Ultrafast phase transformation and strengthening mechanisms in alloys induced by femtosecond laser shock: a novel strategy for intermetallic control

Abstract

This study proposes a novel alloy-strengthening strategy enabled by femtosecond laser shock peening (FLSP), which utilizes ultrahigh peak shock pressures exceeding the intrinsic bond rupture strength of metallic bonds to achieve atomic-level microstructural modification. In contrast to conventional nanosecond laser shock peening (NLSP), FLSP induces a distinct strengthening mechanism through the dynamic fragmentation of intermetallic phases and the controllable precipitation of nanoscale strengthening phases. Through integrating a synergistic experimental investigation with molecular dynamics (MD) simulation, we establish a generalized pressure–dependent phase transformation framework, identifying critical thresholds of shock pressure required to initiate atomic bond rupture and subsequent phase evolution. This framework enables precise tuning of energy input to promote the formation of nanoscale strengthening phases while suppressing undesirable microscale precipitates. Compared to NLSP, FLSP demonstrates superior efficacy in microstructure refinement capabilities, enabling synergistic strengthening through grain refinement, dislocation multiplication, and pressure-mediated phase transformation. Notably, the discovered pressure–sensitive phase evolution behavior provides a transferable paradigm for microstructural design and performance optimization across a wide range of metallic systems. This work advances the fundamental understanding of laser–matter interactions under extreme conditions and offers a physics-informed pathway for the design of high-performance structural materials through targeted laser parameter engineering.