A New Ordered Transformation‐Induced Plasticity Enables Exceptional Strength and Ductility in a B2 Medium‐Entropy Alloy

ABSTRACT Ordered aluminide intermetallics are promising lightweight structural materials but suffer from limited room‐temperature tensile ductility due to the constrained dislocation activity inherent to their ordered lattices. Here, we demonstrate that controlled reduction of phase stability can overcome this limitation in B2‐ordered Ti‐Zr‐V‐Al medium‐entropy intermetallics. By tailoring the Al content to lower the stability of the B2 matrix while preserving long‐range order, the metastable alloy activates an ordered transformation‐induced plasticity (ordered TRIP) effect under tensile loading. This involves the cooperative operation of {110}<111> slip and an unprecedented stress‐induced B2 to D0 19 ‐α 2 martensitic transformation. The transformation follows an orientation relationship of {0001}α 2 //{110}B2 and <11‐20>α 2 //<100>B2, representing an atypical pathway distinct from conventional B2→B19′ or B2→B33 transformations. The designed alloy achieves a tensile elongation of about 7%, an ultimate tensile strength of about 1.1 GPa, and a specific yield strength of about 197 MPa·g −1 ·cm 3 , a combination of strength, ductility, and density that surpasses most reported lightweight B2 intermetallics. By establishing a controlled metastability strategy that couples dislocation plasticity with a novel ordered martensitic transformation, this work provides a new paradigm for designing ductile, high‐strength ordered alloys and may inspire similar approaches in other brittle ordered alloy systems.