Micrograph 12 and full record

Micrograph no

Brief description

Cu 21, Sn 79 (wt%), peritectic transformation

Keywords

alloy

, bronze

, copper, metal, peritectic reaction

, tin

Categories

Metal or alloy

System

Cu-Sn

Composition

Cu 21, Sn 79 (wt%)

Standard codes

Reaction

Processing

As-cast (sand mould)

Applications

Sample preparation

Technique

Reflected light microscopy

Length bar

400 μm

Further information

This microstructure is generated via a peritectic reaction (L+e = eta), which bears some similarities to the more familiar eutectic reaction (L = a + b). Upon cooling from the liquid phase field, primary e is formed, which can be seen here as a slightly darker phase than the sheath of h surrounding it. The h sheath is the product of a peritectic reaction between e and liquid. The peritectic reaction rarely goes to completion, since the formation of h around the e phase separates it from the liquid and inhibits further growth. Eventually, the remaining liquid transforms by a eutectic reaction to h and Sn. In this micrograph, the constituents of the eutectic mixture cannot be distinguished and it appears uniformly dark.

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