Conversely, all TA cup materials contained some pearlite (see Table 2) though only the cooling curve of the three alloys with highest Cu content showed a clear recales- cence or a marked arrest that could be associated with pearlite formation. The minimum temperature recorded in such cases has been labelled Tp,exp


in Figure 2-a. Because the formation of pearlite was not always evident, the cool-


nally, for comparison purposes with other experiments, the cooling rate was evaluated by means of its average value Vcool


, and the corresponding temperature, Ttrans within the range 920-775ºC (1688-1427 °F) again given in Table 2. Table 3. Cooling Curves Characteristics Obtained from the U1-U4 Furnace Experiments*


ing curves were also characterized with the maximum rate of temperature change during the eutectoid transforma- tion, Vtrans


. Fi-


Note: *Reference cooling rate Vcool (K/min), Tα,exp fraction (%) is also listed.


(°C), Tp,exp


(°C), Vtrans


(K/s) and Ttrans


(°C). The ferrite


Time (s) (a)


Ferrite fraction (%) (b)


Figure 3. (a) Temperature-time evolution during heat treatment in the furnace and its derivative during trial U3 on alloy NP6; (b) relationship between ferrite fraction and Vtrans


for the whole series of U samples. 54 International Journal of Metalcasting/Winter 10


Cooling rate (K/s)


Temperature (ºC)


Vtrans


(ºC/s)


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