In-Situ Study on Tensile Deformation and Fracture Mechanisms of Metastable β Titanium Alloy with Equiaxed Microstructure

Abstract

Understanding the mechanisms of deformation and fracture of metastable β titanium alloys is of great significance for improving formability and service life. By combining the in-situ tensile test, TEM characterization and EBSD analysis, the tensile deformation behavior, activation of slip systems, crack initiation, and propagation of a high strength metastable β titanium alloy (Ti-5Cr-4Al-4Zr-3Mo-2W-0.8Fe) with equiaxed microstructure are investigated. The equiaxed microstructure is composed of primary α (αp) phase, transformed β (βt) matrix phase, and secondary α (αs) phase. In contrast to the hexagonal αp grain with limited slip systems, the body-centered βt matrix has more slip systems, however the hindering effect of αs phases on dislocation slip leads to the different deformability of the αp phase and βt matrix. The equiaxed αp grains are more prone to deformation and rotation to coordinate the overall deformation. The shear band leads to the formation of sub-grain boundary and even the fragmentation of αp grains. As a result, the microvoids tend to nucleate at the grain boundary, phase interface, slip band, and shear band. The inhomogeneous deformation in the plastic deformation zone around the crack tip is the primary cause of damage. The crack propagation caused by microvoids coalescence advances along the grain boundaries and phase interfaces in the form of intergranular, and along the activated slip systems and shear bands in the form of transgranular. Pinpointing the situation in the equiaxed microstructure and combining that in other typical microstructures will help to summarize the universal deformation and fracture mechanisms of metastable β titanium alloy, and provide a basis for alloy design and microstructure tailoring.

In Situ Study of Precipitates’ Effect on Grain Deformation Behavior and Mechanical Properties of S31254 Super Austenitic Stainless Steel

“…In recent years, in situ tests have been employed to characterize microstructure evolution in real time during the deformation process [ 25 , 26 , 27 , 28 , 29 ]. However, evidence for the effect of precipitates on crack propagation in SASSs, especially under different temperature conditions, is lacking.…”

Static Globularization Behavior and Artificial Neural Network Modeling during Post-Annealing of Wedge-Shaped Hot-Rolled Ti-55511 Alloy

“…Lamellar α, as a typical microstructure in titanium alloys, has good performance in fracture toughness, but its performance in plasticity is not ideal [ 5 , 6 ]. The equiaxed α, which can be obtained by breaking down the lamellar α, is desirable due to its good ability to match the strength and plasticity [ 7 ]. However, the lamellar α cannot be globularized directly by heat treatment due to the thermal stability of the semicoherent phase interface between α and β phase.…”