Cyclic-Loading Induced Lattice-Strain Asymmetry in Loading and Transverse Directions

Cyclic-loading effects on a nickel-based superalloy are investigated with in-situ neutron-diffraction measurements. The temperature evolution subjected to cyclic loading is estimated based on the lattice-strain evolution. The calculated thermoelastic responses are compared with the measured bulk temperature evolution. Two transitions in the temperature-evolution are observed. The first transition, observed with the neutron-measurement results, is associated with the cyclic hardening/softening-structural transformation. The second transition is observed at a larger number of fatigue cycles. It has a distinct origin and is related to the start of irreversible structural transformations during fatigue. A lattice-strain asymmetry behavior is observed. The lattice-strain asymmetry is quantified as a grain-orientation-dependent transverse/loading parameter. This strain-asymmetry evolution reveals the irreversible plastic deformation subjected to fatigue. The irreversible fatigue phenomena might relate to the formation of the microcracks. At elevated temperatures, the cyclic hardening/softening transition starts at lower fatigue cycles as compared to room temperature. A comparison between the room-temperature and the elevated-temperature fatigue experiments is performed. The asymmetry-parameter evolutions show the same irreversible trends at both the room and elevated temperatures.     

The energetic NeUtral Atom Detector Unit (NUADU) for China''s Double Star Mission and its calibration

An account is provided of an advanced Energetic NeUtral Atom Detector Unit (NUADU) designed for China's Double Star Mission. Special emphasis is given to describing the detector head of the instrument and its calibration.     

Effect of Process and Structural Factors on the Mechanical Properties of Titanium Sintered from Titanium Hydrides

Powder Metallurgy and Metal Ceramics - The paper examines how the preliminary grinding of titanium hydride and the sintering temperature influence the mechanical characteristics of resultant...     

The Influence of the Composition and Particle Size of Starting Titanium Hydride Powders on the Consolidation of Titanium Under Sintering

Powder Metallurgy and Metal Ceramics - The influence of the starting powder composition, grinding conditions, and sintering temperature on the compaction mechanism under sintering and the porosity...     

Mechanical properties of eutectic alloys β-NiAl + γ-Re and spray coatings

We have studied the structure and mechanical properties of eutectic alloys β-NiAl + γ-Re of the ternary system Ni-Al-Re. We have established that the best combination of mechanical characteristics, determined by local loading with a rigid indentor, is exhibited by the alloy containing 2.5 at.% Re, the structure of which consists of the eutectic β-NiAl + γ-Re. Rhenium inclusions can inhibit movement of cracks in the material, and also can play the role of traps for cracks. Brittle intercrystallite fracture is characteristic of the alloy consisting of one-phase intermetallic NiAl. Mixed fracture is typical of the eutectic alloy β-NiAl + γ-Re, with transcrystallite cleavage predominating. We have shown that plastic interlayers of a rhenium phase within the microstructure increase the crack resistance of a detonation coating made from eutectic alloys β-NiAl + γ-Re. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 78–87, March–April, 2006.     

Physical–mechanical properties of coatings by spraying with a hydrogen–oxygen flame

The results of metallographic studies of gas flame coatings, produced by spraying with powder materials using acetylene–oxygen and hydrogen–oxygen flames, are presented. Special features of bonding of the sprayed metal and the parent metal of the components are described and the structural changes in porosity in the surface layer of the components are analysed.     

Interphase Strain Gradients in Multilayered Steel Composite from Microdiffraction

Multilayered steel composites consisting of alternating martensite and austenite layers and exhibiting a combination of high strength and ductility were successfully fabricated. To understand the microplasticity mechanisms responsible for such exceptional mechanical behavior, 3D X-ray microscopy with a submicron beam size was employed to probe the stress/strain distribution within the top two layers during incremental tensile loading. The 3D depth-dependent strain gradients were monitored in situ near the martensite/austenite interfaces as a function of the load level. It was observed that the strain gradients redistributed during loading. Specifically, large compressive strains developed in the top martensite layer transverse to the loading direction, while small tensile strains were found across the layer interface into the underneath austenite layer.