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This is a Experimental Study study.

October 18, 2025

Investigation of the Ductile-to-Brittle Transition during Scratching of Polycrystalline Dual-phase γ-TiAl Alloy

Key Points

The study identifies three deformation regimes during scratching: ductile removal, mixed-mode transition, and brittle fracture.
Critical uncut chip thicknesses for ductile-to-brittle transition onset and completion were found at approximately 6–7 μm and 14–16 μm.
Scratch testing at higher speeds intensified force amplitudes, leading to faster crack onset in the material.
This work enhances understanding of the ductile-to-brittle transition, aiding improvements in micromachining techniques for aerospace applications.

Abstract

This study investigates the ductile-to-brittle transition (DBT) in a polycrystalline dual-phase γ-TiAl alloy through a novel variable-depth, variable-speed scratch testing approach. Continuous grooves (0–40 μm) were created at scratching speeds of 500–4000 mm/min using a diamond conical indenter, with in-situ cutting forces monitored via a Kistler dynamometer and surface morphologies captured using synchronized 3D optical and confocal laser scanning microscopy. The results delineate three distinct deformation regimes: (1) ductile material removal ( 14–16 μm), exhibiting extensive cracking and pronounced force fluctuations. Higher scratching speeds amplified force amplitudes and accelerated crack onset. Critical uncut chip thicknesses for DBT onset and completion were quantified at 6–7 μm and 14–16 μm, respectively. This work provides the synchronized mechanical–morphological analysis of DBT in γ-TiAl at the microscale, offering quantitative insights for optimizing high-speed micromachining processes and enhancing surface integrity in aerospace applications.

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