Zr-BMG和W_f/Zr-BMG力学性能的试验研究

【作者】 侯兵；

【导师】 李玉龙；

【作者基本信息】 西北工业大学 ， 固体力学， 2007， 硕士

【摘要】 大块非晶是一种原子结构呈无序非晶状态的新型合金材料。本文对锆基大块非晶（Zr-BMG）及其钨丝增强复合材料（W_f／Zr-BMG）的力学性能进行了系统的试验研究。主要包括以下几个方面的内容：（1） 对Zr-BMG进行了应变率为3×10^-3／s和2x10³／s，温度从液氮温度77K到高温473K的动静态压缩试验，得出材料屈服应力受温度和应变率影响的规律，在Zr-BMG试样的剪切断面上观察到熔化材料流动所形成的典型脉络网状花样，高温试样形成类似泥浆的流动；（2） 对于W_f／Zr-BMG复合材料，首先研究了渗流温度和钨丝尺寸及含量对材料性能的影响，发现在711K下渗流15min得到的钨丝直径φ=250μm、百分含量V_f=60％的复合材料具有较好的综合性能，并发现随着钨丝含量的增加，复合材料的强度和塑性不断增大，静态压缩的断裂模式由沿单一剪切带破坏逐渐转变为伴随有钨丝的屈曲、弯折和倾斜的纵向劈裂破坏，劈裂裂纹沿钨丝和基体界面以“之”字形方式传播，动态时则为两种破坏模式的混合。（3） 对W_f／Zr-BMG复合材料进行的与Zr-BMG相同的温度和应变率敏感性试验结果表明：复合材料的屈服应力随温度升高而降低，断裂应变则呈现相反的趋势：材料的流动应力具有明显的正应变率敏感性；复合材料的剪切断面上，熔化的基体材料流动形成脉络网状花样，并蔓延过钨丝横截面，高温时基体材料流动比低温更充分。（4） 通过观察复合材料的破坏模式，详细描述了复合材料的变形过程和破坏机制，以及钨丝的增韧机理，认为钨丝加入限制单条剪切带的传播，有利于生成多条剪切带，这是复合材料韧性化的主要原因。（5） 从弹性应变能引发绝热温升的角度分析了大块非晶中剪切带的生成机理，并在此基础上对大块非晶及其钨丝增强复合材料的温度敏感性提出一种微观解释。更多还原

【Abstract】 Bulk metallic glasses (BMGs) is a kind of new emerging materials with no long-rang order of atomic arrangements. The mechanical properties of both Zr based BMGs and the tungsten fiber reinforced metallic glass matrix composite (Wf/Zr-BMG) are studied experimentally. Five aspects are included.(1) Quasi-static and dynamic compressive experiments are performed on Zr-BMG at four temperatures from 77K to 473K. It shows that the yield stress is sensitive to strain rate and temperature. An typical vein-like pattern formed by the flow of the melted material is observed on the shear fracture surface, and an slurry like one is observed when the temperature rises to 473K.(2) As for W_f/Zr-BMG, we firstly studied the influences of infiltration temperature, fiber diameter (Φ) and volume fraction (V_f) to the properties of composite. It is found that the composite obtained under infiltration temperature of 711K with Φ=250μm, V_f=60% has the best performances in general. With V_f increasing, the strength and toughness of W_f/Zr-BMG are increased and the fracture mode of specimen is changed from shear to vertical cleavage with fiber buckling and splitting. This axial cracking runs from fiber to fiber along the interface in a zigzag path. The mixed failure mode of shear and vertical cleavage is found under dynamic loading.(3) The same strain rate and temperature sensitivity experiments are performed on W_f/Zr-BMG. The result indicate that the yield strength increases while the failure strain decreases with decreasing temperature. The dynamic compression shows that the yield stress is higher than that of the corresponding quasi-static compression. Vein-like patter is found again on the shear fracture surfaces, but the melted shear bands are more viscous when更多还原