鐵의 相變化에 따른 熱膨展 및 電氣比抵抗

Thermal Expansion and Electrical Resistivity in the phase Transformation in Iron.

The heat treatment techniques in many alloys had greatly influenced on the physical and mechanical properties of the alloys. A number of crystallographic and thermodynamic theories have been proposed to explain the transformation mechanism. In this thesis the Cavity model and some of the appoximation formulars were proposed to explain the therm al and electrical properties of the phase transformations in iron. In pure iron, the low-temperature a-phase has a body-centered-cubic， (bcc) crystal structure. On heating, this phase is replaced by an fee, r-phase above 910°C, which in turn reverts to the bcc, a-phase above 1390°C. The linear therm al coefficient of expansion in Fe wire for each phase can be calculated from the equation; La:=Lo(1+aLt) Lr=Lo(1+rLt) But there is not a reasonable formular which describes completely the expansions depending on the temperature for three phases with a same formular.