The key difference between austenite and ferrite is that the austenite has face-centered cubic configuration of gamma iron whereas the ferrite has body-centered cubic alpha iron configuration. Further, austenite has a metallic appearance while ferrite has a ceramic-like appearance.
Austenite and ferrite are allotropes of iron. Moreover, these allotropes exist at different temperatures. The allotropes of iron are named differently as alpha iron, beta iron, gamma iron and delta iron. These allotropes exist at standard pressures. There are some allotropes of iron that exist at high pressures. For example, epsilon iron ( also known as ‘hexaferrum’).
CONTENTS
1. Overview and Key Difference
2. What is Austenite
3. What is Ferrite
4. Side by Side Comparison – Austenite vs Ferrite in Tabular Form
5. Summary
What is Austenite?
Austenite is an allotrope of iron known as gamma-phase-iron. Therefore, it is metallic and non-magnetic. This allotrope occurs in different iron alloys at different temperatures. For example, in plain-carbon steel, this allotrope exists at 727°C while in stainless steel, it exists at room temperature. The cubic structure of this allotrope is face-centered cubic structure. When we change the temperature from 912 °C to 1,394 °C, this austenite allotrope forms from another allotrope called ferrite. We call this process austenitization. Austenite is relatively soft and ductile. As a result, it can dissolve more carbon in its solid solution.
What is Ferrite?
Ferrite is an allotrope of iron known as alpha-phase-iron. It has a ceramic-like appearance, and it is paramagnetic. It has the body-centered cubic structure. Moreover, the dissolution of carbon in this allotrope is poor.
Figure 01: Cubic Structures of Allotropes of Iron; Austenite (right) and Ferrite (left)
Furthermore, this material is a ceramic-like material. It has many applications in electronic devices. Since it is hard and brittle, we can find this iron in cast iron and steel.
What is the Difference Between Austenite and Ferrite?
Austenite is an allotrope of iron known as gamma-phase-iron. It has a metallic appearance, and it is soft relatively. Moreover, it is ductile and non-magnetic. Ferrite is an allotrope of iron that we call alpha-phase-iron. It has a ceramic-like appearance, and it is hard. In addition, it is brittle and paramagnetic. This is the main difference between austenite and ferrite.
Summary – Austenite vs Ferrite
Austenite and ferrite are two allotropes of iron. The difference between austenite and ferrite is that the austenite has the face-centered cubic configuration of gamma iron whereas the ferrite has the body-centered cubic alpha iron configuration.
Reference:
1. Britannica, The Editors of Encyclopaedia. “Austenite.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 29 Apr. 2013. Available here
2. “Allotropes of Iron.” Wikipedia, Wikimedia Foundation, 20 June 2018. Available here
Image Courtesy:
1.’IronAlfa&IronGamma’By Trempe_acier_et_mouvements_atomes.svg (CC BY-SA 3.0) via Commons Wikimedia