The Effect of Microstructure on Mechanical Behaviour for Titanium Alloy (Ti-6Al-4V)

Abstract

The characteristics of mechanical behavior are investigated for Ti-6Al-4V alloy. Four kinds of specimens are prepared under different heat treatments in order to produce different microstructures. In the present investigations, impact, tensile and fatigue crack growth tests are performed for each test specimen. The results obtained through the investigations are compared. Additionally, fractal dimensions of crack path are obtained using the box counting method. The results are: 1) the microstructures show as equiaxed, bimodal and lamellar microstructures respectively, 2) the impact energy and elongation are superior for the bimodal microstructure, and the hardness and tensile strength are superior for the lamellar microstructure, 3) the fatigue crack growth rate is similar for all microstructures in the low ΔK region while that of equiaxed microstructure is the largest, and that of lamellar microstructure is the lowest in the high ΔK region respectively, 4) the fractal dimension, D of lamellar microstructure shows higher value than that of the equiaxed and bimodal microstructures under 200 magnification view of the SEM micrographs.

Influence of microstructure and strain rate on adiabatic shearing behavior in Ti–6Al–4V alloys

“…When metals and alloys deform under high strain rate loading, their dynamic properties are closely related to a narrow zone of highly localized deformation, referred to as adiabatic shear band (ASB), which is generally observed in ballistic impact, armor penetration and explosive fragmentation [1][2][3][4][5]. It has been believed that the localization occurs more easily in materials with low strain hardening rate, low strain rate sensitivity and low thermal conductivity.…”

“…It has been believed that the localization occurs more easily in materials with low strain hardening rate, low strain rate sensitivity and low thermal conductivity. Due to the high strength, low thermal conductivity and low strain hardening rate of Ti-6Al-4V alloy, it is reported to be very susceptive to adiabatic shear deformation under high strain rates [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

Heat Treatment, Impact Properties, and Fracture Behaviour of Ti-6Al-4V Alloy Produced by Powder Compact Extrusion

“…Similarly, impact energy values obtained after each heat treatment in this study are better than values reported by Reda et al on as-cast Ti-6Al-4V alloy and Yasa et al who worked on heat treated selective laser-melted material [4,5,12]. However, the other impact toughness values presented in Table 4 are significantly higher than those obtained in this work, mainly because of the variation in oxygen content, processing route, or heat treatment conditions, along with inconsistency in notch shape and dimensions of test specimens [1,6,8,10,22].…”

“…A typical impact toughness of as-cast material in their work was around 11 J with various α + β heat treatments giving only a limited enhancement in toughness. The work done by Kwon et al on heat treatment of rolled plate emphasised that annealing in the α + β phase field followed by ageing is more effective in improving impact absorbed energy (as high as 35 J) compared to material which underwent β annealing plus ageing, where an impact energy around 24 J was attained [8]. Similarly, a study by Buirette et at.…”

“…Another important aspect that lacks significant understanding is crack propagation behaviour of titanium and titanium alloys during impact toughness testing. There are several studies that investigated the fracture surfaces of Ti-6Al-4V alloy after impact testing [1,4,5,6,8,9]. However, there were only a limited number of studies that specifically investigated the crack propagation mechanism during Charpy impact toughness testing on titanium and titanium alloys.…”