Zr48.5Cu46.5Al5 bulk metallic glass (BMG) com- posites with diameters of 3 and 4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural charac- terization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase em- bedded in an amorphous matrix. Room temperature com- pression tests showed that the composites exhibited signifi- cant strain hardening and obvious plastic strain of 7.7% for 3 mm and 6.4% for 4 mm diameter samples, respectively.
利用材料测试系统(MTS)、X-Ray 衍射(XRD)和扫描电镜(SEM)等手段研究了Nd 基大块金属玻璃的变形行为和断裂特征。Nd 基大块金属玻璃样品在室温下是脆性断裂,大约在500 K 时变形模式从非均匀变形转变为均匀变形,在523 K 以上表现出显著的塑性变形。在5×10-4 m/s 的应变速率下,这种Nd 基大块金属玻璃材料在523 K^600 K 之间出现明显的屈服应力下降现象,随后进入1 种稳定的粘性流动状态,而且这种屈服下降现象与温度和应变速率有关。这种在过冷液相区的变形行为与其他大块金属玻璃变形特征相似。合金的这种塑性变形行为表明了其存在稳定的过冷液相区,同时对其变形行为的研究有助于进一步了解Nd 基大块金属玻璃的反常热稳定性。
Mg_ 65Cu_ 25Gd_ 10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.
A kind of novel Ti-based composites was developed by introducing different amounts of carbon element to the Ti50Cu23Ni20Sn7 bulk metallic glass forming alloys. The thermal stability and microstructural evolution of the composites were investigated. Room temperature compression tests reveal that the composite samples with 1% and 3%（mass fraction） carbon additions have higher fracture strength and obvious plastic strain of 2195MPa, 3.1% and 1913MPa, 1.3% respectively, compared with those of the corresponding carbon-free Ti50Ni20Cu23Sn7 alloys. The deformation mechanisms of the composites with improved mechanical properties were also discussed.
