Study on deformation behavior of Ti60 alloy based on multi-physics coupling

Abstract

Titanium alloys are extensively employed in aerospace due to their superior performance, but their development is constrained by limited formability at room temperature, an electrically assisted forming (EAF) process emerges as a promising solution to reduce flow stress, improve formability, and accelerate material recrystallization. This study focuses on elucidating the interplay between pulse current, temperature, and flow stress in Ti60 alloy under combined electrical, thermal, and stress fields. To this end, electrically assisted tensile (EAT) tests were performed on Ti60 alloy using six different current densities. Currently, there is no unified theory for electro-plasticity in metal materials, and the absence of a suitable model hinders finite element simulation in EAF. The investigation encompasses four key areas: the impact of multi-physics coupling on temperature variations, the stress-strain curve characteristics, the microstructural analysis of tensile fractures, and the modification of the Johnson-Cook (MJC) model. Notably, temperature distribution proves more uniform across the width than the length. Tensile elongation initially rises and then falls with increasing current density, peaking at a critical current density (J=30 A/mm2). Higher current densities lead to a transition in fracture features, with deep, numerous dimples and tiny voids supplanting tearing ridges and facets. Despite this, brittle fracture remains the dominant mode, accompanied by granular oxide formation at J= 35, 40 A/mm2. The MJC model aligns closely with experimental outcomes, showing R and EAARE values of 92.7% and 7.15%, respectively. This model accurately predicts Ti60 alloy's deformation under multi-physics conditions, marking a significant advancement in integrating electro-plasticity into constitutive modeling.