1. a combined form of two or more metals, or of a metal with a nonmetal, sometimes using an inferior ingredient with a more costly one.
example: Brass is an alloy of zinc and copper.
2. the relative degree of purity of a metal; fineness.
3. something added that lowers quality or value.
Saving an occasional burst of impatience, or coarse assertion of his mastery, his good-humour remained to him, but it had now a sordid alloy of distrust; and though his eyes should twinkle and all his face should laugh, he would sit holding himself in his own arms, as if he had an inclination to hoard himself up, and must always grudgingly stand on the defensive. (Charles Dickens, Our Mutual Friend)
1. to mix (metals with other metals or with nonmetals) to form an alloy.
Egypt had lost with its liberties its gold coinage, and it was now made to feel a further proof of being a conquered country in having its silver much alloyed with copper. (A. S. Rappoport – History of Egypt From 330 B.C. To the Present Time, Volume 11)
2. to degrade the purity of by the addition of some element; adulterate.
example: A wave of sadness came over him, which alloyed his sense of triumph.
Note on usage:
The first verb sense of “alloy,” the physical mixing of a metal with another metal or other substance, often appears in passive constructions. The passive voice is the norm for scientific and technical discourse, where the knowledge conveyed is expected to be objective, and things possess qualities and act and react independently of human subjectivity. And, although the process of alloying usually involves human agency and intent–unlike, say, the oxidation that produces rust on metal, when the word “alloy” is used, the interest most often lies in the fact of a material being an alloy or in the specific composition of an alloy, or in how an alloy can be made, rather than in who alloyed gold with copper.
When referring to metals, as in the first verb sense, the preposition “with” is used: Egypt’s silver, its coins and artifacts, was alloyed with copper. The finer metal will usually be the subject of the sentence, the thing that is being alloyed with (often) the inferior material.
With the second verb sense of “alloy,” which is a metaphorical extension of the first sense to apply to intangible objects such as states of mind, emotions, and values, it is the effect of the lesser or negative quality that is emphasized. In sense one, A is mixed with B. In sense two, B, or the action of mixing in B, degrades the purity of A. Hence in verb sense two, we say that sadness alloyed his sense of triumph, whereas it would be strictly improper usage to say that copper alloyed the gold. When sense two is used in a passive construction, the preposition is therefore “by.” His sense of triumph was alloyed by sadness, not with sadness. Sense two has a much stronger negative denotation. To alloy something in this sense is to “degrade” it, to reduce its initial or potential purity.
It should be kept in mind, however, that metal alloys usually have some significant advantage over the pure metal: strength and durability (steel) or ductility, for example. When using the word “alloy” in its extended, non-technical senses, the tension between the concepts of purity and utility is there for the writer’s mining. How useful, true, or lasting can unalloyed happiness be?