Predeformation Effects on Shear Response and Microstructure in Pure Titanium-TA2

2007 ◽  
Vol 546-549 ◽  
pp. 1409-1412
Author(s):  
Shu Hua Li ◽  
Fu Chi Wang ◽  
Cheng Wen Tan ◽  
Zhi Yong Chen ◽  
Zhi Sun
Keyword(s):  
Shear Bands ◽  
Pure Titanium ◽  
Adiabatic Shear ◽  
Transmission Electron Micrograph ◽  
Adiabatic Shear Bands ◽  
Hopkinson Pressure Bar ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Pressure Bar

Adiabatic shear properties of pure titanium-TA2 have been investigated using specially designed specimen in a Hopkinson pressure bar at high strain rate of 103s- 1. Microstructural characteristics was investigated using scanning electrion microscopy as well as transmission and high resolution transmission electrion microscopy .The results showed that the shear stress and adiabatic sensitivity for rolled 45% TA2 are higher than forged TA2. Comparing the adiabatic shear bands (ASB) both in the forged and rolled TA2, no evidence in morphology alteration was found except to shear band widths. The transmission electron micrograph of the ASB in forged and rolled TA2 showed the grain size reduction from ~20μm to 200nm. No deformation twins have been observed in ASB. The selected area electron diffraction patterns of the ASB showed reflections of multiple grains, forming discontinuous rings which can be indexed as h.c.p. structure of α-Ti. This indicates that the ASB consists of fine grains of α-Ti and the α-Ti→ β-Ti transformation did not occur.

Study on the Evolution of Adiabatic Shear Band of a High Strength Steel

2015 ◽  
Vol 782 ◽  
pp. 143-150
Author(s):  
Wen Wen Du ◽  
Qian Wang ◽  
Deng Hui Zhao ◽  
Lin Wang
Keyword(s):  
High Strength Steel ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
High Strength ◽  
Heat Treatments ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Hopkinson Pressure Bar ◽  
Static Tensile ◽  
Pressure Bar

The evolution process of a high strength steel which subjected with three different heat treatment proceedings and gets different quasi-static tensile properties was investigated in this paper. To precisely control the plastic deformation of the cylinder and capture the development process of adiabatic shear bands, stopper ring was used in Split Hopkinson Pressure Bar (SHPB). Combining the stress-strain curves and microstructures after SHPB tests, the microstructure evolution from the nucleation of adiabatic shear bands to fracture of the cylindrical steel were observed. The experimental results have demonstrated that there are similar fracture procedures of the steel treated through different heat treatments. Shear bands form firstly, then micro-cracks develop from shear bands, and lead to macro-crack finally. However, the critical strains for nucleation of ASBs and the time spending on the fracture procedure of the steel treated at different heat treatments are different. Samples treated at 900°C/AC exhibit the best resistance to adiabatic shear sensitivity when compressed under high strain rates.

Deformation Behavior of Ti-6Al-4V-0.1B Alloy Loaded under High Strain Rates

2016 ◽  
Vol 849 ◽  
pp. 266-270 ◽  
Author(s):  
Yang Yu ◽  
Qi Gao ◽  
Xun Jun Mi ◽  
Song Xiao Hui ◽  
Wen Jun Ye
Keyword(s):  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
The Matrix ◽  
Split Hopkinson ◽  
Pressure Bar

Deformation and fracture behaviors of Ti-6Al-4V-0.1B alloy with Widmanstätten, equiaxed and bimodal microstructures were investigated by Split Hopkinson Pressure Bar (SHPB) under high strain rates of 2100-3200 s-1. The results showed that the equiaxed and bimodal structures had a higher bearing capacity at high strain rates than that of the Widmanstätten structure. With the same microstructure, the increase of strain rate gave rise to an improved uniform plastic deformation. According to an observation on the deformed microstructure, it was found that adiabatic shear behavior was the main reason for failure and fracture of the alloy. The formation and propagation of adiabatic shear bands (ASBs) was the precursor for the failure and fracture of the material. Cavities at the interface between TiB phase and the matrix readily formed due to the uncoordinated deformation, which are not the dominate reason for the failure and fracture.

The Dynamic Mechanical Behavior and Microstructural Evolution of Commercial Pure Titanium

2014 ◽  
Vol 968 ◽  
pp. 7-11
Author(s):  
Tong Bo Wang ◽  
Bo Long Li ◽  
Mian Li ◽  
Ying Chao Li ◽  
Zuo Ren Nie
Keyword(s):  
Microstructural Evolution ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Pure Titanium ◽  
Adiabatic Shear ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Cold Rolled ◽  
Average Size ◽  
Pressure Bar

The high strain rate deformation behavior of as-annealed and as-cold rolled pure titanium was inspected by Split Hopkinson Pressure Bar (SHPB). The effect of deformation structure on adiabatic shear behavior in pure titanium was analyzed from the aspect of dynamic mechanical response and microstructural evolution. It was found that the strong {0001} basal texture was formed in as-cold rolled pure titanium. There were Geometrically Necessary Boundaries (GNBs) with spacing of 0.6μm and Incidental Dislocation Boundaries (IDBs) with size of 80nm in one grain. The enhancement of adiabatic shear sensitivity in as-cold rolled titanium was attributed to the deformation induced dislocation boundaries. The core of adiabatic shear band (ASB) was full of fine equiaxed grains with average size of 0.4μm, which was induced by dynamic recrystallization.

The Influence of the Microstructure of an HHA Steel on the Formation of Adiabatic Shear Bands, after High Deformation Rates

2020 ◽  
Vol 1012 ◽  
pp. 366-371
Author(s):  
Suzane de Sant’ana Oliveira ◽  
Ricardo Pondé Weber ◽  
Andersan dos Santos Paula ◽  
Sergio Neves Monteiro
Keyword(s):  
Heat Dissipation ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
High Hardness ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Hopkinson Pressure Bar ◽  
Ballistic Performance ◽  
Tempering Temperature ◽  
High Deformation

High hardness armor (HHA) steels, when subjected to high deformation rates, are prone to adiabatic shear bands formation. These heterogeneities, formed in a narrow zone, are the result of an intense plastic deformation in which the rate of heat dissipation is low. The generated shear bands can lead to a decrease in ballistic performance and impose to an armor a catastrophic failures. The appearance of these bands may be related to the microstructure or the deformation rate to which the material is subjected. Therefore, this work aims to analyze the influence of the microstructure of an HHA steel, tempered at 310, 425 and 610° C for 2 h, after high deformation rates, in the appearance of adiabatic shear bands. Specimens were dynamic tested in a split Hopkinson pressure bar. It was shown that tempering temperature at 310 ° C for 2h, which produced bainite and martensite with high hardness, was the most susceptible to the adiabatic shear bands appearance.

scholarly journals Dynamic deformation evolution of the adiabatic shear bands in zirconium alloy formed at a strain rate of about 2300 s-1

2018 ◽  
Vol 183 ◽  
pp. 03011
Author(s):  
Dongli Zou ◽  
Dawu Xiao ◽  
Chao Lu ◽  
Lifeng He ◽  
Yawen Zhao
Keyword(s):  
Strain Rate ◽  
Zirconium Alloy ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Hopkinson Pressure Bar ◽  
Ultrafine Grains ◽  
Dual Beam ◽  
Different Strains

Deformed microstructure of the adiabatic shear bands in zirconium alloy impacted by split Hopkinson pressure bar at a strain rate of about 2300 s-1 was characterized systemically. Four different strains of zirconium alloy subjected to impact loading at same strain rate were designed by means of strain stopper rings. At a strain of 0.30, the transformed bands were distinguished at the tip of crack. The transformed bands mainly composed of the ultrafine and equiaxed grains with the mean diameter of about 100~300 nm were found by a dual beam FIB/TEM system. Besides ultrafine grains in the transformed bands, nanometer fine grain was observed and confirmed by HRTEM. Thus, the transformed bands mainly composed of the mixed microstructure including nanometer and ultrafine grains were confirmed, and n phase transformation and amorphization in transformed bands take place.

Microstructural Development around Crater in Commercial Pure Titanium

2016 ◽  
Vol 849 ◽  
pp. 238-244
Author(s):  
Ying Chao Li ◽  
Bo Long Li ◽  
Tong Bo Wang ◽  
Zhen Qiang Wang ◽  
Zuo Ren Nie
Keyword(s):  
Electron Backscatter Diffraction ◽  
Adiabatic Shear Band ◽  
Shear Bands ◽  
Pure Titanium ◽  
Adiabatic Shear ◽  
Microstructural Development ◽  
Adiabatic Shear Bands ◽  
Titanium Plate ◽  
Commercial Pure Titanium ◽  
Backscatter Diffraction

The commercial pure titanium plate was shot vertically by the projectile with a diameter of 7.62mm at impact velocities ranging from 782m/s to 825m/s. The microstructure around the crater of commercial pure titanium plate was analyzed by optical microscopy (OM) and electron backscatter diffraction (EBSD) methods. It was found that different microstructures were observed along the depth of cater. In upper region of the crater, grains were deformed and fragmented. Adiabatic shear bands (ASBs) were observed in the middle of the crater, and some ASBs were bifurcated. At the bottom of the crater, the grains were less deformed, and the deformation twins were formed. The microstructures in the center of adiabatic shear band were mainly consisted of the dynamic recrystallization grains and sub-grains. The microstructure in the transition region was elongated grains along the shear stress distribution.

The Effect of Secondary Metalworking Processes on Susceptibility of Aircraft to Catastrophic Failures and Prevention Methods

2013 ◽  
Vol 58 (4) ◽  
pp. 1207-1212
Author(s):  
E.S. Dzidowski
Keyword(s):  
Dynamic Recovery ◽  
Fatigue Cracks ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Deformation Mechanisms ◽  
Processing Maps ◽  
Adiabatic Shear Bands ◽  
Flow Localization ◽  
Catastrophic Failures ◽  
Prevention Methods

Abstract The causes of plane crashes, stemming from the subcritical growth of fatigue cracks, are examined. It is found that the crashes occurred mainly because of the negligence of the defects arising in the course of secondary metalworking processes. It is shown that it is possible to prevent such damage, i.e. voids, wedge cracks, grain boundary cracks, adiabatic shear bands and flow localization, through the use of processing maps indicating the ranges in which the above defects arise and the ranges in which safe deformation mechanisms, such as deformation in dynamic recrystallization conditions, superplasticity, globularization and dynamic recovery, occur. Thanks to the use of such maps the processes can be optimized by selecting proper deformation rates and forming temperatures.

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