Age-hardening by metastable phases in an experimental Au–Ag–Cu–Pd alloy

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• 作者：Jae-Ho Lee ; Sang-Joon Yi ; Hyo-Joung Seol ; Yong Hoon Kwon ; Jai-Bong Lee and Hyung-Il Kim
• 关键词：Dental alloys ; Scanning electron microscopy ; X-ray diffraction
• 刊名：Journal of Alloys and Compounds
• 出版年：2006
• 出版时间：30 November 2006
• 年：2006
• 卷：425
• 期：1-2
• 页码：210-215
• 全文大小：1581 K

文摘

The age-hardening mechanism and phase transformation during the age-hardening process were examined for a low carat gold alloy with a composition of 30 wt. % Au–30 wt. % Ag–20 wt. % Cu–20 wt. % Pd. By aging the solution-treated specimen, the fcc α₀ phase was transformed into the Au-containing Ag-rich phase and the Pd-containing AuCu I phase through the metastable state. The phase transformation of the α₀ phase into the metastable Ag-rich α^′₁ and AuCu I′ phases caused the apparent hardness increase. And the phase transformation of the Ag-rich α^′₁ and AuCu I′ phases into the Ag-rich α₁ and AuCu I phases, caused the hardness decrease. The hardness increase in the early stage of the age-hardening process seemed to be caused by an introduction of the coherency strains at the interface between the metastable Ag-rich l3"">l3&_user=10&_cdi=5575&_rdoc=38&_handle=V-WA-A-W-YA-MsSWYWW-UUA-U-AAZCWECADZ-AAZWYDCEDZ-VBWBAWUA-YA-U&_acct=C000050221&_version=1&_userid=10&md5=e24a56d6e80741d726a4ff1e32019a1a"" title=""Click to view the MathML source"">α^′₁ and AuCu I′ phases during the phase transformation of α₀ into Ag-rich α^′₁ and AuCu I′. In the later stage of aging process, the alternative lamellar structure composed of the Au-containing Ag-rich phase and the Pd-containing AuCu I phase grew from the grain boundary consuming the Ag-rich α^′₁ and AuCu I′ phases in the grain interior, which caused the hardness decrease by releasing the coherency strains.