Fractography

About: Fractography is a research topic. Over the lifetime, 5043 publications have been published within this topic receiving 86068 citations.

Effect of Fe content on fracture behavior of Ni–Mn–Fe–Ga ferromagnetic shape memory alloys

Abstract: The effect of Fe content on hardness and toughness of Ni48.7Mn30.1−xFexGa21.2 (x = 0–11, number indicates at.%) alloys is investigated and the relationship between the fracture toughness and the fractography is discussed by observing the fracture morphology and analyzing the propagation of the crack. The micro-Vickers hardness results indicate that the hardness increases with increasing Fe content. The fracture toughness results indicate that Fe doping has improved the toughness of Ni–Mn–Ga alloys, and the toughness increases with increasing Fe content in Ni48.7Mn30.1−xFexGa21.2 (x = 0–11) alloys. Fracture morphology shows typical intergranular fracture with rock candy pattern in the Ni48.7Mn30.1Ga21.2 (x = 0) and river pattern cleavage fracture facets in the Ni48.7Mn19.1Fe11Ga21.2 (x = 11) alloy. The fracture type changing from intergranular fracture to transgranular fracture is the main reason for the improved toughness of Ni–Mn–Ga alloys by addition of Fe.

R-Curve characterization of the fracture toughness of nanocrystalline nickel thin sheets

Abstract: The fracture resistance curves of nanocrystalline nickel and carbon doped nanocrystalline nickel for different annealing temperatures have been generated and studied. The results indicate that crack growth resistance of pure nanocrystalline nickel is very sensitive to annealing temperatures. The crack growth resistance decreased with increasing annealing temperature for the nanocrystalline nickel. Carbon doping greatly reduces crack growth resistance of nanocrystalline nickel. However, the crack growth resistance of carbon-doped nanocrystalline shows improvement through annealing processing. A cluster model was used to explain the crack growth resistance behavior of nanocrystalline nickel.

Relationship between mechanical properties, microstructure, and fracture topography in α + β titanium alloys

Abstract: The influence of forging schedule and subsequent heat treatment on the microstructure and mechanical properties of three a + β titanium alloys has been investigated. The alloys studied were Ti-6Al-4V, Ti-6Al-6V-2Sn, and Ti-6Al-2Sn-4Zr-6Mo. The microstructural comparisons included (a +β) finished and β-processed material, variations in primary a volume fraction, primary a particle aspect ratio, and the nature of the transformation products. Careful selection of forging history and heat treatment permitted comparisons of fracture properties at essentially constant strength levels. This paper describes the influence of forging and heat treatment on the microstructure of these alloys as shown by light and thin foil electron microscopy. The microstructural information was then used to analyze the variations in topography of both fatigue and fast fracture regions as observed by scanning electron microscopy. In some cases, good correlation between fracture topography and microstructure has been established but such correlations depend on microstructure and on loading conditions. For example, fast fracture in the β-processed materials occurs largely along prior β-phase grain boundaries, whereas fatigue cracks propagate by a predominantly transgranular mode. Further, the occurrence of fatigue striations strongly depends on microstructure and on the cyclic stress intensity, with cyclic cleavage predominating at low growth rates in those alloy conditions containing primary a particles which have at least one dimension greater than ∼25 μm. Other correlations between fracture topography, microstructure, and properties were obtained and comments for microstructure selection to control properties are included.

Mechanical Properties and Failure Analysis of Alumina‐Glass Dental Composites

Abstract: Strength measurements and fractography were used to investigate the failure of alumina-glass dental composites containing 75 vol% alumina and 25 vol% glass. Alumina compacts were prepared by slip casting and sintering at 1100°C for 2 h. Dense composites were made by infiltrating partially sintered alumina with glass at 1150°C for 8 h. Young's modulus and the hardness of the composites were 270 GPa and 12 GPa, respectively. The mean strength (460 MPa) and fracture toughness (4.0 MPa·m1/2) of the composites were insensitive to the glass thermal expansion coefficient (αglass= 5.9 × 10−6 to 7.8 × 10−6°C−1). Typical flaws were pores and cracklike voids formed by poor particle packing and differential sintering near agglomerates of alumina in the composite. Crack deflection and crack bridging were observed in indentation cracks. Fracture toughness was single-valued because the alumina particle size was small (∼3 μm). Alumina-glass composites are promising new ceramics for dental crown and bridge applications, because their strength and fracture toughness are ∼2 times greater than those of current dental ceramics.