Volume fraction of austenite

Positive correlation^{[29,33,40,42,44]}

(1) austenite has advantages on plasticity^[42,44];

(2) the compressive stress and shear strain produced by martensitic transformation can reduce the plastic strain^[33];

(3) energy absorption during TRIP process^[40,44];

(4) crack closure caused by TRIP effect^[40,44];

(5) resistance of stress softening during cyclic loading^[29,42,44];

(6) the crack tip passivated by martensitic transformation^[42]

Negative correlation^[45,46,48]

(1) martensite transformation is easy to be used as the source of crack initiation during the TRIP process^[45];

(2) martensite formed by TRIP effect is easy to be used as the path of crack growth^[48];

(3) remarkable cyclic hardening caused by martensitic transformation^[46]

Inconclusive^[47]

There is a competitive relationship between the effect of inhibiting crack growth and inducing crack initiation

Positive correlation^{[46,54,56,57,58,59,60,61]}

(1) austenite has more slip systems, which can slow down dislocation entanglement and reduce local stress concentration, thus delaying the crack initiation^{[46,56,57,58,59,60]};

(2) DARA effect^[61];

(3) the existence of austenite would resist the dislocation moving^[46];

(4) energy absorption during TRIP process^[54,57];

(5) strengthening by TRIP effect^[58];

(6) the higher amount of retained austenite brings more obstacles for fatigue crack growth^[56,57];

(7) crack closure caused by volume expansion during the DIMT process^[46,56]

Negative correlation^[48,62,63]

Showed negative correlation in TRIP steel and martensitic precipitation hardening stainless steel, but lack of theoretical explanation

Stability of austenite

Positive correlation^[47,49]

(1) the film-like retained austenite is beneficial to prevent crack growth^[49];

(2) it can avoid the cracks caused by the stress-strain mismatch between the austenite and matrix due to its high hardness^[49];

(3) the film-like austenite can also bring more RICC effect^[49], and prevent the crack initiation caused by elastic mismatch between the new formed and previous martensite^[47];

(4) the unstable austenite exhibits significant cycle hardening during cycle loading, which is not conducive to the stability of cycle stress^[49]

Negative correlation^[54]

The block retained austenite performs good compatibility deformation ability

Positive correlation^{[43,49,59,60,65]}

(1) the highly stable austenite transformed to martensite after crack initiation which is benefit to fatigue properties^[65];

(2) film-like austenite brings more RICC effect^[49];

(3) production of film-like austenite would refine the microstructure^[60];

(4) the calculated results of FGA show that the blocky-like austenite plays negative role on crack initiation^[59];

(5) the large-size austenite is easy to transform into brittle martensite under elastic deformation, which is unfavorable to fatigue stress^[43]

Negative correlation^[67]

The unstable austenite performs great compatible deformation ability and plasticity