【正文】 w phase called “intermetallic pounds”,such as nickel will dissolve some aluminum, so that at low aluminum contents a solid solution is produced. But if larger amounts of aluminum are added, then produce intermetallic pounds. 17 ? Some of these pounds have a very well defined position ,such as Ni3Al ? Others have quite a wide range of position,such as NiAl 18 Three types of circumstances of intermetallic pounds forming ? The first circumstance:size differenence ? The second circumstance:a large differenence in electronegativity ? The third circumstance:certain ratios of the number of valence electrons to the number of atoms in a structure 19 HumeRothery Rule ? HumeRothery Rule 1:Atomic Size Factor (the 15%) Rule. ? Extensive substitutional solid solution occurs only if the relative difference between the atomic diameters (radii) of the two species is less than 15%. If the difference 15%, the solubility is the atomic radii of solids that form solid solutions, theempirical rule given by HumeRothery is given as： Mismatch= %15100 ???????? ?s ol v e nts ol v e nts ol ut errr20 ? HumeRothery Rule 2:Crystal Structure Rule : For appreciable solid solubility, the crystal structures of the two elements must be identical. ? HumeRothery Rule 3: Valency Rule : A metal will dissolve a metal of higher valency to a greater extent than one of lower valency. The solute and solvent atoms should typically have the same valence in order to achieve maximum solubility. ? HumeRothery Rule 4: The Electronegativity Rule : Electronegativity difference close to 0 gives maximum solubility. The more electropositive one element and the more electronegative the other, the greater is the likelihood that they will form an intermetallic pound instead of a substitutional solid solution. The solute and the solvent should lie relatively close in the electrochemical series. 21 休姆－羅瑟里（ Hume－ Rothery）規(guī)律 （ 1） 形成合金的元素原子半徑之差超過 14％～ 15％ ，則固溶度極為有限；若尺寸差小于 15％， 尺寸因素成為次要的影響因素，固溶度由其他影響因素確定，這就是知名的 15％ 規(guī)律。 ? 銅鎳合金是固溶體合金，由一種金屬原子進(jìn)入另一種金屬的晶胞空隙而形成的。 ? Singlephase b solidsolution. ? α單相固溶體 ? α單相固溶體