Foreign-Particle Reinforcement of a Zr-Cu-X BMG

The yield strength of a Zr-based bulk metallic glass was improved by up to 20% in comparison to the as-received alloy via dispersion of graphite nanoparticles into the matrix. The resulting material also had high plasticity and good elasticity and the use of reinforcement particles was found to suppress heterogeneous nucleation. The graphite nanoparticles additionally improved the alloy’s thermal stability as compared to that of the monolithic alloy.

Si3N4 Nanoparticle Addition to Concentrated Magnesium Alloy AZ81: Enhanced Tensile Ductility and Compressive Strength

This study is aimed at understanding the tensile ductility and compressive strength-enhancing dual function of nanoparticles in a concentrated magnesium alloy (AZ81) nanocomposite. Si3N4 nanoparticles were selected for reinforcement purposes due to the known affinity between magnesium and nitrogen. AZ81 magnesium alloy was reinforced with Si3N4 nanoparticles using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size and hardness to the monolithic alloy, reasonable nanoparticle distribution, and nondominant (0 0 0 2) texture in the longitudinal direction. Compared to the monolithic alloy in tension, the nanocomposite exhibited higher failure strain (+23%) without significant compromise in strength, and higher energy absorbed until fracture (EA) (+27%). Compared to the monolithic alloy in compression, the nanocomposite exhibited similar failure strain (+3%) with significant increase in strength (up to +20%) and higher EA (+24%). The beneficial effects of Si3N4 nanoparticle addition on tensile ductility and compressive strength dual enhancement of AZ81 alloy are discussed in this paper.

Studies on Mechanical Properties and Wear Behaviour of In Situ Al-TiC Composites

In the present work, Al–TiC composites were synthesized by Flux Assisted Synthesis (FAS) route. In this in situ method the TiC particles are generated from the reaction between the mixture of K2TiF6 salt and graphite in the molten aluminium. The XRD peaks have confirmed the presence of the TiC and no other undesirable intermetallics have formed after reaction. After casting the composites were extruded and then aged. All the cast, extruded and aged composites samples have exhibited significant improvement in mechanical properties in comparison with the monolithic alloy. The erosion corrosion test have been performed and found that wear resistance of the composites have significantly improved by the presence of TiC particles. Optical and Scanning electron microscopy were used for microstructural analysis and XRD was used for phase analysis. Mechanical testes were performed as per the ASTM standards.

Anelastic Phenomena at the Fibre-Matrix Interface of the Ti6Al4V-SiCf Composite

The composite, consisting of Ti6Al4V matrix reinforced by unidirectional SiC fibres (SCS-6), has been investigated by mechanical spectroscopy at temperatures up to 1,173 K. For comparison, the same experiments have been performed on the corresponding monolithic alloy. The internal friction (IF) spectrum of the composite exhibits a new relaxation peak superimposed to an exponentially increasing background. This peak, which is not present in the monolithic alloy, has an activation energy H = 186 kJ mol-1 and a relaxation time 0 = 2.3 x 10-15 s. The phenomenon has been attributed to a reorientation of interstitial-substitutional pairs in the  phase of Ti6Al4V matrix around the fibres. This explanation is supported by the results of micro-chemical characterization carried out by X-ray photoelectron spectroscopy (XPS) combined with Ar ion sputtering.

The Microstructure and Creep Behavior of a Boron-Modified Ti-15Al-33Nb (at%) Alloy

The affect of boron (B) on the microstructure and creep behavior of a Ti-15Al-33Nb (at%) alloy was investigated. In addition to the normal constituent phases present in the monolithic alloy, the B-modified alloy contained borides enriched in titanium and niobium. These borides were present in the form of needles/laths up to 50 μm long and 10 μm wide which took up 5-9% of the volume. Constant load, tensile-creep experiments were performed in the stress range of 150-340 MPa and the temperature range of 650-710°C, in both air and vacuum environments. An addition of 0.5 at% B did not improve the creep resistance of the monolithic alloy, while the addition of 5 at% B significantly improved the creep resistance.

Mechanical and Fracture Behaviour of a SiC-Particle-Reinforced Aluminum Alloy at High Temperature

The compressive characteristics and fracture behavior of CW67 aluminum alloy and of a composite based on CW67 alloy were studied under unaxial compressive loading in the temperature range 25-400°C, at a constant strain rate of 1 - 3 10 4 . 2 s × . The yield strength values of the composite were higher than those of the monolithic alloy at all temperatures. The ultimate strength values of the composite were lower at room temperature, but higher at elevated temperatures when compared with those of the monolithic alloy. The composite exhibited lower ductility than the monolithic alloy in the entire temperature range. High concentration of SiC particles in the structure of CW67 composite affected its compressive properties. At higher temperatures, it behaved like a typical precipitation hardened alloy, in other words, with temperature increase the main influence on the mechanical properties occurred in its matrix. When temperature rises, the fracture process changes from particle cracking and particle agglomerate decohesion (at room temperature) to particle matrix debonding (at high temperature).