Thermal and mechanical properties of Cu60−xZr25Ti15Nix bulk metallic glasses with x=0, 1, 3, 5, 7, 9 and 11 at.%

Suh

et al. 2015

In order to improve mechanical properties of Ti-based amorphous matrix composites basically composed of ductile b-Ti dendrites and brittle amorphous matrix by overcoming their inherent brittle nature, their fracture mechanisms should be verified in relation with microstructure, stress intensity factor level, and crack growth rate. In this study, thus, detailed fractographic observations including the unique appearance of lamellar cleavage patterns, which has not been reported in previous studies on conventional metals and alloys, were conducted. According to fractographic results, lamellar cleavage patterns were formed by repeated interruptions of crack propagation on {100} cleavage planes by difference between dendrite orientation and loading direction. Ductile-to-brittle transition phenomenon (ductile dimpled fracture fi lamellar cleavage fracture fi ordinary cleavage fracture in dendrite areas, and vein pattern fi smooth pattern in amorphous matrix areas) occurred with increasing crack growth rate was also plausibly explained by the concept of time required for crack growth as well as dendrite orientation.

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Section: Recently Advances In Bulk Amorphous Alloysmentioning

confidence: 99%

Unique Appearance of Lamellar Cleavage Patterns on Fracture Surfaces of Ti-Based Amorphous Matrix Composite

Suh

et al. 2015

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“…[21] Microfracture processes were directly observed by using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber, and microfracture mechanisms were investigated by focusing on how dendrites affect the initiation and propagation of cracks. [22][23][24][25] This experiment enabled us to examine the crack initiation and propagation behavior occurring at a sharp notch tip and to study the R-curve behavior in which the fracture resistance increases with the crack growth. [26,27] II.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of Fracture Toughness and R-Curve Behavior by Direct Observation of Microfracture Process in Ti-Based Dendrite-Containing Amorphous Alloys

et al. 2015

Fracture properties of Ti-based amorphous alloys containing ductile b dendrites were explained by directly observing microfracture processes. Three Ti-based amorphous alloys were fabricated by adding Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy by a vacuum arc melting method. The effective sizes of dendrites varied from 63 to 104 lm, while their volume fractions were almost constant within the range from 74 to 76 pct. The observation of the microfracture of the alloy containing coarse dendrites revealed that a microcrack initiated at the amorphous matrix of the notch tip and propagated along the amorphous matrix. In the alloy containing fine dendrites, the crack propagation was frequently blocked by dendrites, and many deformation bands were formed near or in front of the propagating crack, thereby resulting in a zig-zag fracture path. Crack initiation toughness was almost the same at 35 to 36 MPaÖm within error ranges in the three alloys because it was heavily affected by the stress applied to the specimen at the time of crack initiation at the crack tip as well as strength levels of the alloys. According to the R-curve behavior, however, the best overall fracture properties in the alloy containing fine dendrites were explained by mechanisms of blocking of the crack growth and crack blunting and deformation band formation at dendrites.

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“…Under dynamic loading, the resistance to deformation or fracture is generally reduced in comparison with quasi-static loading cases, and localized deformation often occurs in a highly narrowed region. [21][22][23][24][25] According to Qiao et al [26] on the dynamic compressive behavior of Zr-based amorphous alloys, multiple shear bands were not sufficiently formed under dynamic loading, which resulted in lower plastic strains than those measured under quasi-static loading. Jeon et al [27] investigated the dynamic compressive behavior of Ti-based amorphous composites, and found that dendrites played an important role in improving the ductility by forming deformation bands.…”

mentioning

confidence: 99%

Effects of Effective Dendrite Size on Dynamic Tensile Properties of Ti-Based Amorphous Matrix Composites

Park

et al. 2016