What is the difference between metal compounds and metal solid solutions?
Solid solution refers to the alloy phase in which the solute atoms are dissolved into the solvent lattice and remain solvent type. A crystalline substance consisting usually of atoms or molecules in which a chemical substance is dissolved as a base; other substances are found in alloys and silicate systems; also present in polyatomic substances. The mixture can be treated as a solution when the crystal structure of the solvent can be stabilized and homogeneous after addition of solute. Some mixtures can form solid solutions in many concentrations, while some mixtures do not form solid solutions at all.
Sigma phase belongs to Affirmative system, there are 30 atoms in the unit cell, two element alloy, sigma phase formation is related with the following conditions: (1) the atomic size difference, phase difference between the maximum sigma atomic radius of a tungsten cobalt, the atomic radius difference is 12%. (2) there is a set of cubic lattice elements (coordination number 8), and another component is face centered cubic or dense six square lattice (coordination number is 12). (3) appear in "average number of races" (s+d layer electron number) in the range of 5.7 ~ 7.5. The region of the presence of sigma in the two - element alloy is shown in table 3. In the three element system, the concentration and temperature range of the formation of the sigma phase are affected by the addition of third components. Usually in chromium stainless steel in Fe Cr phase, in Fe - Cr - Mn three yuan, sigma phase iron chromium and chromium can form Mn two element, when the addition of manganese in stainless steel, will promote the formation of sigma phase, and stabilizes the wide temperature range. Many of the Fe Cr alloy elements. The phase temperature range increases. In less than 820C stable Fe Cr phase, silicon promotes the formation of D phase and the stable temperature increased to 900 to 960 DEG C, manganese and molybdenum can improve the temperature stability of sigma phase to 1000 DEG C.
A series of intermetallic compounds occurring between transition metals in intermetallic compounds. The most important are L sigma sigma phase and ves phase, they are topologically close packed (TcP) phase, they consist of a small atomic radius of a dense layer, which is inlaid with a large atomic radius of atomic structure, this is a highly dense pile. In addition to atomic size factors, their formation is also influenced by the concentration of electrons.