Alloying elements (Ni, Mo) were added to grey cast iron, and the effect of Ni, Mo on microstructure and mechanical properties were analysed in this study. When Ni was added alone, the precipitation of graphite was inhibited at the early stage of solidification, and part of graphite was formed between the dendrites, resulted in an uneven distribution of graphite. Ni played a role of solution strengthening and reduced the pearlite interlammer spacing, improved the mechanical properties. The addition of Mo refined the austenite dendrites and made the carbon unevenly distributed, which led to the abnormal growth of graphite. Mo increased the eutectoid supercooling degree, reduced the pearlite interlammer spacing and improved tensile strength. When Ni and Mo were added together, the elements beneficial to strength (Mo, Sn) were not uniformly distributed, and the influence on graphite size and pearlite interlammer spacing was not obvious, resulted in poor mechanical properties.

Hollow glass microspheres (HGMs)/epoxy syntactic foam reinforced by multiwalled carbon nanotubes (MWCNTs) was prepared in this study. The effect of MWCNTs on the density, mechanical properties and water absorption of HGMs/epoxy syntactic foam was investigated. Because of the low density and low content of MWCNTs, the density of HGMs/epoxy syntactic foam does not change much with adding MWCNTs. In addition, the compression strength of HGMs/epoxy is enhanced by 17–25% when adding 0.3 wt% MWCNTs. The fracture surfaces of specimens were examined with scanning electron microscopy (SEM), and results indicated that the bridging effect of MWCNTs is the reinforcement mechanism. Analyzing the water absorption testing results, it is concluded that MWCNTs may decrease the water absorption content due to the hydrophobicity. Bigger inorganic ions in salt water could prevent the water diffusion, which results in a decrease of water absorption. In addition, the water absorption rate decreases with the extension of testing time.

In this study, the influence of Er addition on the microstructure, type transformation of second phases, and corrosion resistance of an Al–Zn–Mg–Cu alloy were explored. The results revealed that the added Er element could significantly refine the alloy grains and change the second-phase composition at the grain boundary of the alloy. In the as-cast state, the Er element significantly enhanced the corrosion resistance of the alloy due to its refining effect on the grains and second phases at the grain boundary. The addition of the alloying element Er to the investigated alloy changed the type of corrosion attack on the alloy’s surface. In the presence of Er, the dominant type of corrosion attack is pitting corrosion, while the alloy without Er is prone to intergranular corrosion attack. After a solution treatment, the Al₈Cu₄Er phase was formed, in which the interaction with the Cu element and the competitive growth relation to the Al₃Er phase were the key factors influencing the corrosion resistance of the alloy. The anodic corrosion mechanism of the Al₈Cu₄Er and Al₃Er phases evidently lowered the alloy corrosion rate, and the depth of the corrosion pit declined from 197 μm to 155 μm; however, further improvement of corrosion resistance was restricted by the morphology and size of the Al₈Cu₄Er phase after its formation and growth; therefore, adjusting the matching design of the Cu and Er elements can allow Er to improve the corrosion resistance of the Al–Zn–Mg–Cu aluminum alloy to the greatest extent.