On the non-isothermal precipitation of copper-rich phase in 17-4 PH stainless steel using dilatometric techniques

The kinetics of the precipitation of copper-rich phase in 17-4 PH stainless steel was studied in this paper by non-isothermal dilatometric experiments. The dilatometric curve was analyzed and the conversion degree of the precipitates was associated with the area under the derivative curve of the thermal expansion as a function of temperature. The apparent activation energy associated with the formation of the precipitates was calculated and the obtained results were compared with the data calculated from the isothermal dilatometric tests presented in a previous paper. The data well agree, so confirming that nonisothermal dilatometry can be considered a powerful method to study the precipitation kinetics of PH stainless steels. Finally, the conversion degree for any isothermal treatment was calculated starting from the parameters obtained by non-isothermal dilatometric tests and compared with the conversion degree calculated from the hardness values during heat treatments.