A.A. Tsarkov

Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

Studies of the structure and mechanical properties of Ti43.2Zr7.8Cu40.8Ni7.2Co1 alloy containing amorphous and crystalline phases

The structure and mechanical properties of Ti43.2Zr7.8Cu40.8Ni7.2Co1 alloy cast into a massive copper mold are studied. It has been shown that, after the fast cooling of the alloy, the structure consists of amorphous matrix and crystal particles distributed in the matrix; hence, the alloy displays high strength (higher than 1600 MPa) and relatively high plasticity (1%). Modeling the strain of the alloy using the finite elements method has shown that the crystal particles in the amorphous matrix are effective barriers for the propagation of shear bands, thus stimulating nucleation and the development of new shear bands and increasing the plasticity of the material in general.

Effect of Multiple Alloying Elements on the Glass-Forming Ability, Thermal Stability, and Crystallization Behavior of Zr-Based Alloys

Effect of multiple alloying elements on the glass-forming ability, thermal stability, and crystallization behavior of Zr-based glass-forming alloys were studied in the present work. We investigated the effect of complete or partial substitution of Ti and Ni with similar early and late transition metals, respectively, on the glass-forming ability and crystallization behavior of the Zr50Ti10Cu20Ni10Al10 alloy. Poor correlation was observed between different parameters indicating the glass-forming ability and the critical size of the obtained glassy samples. Importance of the width of the crystallization interval is emphasized. The kinetics of primary crystallization, i.e., the rate of nucleation and rate of growth of the nuclei of primary crystals is very different from that of the eutectic alloys. Thus, it is difficult to estimate the glass-forming ability only on the basis of the empirical parameters not taking into account the crystallization behavior and the crystallization interval.

Influence of Al3Ni crystallisation origin particles on hot deformation behaviour of aluminium based alloys

Abstract Binary Al–Ni, Al–Mg and ternary Al–Mg–Ni alloys containing various dispersions and volume fraction of second-phase particles of crystallisation origin were compressed in a temperature range of 200–500 °C and at strain rates of 0.1, 1, 10, 30 s−1 using the Gleeble 3800 thermomechanical simulator. Verification of axisymmetric compression tests was made by finite-element modelling. Constitutive models of hot deformation were constructed and effective activation energy of hot deformation was determined. It was found that the flow stress is lowered by decreasing the Al3Ni particle size in case of a low 0.03 volume fraction of particles in binary Al–Ni alloys. Intensive softening at large strains was achieved in the alloy with a 0.1 volume fraction of fine Al3Ni particles. Microstructure investigations confirmed that softening is a result of the dynamic restoration processes which were accelerated by fine particles. In contrast, the size of the particles had no influence on the flow stress of ternary Al–Mg–Ni alloy due to significant work hardening of the aluminium solid solution. Atoms of Mg in the aluminium solid solution significantly affect the deformation process and lead to the growth of the effective activation energy from 130–150 kJ/mol in the binary Al–Ni alloys to 170–190 kJ/mol in the ternary Al–Mg–Ni alloy.