Quantitative Process-microstructure-property Interplay in Ti60 Alloy: A Mechanistic Model for Residual Stress and Grain Refinement Gradients Induced by Impact Post-treatment
Abstract
This study systematically compares the effects of laser shock peening without coating (LSPwC) and shot peening (SP) on the microstructure and mechanical properties of near-α Ti60 alloy, addressing the knowledge gap in strain-rate-dependent deformation mechanisms and residual stress gradients. Through multi-scale characterization (EBSD, XRD, FWHM), we reveal that under 0.3 mmA intensity, SP induces the finest surface grains (32.5% of base material size) and highest compressive stress (-594.8 MPa) but limited depth (~200 μm). In contrast, LSPwC at 80 mJ energy achieves deeper stress penetration (~370 μm) with stable dislocation configurations (54.8–55.1% low-angle grain boundaries) and moderate residual stress (-392.1 MPa). Both processes prioritize dislocation slip over twinning, yet SP triggers dynamic recovery with non-monotonic stress decay, while LSPwC maintains uniform grain refinement (CV=0.18) and geometrically necessary dislocation density (>15×1014/m2). These findings establish a quantitative process-microstructure-property framework, demonstrating that SP is optimal for surface-dominated hardening, whereas LSPwC-80mJ balances depth and uniformity for thick-section components in extreme environments like aerospace and deep-sea engineering.