Phase Transformation in Tantalum under Extreme Laser Deformation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Metallurgy

Background:

• Phase transformations critically influence the mechanical properties of metals, such as the strength and toughness of steel.
• Discovering new phase transformations is challenging, often requiring integrated experimental and computational approaches.
• Extreme conditions of pressure and temperature can unlock novel material behaviors and phase formations.

Purpose of the Study:

• To investigate the potential for new phase transformations in tantalum under extreme conditions.
• To explore the use of high-energy pulsed lasers for discovering novel material phases.
• To understand the role of shear stress in shock-induced phase transitions.

Main Methods:

• Subjecting monocrystalline body-centered cubic tantalum to high-energy pulsed laser irradiation.
• Analyzing recovered tantalum samples using transmission electron microscopy.
• Measuring shock pressure with VISAR (Velocity Interferometer System for Any Reflector) experiments.
• Conducting molecular dynamics simulations to model phase transformations under stress.

Main Results:

• Observation of a hexagonal omega phase in tantalum subjected to 70 GPa.
• Identification of the omega phase and twinning using transmission electron microscopy.
• Molecular dynamics simulations confirmed the body-centered cubic to hexagonal close-packed transformation under simulated shock conditions.

Conclusions:

• High-energy pulsed lasers can induce and reveal new phase transformations in metals.
• Shear stresses from uniaxial strain during shock compression are crucial for the observed body-centered cubic to hexagonal omega phase transformation.
• This work expands the understanding of phase transitions in refractory metals under extreme conditions.