1,359,266 research outputs found
Anomalous kinetics of lath martensite formation in stainless steel
No full textThe kinetics of lath martensite formation in Fe-17·3 wt-%Cr-7·1 wt-%Ni-1·1 wt-%Al-0·08 wt-%C stainless steel was investigated with magnetometry and microscopy. Lath martensite forms during cooling, heating and isothermally. For the first time, it is shown by magnetometry during extremely slow isochronal cooling that transformation rate maxima occur, which are interrupted by virtually transformation free temperature regions. Microscopy confirms martensite formation after athermal nucleation of clusters followed by their time dependent growth. The observations are interpreted in terms of time dependent autocatalytic lath martensite formation followed by mechanical stabilisation of austenite during the transformation process
The kinetics of lath martensitic transformation
No full textThe multicomponent solution thermodynamics, a model for barrierless heterogeneous martensitic nucleation, a model for the composition and temperature dependence of the shear modulus, and a set of unique interfacial kinetic parameters are integrated to model the kinetics of lath martensitic transformation. It is shown that in multicomponent alloys can be predicted within 40K. The geometrie partitioning of austenite grain and the dependence of average lath volume on the fraction transformed is established by a careful analysis of lath microstructure. The main contribution of lath martensitic transformation is due to autocatalytically generated defects
Modeling dislocation interactions with grain boundaries in lath martensitic steels
No full textMartensitic steels are widely used as a structural material in critical components of fossil fuel and nuclear power plants, such as boilers, pipes, and fittings. Martensitic steels are known to have a hierarchical microstructure that follows the Kurdjumov–Sachs (K–S) orientation relationship, where a prior austenite grain is composed of packets separated by high angle grain boundaries or packet boundaries, which are, in turn, divided into blocks or variants segregated by high angle grain boundaries called block boundaries. Blocks themselves are an agglomeration of laths divided by low angle grain boundaries named lath boundaries which have precipitates scattered on them. This work seeks to examine, using a couple dislocation dynamics—continuum mechanics approach called multiscale dislocation dynamics plasticity (MDDP), the interactions between dislocations and packet, block, lath boundaries, and precipitates under uniaxial tension loading and their effect on the mechanical response of the material. The simulations are conducted at a strain rate of 105 s−1 at room temperature. The main crystallographic features that arise during the deformation process were extracted and analyzed in terms of their contribution to the mechanical response of the material. The orientation relationship governing the microstructure of martensitic steels, namely, the K–S orientation relationship, was incorporated in MDDP in an effort to accurately capture the deformation behavior of the material in question. The strength of lath martensitic steel was analyzed as a function of the lath width, block size, and packet size to determine the appropriate effective grain size. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature
Buck Tavern lath framing
No full textThis negative shows a close view of the lath framing inside the walls of the Buck Tavern
Buck Tavern lath framing
No full textThis negative shows a close view of the lath framing inside the walls of the Buck Tavern
Lath martensite substructure evolution in low-carbon microalloyed steels
No full textLath martensite substructures in as-quenched plain carbon steels exhibit dislocation-like contrast in the transmission electron microscope. More recent observations reported internal twins and nanoscale auto-tempered intra-lath carbides as additional lath substructures in ultra-low-C binary Fe–C steels. Modern microalloyed steels often have similar ultra-low C contents besides microalloying elements like Ti, Nb or V and, more recently, Mo, to achieve high strength, toughness and weldability. Nonetheless, little is known about the lath substructure evolution in the as-quenched state of microalloyed steels. This study investigates the hierarchical martensite substructure evolution post-quenching of microalloyed Nb and NbMo steels with 0.1 wt% C. Hierarchical microstructure characterization was done using scanning and transmission electron microscopy, and electron backscatter diffraction methods including parent grain reconstructions with MTEX. Thermokinetic simulations using MatCalc to determine the carbide evolution during auto-tempering were corroborated with site-specific transmission electron microscopy. Mo addition led to lowering of the martensite start temperature, yet the Nb steel showed a finer hierarchical microstructure. Finer laths with in-lath dislocations, short and long twins, and lath boundary decoration of carbides were found in the Nb steel. Conversely, laths in the NbMo were wider, with frequent intra-lath auto-tempered precipitates in the vicinity of dislocations, without twins
Lath Palace
No full textKoi (carp) in Lilly Pond outside the Botanical Building; Built for the 1915-1916 Exposition, along with the adjacent Lily Pond, the historic building is one of the largest lath structures in the world. The Botanical Building plantings include more than 2,100 permanent plants including collections of cycads, ferns, orchids, other tropical plants, and palms. The first drawing for the building by Carleton M. Winslow, Goodhue's architect on site, shows another ornate Spanish-Renaissance front and lateral wings, but the end design was more simplified and functional. Steel trusses in vaults and dome support 70,000 feet of redwood lath (used to shade the plantings), which is curved to conform to the shape of the building. The Lily Pond is a result of Goodhue's exposure to reflecting pools on a trip to Persia in 1902. The structure was restored and repainted in 2002. (The dark brown color is not original). Source: San Diego History Center; https://www.sandiegohistory.org/ (accessed 7/24/2013
Microstructure of ausformed lath martensite in 18%Ni maraging steel
No full textThe microstructure of ausformed lath martensite in 18%Ni maraging steel was studied by analyzing electron backscatter diffraction pattern obtained by scanning electron microscopy and Kikuchi diffraction pattern obtained by transmission electron microscopy. In non-ausformed lath martensite structure, blocks and packets are clearly observed by optical microscopy. By ausforming of 60% at 773 K, packet and block widths of lath martensite decrease whereas the packet is elongated along rolling direction. A packet of ausformedlath martensite contains some laths which belong to a crystallographically different packet. The dislocation density in ausformed lath martensite is higher than that in conventional lath martensite. It is concluded that ausforming refines the effective grain size and increases the dislocation density in lath martensite structure
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