Phase Transformation Mechanisms in Metallic Alloys

Phase transformations in metallic alloys encompass a spectrum of processes by which the crystal structure of a metal changes in response to thermal, mechanical or chemical stimuli. These include diffusion‐controlled transformations such as precipitation and ageing, as well as diffusionless (martensitic) transformations driven by shear and local atomic rearrangements. In many alloys, the interplay of dislocation movement, twinning and atomic shuffle governs the nucleation and growth of new phases, often yielding complex orientation relationships between parent and product lattices. Control of these mechanisms underlies enhancements in strength, toughness and formability of structural materials used in aerospace, automotive and energy sectors. Recent advances combine high‐resolution microscopy, atomistic simulation and first-principles calculation to reveal transformation pathways at the nanoscale, enabling predictive design of alloys with tailored phase stability and mechanical performance.

Research from Nature Portfolio

Recent studies have elucidated the nucleation and growth of face-centred cubic (fcc) regions within hexagonal close-packed (hcp) matrices in titanium alloys. Foundational work demonstrated that rolling-induced fcc titanium forms via a pure-shuffle mechanism with a critical thickness of three atomic layers, progressing through shear-shuffle processes mediated by disconnections on basal planes. A complementary investigation using first-principles calculations and experimental validation proposed a three-stage hcp→fcc transition in titanium, incorporating slip of Shockley partial dislocations, spontaneous interplanar adjustment and volume expansion. These insights clarify the crystallographic orientation relationship between hcp and fcc phases and resolve longstanding debates on transformation energetics and lattice strains.

Phase Transformation Mechanisms in Metallic Alloys publication trend

The graph below shows the total number of articles in phase transformation mechanisms in metallic alloys across all publications each year (not limited to Nature Index journals).

Technical terms

Dislocation: A line defect in a crystal lattice enabling slip and accommodating plastic deformation.

Twinning: A shear-induced mechanism producing a mirror­-symmetric lattice region across a specific plane.

Atomic shuffle: Local rearrangement of atoms without macroscopic shear, often initiating a new phase.

Orientation relationship: The specific alignment of crystal directions and planes between parent and product phases.

Stacking fault energy: The energy penalty associated with inserting an extra partial plane in the close-packed stacking sequence, influencing ease of phase change.

References

1. In situ TEM observation of HCP to FCC transitions in hexagonal close-packed titanium. Materials Research Letters (2024).
2. Rolling-induced Face Centered Cubic Titanium in Hexagonal Close Packed Titanium at Room Temperature. Scientific Reports (2016).
3. Proposed mechanism of HCP → FCC phase transition in titianium through first principles calculation and experiments. Scientific Reports (2018).
4. Study on Phase Transformation Orientation Relationship of HCP-FCC during Rolling of High Purity Titanium. Crystals (2021).
5. Influence of Nonmetallic Interstitials on the Phase Transformation between FCC and HCP Titanium: A Density Functional Theory Study. Metals (2022).