Effects of the phase interface on initial spallation damage nucleation and evolution in dual phase titanium alloy

Abstract

A B S T R A C TThe Ti-6Al-4V dual phase alloy samples were dynamic loaded by one-stage light gas gun experiment and samples with initial spallation were softly recovered. During the loading experiment, the velocity of free surface particles was measured by photonic doppler velocimetry (PDV). The effect of α/β phase interface on nucleation, growth, and coalescence of dynamic damage in Ti-6Al-4V were investigated by 2-D or 3-D testing techniques, such as optical microscopy(OM), x-ray computer tomography(XRCT), and electron backscattered diffraction(EBSD). The results showed that the majority of voids were nucleated within α phases, rather than on the α/β phase interface as predicted by quasi-static damage theory. Due to the effects of reflection and transmission of shock wave at the phase interface, a tensile pulse would be formed within α phase when the shock wave transmit from α phase with high impedance to β phase with low impedance. When this tensile pulse was large enough, voids would be formed within α phase. The analyses of OM and XRCT indicated that the voids at the beginning of nucleation were nearly spherical, then grew up along the direction of 45°with the shock loading direction, and finally the rod-shaped voids were formed. Besides, the voids were not randomly nucleated within α phase, and the EBSD analysis showed that the voids were mainly nucleated at grain boundary triple points which composed of grains with large difference of Taylor Factor(TF) value within α phase. This is because the difference of plastic deformation capacity of this grains is larger, and it is easier to produce stress concentration. Thus these sites became the prior nucleation position of voids.

Research and Analysis of TC4 Titanium Alloy Cutting Based on Crystal Plasticity Theory

“…Titanium and its alloys find widespread applications in aerospace, advanced manufacturing, nuclear industries, and chemical engineering due to their low density, high strength, exceptional plasticity, remarkable corrosion resistance, and biocompatibility [1][2][3][4][5][6][7][8] . In-depth research and analysis of the microstructure, structure, and mechanical processing performance of titanium alloys are essential.…”

Shock-Induced Mechanical Response and Microstructure Evolution of Titanium Alloys

“…Presently, titanium materials have been widely used in aerospace, medical, and chemical industries [1][2][3]. They will undoubtedly play an important role in military fields such as warheads and lightweight armor, due to the many advantages mentioned above [4,5].…”

Deformation Behavior and Tensile Properties of the Semi-Equiaxed Microstructure in Near Alpha Titanium Alloy

“…However, inconsistencies between the stress and strain easily occur at the interface during loading, resulting in stress concentration at the phase interface due to the differences in the physical, mechanical properties, and grain orientation between the α phase and β phase. Therefore, the phase interface is the preferred site for crack nucleation and propagation under tensile [ 10 ] or fatigue loading [ 12 ], which is detrimental to the mechanical properties of the alloy [ 13 , 14 ]. The stress concentration caused by dislocation pile-up can be reduced by refining the α phase in titanium alloy [ 15 ], but the stress concentration at the interface has not been effectively alleviated.…”