Manufacturing And Investigation Of Microstructure, Precipitation Hardening And Tarnishing Of Ag-Cu-Ge Argentium® Alloy

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Khosravi, Babak | 2015

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 48577 (07)
University: Sharif University of Technology
Department: Chemical and Petroleum Engineering
Advisor(s): Abbachi, Parvin; Hamdi, Farzad
Abstract:
In this study melting and casting process of Ag-6.3%wt Cu-1.2%wt Ge alloy with NaBH4 additive for grain refining was investigated. ICP and XRF chemical analysis was used for calculating of Boron and Germanium lost in the processing section then an appropriate route for manufacturing of this alloy was suggested. With SEM and EDS chemical analysis which was installed on SEM sample’s microstructures after cold work and heat treatment was investigated. Solidification’s phases were identified with using DTA, XRD and EDS. To introduce a mechanism for increasing of tarnishing resistance in Argentium alloy, XPS analysis were employed. Optical microscope images reveals that casting samples with grain refiner are 5 fold finer than casting samples without grain refiner. E1 ternary eutectic with the melting point of 635℃ were proved by DTA thermal analysis and EDS elemental analysis. XRD scattering pattern from overaged and quenched samples during precipitating process prove existence of ε-Cu3Ge precipitates. XPS result show that protecting oxidized germanium layer is forming in 600℃ with protecting atmosphere. Presence of GeO2 oxide layer also proved by these results
Keywords:
Precipitation Hardening ; Argentium ; Passive Layer ; Tarnishing ; Firescale

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