Topic
Fractography
About: Fractography is a research topic. Over the lifetime, 5043 publications have been published within this topic receiving 86068 citations.
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TL;DR: In this paper, the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets was investigated with the aim of reviewing the effects of microstructures on fatigue properties where suboptimal microstures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding.
Abstract: The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicular martensite, Widmanstatten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstatten, and acicular martensite microstructure.
42 citations
TL;DR: In this paper, the tensile fractography of an AI-20Si-3Cu-1 Mg alloy was investigated using optical and electron microscopy, and related to the processing conditions and tensile behavior of the alloy at room and elevated temperatures.
Abstract: The tensile fractography of an AI-20Si-3Cu-1 Mg alloy consolidated from rapidly solidified powder by extrusion has been investigated using optical and electron microscopy, and related to the processing conditions as well as the tensile behaviour of the alloy at room and elevated temperatures. The alloy studied shows distinct fracture features owing to the presence of dispersed silicon crystal particles with a bimodal distribution in size and of prior powder particle boundaries in the extrudate. It has been found that at room temperature cracks initiate by cracking the primary silicon crystal particles. Crack propagation occurs along the interfaces between the eutectic silicon crystal particles and the matrix and also between the prior powder particles, where microvoids are formed by the interfacial decohesion. At 300 °C, the fracture of the alloy involves microvoid nucleation, growth and coalescence at the interfaces between the silicon crystal particles and the aluminium matrix and between the prior powder particles. It has also been observed that the fractographic features of the alloy correspond well to the processing conditions including extrusion temperatures and subsequent heat treatment. The importance of minimizing the coarsening of the silicon crystals in processing in order to use the full strength potential of the alloy investigated is emphasized.
42 citations
TL;DR: In this paper, the effect of grain size on fatigue crack growth was examined on aluminium magnesium alloy Al 5754 with four different grain sizes in order to examine the impact of grain sizes on fatigue cracks.
Abstract: Fully reversed uniaxial fatigue tests were performed on aluminium magnesium alloy Al 5754 with four different grain sizes in order that the effect of grain size on fatigue crack growth could be examined. Surface cracks were monitored by a plastic replication technique. Fatigue strength was shown to improve with a decrease in grain size. The endurance stress is a function of the inverse square root of the grain size and is described empiricdty by a Hall-Petch type relation. The effect of grain size on fatigue crack growth is most significant when the crack length is of the order of the microstructure. Fluctuations in the growth rate of microstructurally short cracks are most marked in a fine grained microstructure and may be related to the need to transfer slip to adjacent grains. Crack path deviation is greatest in the coarsest grained microstructure and SEM fractography reveals a more pronounced crack surface roughness in the coarser grained alloy than in the finer grained alloy.
42 citations
TL;DR: In this article, the initiation and propagation of cracks and its geometric specifications were determined and a three-dimensional boundary element method was used for fatigue crack growth under stress field, and the modified Paris model was used to estimate fatigue cracks growth rates.
42 citations
TL;DR: In this article, the fracture toughness of bainitic ductile iron transformed at various austempering temperatures and times was evaluated by using compact tension specimens and compared with the fracture strength of bulleye casting structure.
Abstract: — The fracture toughness of bainitic ductile iron transformed at various austempering temperatures and austempering times was evaluated by using compact tension specimens and compared with the fracture toughness of bulleye casting structure. Using Scanning Electron Microscopy, the mechanism of the fracture mode can be understood by observing the fracture surface. An X-ray diffractometer was used to determine the volume fraction of retained austenite. From the results of fracture toughness properties, it can be concluded that the most suitable austempering temperature of the material used in the present study is from 300 to 350°C.
42 citations