AN ISOTHERMAL TRANSFORMATION STUDY OF THE BETA PHASE DECOMPOSITION IN A HYPO- EUTECTOID COPPER-INDIUM ALLOY

摘要

The copper-indium alloy containing 69.30 wt-% copper and 30.65 wt-% indium has many structures which are similar to those found in the hypo-eutectoid iron-carbon alloy. Upon isothermally transforming this alloy above the eutectoid temperature, the pro-eutectoid а phase precipitates out from the parent β phase in a manner analogous to the precipitation of а iron from γ -iron in the ironcarbon system. The lower limit of theβ phase field for this alloy was deter¬mined to be 633.4 ± 2.1°C. Below the eutectoid temperature theаphase separates out in a number of different patterns. The number of precipitation sites for theаphase tends to increase as the transformation temperature is lowered. During isothermal transformation of theβphase, just below the eutectoid temper¬ature, the eutectoid pearlite forms into lamellar nodules similar to the pearlite of the iron-carbon system. The original lamellar pearlite, as well as the inter¬woven type pearlite formed at lower temperatures, will coarsen, on continued transformation, to form secondary pearlite.