Mingliang Wang

Compressive behavior of high particle content B4C/Al composite at elevated temperature

Abstract The compressive properties of the aluminum matrix composite reinforced with 55% B 4 C (volume fraction) particles were characterized using Gleeble 3500 thermal-mechanical testing machine. The compressive stress—strain curves were obtained at the temperature ranging from 298 to 773 K and strain rate ranging from 1×10 −3 to 5 s −1 . The results showed that the dynamic compressive strength decreased more slowly than the quasi-static compressive strength at elevated temperatures, which was attributed to the different failure modes of the composite under dynamic and quasi-static load. The strain rate sensitivity increased from 0.02 to 0.13 when the temperature increased from room temperature to 773 K, suggesting that the strain rate sensitivity of this type of composite is a function of temperature.

First-principles investigation of thermodynamic, elastic and electronic properties of Al3V and Al3Nb intermetallics under pressures

The thermodynamic, elastic, and electronic properties of D022-type Al3V and Al3Nb intermetallics were studied using the first-principle method. The results showed the pressure has profound effects on the structural, mechanical and electronic properties in both Al3V and Al3Nb. Thermodynamically, the formation enthalpies for Al3V and Al3Nb were derived, which agreed well with available experimental and theoretical values. Comparably, Al3Nb was a more stable phase with the more negative Hf than Al3V. Mechanically, the calculated elastic constants showed linearly increasing tendencies, and satisfied the Borns criteria from 0–20 GPa, indicating the mechanically stability of Al3V and Al3Nb under this pressure range. Further, the mechanical parameters (i.e., bulk modulus (B), shear modulus (G), and Youngs modulus (E)) were derived using the Voigt-Reuss-Hill (VRH) method, and in good agreement with available experimental results at the ground state. All these parameters presented the linearly increasing depende...

Study on the load partition behaviors of high particle content B4C/Al composites in compression

High particle content B4C/Al composites reinforced with different particle sizes were fabricated. Based on the tensile and compressive stress–strain behaviors of these composites, the effective medium approach was employed to investigate the load partition behaviors between the matrix and reinforcement. The results showed that the load borne by the particles increased in compression, which lead to larger compressive strength than the tensile strength. Meanwhile, the load borne by particles increased with decreasing particle size during compression. These observations were rationalized based on the combined theories of geometrically necessary dislocations and metal-based cemented granular material behaviors.

Structural, elastic and thermodynamic properties of A15-type compounds V3X (X = Ir, Pt and Au) from first-principles calculations

The structural, elastic and thermodynamic properties of the A15 structure V3Ir, V3Pt and V3Au were studied using first-principles calculations based on the density functional theory (DFT) within generalized gradient approximation (GGA) and local density approximation (LDA) methods. The results have shown that both GGA and LDA methods can process the structural optimization in good agreement with the available experimental parameters in the compounds. Furthermore, the elastic properties and Debye temperatures estimated by LDA method are typically larger than the GGA methods. However, the GGA methods can make better prediction with the experimental values of Debye temperature in V3Ir, V3Pt and V3Au, signifying the precision of the calculating work. Based on the E–V data derived from the GGA method, the variations of the Debye temperature, coefficient of thermal expansion and heat capacity under pressure ranging from 0 GPa to 50 GPa and at temperature ranging from 0 K to 1500 K were obtained and analyzed for all compounds using the quasi-harmonic Debye model.

Stability of nanopore formation in aluminum anodization in oxalic acid

Abstract The effect of applied voltage on nanopore formation stability of porous anodized alumina (PAA) in oxalic acid electrolyte was investigated. The Al anodization at a constant applied voltage is a popular electrochemical method to synthesize PAA templates. The experimental observations of Al anodization are used to compare the predictions of the THAMIDA model for interpore distance and the stability criterion of the SINGH model. It is found that, in the electrolyte of pH = 0.96, the interpore distance—applied voltage has a linear dependence coefficient of 2.24 nm/V, which agrees well with the THAMIDA model. It has also been confirmed that pore formation is instable at above 60 V which can be predicted by SINGH model. A second unstable growth regime below 30 V is also observed, which is not predicted by any of the models.

Simultaneously increasing strength and ductility of nanoparticles reinforced Al composites via accumulative orthogonal extrusion process

ABSTRACT Ceramic particles have been introduced into metal matrices to improve the strength and stiffness of metals, albeit at the cost of the ductility unfortunately. Simultaneously increasing the strength and ductility of metal matrix composites (MMCs) is still a challenge. Accumulative orthogonal extrusion process (AOEP), which disperses nanoparticles and refines grain structures of particles reinforced MMCs via severe plastic deformation, is proposed in this paper. The high strength (687 MPa) and superior ductility (14.8%) are simultaneously achieved in the resultant TiB2 particles reinforced Al–Zn–Mg–Cu matrix composites, and the underlying mechanisms are discussed in terms of particles’ influences. GRAPHICAL ABSTRACT IMPACT STATEMENT An easily realized SPD technology is proposed to effectively optimize the structures of nanoparticles reinforced composites in industrial scale. High strength and good ductility are simultaneously achieved in the resultant composites.

Improvement of yttrium on the hot tearing susceptibility of 6TiB2/Al-5Cu composite

Abstract To improve the severe hot tearing susceptibility of TiB 2 reinforced Al-5Cu matrix composites, the present research investigated the influence of Y on the hot tearing susceptibility of 6TiB 2 /Al-5Cu composite. For the composite added with Y, the solidification temperature range was shortened, which was caused by the novel τ 1 -Al 8 Cu 4 Y phase. The grain size of 6TiB 2 /Al-5Cu composite was 39.8 µm. The addition of Y promoted the grain refinement, and the grain sizes were 36.33, 33.42 and 26.77 µm for 6TiB 2 /Al-5Cu with 0.2 wt.%, 0.5 wt.% and 1 wt.% Y, respectively. The decrease of solidification temperature range and grain size was beneficial to the hot tearing susceptibility improvement. Furthermore, the hot tearing initiation force increased from 44 to 288 N, when 1 wt.% Y was added in 6TiB 2 /Al-5Cu. For the above significant influence, the hot tearing susceptibility values were reduced by 12.2 wt.%, 57.7 wt.% and 66.8 wt.% for 6TiB 2 /Al-5Cu with 0.2 wt.%, 0.5 wt.% and 1 wt.% Y, accordingly.

Microstructure and mechanical properties of magnesium matrix composite reinforced with magnesium borate whisker

The microstructure, mechanical properties and fracture behavior of AZ91D magnesium matrix composite reinforced with magnesium borate whisker fabricated by squeeze casting technique were investigated. The results indicate that magnesium borate whisker can improve the mechanical properties of AZ91D alloy significantly. Transmission electron microscope observation shows that a continuous magnesium oxide interfacial layer of about 25 nm thick is formed at the magnesium borate whisker/matrix interface, which is formed from the interfacial reaction between the liquid Mg and oxygen absorbed at the surface of magnesium borate whisker. The magnesium oxide interfacial layer can act as a barrier layer to prevent the further reaction between magnesium borate whisker and the liquid Mg, and may play an important role in the improvement of the mechanical properties of the composite.

Phase stability, elastic and electronic properties of Hf–Rh intermetallic compounds from first-principles calculations

The phase stability, elastic and electronic properties of binary Hf–Rh compounds have been studied using first-principles calculations based on density functional theory. The equilibrium lattice constants, formation enthalpies, elastic constants, and elastic moduli are presented. Among the binary Hf–Rh compounds, Hf3Rh5 is the most stable with the lowest formation enthalpy. For the equiatomic HfRh phase, it tends to crystallize in the ZrIr-type structure, followed by L10, and then B2 at the ground state based on the analysis of formation enthalpies. Therefore, the crystal structure of the lower temperature HfRh phase is suggested to be the ZrIr-type. This conclusion is in agreement with the experimental reports in the literature. Besides, Hf3Rh4 are proposed to be the Pu3Pd4-type for the first time. Furthermore, our calculated elastic constants for Hf2Rh, ZrIr-HfRh, L10-HfRh, B2-HfRh, Hf3Rh4, Hf3Rh5 and HfRh3 can all satisfy the Born criteria, indicating their mechanical stabilities. When ZrIr-HfRh is adopted, the bulk modulus (B) increases linearly with the growing Rh atomic concentration. Meanwhile, Youngs modulus linearly increases with growing shear modulus, and the compound with a higher Poissons ratio owns a higher B/G ratio simultaneously. Overall, the results also indicate that all the considered Hf–Rh compounds should be ductile. Finally, the electronic structure is analyzed to understand the essence of structural stability of the binary compound.

Assessment on the structural, elastic and electronic properties of Nb3Ir and Nb3Pt: A first-principles study

The pressure dependent behaviors on the structural, elastic and electronic properties of the A15 structure Nb3Ir and Nb3Pt were studied using first-principles calculations based on the density functional theory within generalized gradient approximation and local density approximation methods. Initially, the optimized lattice constants of Nb3Ir and Nb3Pt are consistent with the available experimental and theoretical results. Furthermore, Nb3Ir is found to be more thermodynamically stable than Nb3Pt due to its lower formation enthalpy and higher melting temperature. In addition, the elastic constants of Nb3Ir and Nb3Pt show an increasing tendency, and keep mechanically stable structures under pressures to 40 GPa. Besides, the increasing Cauchy pressures and B/G values have indicated that higher pressures can improve their ductility in both Nb3Ir and Nb3Pt. Finally, the pressure-dependent behaviors on the density of states, Mulliken charges and bond lengths are discussed for both compounds.