up to a certain limits carbon is responsible for austenite stabilizer around 5-10%, when ever carbon reacts with nitrogen atmosphere

(above the critical temperature) it stabilize the austenite on the surface..

Dear Nazrin Babashova ,

Ferritic steels are made up of ferrite crystals, a form of iron that contains only a very small amount (up to 0.025%) of carbon. Ferrite absorbs less amount of carbon because of its body-centered cubic crystal structure - one iron atom at each corner, and one in the middle. This central iron atom gives the ferritic stainless steel its magnetic properties.

while austenitic stainless steels contain more carbon than ferrite. Austenite is created by heating ferrite to 912 degrees C, at which point it transitions from a body-centered cubic crystal structure to a face-centered cubic crystal structure. Face-centered cubic structures absorb up to 2% carbon.

for more details can go through the following reference;

https://www.accu.co.uk/en/p/112-what-is-the-difference-between-ferritic-austenitic-martensitic-stainless-steels-accu

the lattice structure of austenite is FCC and carbon locates in the larger octahedral sites and causing less lattice distortion.