The Collaborative East Antarctic Marine Census (CEAMARC) surveys to the Terre Adélie and George V continental margin highlight the requirement for a revised high-resolution bathymetry model that can be used as a spatial tool for improving information on the physical environment of the region. We have combined shiptrack singlebeam and multibeam bathymetry, coastline data, and land and ice sheet topographic data to develop a new regional-scale bathymetry grid, called GVdem (short for George V digital elevation model). The GVdem grid spans an area between 138–148°E and 63–69°S, with a cell pixel size of 0.001-arcdegree (c. 100 m). The revised digital elevation model is a large improvement over previously available regional-scale grids from the area, and highlights seabed physiographic detail not formerly observed in this part of East Antarctica. In particular, the extent and complexity of the rugged inner-shelf valleys are revealed, and their spatial relationship with large shelf basins and adjacent flat-topped banks. The new grid also reveals further insight into the spatial distribution of the submarine canyons found on the continental slope.

Dense coral-sponge communities on the upper continental slope at 570–950 m off George V Land, East Antarctica have been identified as Vulnerable Marine Ecosystems. The challenge is now to understand their probable distribution on other parts of the Antarctic margin. We propose three main factors governing their distribution on the George V margin: 1) their depth in relation to iceberg scouring, 2) the flow of organic-rich bottom waters, and 3) their location at the head of shelf cutting canyons. Icebergs scour to 500 m in this region and the lack of such disturbance is a probable factor allowing the growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons which receive descending plumes of Antarctic Bottom Water formed on the George V shelf, which could entrain abundant food for the benthos. The canyons harbouring rich benthos are also those that cut the shelf break. Such canyons are known sites of high productivity in other areas due to strong current flow and increased mixing with shelf waters, and the abrupt, complex topography. These proposed mechanisms provide a framework for the identification of areas where there is a higher likelihood of encountering these Vulnerable Marine Ecosystems.

Laser polishing of indirect-SLS parts made from 420 stainless powder infiltrated with bronze has been achieved using CO2 and Nd:YAG lasers. Two mechanisms have been previously proposed for the reduction in surface roughness, namely: shallow surface melting (SMM) and surface over-melt (SOM). In SMM reflow of the molten surface minimizes the peak-valley height driven by capillary pressure and liquid curvature. On the other hand, during SOM the melting depth is such that the entire surface becomes liquid and formation of surface periodical structures dominates driven by a surface tension gradient. This surface morphology was identified by means of optical and scanning electron microscopy (SEM). The onset of this regime is dictated by the energy density (i.e., ratio of laser power to scan speed and beam diameter) as well as the initial roughness Ra value prior to laser surface polishing. In contrast with SMM, onset of the latter mechanism increases the roughness Ra with speed reduction. A thermo-physical model is presented, signaling good agreement with roughness Ra and characteristic surface wavelength results obtained for varying laser beam scan speeds. Understanding the surface over-melt mechanism is critical for determining the optimum polishing conditions that minimize roughness.

A combination of Selective Laser Sintering and colloidal infiltration has been used to create partially stabilized zirconia molds for titanium casting. The mold material system was chosen for its low reactivity with molten titanium and thermal shock resistance. The base material, stabilized zirconia mixed with a copolymer binder, was pre-processed before laser sintering into the desired green shape. The average density of the fired parts could be increased to twice that of the green density. Hole sizes as small as 180 m are possible in thin ceramic components.

This paper presents the development of Selective Laser Sintering/Hot Isostatic Pressing (SLS/HIP) technology for production of functional high performance components in the titanium alloy Ti-6AI-4V. SLS/HIP is a net shape manufacturing technique that combines and exploits the freeform shaping capability of selective laser sintering and the full densification capability of hot isostatic pressing. The advantages of SLS combined with in situ HIP encapsulation include single step net shape canning, full densification by containerless HIP, no container-powder adverse interactions, reduced pre-processing time, and minimal post-process machining compared to conventional HIP of canned powders. Microstructure and mechanical properties of SLS processed and HIP post-processed Ti-6A1-4V are consistent with conventionally processed material. The potential of SLS/HIP technology was demonstrated by net shape fabricating a component to specification, namely the titanium guidance section housing base for the AIM-9 Sidewinder missile.

The Rapid Omnidirectional Compaction (ROC) technique has been applied successfully to the densification of TZP (3 mole % yttria) ceramics at 1260°C. The combination of high pressure (830 MPa) and temperature results in the plastic deformation of the ceramic particles. The extent of deformation, and consequently, the ROCing temperature, can be determined by using hot hardness of the ceramic material as an approximation of the ceramic's yield stress. The materials ROCed at 1260°C are characterized by a grain size of 0.15 gim, a flexure strength of 1300 MPa, a hardness of 1340 kg/mm2, and a fracture toughness of 5.0 MPa m1/2.