Title of article :
Ductile to brittle transition in the Zr41.2Ti13.75Cu12.5Ni10Be22.5 bulk metallic glass
Author/Authors :
Raghavan، نويسنده , , R. and Murali، نويسنده , , P. and Ramamurty، نويسنده , , U.، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2006
Pages :
4
From page :
1051
To page :
1054
Abstract :
The variation of impact toughness, Γ, of a Zr41.2Ti13.75Cu12.5Ni10Be22.5 (Vitreloy-1) bulk metallic glass (BMG) within the temperature range of 123–423 K was evaluated by using an instrumented Charpy impact testing machine, in order to examine if the BMGs exhibit ductile-to-brittle transition (DBT) that is seen in rapidly quenched glasses. Results show an abrupt reduction in Γ when the testing temperature is lowered to below 150 K, implying that the BMGs are also prone to the DBT. Fractographic observations indicate a transition in the fracture mode; from ductile vein-like morphology above DBT to a cleavage-dominant fracture mode below it. Complimentary Vickers indentation measurements show no variation in hardness with temperature. However, the shear banded plastic regions that are typically seen around the indents were observed to be completely absent around the indents that were made at low temperatures, indicating that the inhomogeneous plasticity mediated by shear bands becomes inoperative below a critical temperature resulting in the DBT. This observation suggests that the minimum amount of free volume required for extensive plasticity (and hence high toughness) in metallic glasses is strongly dependent on the temperature. Testing of the structurally relaxed samples (through annealing at 530 K for 2.5 h that induces severe embrittlement at room temperature) at 423 K reveal almost complete recovery of Γ, supporting this hypothesis.
Keywords :
B. Brittleness and ductility , F. Mechanical testing , metallic , B. Glasses
Journal title :
Intermetallics
Serial Year :
2006
Journal title :
Intermetallics
Record number :
1503627
Link To Document :
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