Characteristic of improved fatigue performance for Zr-based bulk metallic glass matrix composites (original) (raw)

Tension-Tension-Fatigue Behaviors of a Zr-Based Bulk-Metallic-Glass-Matrix Composite

Metallurgical and Materials Transactions A, 2011

An improved tension-fatigue limit of 473 MPa is gained for Zr 58.5 Ti 14.3 Nb 5.2 Cu 6.1 Ni 4.9 Be 11.0 bulk-metallic-glassmatrix composites (BMGMCs). High volume-fraction dendrites within the glass matrix induce increased effectiveness on the blunting and propagating resistance of the fatigue-crack tip. Each fine striation is created during one stress cycle on the basis of analysis of experiments and calculations. A distinguishingly decreased crack-growth rate for the BMGMCs, compared to the monolithic BMGs, prevails, due to the plastic deformation of the dendrites, evidenced by the synchrotron X-ray results.

A Highly Fatigue-Resistant Zr-Based Bulk Metallic Glass

The strength-normalized fatigue endurance strength of the bulk metallic glass (BMG) Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (Vitreloy 105) has been reported to be the highest for any BMG; however, to date, there has been no explanation of why this material is so much better than other Zr-based compositions. In this study, the fatigue-crack growth behavior of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 was compared in ambient air vs dry nitrogen environment. The excellent fatigue life behavior is attributed to a relatively high fatigue threshold (DK TH % 2 MPaÖm) and a lack of sensitivity to environmental effects on fatigue-crack growth in ambient air, as compared to other Zr-based BMGs. Fatigue life experiments conducted in ambient air confirmed the excellent fatigue life properties with a 10 7 -cycle endurance strength of~0.24 of the ultimate tensile strength; however, it was also found that casting porosity, even in limited amounts, could reduce this endurance strength by as much as~60 pct. Overall, the BMG Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 appears to have excellent strength and fatigue properties and should be considered as a prime candidate material for future applications where good mechanical fatigue resistance is required.

Mechanisms of Fatigue Damage Formation and Evolution in Zr-Based Bulk Metallic Glass

Zr-based bulk metallic glasses (BMGs) are surprisingly susceptible to cyclic fatigue processes. However, the mechanisms of fatigue damage initiation and evolution in bulk metallic glasses (BMGs) are not well understood, limiting their use in safety-critical structural applications. We present recent experimental and modeling studies of both the initiation of fatigue damage obtained from stress-life experiments on smooth specimens, and the growth of fatigue cracks measured under stable and transient cyclic loading conditions.

Effects of loading modes on the fatigue behavior of Zr-based bulk-metallic glasses

Journal of Alloys and Compounds, 2009

The fatigue behavior of a Zr-based bulk-metallic glass (BMG), Zr 50 Cu 37 Al 10 Pd 3 (in atomic percent), was systematically investigated under uniaxial tension-tension, uniaxial compression-compression, and bending loading. The fatigue results show that the fatigue limits of Zr 50 Cu 37 Al 10 Pd 3 under tension-tension and compression-compression loading are comparable. However, the fatigue lifetimes above the fatigue limit under compression-compression loading are longer than that under tension-tension loading. Similarly, Zr 50 Cu 37 Al 10 Pd 3 demonstrates the comparable fatigue limits and lifetimes under three-and four-point bending loading. In addition, the fatigue-endurance limits of Zr 50 Cu 37 Al 10 Pd 3 under tension-tension and compression-compression loading were found to be greater than those under three-and four-point bend loading. The influence of the loading mode on the fatigue behavior of Zr-based BMGs is clarified.

Enhanced Plasticity of Zr-based Bulk Metallic Glass Matrix Composite with Ductile Reinforcement

Journal of Materials Research, 2005

A composite material containing uniformly distributed micrometer-sized Nb particles in a Zr-based amorphous matrix was prepared by suction cast. The resulting material exhibits high fractured strength over 1550 MPa and enhanced plastic strain of about 29.7% before failure in uniaxial compression test at room temperature. Studies of the serrations on the stress–strain curves and the shear bands on the fractured samples reveal that the amplitude of the stress drop of each serration step corresponds to the extent of the propagation of a single shear band through the materials. The composite exhibits more serration steps and smaller amplitude of stress drop due to the pinning of shear band propagation by ductile Nb particles.