Activity Measurements of Mg in the Ternary Cu-Mg-Si System Using Thermogravimetric Knudsen Effusion Method
- PDF / 557,500 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 111 Downloads / 183 Views
TRODUCTION
LIGHT metals such as Al and Mg are typically alloyed with Cu, Si, and Zn, and thus, their combined alloys have technological importance. The determination of the thermodynamic properties and the construction of their phase diagrams are technically required. Therefore, the fundamental studies have included various binary alloy systems. It is also important to explore the ternary systems. Cu-Mg-Si ternary alloy is a subgroup of these light alloys, and its binary and ternary intermetallic phases cause precipitation hardening. Phase diagrams can be constructed using different theoretical thermodynamic models. However, the phase diagrams that are constructed by using the experimental findings play an important role in industrial applications. Due to the high vapor pressure of Mg and its high affinity to O2, difficulties are encountered during the conduction of experiments with Mg-containing alloys. Portevin and Bonnot[1] pointed out that the intermetallic Cu3Mg2Si (s phase) can be formed in the ternary CuMg-Si system. Laves and Witte[2] investigated the relationship between the valence electron concentrations and structure kind in various Mg ternary alloys. Witte found that Cu16Mg6Si7 (r phase) existed in the ternary Cu-MgSi system together with s phase.[3] Nagorsen and Witte[4] explained the crystal structure of r phase and its crystal ALIYEARABACI,AssistantProfessor,andIBRAHIMYUSUFOGLU, Professor, are with the Department of Metallurgical and Materials Engineering, Engineering Faculty, Istanbul University, Avcilar, 34320, Istanbul, Turkey. Contact e-mail: [email protected] Manuscript submitted June 12, 2013. Article published online Decmber 4, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
parameters. Bergman and Waugh[5] re-determined the positions of the atoms in the crystal structure of r phase. Aschan[6] examined the Cu corner of ternary Cu-Mg-Si system by X-ray diffraction and thermal analysis. Komura and Matsunaga[7] found a new, ordered structure and explained its composition as Mg(Cu0.8Si0.2)2.5. Matsunaga et al.[8] found that a phase existed in the ternary CuMg-Si system with the nonstoichiometric composition of Cu57.9Mg28.4Si13.7. Matsunaga[9] evaluated the above information in detail. Ganesan and Ipser and Ganesan et al.[10,11] investigated the ternary Cu-Mg-Si system measuring the vapor pressure of Mg according to the isopiestic technique along the XCu:XSi = 7/3 isopleth and determined the thermodynamic properties of liquid ternary Cu-Mg-Si alloys. Miettinen and Vassilev[12] carried out a thermodynamic assessment of the ternary Cu-Mg-Si system in its copper-rich region in relation with the development of a thermodynamic database and described the solution phases with the substitutional solution model and treated the intermetallic compounds as plain semi-stoichiometric phases. They used the chemical formula Cu55Mg22Si23 for r phase instead of the chemical formula of Cu16Mg6Si7. These phases described above have significant contribution to the precipitation hardening of aluminum alloys. In the current
Data Loading...
