Takuichi Morinaga1, Takeo Goto2, Tsuneo Takahashi1 and Iwao Mamiya2
1Department of Metallurgy, Tokyo Institute of Technology, Tokyo
The transformation of constituent α and β phases during the higher temperature tempering of hypoeutectoid Cu-Be alloys has been studied.
In connection with a selection of the ageing temperature, the eutectoid temperature of the specimen was also investigated. In order to confirm whether a newly accepted eutectoid horizontal of 605° ∼ 608°C is applicable, the specimens were held at 800°C and some of them were isothermally transformed at 600°C, others were quenched and temperd at 575°C up to 620°C, then they were subjected to micrographic and X-ray tests.
The tempering charactristics at 450°, 500°, 550° and 600°C were studied with micrographic and microhardness tests.
The results obtained can be summarized as follows.
(1) The eutectoid horizontal of the system is considered to lie between 605° and 610°C which is nearly equal to Fillnow's result.
(2) On tempering at temperatures higher than 450°C, the hardening rate in the β phase region is accelerated remarkably as compared with that of the α phase.
(3) The suppressed hardenability in the α phase region by these high temperature ageing is attributed to the direct formation of the equilibrium precipitate γ phase without going thorugh the intermediate γ' precipitate.
(4) Microscopic observation indicates a rapid growth of pearlitic nodules in both α and β phases, which corresponds to the softening of the specimen.
Please do not copy without permission.