Microstructural, mechanical and electrochemical behaviour of a 7017 Al–Zn–Mg alloy of different tempers

The objective of the present study is to carry out high strain rate tensile tests on 7017 aluminium alloy under different strain rates ranging from 0.01, 500, 1000 and 1500 s−1 and at temperatures of 25, 100, 200 and 300 °C. Quasi-Static tensile stress–strain curves were generated using INSTRON 8500 machine. Johnson-Cook (J-C) constitutive model was developed for 7017 aluminium alloy based on high strain rate tensile data generated from split Hopkinson tension bar (SHTB) at various temperatures. This study evidently showed an improvement in dynamic strength as the strain rate increases. The predictions of J-C model are observed to be in consistence with the experimental data for all strain rates and temperatures. The fracture surfaces of specimens tested were studied under SEM. The change in fracture mode has been observed at different strain rates. The shear mode of fracture is dominant at lower strain rates (0.01 and 500 s−1); whereas cup- and cone-like surface representing dimple structure is found at the higher strain rates (1000 and 1500 s−1). The numbers of dimples at high strain rates are more than the quasi-static and intermediate strain rates. It is also observed that the flow stress decreases with increase in temperature. The 7017 aluminium alloy demonstrates thermal softening at higher temperatures. So when the temperature is more than 200 °C at these strain rates, thermal softening is predominant mode of deformation mechanism. It is found that when the temperature increases to 200 °C, the number of dimples rises and the dimple size of 7017 aluminium alloy is larger than at lower temperatures.

Tensile behaviour of aluminium 7017 alloy at various temperatures and strain rates

The relationship between Vickers hardness and yield stress was investigated by using data from nineteen datasets from sixteen independent studies, covering six commercial and four experimental alloys. In these datasets, six different product forms that ranged from single crystals to extrusions were used. All datasets showed a linear yield stress–Vickers hardness behavior with the same slope, which was recently reported by the author and his colleagues for alloy 7010 [M. Tiryakioglu et al., Mater. Sci. Eng. A, 631 (2015) 196–200]. The y-intercept, which represents the increase in stress under the indenter during Vickers hardness testing, was different for each dataset. The coefficient of determination, R2, values for the fits of combined data were 0.982 and 0.971 for commercial and experimental alloys, respectively.

On the relationship between Vickers hardness and yield stress in Al–Zn–Mg–Cu Alloys

The ballistic performance of SiC–AA7075 functionally graded composite produced by powder metallurgy

In this study, the density, hardness, impact toughness, transverse rupture strength, tensile strength and ballistic resistance of Al 6061 alloy reinforced with boron carbide (B4C) powders were studied to elucidate the influence of the ceramic content and production process on the physical and ballistic properties of the resulting composites. Powder-metallurgy and hot-extrusion techniques were used to manufacture the Al 6061-based metal matrix composites reinforced with 5 wt%, 10 wt%, 15 wt% and 20 wt% B4C. The hot-rolling process was performed on a group of specimens to examine the effect on the mechanical and ballistic behaviors. The results revealed that a uniform particle distribution was achieved in a matrix structure and higher relative density values were measured in all specimens. The hardness, transverse rupture strength and tensile strength were improved and impact toughness was decreased with increasing volume fraction of B4C particle reinforcement for both hot-extruded and hot-rolled specimens. The highest flexural strength was measured in hot-extruded specimens and the maximum tensile strength was obtained in hot-rolled composites. The deformation tests showed that transgranular cracking occurred on B4C particles and particles were retained in the matrix. The hot-extruded, hot-rolled and laminated with two hot-rolled specimens were subjected to a ballistic test with a 7.62 mm × 51 mm M80 projectile for Type III and the ballistic resistance investigated by analyzing the hole surface in the armor. The hot-rolled and hot-extruded specimens were perforated in ballistic tests and exhibited ductile behavior with the petal failure mechanism. The two-layer hot-rolled specimens successfully absorbed the impact energy of the bullet with the lowest depth of penetration and smooth bulging.

Study on mechanical and ballistic performances of boron carbide reinforced Al 6061 aluminum alloy produced by powder metallurgy

Effect of heat treatment on the behavior of an AA7055 aluminum alloy during ballistic impact

Effect of tempering temperature, plate thickness and presence of holes on ballistic impact behavior and ASB formation of a high strength steel

The present paper describes a steel with yield strength exceeding 1900 MPa and fracture toughness in the range of 40–50 MPa m1/2, in its optimum heat treated condition. Its strength is similar to that of 18 Ni (300) grade of maraging steel with good fracture toughness. When tempered at 300°C, it shows tempered martensite along with a small amount of retained austenite phase. The steel shows nearly 25% reduction in weight over typical rolled homogeneous armour (RHA) steel against high velocity hard steel core projectiles. The processing, microstructure, mechanical and ballistic properties of the steel are demonstrated.

T.B. Bhat

Papers

Effect of heat treatment on the behavior of an AA7055 aluminum alloy during ballistic impact

Effect of tempering temperature, plate thickness and presence of holes on ballistic impact behavior and ASB formation of a high strength steel

Development of an ultrahigh strength low alloy steel for armour applications