age-hardening and softening mechanism of a low-gold Au-Cu-Ag-Pd dental alloy. Aging in this context refers to the time-delay that occurs wherein such alloys are kept at elevated temperatures for periods upto many hours to allow precipitation or ordering to take place. During the period of increasing hardness, the matrix was separated into the Ag-rich α1 and AuCu I phases through the metastable phases, forming block-like structure. The apparent hardening was attributed primarily to lattice strain due to the tetragonality of AuCu I′ [the primer (′) here indicates a metastable phase; likewise (I) and (I′) indicate stable AuCu I and metastable AuCu I′ phases, respectively] and AuCu I phases along the c-axis, secondarily to the coherency or semicoherency strain between the metastable α1′ and AuCu I′ phases and between the α0 and AuCu I phases along the a-axis. The apparent softening was caused primarily by growth and coarsening of the lamellar structure in the grain boundaries, secondarily by coarsening of the block-like structure in the grain interior.


Corresponding author

a)Address all correspondence to this author. e-mail:


Hide All
1.Labarge, J.J., Tréheux, D., and Guiraldeng, P.: Hardening of gold-based dental casting alloys. Gold Bull. 12, 46 (1979).
2.Wataha, J.C. and Messer, R.L.: Casting alloys. Dent. Clin. N. Am. 4, 499 (2004).
3.Lu, K., Lu, L., and Suresh, S.: Strengthening materials by engineering coherent internal boundaries at the nanoscale. Science 324, 349 (2009).
4.Lu, L., Shen, Y., Chen, X., Qian, L., and Lu, K.: Ultrahigh strength and high electrical conductivity in copper. Science 304, 422 (2004).
5.Lee, J.H., Yi, S.J., Seol, H.J., Kwon, Y.H., Lee, J.B., and Kim, H.I.: Age-hardening by metastable phases in an experimental Au-Ag-Cu-Pd alloy. J. Alloys Compd. 425, 210 (2006).
6.Hamasaki, K., Hisatsune, K., Udoh, K., Tanaka, Y., Iijima, Y., Takagi, O., and Naruse, S.: Ageing behaviour in a dental low-gold alloy with high copper content. J. Mater. Sci. 9, 213 (1998).
7.Yasuda, K.: Age-hardening and related phase transformation in dental gold alloys. Gold Bull. 20, 90 (1987).
8.Nakagawa, M. and Yasuda, K.: Age-hardening and the associated phase transformation in an Au-55.2 at% Cu-17.4 at% Ag ternary alloy. J. Mater. Sci. 23, 2975 (1988).
9.Tanaka, Y., Udoh, K., Hisatsune, K., and Yasuda, K.: Early stage of ordering in stoichiometric AuCu alloy. Mater. Trans., JIM 39, 87 (1998).
10.Yasuda, K. and Ohta, M.: Difference in age-hardening mechanism in a dental gold alloys. J. Dent. Res. 61, 473 (1982).
11.Prasad, A., Eng, T., and Mukherjee, K.: Electron microscopic studies of hardening in type III dental alloy. Mater. Sci. Eng. 24, 179 (1976).
12.Hero, H., Jorgensen, R., and Sorbroden, E.: Precipitations in a dental Ag-Pd-Cu-Au dental alloy. J. Dental. Res. 61, 673 (1982).
13.Villars, P. and Calvert, L.D.: Pearson’s Handbook of Crystallographic Data for Intermetallic Phases (ASM International, Metals Park, Novelty, OH, 1985), p. 1198.
14.Krawitz, A. and Sinclair, R.: On the lattice parameter of non-random solid-solutions. Philos. Mag. 31, 697 (1975).
15.Han, K.H. and Lee, H.E.: A microstructural of rapidly solidified and heat-treated austenitic Fe-Mn-Al-Mo-W-Nb-C alloys. J. Mater. Res. 10, 1371 (1995).
16.Suryanarayana, C. and Norton, M.G.: X-Ray Diffraction: A Practical Approach (Plenum Publishing Corp, New York, 2006), p. 89.
17.Kawashima, I., Ohno, H., and Sarkar, N.K.: Effect of Pd or Au addition on age-hardening in AgMn-based alloy. Dent. Mater. 16, 75 (2000).
18.Jena, A.K. and Chaturvedi, M.C.: Phase Transformations in Materials (Prentice Hall, New Jersey, 1995), p 77.
19.Cho, M.H., Kim, Y.O., Kwon, Y.H., Kim, H.I., and Seol, H.J.: Grain interior precipitation and related lamellar forming grain boundary reaction in Ag-Pd-Cu-Au-Zn alloy. Mater. Sci. Technol. 27, 958 (2011).
20.Massalski, T.B.: Binary Alloy Phase Diagrams, 2nd ed. (ASM International, Materials Park, Novelty, OH, 1990), p. 28.


Related content

Powered by UNSILO

Microstructural changes in grain interior and grain boundary by formation of metastable and stable phases related to age-hardening in an Au-Cu-Ag-Pd alloy

  • Su-Yoen Cho (a1), Gwang-Young Lee (a1), Ji-In Jeong (a1), Yong Hoon Kwon (a1), Hyung-Il Kim (a1) and Hyo-Joung Seol (a1)...


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.