•The high-Li-content in-situ TiB2/Al-Li-Cu composite was successfully synthesized.•The precipitation behavior of the novel cast composite was studied.•The hardness change was dominated by the evolution of T1 (Al2CuLi) and δ′ (Al3Li).The microstructural evolution and mechanical properties of the cast in-situ TiB2/Al-3.3Li-1.2Cu composite during heat treatment were systematically investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Vickers hardness (HV). The nano TiB2 particles mainly agglomerated along the grain boundaries, showed a clean and clear interface between matrix. Much fine δ′ (Al3Li) particles were distributed homogeneously after quenching, and its size increased with the increase of aging time. Primary θ′ and T1 precipitates were visible in the under-aged (UA) state, which contributes to a rapid increase in hardness. And the plate-like T1 precipitates of very high aspect ratio were precipitated with prolonging aging time. It was worth mentioning that the thickness of this plate-like T1 precipitates was stable as the aging proceeded. The studied composite, which was largely strengthened by the δ′ and T1 phases in the peak-aged condition, had a strong age-hardening response. After aging at 175 °C for 214 h, a peak-hardness, which was nearly double than that of the as-quenched, was obtained.

Squeeze casting technique was used to fabricate Mg2B2O5w/AZ91D singular composite and (Mg2B2O5w + B4Cp)/AZ91D hybrid composite to study the effect of Mg2B2O5w and B4Cp hybrid reinforcements on magnesium alloy. The microstructure, mechanical properties and fracture features of the composites were investigated. The results show that the additions of Mg2B2O5w and B4Cp can remarkably enhance the flexural properties of the composites. Especially, B4Cp has a larger contribution to the flexural strength and flexural modulus of the hybrid composite. The flexural strength of the hybrid composite is 29% higher than that of the singular composite. The reason can be ascribed to the higher dislocation density in the matrix of the hybrid composite due to larger differences in the elastic modulus and CETs between B4Cp and the matrix than those between Mg2B2O5w and the matrix. On the fractured surfaces of the composites, most of Mg2B2O5w and B4Cp fracture in the matrix, suggesting that the interfacial bonding strength between the reinforcements and the matrix is relatively strong.Highlights► Mg2B2O5w/AZ91D singular and (Mg2B2O5w + B4Cp)/AZ91D hybrid composites were fabricated. ► The hybrid composite has higher mechanical properties than the singular composite. ► The improvement in mechanical properties of the hybrid composite was discussed.

55 vol.% B4C/Al composites reinforced with 3 μm and 20 μm particles respectively were prepared by squeeze casting. Effect of particle size on quasi-static and dynamic compression behaviors of the composites was investigated. The results show that the quasi-static compression strength of the composite with 3 μm particles is almost twice that of the composite with 20 μm particles. The reason is that the connectivity architectures of the composite with small particles are more stable than that of the composite with big particles due to the enhancement of in situ matrix by geometrically necessary dislocation. In addition, the dynamic compression strength and the fracture strain first increase with the increasing impact velocity and then decrease when the impact velocity is increased from 28 m/s to 33 m/s for the composite with 20 μm particles, and no similar phenomenon occurs for the composite with 3 μm particles. The size-dependent architecture stability of the connected reinforcement is the main contribution to the different dynamic deformation behaviors of the composites during adiabatic compression.Highlights► Effect of particle size on deformation behaviors is observed for high particle content composites. ► The ceramic network stability is different due to various enhanced in situ matrix. ► The compression strength of the composite with small particles is bigger than that with big particles for different architecture. ► Composite reinforced with small particles is more efficient to resist the soften mechanism.

To study the possibility of utilizing piezoelectric effect, damping properties of poly- and single-domain LiNbO3 particle-filled pure aluminum composites were investigated by a dynamic mechanical thermal analyzer. The damping capacity of single-domain LiNbO3/Al composite is always higher than that of poly-domain LiNbO3/Al composite over the whole testing temperature range from 30 to 300 °C. At room temperature the single-domain LiNbO3/Al composite shows twice the damping capacity of the poly-domain LiNbO3/Al composite. Domain structures were observed by an optical microscope. Effect of the domain structure on the properties of LiNbO3 single crystal was studied based on the measurements of d33 piezoelectric constant, damping capacity and coefficient of thermal expansion (CTE). Then effect of the domain structure on the damping properties of the composites was investigated. The difference of the damping capacity between poly- and single-domain LiNbO3/Al composites is mainly attributed to the piezoelectric effect.

The dependence of viscosities on the particle size distribution of lead-free solder powders (Sn/Ag/Cu) is investigated using a parallel-plate rheometer. Experimental results show that for a fixed weight fraction of particles, as the increase of size ratios, the viscosities of the solder paste decrease especially at low shear rates. In addition, for solder paste with more small particles introduced, shear-thickening appears before the onset of shear thinning. The higher the relative fraction, the more dramatically viscosities increase, which is consistent with modeling results using Cross equation. A possible mechanism is proposed to reveal the relationship between microstructure and corresponding rheological behaviors.

A new type of piezo-damping aluminum matrix composite containing ZnO:Al-coated LiNbO3 particles was prepared. The dependence of the damping properties of composites on the resistivity of ZnO:Al coatings, altered by Al doping concentration, was investigated. Dynamic mechanical thermal analysis revealed that decreasing the resistivity of ZnO:Al coatings causes the loss factors of the composites to initially increase until the maximum value, before rapidly decreasing. Based on this piezo-damping material, the LiNbO3 particles contribute to the transformation of mechanical vibration energy into electric energy, which is then converted into Joule's heat in the networks within the ZnO:Al coatings and metal matrix. An optimum formulation for piezo-damping metal matrix composites can be designed based on the results of this study.

In order to improve the quantum efficiency of TiO2 nanotube film, Si-doped TiO2 nanotubes were prepared by anodizing Ti in HF/Na2SiF6 solution. The experimental results show that the presence of Si can separate photogenerated electrons and holes effectively. It was found that the photocurrent density of Si-doped TiO2/Ti electrode is 2–3 times higher than that of undoped TiO2/Ti electrode, and the photoelectrocatalytic degradation rate of Si-doped TiO2/Ti electrode is increased by 76.6% over that of normal TiO2/Ti electrode at an applied potential of 1.5 V.

The agglomerates of TiB2 particulates and Si phases badly break the continuity of anodized film of in situ TiB2p/A356 composite, which will restrict the improvement of corrosion resistance. In this study, cerium conversion coatings were successfully deposited on anodized TiB2p/A356 composite by electrolysis treatment. Scanning electron microscope observations show that the conversion coatings effectively cover the whole surface of anodized composite. The conversion coatings on continuous porous anodic film are composed of many spherical nano-particulates; however, at the regions without anodic film the conversion coatings present a planar structure. The different morphologies are attributed to the different formation characteristics of cerium conversion coatings at different regions of anodized composite. X-ray photoelectron spectroscopy analysis indicates that the conversion coatings consist of CeO2, Ce2O3, Ce(OH)4, and Ce(OH)3. The potentiodynamic polarization results testify that the integrated surface coatings of anodic film and cerium conversion coating provide a higher degree of protection for in situ TiB2p/A356 composite in a chloride-containing environment.

The damping capacity of in situ aluminium (Al)/TiB2 composite and composite with Ti excess was investigated. The composites were fabricated with an exothermic reaction process via K2TiF4 and KBF4 salts. The damping behavior of materials over a temperature range of 30–300 °C was investigated using a dynamic mechanical thermal analyzer. Experimental findings indicate that damping capacity of composite with Ti excess is lower than that of Al/5 wt% composite when temperature below 110 °C and higher than of Al/5 wt% composite above 110 °C. The main effect of Ti is the formation of thin layer on TiB2 particulates resulted in the change of damping capacity.

The damping capacity of as cast Mg–9Al–Si alloys was investigated. A damping peak exhibits at around 420 K for a frequency of about 1 Hz and it was correlated to the characteristic grain boundary peak of magnesium. The activation energy of damping peak is lower than self-diffusion activation energy of pure magnesium, but higher than activation energy of AZ91 reported. The effect of measurement conditions including strain amplitude, heating rate and consecutive measurement number on damping peaks has also been discussed.

A new idea of using a stiffer metallic compound Mg2Si to enhance the damping capacities of pure magnesium and its alloys is successfully attempted. The present paper focuses on the relation between damping capacities and the addition amount of Si. The results show that damping capacities increase with increasing amount of Si. Particular emphasis is placed on the increasing dislocation density around matrix–particulate interface and the refinement of grain size promoted by big growth restriction factor of Si.

The moduli of the A356/TiB2p and A132/TiB2p composites can be notably improved by TiB2 particles. The increments of the moduli of the two composites are close to each other at low fraction. However, the increment of modulus of 9.5 vol.%A132/TiB2p can reach 24 GPa, which is 41.2% higher than that of 9.5 vol.%A356/TiB2p. A new analytical method is put forward.

The eutectic Al–Si alloy composites reinforced with sub-micron TiB2 particles were successfully fabricated by means of reaction processing method. The TiB2 particles were formed in situ through the reaction of Ti and B bearing salts and Al alloy. The test results showed that the ultimate tensile strength of the composites were higher than that of Al–Si master alloy at the temperature ranging from 25 to 400 °C, and the contribution ratio of the particles to the ultimate tensile strength reached its peak value at 260 °C, and the mechanism is also discussed in this essay.

Damping capacity of in situ Al/TiB2 composite and composite with Ti addition was investigated. The composites were fabricated with an exothermic reaction process via K2TiF4 and KBF4 salts. Experimental results indicate that existence of Ti alters the TiB2/aluminum interface, resulting in a change in damping of the Al/TiB2 composite.

Damping capacity of in situ TiB2 particulate reinforced aluminum composites with Ti and Mg excess were investigated. The composites were fabricated with an exothermic reaction process via K2TiF4 and KBF4 salts. The damping behavior of materials over a temperature range of 30–300 °C was investigated by using a dynamic mechanical thermal analyzer. Experimental findings indicate that the damping capacity of composites with Ti, Mg excess, respectively is lower than that of Al/5 wt.% composite when temperature is below 180 °C and is higher than of Al/5 wt.% composite above 180 °C. The main effects of these elements are the formation of thin layers on TiB2 particulates, which resulted in the change of damping capacity.