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In the present work the influence of technological parameters of wire-feed electron beam additive manufacturing on the size of γ'-phase precipitations the in the product of Ni-Al system of a heat-resistant nickel-based superalloy was investigated. It was shown that the size of γ'-phase precipitations in the form of nanoscale and submicrocrystalline cuboids in the material of the additively formed product was smaller than in the initial as-cast state. Depending on the distance to the substrate, the average size of cuboids ranged from 43 to 207 nm, which was 13 to 2.7 times smaller than in the as-cast state. It was found that, depending on the height of the additive product, the size of γ'-phase precipitations reached an extremum at a distance of about 20 mm to the substrate. The average size of γ'-phase cuboids did not exceed 133 nm in the final material layers of the additive product with a height of 34 mm. The extreme dependence of the size of γ'-phase precipitations along the height of the additive product was caused by a combination of a given monotonic decrease in the heat input and heat accumulation in the product material as it was being formed. [ABSTRACT FROM AUTHOR]

In the present study, samples of products from nickel-based superalloy were obtained by wire-feed electron beam additive technology with various value of beam current and printing velocity. It was shown that defects inherent in cast materials (freckles and block structure) and materials obtained by powder-bed additive manufacturing (shrinkage and homogenization porosity) are uncharacteristic of wire-feed additive manufacturing. Also, the dependence of the different defect formation (peeling of the deposited material from the substrate, cracking and porosity in the area of the intensive mixing of the substrate with nickel-based superalloy, presence of cracking on dendrites colony boundaries) on parameters of additive growing is shown. [ABSTRACT FROM AUTHOR]

In the present study, wall-shape products from nickel-based superalloy ZhS6U were obtained by the wire-feed electron beam additive manufacturing (3D-printing). Product was formed on the substrate from austenitic steel AISI 321 with water cooling. Investigations provided by optical metallography method, scanning electron microscopy and X-ray diffraction analysis show presence of a microstructural and elemental gradient along the height of the sample. It was established that dendrite growth (by means of primary order symmetry arms) occurs antiparallel to the direction of the temperature gradient. The material of the formed product is made by the focused colonies of column dendrites without internal misorientations. Colonies of columnar dendrites are mainly oriented by crystallographic directions of type 〱001〉 along the direction of additive growing of the product. [ABSTRACT FROM AUTHOR]

The effect of the geometric shape of alumina nanoparticles (ball-, plate- and sheet-shaped ones) on the microstructure, microhardness and nanoparticles distribution in the aluminum matrix of the nanocomposite Al-Al2O3 fabricated by accumulative roll bonding is investigated. It is found that the plate-shaped nanoparticles have the most homogeneous distribution and the least tendency to agglomeration. Mainly the fraction of ball-shaped nanoparticles distributed as separate nanoparticles assists the structural refinement of the matrix. The shape of nanoparticles has no effect on the microhardness due to nanoparticles agglomeration. [ABSTRACT FROM AUTHOR]

The results of the research show that it is possible to make axisymmetric blanks of satisfying quality and geometrical sizes using the process of wire feed electron additive manufacturing (3D-printing). Yield strength of blank’s material achieves 317 MPa, which is higher than that of base cast metal (SS321). It was figured out that varying the additive manufacturing parameters such as wire feed rate and substrate rotation rate one may finally obtain printed components of various microstructure and mechanical characteristics. In other words, the parameters of the process can be operated and combined in order to gain needed mechanical characteristics’ anisotropy of the material manufactured by wire feed 3D printing. [ABSTRACT FROM AUTHOR]

Experimental studies of severe plastic deformation (SPD) by ABC forging and rolling methods have been carried out. The optimal values of accumulated strain and the deformation temperature for obtaining defect-free samples have been determined. Mechanical properties were established experimentally under compression and tension at ambient temperature. The possibility of increasing the yield strength, strength and ductility due to annealing of deformed samples was studied. According to confocal laser scanning microscopy, a change in the fracture mechanism of the samples was established, which is the main reason for the increase in the relative elongation of the annealed samples. [ABSTRACT FROM AUTHOR]

An experimental investigation of the effect of equal-channel angular pressing (ECAP) on structural changes and mechanical properties of Cu–Zn brass with a low stacking fault energy has been undertaken. It is shown that the main mechanism of deformation is twinning. As the number of passes increases, the density of twins increases too. The shift in the intersecting planes leads to the curvature and distortion of the twin systems formed after preceding passes. As a result of ECAP, both yield strength and strength limit increased while plasticity decreased. Fracture of samples occurs mainly as a result of loss of plasticity, but after 2 and 3 ECAP passes samples also reveal some plastic viscous fracture regions. [ABSTRACT FROM AUTHOR]

Here we present data on the structure of AA5056 alloy after friction drilling to unveil potentials of the process for use in model experiments on friction stir welding. Our analysis of the average size and volume content of precipitates shows that their content decreases immediately beneath the friction surface and that the structure of this zone is the same as the structure of stirring zones formed in friction stir welding. The data suggest that both processes provide similar metal structures. [ABSTRACT FROM AUTHOR]

The effect of friction drilling on the structural evolution in aluminum alloy 3005 has been investigated using optical and scanning electron microscopies. Both the mean size and volume content of the precipitates in each of the modified metal zones were obtained in addition to microhardness characterization. It is found that there is a zone depleted by precipitates in the vicinity of the boundary between thermomechanically affected and stirred metal. [ABSTRACT FROM AUTHOR]