Effect of nanodiamond particle sizes on damping properties of ZK60 magnesium matrix composites

The aim of the research is to ensure that the material has functional mechanical properties as well as high-damping value. The microstructure, elemental composition, second phase distribution and interface structure of the Mg-based composite with different particle sizes were characterized by Optical Microscope(OM), X-Ray Diffractometer(XRD), Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM) and Energy Dispersive Spectrometer (EDS). The mechanical and damping properties of the ZK60 magnesium matrix composites were investigated an Instron5982 universal tester and Dynamic Mechanical Analysis (DMA). The results indicate that nanodiamond(ND) can disperse well in the composites. The elastic modulus of composite can reach 9.9GPa after reinforcement phase being added. Under certain conditions,the damping value can reach beyond 2.5×10-1, which is 117% of other composite. High-temperature damping depends on grain boundary slip and interface slip. The interfacial damping depends on the difference in the incoherent interface and thermal expansion coefficient between the nanodiamond and ZK60 matrix to slip and improve the damping value.

The microstructure and corrosion resistance of SiC reinforced magnesium matrix composites with laminated gradient structure

The laminated gradient of the SiC reinforced Mg-MMCs has been report few. In this paper, the laminated gradient structure of Mg-3Al-3Sn+xSiC alloys (x=0, 0.5, 1.0 and 2.0 wt %) were prepared via powder metallurgy and spark plasma sintering method, and the effects of different sintering rate (60℃/min, 70℃/min and 80℃/min) on the phase, morphology and corrosion resistance of as-sintered and rolled-state samples with laminated gradient structure are characterized. The results shows that, from the surface to core, the grain size of samples gradually decreased with the contents of SiC addition decreasing. Compared to the as-sintered samples, the micro-hardness of rolled-state reach to 105 HV, and the electrochemical test results shows that corrosion resistance of rolled states samples prepared at 70℃/min increased by 88 %, and the corrosion potential (Ecorr) value is -1.3162 VSCE, which is better than other samples; the samples prepared at 60℃/min increased by 36%, and the samples prepared at 80℃/min only decreased by 5%. It provides a new method to prepare the laminated gradient structure of magnesium alloy composites.

Machining and corrosion studies on HfC reinforced ZE41 magnesium matrix composites

In this paper, Hafnium Carbide (HfC) reinforced ZE41 Magnesium Matrix Composites (MMCs) were prepared by using stir casting method. Using three different reinforcement percentages of HfC such as 5%, 10% and 15% by wt., ZE41-HfC MMCs were prepared. The mechanical characteristics of ZE41-HfC MMCs were evaluated by subjecting them to tensile and surface micro-hardness studies. Using X-Ray diffraction (XRD) studies, chemical compounds formed in the interfacial layer between HfC & ZE41 Mg was observed. Using optical microscopy (OM) and scanning electron microscopy (SEM), the surface modifications in the composites due to HfC addition was studied. Using electron backscatter diffraction analysis (EBSD), the changes in particle grain sizes and orientation of ZE41-HfC MMCs were studied. Energy Dispersive Spectroscopy (EDS) analysis was used to identify the variations in elemental composition of the prepared ZE41-HfC MMCs. ZE41-HfC MMCs were subjected to drilling studies for identifying the variations in cutting forces. Using electrochemical studies, the corrosion resistance of ZE41-HfC MMCs was observed. SEM images of corroded ZE41-HfC MMCs revealed micro cracks and dense pits near HfC agglomerated region.

Types of Component Interfaces in Metal Matrix Composites on the Example of Magnesium Matrix Composites

In this paper, a summary of investigations of the microstructure of cast magnesium matrix composites is presented. Analyses of the interfaces between the reinforcing particles and the magnesium alloy matrices were performed. Technically pure magnesium and four various alloys with aluminum and rare earth elements (RE) were chosen as the matrix. The composites were reinforced with SiC and Ti particles, as well as hollow aluminosilicate cenospheres. Microstructure analyses were carried out by light, scanning, and transmission electron microscopy. The composites with the matrix of magnesium and magnesium–aluminum alloys with SiC and Ti particles exhibited coherent interfaces between the components. In the composites based on ternary magnesium alloy with Al and RE with Ti particles, a high-melting Al2RE phase nucleated on the titanium. Different types of interfaces between the components were observed in the composites based on the magnesium–rare earth elements alloy with SiC particles, in which a chemical reaction between the components caused formation of the Re3Si2 phase. Intensive chemical reactions between the components were also observed in the composites with aluminosilicate cenospheres. Additionally, the influence of coatings created on the aluminosilicate cenospheres on the bond with the magnesium matrix was presented. A scheme of the types of interfaces between the components is proposed.