Characterisation of galvanneal coatings on strip steel

Galvanneal is a form of zinc-coated sheet steel, where steel is dipped in molten zinc, and then heat treated in a furnace to produce a complex iron-zinc coating. Many industries, such as automotive, use galvanneal for components fabricated from sheet steel. The microstructural properties of galvanneal have a significant influence on how well the sheet metal changes shape on stamping. By means of optical microscopy, scanning electron microscopy, and glow-discharge optical emission spectrometry, we present a study of the microstructure of several galvanneal samples, both stamped and unformed, relating the phases and morphology of the coatings to performance in stamping operations. Samples of galvanneal were subjected to different heat-treatment temperatures. The frequency of defects in stamped components was found to be related to the average alloy content in the coatings, which varied with furnace temperature. An increased average iron content in the coatings was related to increased powdering defects in stamping operations that use galvanneal coated sheet steel.<br /

Sensitivity of Surface Materials and Vegetation to Disturbance in the Queen Elizabeth Islands: An Approach and Commentary

Concern about potential and actual disturbance of surface materials, vegetation and wildlife of the Queen Elizabeth Islands has risen sharply in the last few years. The purpose of this paper is to outline an approach to the problem, based on terrain studies, and to offer a commentary on the recent paper by T.A. Babb and L.C. Bliss in Arctic. &hellip; For a rational assessment of the problem, information is required on: a) surface materials - ice content, texture, engineering properties; b) topography and landforms; c) geomorphic processes; d) drainage - seasonal change and single events; e) vegetation - percentage cover and composition by species; f) summer temperatures, and moisture balance in soil; g) wildlife. &hellip; Surface materials are very significant elements of the terrain, especially when potential for disturbance is being considered. Hence, surface materials are used by the present writers as a nucleus around which other elements of the terrain are grouped. &hellip; Two of the present writers undertook in 1972 an exercise in the mapping of sensitivity at a scale of 1:500,000 of the Queen Elizabeth Islands, based primarily on bedrock maps and extensive personal communications, but found it unsatisfactory because the degree of detail was insufficient to reflect the variability in the sensitivity of the terrain. &hellip; [In evaluating the paper by Babb and Bliss, the present authors conclude that]: The overall objective of these authors in emphasizing the "susceptibility of the soils and vegetation to surface disturbance" is good. However the methods used to achieve this objective are inconsistent, and in several cases the results are inaccurate. A serious deficiency is that the criteria for determining categories of "susceptibility" are obscure. &hellip; The "Polar Desert" category is described as an area with 10% or less plant cover, low susceptibility to disturbance and low ground ice content. One interpretation of this seems to be that poorly-vegetated areas are less susceptible to disturbance of vegetation than are more densely vegetated areas. Only in so far as a low plant density lessens the probability of direct impact of vehicles on plants is this interpretation obviously true. A sparsely vegetated area may be an important, or even critical, range for ungulates; therefore the effect of disturbance of it could be great. The type of vegetation - such as willow, sedge, saxifrage, grass or bryophyte - is a vital consideration. An alternative interpretation is that unvegetated areas (90% of the Polar Desert category, classed as "soils") have a low sensitivity to surface disturbance. This is not true for some major areas of both eastern Melville Island and Western Ellesmere Island where highly sensitive surfaces, almost devoid of vegetation, are subject to extensive slope failure or thermokarst development, even without disturbance. Where the authors have left their major field of expertise and have commented on geology and geomorphology, weaknesses are evident. They appear to draw a direct relationship between active-layer soil moisture and "susceptibility". For overland travel this is generally true, but if excavation penetrates the shallow active layer and the frost table, then the relationship certainly no longer holds. Furthermore, the implication of a relationship between susceptibility, ice content and vegetation cover is simplistic and can be misleading. The assertion that "10% or more vegetation cover indicates the existence of sufficient moisture for the segregation of horizontal ice layers" is without basis. The present writers have drilled over 300 shallow (1-6 m) holes in eastern Melville Island and western Ellesmere Island to evaluate ice content and have found the relationship between vegetation, ground ice and materials to be complex. &hellip

Late quaternary climate history of Heart Lake and Pup Lagoon (Larsemann Hills, East Antarctica)

Information on East-Antarctic coastal environments during the Holocene is relatively sparse. This is surprising as sedimentary records from the interface between land and sea can provide chronologies of climate change, isostatic uplift, relative sea level and the colonisation of newly formed biomes. Here we examine a sediment core from Pup Lagoon and Heart Lake (Larsemann Hills, East Antarctica). Sediment stratigraphy, fossil pigments and diatoms were used to infer the sequence of Holocene environmental and climate change. Results show that between 5800 and 4785 corr. yr BP the marine coast of Prydz bay was characterized by stratified, open water conditions during spring and summer and seasonally warm conditions. From 4785 to 2615 corr. yr BP sea ice duration in Prydz Bay increased with the coast being ice-free for 2-3 months each year, conditions which are similar to the present day. A return to stratified, open water conditions and a reduction in winter sea ice extent between 2615 corr. yr BP - 2200 uncorr. yr BP is signaled by enhanced biogenic production and more open water diatom taxa

Ice stream subglacial access for ice-sheet history and fast ice flow: the BEAMISH Project on Rutford Ice Stream, West Antarctica and initial results on basal conditions

Three holes were drilled to the bed of Rutford Ice Stream, through ice up to 2154 m thick, to investigate the basal processes and conditions associated with fast ice flow and the glacial history of the West Antarctic Ice Sheet. A narrative of the drilling, measuring and sampling activities, as well as some preliminary results and initial interpretations of subglacial conditions, is given. These were the deepest subglacial access holes ever drilled using the hot-water drilling method. Samples of bed and englacial sediments were recovered, and a number of instruments were installed in the ice column and the bed. The ice–bed interface was found to be unfrozen, with an existing, well-developed subglacial hydrological system at high pressure, within ~1% of the ice overburden. The bed itself comprises soft, water-saturated sediments, consistent with previous geophysical interpretations. Englacial sediment quantity varies significantly between two locations ~2 km apart, and possibly over even shorter (~20 m) distances. Difficulties and unusual observations encountered while connecting to the subglacial hydrological system in one hole possibly resulted from the presence of a large clast embedded in the bottom of the ice

Antarctic Climate Change and the Environment

The Antarctic climate system varies on timescales from orbital, through millennial to sub-annual, and is closely coupled to other parts of the global climate system. We review these variations from the perspective of the geological and glaciological records and the recent historical period from which we have instrumental data (the last 50 years). We consider their consequences for the biosphere, and show how the latest numerical models project changes into the future, taking into account human actions in the form of the release of greenhouse gases and chlorofluorocarbons into the atmosphere. In doing so, we provide an essential Southern Hemisphere companion to the Arctic Climate Impact Assessment

Snow petrel stomach-oil deposits as a new biological archive of Antarctic sea ice

Where snow petrels forage is predominantly a function of sea ice. They spit stomach oil in defence, and accumulated deposits at nesting sites are providing new opportunities to reconstruct their diet, and, in turn, the sea-ice environment over past millennia