“…22–24 Combination of the Hall–Petch strengthening and the Orowan strengthening seems to be the controlling mechanism for the nanocomposites materials with reinforcement particles of size below 1 µm. 23,25–27 Figure 5.Indentation hardness versus load rate for the Mg nanocomposite materials and the pure Mg.Mg: magnesium.…”
Section: Resultsmentioning
confidence: 99%
“…In a particulate reinforced nanocomposite, the Orowan effect can be expressed as: 32 where M is the Taylor factor, b is Burger's vector, υ is the Poisson's ratio, G is the matrix shear modulus, and v p is the volume fraction of the particles. Based on equation (2), with decrease in the particle size and increase in the volume fraction of the particles, the Orowan strengthening effect becomes more pronounced and that is why nanoparticles are better candidates to enhance the strength compared with micro-sized particles.…”
Magnesium nanocomposites, considered as energy-saving lightweight materials of future, are a fairly new family of composite materials with enhanced specific strength and ductility compared to pure magnesium and/or magnesium alloys. In the present study, time-dependent plastic deformation of novel light-weight magnesium/boron nitride nanocomposites containing 0.5, 1.5 and 2.5 vol% of nano-boron nitride particulates is studied through a depth-sensing indentation approach against monolithic pure magnesium. The synthesis of magnesium–boron nitride nanocomposites was accomplished using powder metallurgy technique coupled with microwave sintering, followed by hot extrusion (end products are 8-mm diameter rods). The depth sensing indentation creep tests were conducted at room temperature (∼0.32Tm of magnesium) using an instrumented indentation platform via a self-similar pyramidal (Berkovich) indenter. To assess the influence of loading rate on the indentation-induced deformation behavior of the materials, a dual stage indentation creep including a constant loading rate followed by a constant load-holding scheme was used; indentation tests were performed on the specimens. The specimens were loaded at rates of 0.05, 0.5, 5, and 50 mN/s to a peak load of 50 mN then force was held constant for 400 s while load/displacement/time data were recorded continuously. The results of the depth sensing indentation tests were correlated and explained using the microstructural characteristics placing special emphasis on the volume fraction of reinforcement and the indentation loading rate. Finally, the controlling creep mechanisms of the magnesium–boron nitride nanocomposites and the base metal (pure magnesium) were discussed in the present paper. The results of this paper can be used as a baseline for high-temperature creep analysis of magnesium–boron nitride nanocomposites which is of engineering significance.
“…22–24 Combination of the Hall–Petch strengthening and the Orowan strengthening seems to be the controlling mechanism for the nanocomposites materials with reinforcement particles of size below 1 µm. 23,25–27 Figure 5.Indentation hardness versus load rate for the Mg nanocomposite materials and the pure Mg.Mg: magnesium.…”
Section: Resultsmentioning
confidence: 99%
“…In a particulate reinforced nanocomposite, the Orowan effect can be expressed as: 32 where M is the Taylor factor, b is Burger's vector, υ is the Poisson's ratio, G is the matrix shear modulus, and v p is the volume fraction of the particles. Based on equation (2), with decrease in the particle size and increase in the volume fraction of the particles, the Orowan strengthening effect becomes more pronounced and that is why nanoparticles are better candidates to enhance the strength compared with micro-sized particles.…”
Magnesium nanocomposites, considered as energy-saving lightweight materials of future, are a fairly new family of composite materials with enhanced specific strength and ductility compared to pure magnesium and/or magnesium alloys. In the present study, time-dependent plastic deformation of novel light-weight magnesium/boron nitride nanocomposites containing 0.5, 1.5 and 2.5 vol% of nano-boron nitride particulates is studied through a depth-sensing indentation approach against monolithic pure magnesium. The synthesis of magnesium–boron nitride nanocomposites was accomplished using powder metallurgy technique coupled with microwave sintering, followed by hot extrusion (end products are 8-mm diameter rods). The depth sensing indentation creep tests were conducted at room temperature (∼0.32Tm of magnesium) using an instrumented indentation platform via a self-similar pyramidal (Berkovich) indenter. To assess the influence of loading rate on the indentation-induced deformation behavior of the materials, a dual stage indentation creep including a constant loading rate followed by a constant load-holding scheme was used; indentation tests were performed on the specimens. The specimens were loaded at rates of 0.05, 0.5, 5, and 50 mN/s to a peak load of 50 mN then force was held constant for 400 s while load/displacement/time data were recorded continuously. The results of the depth sensing indentation tests were correlated and explained using the microstructural characteristics placing special emphasis on the volume fraction of reinforcement and the indentation loading rate. Finally, the controlling creep mechanisms of the magnesium–boron nitride nanocomposites and the base metal (pure magnesium) were discussed in the present paper. The results of this paper can be used as a baseline for high-temperature creep analysis of magnesium–boron nitride nanocomposites which is of engineering significance.
“…For the Al-Zn-Mg-Cu alloy, σ0 is ~16 MPa [48], K is ~0.12 MPa·m 1/2 , and the value of d was 44–78 nm. The yield strength of S30 was calculated as 445–588 MPa.…”
In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in α-Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2–5 μm. The α-Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of α-Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the α-Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.
“…where V P is the volume fraction of reinforced particles (~6.4%), k is a coefficient (~1.6), G m is the shear modulus of the matrix (~102.4 GPa), b is the Burger vector (~0.286 nm 23 ) and the dislocated density ρ can be calculated by the equation below:…”
Section: Resultsmentioning
confidence: 99%
“…Ceramic particles have been used as reinforcement in high entropy alloy matrix composites, which have distinct properties with regard to the matrix. For example, AlZnMgCuZr lightweight high entropy alloy based composites were prepared by incorporating 10% of TiB 2 23 ; the compressive strength, hardness and elastic modulus of the composites were greatly enhanced due to the grain refinement. Lukasz et al .…”
FeCrNiCu based high entropy alloy matrix composites were fabricated with addition of Si and C by vacuum electromagnetic induction melting. The primary goal of this research was to analyze the reaction mechanism, microstructure, mechanical properties at room temperature and strengthening mechanism of the composites with addition of Si and C. The reaction mechanism of powders containing (Si, Ni and C) was analyzed, only one reaction occurred (i.e., Si + C → SiC) and its activation energy is 1302.8 kJ/mol. The new composites consist of a face centered cubic (FCC) structured matrix reinforced by submicron sized SiC particles. The addition of Si and C enhances the hardness from 351.4 HV to 626.4 HV and the tensile strength from 565.5 MPa to 846.0 MPa, accompanied by a slight decrease in the plasticity. The main strengthening mechanisms of SiC/FeCrNiCu composites were discussed based on dislocation strengthening, load bearing effect, Orowan mechanism and solid solution hardening, whose contributions to the tensile strength increase are 58.6%, 6.3%, 14.3% and 20.8%, respectively.
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