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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, a fractographic study has been carried out on transgranular stress-corrosion cracks produced in both tensile and bend specimens of a Mg-7.5 Al alloy tested in an aqueous NaCl-K2CrO4 solution.
Abstract: A fractographic study has been carried out on transgranular stress-corrosion cracks produced in both tensile and bend specimens of a Mg-7.5 Al alloy tested in an aqueous NaCl-K2CrO4 solution. It is concluded that the complex fractography reported in earlier papers is fully consistent with the view that failure occurs basically by cleavage on planes. Thus the coarse markings reported previously are shown to correspond to a stepped or pfeated topography consisting of alternate faces produced by cleavage and ductile rupture parallel to (0001), the latter exhibiting flutings of the type observed in other HCP alloys. The reasons for the occurrence of the ductile component are discussed.

37 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the creep rupture behavior of lead-free solders at three temperatures ranging from room temperature (RT) to 90 °C, under a tensile stress range of σ/E=10−4 to 10−3.
Abstract: The aim of this study is to investigate the creep rupture behavior of lead-free Sn-3.5Ag and Sn-3.5Ag-0.5Cu solders at three temperatures ranging from room temperature (RT) to 90 °C, under a tensile stress range of σ/E=10−4 to 10−3. The ultimate tensile strength (UTS) and creep resistance were found to be decreased with increasing temperature for each given lead-free solder. Both the binary and ternary Ag-containing alloys exhibited superior UTS and creep strength to the conventional Sn-37Pb solder at a similar temperature. Due to a more uniform distribution of eutectic phases and a larger volume fraction of intermetallic compounds (IMCs), the Sn-3.5Ag-0.5Cu alloy had greater UTS and creep strength than did the eutectic Sn-3.5Ag solder at each testing temperature. The stress exponents (n) of minimum strain rate (˙emin) were decreased from 7 and 9 at RT to 5 and 6 at 60 and 90 °C, for the binary and ternary lead-free alloys, respectively. Fractography analyses revealed typical rupture by the nucleation and growth of voids/microcracks at IMCs on the grain boundaries. Both Monkman-Grant and Larson-Miller relationships showed good results in estimating the rupture times under various combinations of applied stress and temperature. A model, using a term of applied stress normalized by Young’s modulus, was proposed to correlate the rupture times at various temperatures and could explain the rupture time data reasonably well for the given two lead-free solders.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the room-temperature tensile and high-cycle fatigue behavior of orthorhombic Ti-22Al-27Nb alloy with varying lamellar morphology was investigated.
Abstract: The room-temperature tensile and high-cycle fatigue (HCF) behavior of orthorhombic Ti-22Al-27Nb alloy with varying lamellar morphology was investigated. Varying lamellar morphology was produced by changing the cooling rate after annealing in the single B2 phase region. A slower cooling rate of 0.003 K/s, for example, resulted in several large packets or colonies of similarly aligned O-phase lamellae and a nearly continuous massive α 2 phase at the prior B2 grain boundaries, while a faster cooling rate of 0.1 K/s led to the refinement of colony sizes and the O-phase lamellae. The interface of O-phase lamellae and B2 phases was semicoherent. Water quenching produced a very fine tweed-like microstructure with a thin continuous O phase at the prior B2 grain boundaries. The 0.2 pct yield stress, tensile strength, and HCF strength increased with increasing cooling rate. For example, the tensile strength and HCF strength at 107 cycles of 0.003 and 0.1 K/s-cooled were 774 and 450 MPa, and 945 and 620 MPa, respectively. Since the fatigue ratio, which is the ratio of HCF strength at 107 cycles to tensile strength, did not show a constant value, but instead increased with increasing cooling rate, part of the fatigue improvement was the result of improved resistance to fatigue associated with the microstructural refinement of the lamellar morphology. Fatigue failure occurred by the subsurface initiation, and every initiation site was found to contain a flat facet. Concurrent observation of the fatigue initiation facet and the underlying microstructure revealed that the fatigue crack initiated in a shear mode across the colony, irrespective of colony size, indicating that the size of the initiation facet corresponded to that of the colony. Therefore, the colony size is likely a major controlling factor in determining the degree of fatigue improvement due to the microstructural refinement of lamellar morphology. For the water-quenched specimens, fatigue crack initiation appeared to be associated with shear cracking along the boundary between the continuous grain boundary O phase and the adjacent prior B2 grain.

37 citations

Journal ArticleDOI
TL;DR: Carbon nanotubes (CNTs), grown by chemical vapor deposition, improved the interlaminar strength of composites, as shown by a mode I double cantilever beam test as discussed by the authors.
Abstract: Carbon nanotubes (CNTs), grown by chemical vapor deposition, improved the interlaminar strength of composites, as shown by a mode I double cantilever beam test. Failed specimens were inspected with a scanning electron microscope to determine the failure modes using fractography. The key findings indicated that exposure to high temperature must be limited to prevent fiber damage, and nanotubes longer than two times the fiber diameter reduce interlaminar strength, while high densities of short nanotubes improve interlaminar strength. Gains of up to 29.4% in glass, and 36.2% in IM7 are seen.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the mechanical behavior of pure tungsten and its alloys (2.5% Y2O3 and 4.5%) was compared in the temperature interval of 25°C to 1000°C.

37 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023120
2022254
2021229
2020206
2019205
2018176