Observations on metallurgical bonding between plasma sprayed tungsten and hot tungsten substrates

Metallurgical bonding between plasma sprayed tungsten & hot tungsten substrates - interface & recrystallizatio

Processing and mechanical properties of magnesium-lithium composites containing steel fibers

Deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers were prepared by infiltrating a preform of steel wool with the molten matrix. The Li content was varied to control the crystal structure of the matrix; Mg-4 wt pct Li is hexagonal close packed (hcp), while Mg-12 wt pct Li is body-centered cubic (bcc). The low carbon steel used as the reinforcing fiber is essentially bcc. The hcp/bcc and bcc/bcc composites were subsequently deformed by rolling and by extrusion/swaging and mechanically tested to relate the tensile strength of the composites to true deformation strain. The hcp/bcc composites had limited formability at temperatures up to 400 °C, while the bcc/bcc composites had excellent formability during sheet rolling at room temperature but limited formability during swaging at room temperature. The tensile strengths of the hcp/bcc composite rod and the bcc/bcc composite sheet and rod increased moderately with deformation, though less than predicted from rule-of-mixtures (ROM) calculations. This article presents the experimental data for these DMMC materials and comments on the possible effect of texture development in the matrix and fiber phases on the deformation characteristics of the composite material

High strength-high conductivity Cu--Fe composites produced by powder compaction/mechanical reduction

A particulate mixture of Cu and Fe is compacted and mechanically reduced to form an in-situ Cu-Fe composite having high strength and high conductivity. Compaction and mechanical reduction of the particulate mixture are carried out at a temperature and time at temperature selected to avoid dissolution of Fe into the Cu matrix particulates to a harmful extent that substantially degrades the conductivity of the Cu-Fe composite

Hall effect and transmission electron microscopy of epitaxial MnSi thin films

We present Hall effect measurements on MnSi/Si(111) epilayers and find an anomalous Hall contribution that is significantly smaller than in bulk crystals, which enables the observation of an additional contribution to the anomalous signal previously overlooked in MnSi. Our measurements indicate the signal is not due to skyrmions in MnSi thin films, which are absent in out-of-plane fields, but rather are the result of scattering from the cone phase. The absence of magnetic contrast in the transmission electron microscopy (TEM) measurements are consistent with this interpretation. We provide a method to model TEM images of skyrmions lattices to determine the conditions necessary for their observation in other B20 epilayers with an anisotropy that is favourable to their formation.T.L.M. and M.N.W. acknowledge support from NSERC and the support of the Canada Foundation for Innovation, the Atlantic Innovation Fund, and other partners which fund the Facilities for Materials Characterization, managed by the Institute for Research in Materials. Work done by J.C.L. was funded by the Royal Society. The work of F.N.R. was supported by RFBR, research project No. 14-02-31012.This is the accepted manuscript of a paper published in Physical Review B (SA Meynell, MN Wilson, JC Loudon, A Spitzig, FN Rybakov, MB Johnson, TL Monchesky, Physical Review B 2014 90, 224419)

Everglades Ridge, Slough, and Tree Island Mosaics: Year 2 Annual Report

Status and history of the Ridge-Slough Mosaic The Florida Everglades is a large subtropical wetland with diverse hydrologic, edaphic, and vegetative characteristics. Historically, a significant portion of this system was a slow moving river originating from the Kissimmee River floodplain, flowing into the vast but shallow Lake Okeechobee, and draining south-southwest over extensive peatlands into Florida Bay (McVoy 2011). Human-induced alterations to the hydrologic regime, including reduction, stabilization, and impoundment of water flow through diversion and compartmentalization of water via canals and levees have degraded pre-drainage vegetation patterns and microtopographic structure (Davis and Ogden 1994, Ogden 2005, McVoy 2011). The Everglades peatland emerged 5,000 years ago with the stabilization of sea level at approximately current elevations (Loveless 1959, Gleason and Stone 1994). This, combined with subtropical rainfalls, allowed a vast mass of water to slowly flow over a limestone bedrock platform 160 km long and 50 km wide at a near uniform descent totaling about 6 m, ultimately reaching Florida Bay (Stephens 1956, Gleason and Stone 1994, McVoy 2011). Vegetation quickly colonized the area, and peat, in the absence of adequate respiration, accumulated on the limestone bedrock to a depth of 3-3.7 m (Gleason and Stone 1994, McVoy et al. 2011). The “River of Grass” referenced by Douglas (1947) alludes to the dually intertwined processes of the historic riverine nature of the Everglades and the vast sawgrass (Cladium jamaicense) communities that have dominated the landscape for about the last 1,000 years (Bernhardt and Willard 2009)

Development Of Al-B-C Master Alloy Under External Fields

This study investigates the application of external fields in the development of an Al-B-C alloy, with the aim of synthesizing in situ Al3BC particles. A combination of ultrasonic cavitation and distributive mixing was applied for uniform dispersion of insoluble graphite particles in the Al melt, improving their wettability and its subsequent incorporation into the Al matrix. Lower operating temperatures facilitated the reduction in the amount of large clusters of reaction phases, with Al3BC being identified as the main phase in XRD analysis. The distribution of Al3BC particles was quantitatively evaluated. Grain refinement experiments reveal that Al-B-C alloy can act as a master alloy for Al-4Cu and AZ91D alloys, with average grain size reduction around 50% each at 1wt%Al-1.5B-2C additions

Deformation-induced microstructural banding in TRIP steels

Microstructure inhomogeneities can strongly influence the mechanical properties of advanced high-strength steels in a detrimental manner. This study of a transformation-induced plasticity (TRIP) steel investigates the effect of pre-existing contiguous grain boundary networks (CGBNs) of hard second-phases and shows how these develop into bands during tensile testing using in situ observations in conjunction with digital image correlation (DIC). The bands form by the lateral contraction of the soft ferrite matrix, which rotates and displaces the CGBNs of second-phases and the individual features within them to become aligned with the loading direction. The more extensive pre-existing CGBNs that were before the deformation already aligned with the loading direction are the most critical microstructural feature for damage initiation and propagation. They induce micro-void formation between the hard second-phases along them, which coalesce and develop into long macroscopic fissures. The hard phases, retained austenite and martensite, were not differentiated as it was found that the individual phases do not play a role in the formation of these bands. It is suggested that minimizing the presence of CGBNs of hard second-phases in the initial microstructure will increase the formability

The analytic solution of near-tip stress fields for perfectly plastic pressure-sensitive material under plane stress condition

Different from dense metals, many engineering materials exhibit pressure-sensitive yielding and plastic volumetric deformation. Adopting a yield criterion that contains a linear combination of the Mises stress and the hydrostatic stress, the analytic solutions of plane-stress mode I perfectly-plastic near-tip stress fields for pressuresensitive materials are derived. Also, the relevant characteristic fields are presented. This perfectly plastic solution, containing a pressure sensitivity parameter μ, is shown to correspond to the limit of low-hardening solutions, and when μ=0 it reduces to the perfectly plastic solution of near-tip fields for the Mises material given by Hutchinson [1]. The effects of material pressure sensitivity on the near-tip fields are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42771/1/10704_2004_Article_BF00034180.pd