Department of Mechanical Engineering & Materials Science, Yale University, New Haven, Connecticut 06511, USA.
Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072, China.
Phys Rev Lett. 2015 Dec 31;115(26):265502. doi: 10.1103/PhysRevLett.115.265502. Epub 2015 Dec 22.
We studied the effect of crystallization on the embrittlement of bulk metallic glasses. Specifically, we measured fracture toughness for Zr(44)Ti(11)Cu(10)Ni(10)Be(25) and Pd(43)Cu(27)Ni(10)P(20) after annealing at various times to introduce controlled volume fraction of crystallization. We found that crystallization of up to ∼6% by volume does not measurably affect fracture toughness. When exceeding ∼6%, a dramatic drop in fracture toughness occurs; an additional 1% of crystallization reduces fracture toughness by 50%. Such a dramatic transition can be explained by the interaction among the crystals' stress fields in the amorphous matrix that becomes effective at ∼7% crystallinity. Our findings of a critical crystallization for embrittlement of metallic glasses help in designing tough metallic glasses and their composites, as well as defining processing protocols for the unique thermoplastic forming of metallic glasses to avoid embrittlement.
我们研究了结晶对块状金属玻璃脆化的影响。具体来说，我们测量了 Zr(44)Ti(11)Cu(10)Ni(10)Be(25) 和 Pd(43)Cu(27)Ni(10)P(20) 在不同退火时间下的断裂韧性，以引入受控的体积分数结晶。我们发现，体积分数高达约 6%的结晶不会显著影响断裂韧性。当超过约 6%时，断裂韧性会急剧下降；结晶增加 1%，断裂韧性会降低 50%。这种显著的转变可以通过在约 7%的结晶度下，晶体的应力场在非晶基体中的相互作用来解释。我们发现金属玻璃脆化的临界结晶有助于设计韧性金属玻璃及其复合材料，并为避免脆化定义金属玻璃独特的热塑性成形的加工方案。
