Final answer:
Austenite is a ductile, non-magnetic phase of steel with a face-centered cubic structure, high carbon solubility, and good formability. It exists above 723°C and can be transformed into other microstructures to control steel's mechanical properties.
Step-by-step explanation:
Austenite, also known as gamma phase (γ-phase), is a metallic non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 723°C, becoming a γ-phase that is soft and ductile.
Properties of austenite include:
- A face-centered cubic (FCC) crystal structure.
- High solubility for carbon, compared to other structures like ferrite (alpha phase).
- It is non-magnetic.
- It is more ductile and less hard than other phases and can be transformed into other microstructures like martensite through quenching.
- Good formability and weldability due to its ductility.
The presence of austenite in steel alloys is crucial in controlling the mechanical properties of the steel, such as toughness, ductility, and tensile strength, through heat treatment and other processing methods.