Metallic Glass-Reinforced Metal Matrix Composites: Design, Interfaces and Properties

Effect of Stacking Sequence on Mechanical Properties and Microstructural Features within Al/Cu Laminates

The study presents a method to prepare Al/Cu laminated conductors featuring two different stacking sequences using rotary swaging, a method of intensive plastic deformation. The primary focus of the work was to perform detailed characterization of the effects of room temperature swaging on the development of microstructures, including the Al/Cu interfaces, and internal misorientations pointed to the presence of residual stress within the laminates. The results revealed that both the Al and Cu components of the final laminates with 5 mm in diameter featured fine, more or less equiaxed, grains with no dominating preferential texture orientations (the maximum observed texture intensity was 2.3 × random for the Cu components of both the laminates). This fact points to the development of dynamic restoration processes during swaging. The analyses of misorientations within the grains showed that residual stress was locally present primarily in the Cu components. The Al components did not feature a substantial presence of misorientations, which confirms the dynamic recrystallization. Tensile testing revealed that the laminates with both the designed stacking sequences exhibited comparable UTS (ultimate tensile strength) of almost 280 MPa. However, notable differences were observed with regard to the plasticity (~3.5% compared to less than 1%). The laminate consisting of Al sheath and Cu wires exhibited very low plasticity as a result of significant work hardening of Al; this hypothesis was also confirmed with microhardness measurements. Observations of the interfaces confirmed satisfactory bonding of both the metallic components.

Interface Characteristics of Tungsten-Particle-Reinforced Zr-Based Bulk-Metallic-Glass Composites with Different Tungsten Particle Sizes

This study investigated the interfacial characteristics of tungsten-particle-reinforced Zr-based bulk-metallic-glass composites (Wp/Zr-BMGs) with varying tungsten-particle sizes. To this end, Wp/Zr-BMGs with three different Wp sizes were fabricated using spark plasma sintering. Subsequently, the microstructures and interfacial structures of the Wp/Zr-BMGs were extensively examined, and the mechanical properties of the microzone at the Wp/Zr-BMG interface were evaluated using a nanoindentation method. The results revealed that the interfaces of Wp/Zr-BMGs, irrespective of the Wp size, exhibited dissolution-diffusion characteristics. Moreover, the thickness of the interface diffusion layer was positively correlated to the size of Wp. The addition of Wp enhanced the elastic modulus and hardness of Zr-BMGs at the interface, as these effects are inversely related to the Wp size. Furthermore, this study established a relationship between the interfacial mechanical properties and the interfacial characteristics of particle-reinforced bulk-metallic-glass composites. Thus, this study can serve as a guide for future research in the field of Wp/Zr-BMGs and similar particle-reinforced composites.

Powder Metallurgy: Materials and Processing

This Special Issue (SI) of Materials, "Powder Metallurgy: Materials and Processing", focuses on the fundamental and applied aspects of materials fabrication by powder metallurgy [...].

Towards a Better Understanding of the Interaction of Fe66Cr10Nb5B19 Metallic Glass with Aluminum: Growth of Intermetallics and Formation of Kirkendall Porosity during Sintering

Metallic-glass-reinforced metal matrix composites are a novel class of composite materials, in which particles of alloys with an amorphous structure play the role of reinforcement. During the fabrication of these composites, a crystalline metal is in contact with a multicomponent alloy of an amorphous structure. In the present work, the morphological features of the reaction products formed upon the interaction of Fe66Cr10Nb5B19 metallic glass particles with aluminum were studied. The composites were processed via spark plasma sintering (SPS), hot pressing or a combination of SPS and furnace annealing. The reaction products in composites with different concentrations of the metallic glass and different transformation degrees were examined. The products of the interaction of the Fe66Cr10Nb5B19 metallic glass with Al were observed as dense layers covering the residual alloy cores, needles of FeAl3 protruding from the dense shells as well as needles and platelets of FeAl3 distributed in the residual Al matrix. The possible role of the liquid phase in the structure formation of the reaction products is discussed. The formation of needle- and platelet-shaped particles presumably occurred via crystallization from the Al-Fe-based melt, which formed locally due to the occurrence of the exothermic reactions between aluminum and iron. At the same time, aluminum atoms diffused into the solid Fe-based alloy particles, forming an intermetallic layer, which could grow until the alloy was fully transformed. When aluminum melted throughout the volume of the composite during heating of the sample above 660 °C, a similar microstructure developed. In both Al–Fe66Cr10Nb5B19 and Al–Fe systems, upon the reactive transformation, pores persistently formed in locations occupied by aluminum owing to the occurrence of the Kirkendall effect.