Glass forming ability and thermodynamic properties in novel La-Al-Cu-Co bulk metallic glasses

The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-A1-Cu-Co alloys was well-correlated with the supercooled liq- uid region, ATx, and the parameter, 7; but not with the reduced glass transition temperature, Trg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the pre- sent alloys exhibited a dependence on the relative number of AlqEo and AI-Cu atomic pairs, i.e., on the AI：Co and AI：Cu ratios, which were -2.3 and 0.85, respectively.

Microstructural evolution of h-BN matrix composite ceramics with La-Al-Si-O glass phase during hot-pressed sintering

BN/La-Al-Si-O composite ceramics were fabricated by hot-pressed sintering using hexagonal boron nitride(h-BN),lanthanum oxide(La_(2)O_(3)),aluminia(Al_(2)O_(3)),and amorphous silica(SiO_(2))as the raw materials.The effects of sintering temperature on microstructural evolution,bulk density,apparent porosity,and mechanical properties of the h-BN composite ceramics were investigated.The results indicated that La-Al-Si-O liquid phase was formed during sintering process,which provided an environment for the growth of h-BN grains.With increasing sintering temperature,the cristobalite phase precipitation and h-BN grain growth occurred at the same time,which had a significant influence on the densification and mechanical properties of h-BN composite ceramics.The best mechanical properties of BN/La-Al-Si-O composite ceramics were obtained under the sintering temperature of 1700℃.The elastic modulus,flexural strength,and fracture toughness were 80.5 GPa,266.4 MPa,and 3.25 MPa·m^(1/2),respectively.