Thermodynamic description, diffusivities and atomic mobilities in binary Ni–Os system

The Microstructure, Solidification Path, and Microhardness of As-Cast Ni-Al-Cr-Os Alloys in a Ni-Rich Region

“…All the samples were smelted by melting a mixture of raw materials-Ni, Al, Cr, and Os (purity: >99.9%, provided by China New Metal Materials Technology Co., Ltd., Beijing, China)-in an arc melting furnace (WK-I, Physcience Opto-electronics Co., Ltd., Beijing, China) under a high-purity argon atmosphere in a water-cooled copper hearth with a non-consumable tungsten electrode, with titanium metal pieces used as getters. In order to ensure that the refractory element (Os) was adequately and uniformly melted into the alloy ingot, samples were prepared according to the following three steps [12]. The master Ni-Os ingots were melted first.…”

“…One research hot spot in this field lies in the development of new single-crystal superalloys with less or even no Re [8][9][10][11]. In our latest studies on the determination of interdiffusion coefficients in a series of nickel binary and ternary alloys [12,13], our research group discovered that the interdiffusion coefficients in nickel-based alloys containing Os element are lower than those containing Re when the temperature is above 1300 • C. Therefore, we conclude that the addition of Os to nickel-based single-crystal superalloys may help to retain or even improve their creep resistance.…”

“…Accurate phase equilibria and/or thermodynamic descriptions of nickelbased alloys with Os are both essential; unfortunately, relevant research on such topics remains rare [14,15]. In order to remedy this situation, a project that measured the accurate phase equilibria in nickel-based alloys with Os and established their accurate thermodynamic database was carried out by our research group [12,16]. In 2015, Chen et al [12] performed a thermodynamic assessment of a binary Ni-Os system based on the experimental phase equilibria reported in the literature [15].…”

“…In order to remedy this situation, a project that measured the accurate phase equilibria in nickel-based alloys with Os and established their accurate thermodynamic database was carried out by our research group [12,16]. In 2015, Chen et al [12] performed a thermodynamic assessment of a binary Ni-Os system based on the experimental phase equilibria reported in the literature [15]. After that, three of the present authors [16] conducted a thorough experimental measurement of the isothermal sections of a Ni-Al-Os system at 1000 and 1200 • C, as well as the isothermal tetrahedron of a Ni-Al-Cr-Os system at 1200 • C in a Ni-rich region.…”

Application of numerical inverse method in calculation of composition-dependent interdiffusion coefficients in finite diffusion couples

“…The solid semi-infinite diffusion couple is the frequently used experimental technique for measurement of interdiffusion coefficients in the target phase. Numerous investigations on the measurement of interdiffusion coefficients by using the semi-infinite diffusion couple together with either the traditional Bolzmann-Matano method and its variants [3][4][5] for binary systems or the Matano-Kirkaldy method [6] for ternary systems can be found in the literature [2,[7][8][9][10][11][12]. Sometimes, when the total thickness of the diffusion couple is not large enough or the diffusion time is too long, diffusion distance may exceed the entire domain.…”