Component : components are pure metals and/or compounds of which an
alloy is composed.
System: which has two meanings. First, ‘‘system’’ may refer to a specific
body of material under consideration (e.g., a ladle of molten steel). Or, it
may relate to the series of possible alloys consisting of the same
components, but without regard to alloy composition (phase diagram)
(e.g., the iron–carbon system).
Solubility limit: For many alloy systems and at some specific
temperature, there is a maximum concentration of solute atoms that may
dissolve in the solvent to form a solid solution.
Phase: A phase may be defined as a homogeneous portion of a system
that has uniform physical and chemical characteristics. Every pure
material
組件：組件是純金屬和/或它的合金組成的化合物
系統：這有兩個意思。第一，“系統”是旨在考慮範圍下的某材料體
(一杓的熔融鋼液)第二，在不考慮合金之化學成分的條件下，系統可
以說是一系列由相同組成構成的合金(例如，鐵-碳系統)
溶解度限:許多合金系統在某特定溫度下，溶質原子可以固溶於溶劑
中的最大濃度稱為溶解度限。
相:可以定義為一個系統內有相同的物理和化學特性的一個均質部
份。每一個純物質以及每一個固溶體、液態溶體和氣態溶體都被認為
是一個相。
For example, the sugar– water syrup solution just discussed is one
phase, and solid sugar is another. Each has different physical properties
(one is a liquid, the other is a solid); furthermore, each is different
chemically (i.e., different chemical composition); one is virtually pure
sugar, the other is a solution of H2O and O11 . If more than one phase is
present in a given system, each will have its own distinct properties, and a
boundary separating the phases will exist across which there will be a
discontinuous and abrupt change in physical and/or chemical
characteristics.
例如，糖-水糖漿溶液就是一個相，而固體糖則是另一個相，每一個
相有不同的物理性質(一個是液體，另一個是固體)以及不同的化學性
質(例如，化學成分不同);一個基本上是純糖，另一個是水和蔗糖的溶
液。如果一個系統內有超過一個以上的相存在，每一個相有其不同的
性質，由於他們在物理或化學特性的中斷與突然改變，使得不同的相
與相之間形成邊界將彼此隔開。
Microstructure 顯微組織
Many times, the physical properties and, in particular, the mechanical
behavior of a material depend on the microstructure. Microstructure is
subject to direct microscopic observation, using optical or electron
microscopes. In metal alloys, microstructure is characterized by the
number of phases present, their proportions, and the manner in which
they are distributed or arranged. The microstructure of an alloy depends
on such variables as the alloying elements present, their concentrations,
and the heat treatment of the alloy (i.e., the temperature, the heating time
at temperature, and the
rate of cooling to room temperature).
很多時候，材料的物理性質與化學性質常常受顯微組織的影響。觀察
顯微組織必須經由光學或電子顯微鏡觀察。在金屬合金裡，顯微組織
的特徵是向的數目、比例和他們的分布與安置的狀態等，而一合金的
顯微組織取決於合金的元素、他們的濃度、合金的熱處理(及溫度、
在某溫度的加熱時間與冷卻至室溫的速率)等變數。
Equilibrium 平衡
Equilibrium is best described in terms of a thermodynamic quantity called
the free energy. A system is at equilibrium if its free energy is at a
minimum under some specified combination of temperature, pressure,
and composition. In a macroscopic sense, this means that the
characteristics of the system do not change with time but persist
indefinitely; that is, the system is stable. A change in temperature,
pressure, and/or composition for a system in equilibrium will result in an
increase in the free energy and in a possible spontaneous change to
another state whereby the free energy is lowered.
對平衡最好的描述是利用熱力學上的一個稱為自由能的量。簡單來
說，自由能是一個系統內部能量的函數，也是原子或分子的亂度或不
規則性(或稱為熵)當一個系統處於平衡狀態，即表示溫度、壓力和成
分的特定組合，使得自由能達到及小值。從巨觀來看，就是指該系統
的特性永遠不隨時間而改變;也就是說，該系統是穩定的。再平衡狀
態下改變一個系統的溫度、壓力或成分都會導致自由能的改變以及可
能同時改變系統至另一狀態，使自由能降低。
Equilibrium as it applies to systems in which more than one phase
may exist. Phase equilibrium is reflected by a constancy with time in
the phase characteristics of a system
相平衡是將平衡應用於同時存在一個以上的相的系統中。相平衡表現
在一個系統內，相的特性不隨時間改變
A metastable state or microstructure may persist indefinitely,
experiencing only extremely slight and almost imperceptible changes as
time progresses. Often, metastable structures are of more practical
significance than equilibrium ones. For example, some steel and
aluminum alloys rely for their strength on the development of metastable
microstructures during carefully
designed heat treatments
介穩定狀態或其顯微組織可能無限期的持續下去，隨著時間過去只有
極細微或幾乎察覺不到的改變。介穩態的組織往往在實際上比平衡狀
態來的重要，例如，有些鋼和鋁合金就是藉由週密設計的熱處理造成
介穩定顯微組織的發展來增強其強度。