CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 2
The twins are identified as bands with parallel sides, and are formed when changes in the stalking
of atoms on close-packed (1 1 1) planes occur during crystallization and grain growth. However,
single phase austenite structure is an ideal structure, and steels heated into austenite phase in
general contain other phases such as inclusions, carbides, and precipitates of alloying elements.
Austenitic stainless steels are annealed at high temperatures to accomplish recrystallization. The
microstructure of austenitic stainless steel is shown in Fig. 2.5 [36].
Fig. 2.5: Microstructure of austenitic stainless steel [36]
In as cast state, the microstructure is characterised by an austenite matrix with some
precipitated carbide. The carbides lie along the grain boundaries, and in interdendritic areas within
grains. Occasionally, interdendritic carbides can be fairly massive especially at triple points and
are sometimes surrounded by lamellar carbide zones.
2. 5 Physical properties of austenitic stainless steel
The major physical properties of austenitic stainless steel considered important in regard to
the functional application and successful implementation includes; (a) density, (b) modulus of
elasticity, (c) melting range, (d) coefficient of thermal expansion, (e) thermal conductivity, (f) heat