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In this study, the effect of size and percentage of MgO reinforcing particles on Mg properties was investigated. For this purpose, the reinforcing powders, in both 60 μm and 20 nm sizes and at different volume percentages, were mixed separately with Mg powder for 1 h in a planetary ball milling and then produced under the pressure of 600 MPa at 450°C for 20 min time duration. The relative density, microhardness, stress-strain under static loading, wear and corrosion behavior of the fabricated nano/microcomposite samples were explored. The results showed that nano- and microcomposite samples were produced with a relative density above 90%. Furthermore, with increased reinforcement percentage, the relative density of the produced samples decreased. In contrast, microhardness, wear resistance and compression strength increased. The microhardness of Mg–5 vol.% MgO-nano sample was 14% higher than the Mg–5 vol.%MgO-micro sample. The wear rate of Mg–5 vol.%MgO-nano sample was 9.8 and 45% lower than those of Mg–5 vol.%MgO and Mg-micro samples, respectively. Compressive strengths of Mg–5 vol.%MgO-nano sample and Mg–5 vol.% MgO-micro sample exceeded tose of the Mg sample by 57 and 54%, respectively. Besides, the corrosion rate of the samples increased with the volume percentage and size of the reinforcements. The corrosion rate of the Mg sample was 1200 and 160% lower than those of Mg–1.5 vol.% MgO-micro sample and M–1.5 vol.%MgO-nano sample, respectively. To validate the results of wear rate, compression strength and corrosion, the SEM examination of the samples was performed. [ABSTRACT FROM AUTHOR]

The effect of reinforcing particle size on microstructure, relative density and indentation of Mg reinforced by 0, 1.5, 3, 5 and 10% volume fractions of nano- and micro-sized B4C was investigated. The composites were fabricated through powder compaction technique at strain rates of 1.6 × 103 s−1, 8 × 102 s−1 and 8×103 s−1 using split Hopkinson bar, drop hammer and Instron, respectively. The results indicated that the size of B4C and loading rate had significant effect on relative density. For example, the relative density of Mg-10 vol.% B4C nanocomposite was around 2.5% higher than that of its corresponding microcomposites. The relative density of the samples produced at high rate of loading was in average 1.2% higher than that of the samples fabricated quasi-statically. The results of indentation tests on the produced nanocomposite and microcomposite samples also revealed that loading rate and B4C particle size had significant effect on strength of specimens. For example, for Mg-5 vol.% B4C, the maximum load in load–depth curve of the specimens produced by split Hopkinson bar increased from 530 N for micron-sized B4C to 780 N for nano-sized B4C, around 45% improvement. Moreover, nanocomposites had better indentation resistance compared to similar micro composites fabricated using the three methods. [ABSTRACT FROM AUTHOR]

Mg–SiC nanocomposite samples were fabricated using split Hopkinson pressure bar for different SiC volume fractions and under different temperature conditions. The microstructures and mechanical properties of the samples including microhardness and stress–strain curves were captured from quasi-static and dynamic tests carried out using Instron and split Hopkinson pressure bar, respectively. Nanocomposites were produced by hot and high-rate compaction method using split Hopkinson pressure bar. Temperature also significantly affects relative density and can lead to 2.5% increase in density. Adding SiC-reinforcing particles to samples increased their Vickers microhardness from 46 VH to 68 VH (45% increase) depending on the compaction temperature. X-ray diffraction analysis showed that by increasing temperature from 25℃ to 450℃, the Mg crystallite size increases from 37 nm to 72 nm and decreases the lattice strain from 45% to 30%. In quasi-static tests, the ultimate compressive strength for the compaction temperature of 450℃ was improved from 123% for Mg–0 vol.% SiC to 200% for the Mg–10 vol.% SiC samples compared with those of the compaction at room temperature. In dynamic tests, the ultimate strength for Mg–10 vol.% SiC sample compacted at high strain rate increased remarkably by 110% compared with that for Mg–0 vol.% SiC sample compacted at low strain rate. [ABSTRACT FROM AUTHOR]

Functionally graded material (FGM) is a heterogeneous composite material that consists of two or more constituent phases with continuous changes in the microstructure from one material to another with adjustable through thickness properties. FGMs are utilized in medical applications, such as dental implants, due to their excellent mechanical and tribological properties. In this study, the powder metallurgy method (PMM) is used to produce Titanum/Hydroxyapatite (Ti/HA) and Titanum/Silicon dioxide (Ti/SiO 2) FGM samples. A new designed blender is employed to mix the particles constituting the FGM samples. The mixed particles are then compacted at different strain rates from quasi static loading, using a universal testing apparatus, to dynamic loadings, using a drop hammer and a split Hopkinson bar. The effect of strain rate on mechanical properties and microstructure of specimens is studied by conducting various tests such as indentation and compression tests and by microstructural examinations using scanning electron microscopy (SEM). The results showed that the relative density of fabricated specimens was increased with the increase of the strain rate. The highest relative density for the Ti/HA composite was achieved for the specimens produced by the split Hopkinson bar. For both of Ti/HA and Ti/SiO 2 FGMs the maximum indentation force and indentation energy, obtained from the load-penetration depth curve, and the ultimate strength, obtained from the compressive stress-strain curve, were increased with the increase in strain rate. The results also indicated that the increase in volume fraction of reinforcing ceramic particles (HA or SiO 2) led to the decrease of the maximum indentation force and indentation energy. [ABSTRACT FROM AUTHOR]

In this study, the effect of the compaction velocity as well as the size and volume fraction of the reinforcing particles on the corrosion properties of Mg–B 4 C composites were investigated. Micron/nano particles of boron carbide at different volume fractions (0, 5, and 10%) were added to the matrix (magnesium powder). Powder mixtures were milled in a planetary ball mill and compacted at 450 °C and different strain rates, using Split-Hopkinson bar (SHB), drop hammer, and Instron devices. Microstructural analysis and corrosion tests were carried out on the produced samples. The results indicated that the samples produced at higher compaction velocities had the lower corrosion rate mainly due to the lower porosity and higher relative density of the samples. For example, the measured corrosion rates for the magnesium samples reinforced with 5 vol% of micron B 4 C particles and compacted by the SHB method were 54 and 76% lower than the similar samples produced by the drop hammer and Instron device, respectively. It was also shown that decreasing the size and content of the reinforcing particles resulted in a reduction in the corrosion rate values. The recorded corrosion rate values for the samples reinforced with 5 and 10 vol% of B 4 C nanoparticles and compacted by the drop hammer device were 18.3 and 29.18 mm/year, respectively. These valuses were approximately 16 and 13% lower compared to the similar composites reinforced with micron-sized particles. The lowest corrosion rate (1.84 mm/year) was observed in the pure magnesium sample compacted by the SHB which was 29.42% lower than that of the magnesium sample reinforced with 10 vol% of micron-sized B 4 C. • Mg–B4Cnp samples had lower corrosion rate compared to Mg–B4Cmp composite samples. • Samples produced at higher strain rates exhibited higher corrosion resistance. • The size and content of the reinforcing particles is directly proportional to the corrosion rate. • Higher grain boundary density and density are primary reasons of improved corrosion properties. [ABSTRACT FROM AUTHOR]

In this study, the physical, tribological and corrosion properties of Mg matrix nanocomposite reinforcement were investigated by Al 2 O 3 nanoparticles fabricated using the single-action press (SP) and double-action press (DP) at 300, 500, and 700 MPa pressures with different volume percentages (0, 1.5, 3, and 5%) of Al 2 O 3 reinforcement nanoparticles. The samples were sintered in 450 °C argon gas for 2 h. The results showed an increase in the experimental density as well as green density in DP compared to SP. The experimental density of Mg-5 vol% Al 2 O 3 nanocomposite compacted at 700 MPa by DP was achieved to be 3% higher than the experimental density of the same specimen compacted at 700 MPa by SP. Furthermore, the relative density of this sample compacted at 700 MPa by DP was achieved to be 5.5% higher than the relative density of this sample compacted at 300 MPa by SP. The wear rate of the Mg-5 vol% Al 2 O 3 fabricated at 700 MPa by DP was achieved as 14%, 50%, and 35% lower than that of Mg-5 vol% Al 2 O 3 sample fabricated at 700 MPa by SP and the Pure Mg compacted at 700 MPa by SP and DP, respectively. The corrosion test results showed that the corrosion rate increased with increasing the percentage of nanoparticles so that the corrosion rate of the Mg-5 vol% Al 2 O 3 sample was achieved 520% higher than the Pure Mg fabricated at 700 MPa by DP. • Increasing pressure and using DP method, increased density and reduced wear rate. • The minimum wear rate was obtained for Mg-5 vol% Al2O3-700 MPa-DP sample. • The wear rate of the 5 vol%-700 MPa-DP was 14% lower than 5 vol%-700 MPa-SP. • The corrosion rate increased with increasing the percentage of nanoparticles. • The corrosion rate of the 5 vol% was 520% higher than the pure Mg-700 MPa-DP. [ABSTRACT FROM AUTHOR]

Mg metal matrix nanocomposites reinforced by 0, 1.5, 3 and 5 vol fractions of TiO 2 and ZrO 2 nanoparticles were fabricated using hot quasi-static compaction method under the pressure of 600 MPa at 450 °C for 25 min. The density, hardness, ultimate compressive strength (UCS) and coefficient of thermal expansion (CTE) of the samples were experimentally measured. The results indicated that by increasing the volume fraction of nanoparticles, the relative density and CTE were reduced but hardness and UCS were improved. The results also indicated that relative density of Mg-ZrO 2 was higher than that of Mg-TiO 2. The CTE of the nanocomposites was decreased by 1.1 and 1.4% for the 5 vol % fraction of the TiO 2 and ZrO 2 reinforcing particles, respectively. The highest hardness was obtained for the Mg-5vol. % ZrO 2. UCS of samples was improved by 22% and 10% for the material reinforced by 3 vol % and 5 vol % of ZrO 2 and TiO 2 , respectively. • The relative density of Mg-ZrO2 samples was measured higher than Mg-TiO2. • The maximum micro hardness was obtained for Mg-5vol. %ZrO2. • 3 vol %TiO2 and 5 vol % ZrO2 enhanced the ultimate strength by 10% and 22%. • Up to 5 vol % of TiO2 and ZrO2 reduced CTE by 1.1% and 1.4%. [ABSTRACT FROM AUTHOR]