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Retained austenite plays a significant role in the strength-ductility balance of medium Mn steels. In this contribution, a new processing route (Flash-Austenite Reversion Treatment, Flash-ART) was proposed to design retained austenite with a compositional core-shell structure in an Fe-0.20C-7.76Mn-1.99Al (wt%) steel. It was interestingly found that the austenite core, which should transform into martensite based on its composition and size, was stabilized by the Mn enriched shell. Flash-ART allows us to obtain more retained austenite compared with the conventional ART.

Single crystals of E21 (L12) Ni3AlC1-x were prepared by the unidirectional solidification using the optical floating zone melting method to determine their mechanical properties. Particularly the effects of interstitial carbon atoms on mechanical properties were evaluated by compression tests at room temperature. Operative slip system of E21 Ni3AlC is {111} type which is the same as that of L12 Ni3Al. Strength of Ni3AlC single crystals increases with carbon concentration due to the solid solution effect, though the stress relief of yielding behavior is enhanced at the intermediate carbon content at around 3at%. A large gap appears in the carbon concentration dependence of critical resolved shear stress (as well as yield stress) at almost the same carbon content. This discontinuity in strengthening is attributed to the interaction between multiple solute carbon atoms and mobile dislocations.

The structure of the martensite (α″)/martensite (α″) and parent (β)/martensite (α″) interfaces in a series of binary Ti–Nb alloys with Nb content ranging from 20 to 24 at.% was investigated. Both the α″/α″ and β/α″ interfaces comprised a series of { 2 1 ¯ 1 } β / / { 1 1 0 } α ″ terraces and steps when viewed edge-on (close to [ 0 0 1 ] α ″ ). Interfacial defects, particularly the transformation disconnections (b, h) superimposed along the terrace–step interface structure, have been identified. They were responsible for accommodating most of the transformation strain along the α″/α″ and β/α″ interfaces. Using the parameters b and h, the prediction of the α″ habit plane based on the topological model agreed well with the prediction from the phenomenological theory as well with experimental observations. The α″ habit plane in Ti–20Nb alloy is close to { 7 5 ¯ 5 ¯ } β and moves towards { 4 3 ¯ 3 ¯ } β in Ti–22Nb and Ti–24Nb alloys. The remaining transformation strain along the β/α″ interface was found to be accommodated by Type 1 twinning on ( 1 1 1 ) α ″ with Burgers vector bLIS close to 〈 2 ¯ 1 ¯ 3 〉 α ″ ( ≡ 〈 1 ¯ 1 ¯ 2 ¯ 〉 β ) .