eutectoidadj.n.
/juːˈtɛktɔɪd/ Metallurgy.
A. adj.
That is a eutectoid; of or pertaining to a eutectoid or its transformation; eutectoid point, the transformation temperature of a eutectoid, or the point representing it in a constitutional diagram.
ΚΠ
1910 Encycl. Brit. XIV. 805/1 Excess of iron over this eutectoid ratio.
1946 Thorpe's Dict. Appl. Chem. (ed. 4) VII. 596/2 In this case..it is the solid solution beta breaking down into the two solutions alpha and gamma, and the point P is known as a eutectoid point.
1950 Engineering 15 Dec. 492/3 Austenite in a plain eutectoid steel could decompose isothermally.
1961 J. N. Anderson Appl. Dental Materials (ed. 2) vi. 56 One such reaction..is known as a eutectoid reaction. This involves the breakdown as a solid solution at a definite temperature to produce an intimate mechanical mixture of two solids.
B. n.
A solid analogous to a eutectic, in which the high temperature phase is a solid solution instead of a liquid and the constituents separate out simultaneously when it is cooled to the transformation temperature.
ΚΠ
1903 H. M. Howe Iron, Steel, & Other Alloys 440 The word ‘eutectoid’ occurred to me (June 7, 1903)... It suggests having the shape or other important properties of the ‘eutectic’, while the two words differ from each other enough to indicate that they refer to really distinct things.
1910 Encycl. Brit. XIV. 805/1 Far below the freezing-point, transformations may take place in the solid metal, and follow a course quite parallel with that of freezing, though with no suggestion of liquidity. A ‘eutectoid’ is to such a transformation in solid metal what a eutectic is to freezing proper.
1925 Jrnl. Iron & Steel Inst. 111 584 The eutectoid occurring at 0·89 per cent. carbon theoretically should be regarded as a eutectoid of iron and a solid solution containing about 2·0 per cent of carbon.
This entry has not yet been fully updated (first published 1972; most recently modified version published online March 2018).
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adj.n.1903