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THE use of metals at temperatures in excess of 1,200 deg. F. and up to temperatures in the vicinity of their melting points is a challenging and fascinating portion of the fight to pass the heat barrier in the design and performance of aircraft and their power plants. The materials available for service in this temperature range are restricted. The considerations of designing structural components involve many more problems than the old criteria of strength to weight ratio and fabrication costs. Such properties as thermal expansion, heat conductivity, surface emissivity and scaling resistance are as important in determining which metal should be used for a given application as are the various measurements of strength heretofore the primary considerations in material selection.

A Survey of the Development of Creep‐resisting Alloys: N. P. Allen (Superintendent of the Metallurgy Division of the National Physical Laboratory, Teddington). Official summaries of the papers presented at the Symposium held by the Iron and Steel Institute at the Institution of Civil Engineers on February 21 and 22, 1951. The development of creep‐resisting alloys, both ferritic and austenitic, in the period between the two wars is briefly described, and a rather more detailed account is given of the general trend of the researches undertaken after 1939 in Great Britain, America, and Germany to provide improved materials for use in gas turbines. The properties of alloys that were relied upon in each country are described in terms of the stresses giving plastic deformations of the order of 0.1 per cent in 1,000 hr. (FIGS. 1, 2, 3).

Guidelines for making a wise choice when selecting high temperature alloys are provided. Four groups of alloys are discussed, along with helpful selection criteria. Substantial benefits accrue from contemporary alloy manufacturing techniques. Process databases and state‐of‐the‐art forging equipment significantly impact product quality, consistency and cost effectiveness. Finally, the author suggests that the elimination of unnecessary test requirements offers potential for savings in time and money. He feels that alloy integrity can be assured by any producer who can demonstrate narrow limits of compositional control, as well as melting, remelting and hot working controls.

The aim of this study was to explore the application of rapid manufacturing (RM) to the production of patient specific, custom‐fitting removable partial denture (RPD) alloy frameworks. RPDs are metal frameworks designed to retain artificial replacement teeth in the oral cavity.

The study was undertaken by applied case study. An RPD was designed using computer‐aided design software according to well‐established dental technology design principles, based on a digitally scanned cast produced from an impression of the patient's mouth. The RPD design was then exported as an STL file in preparation for direct manufacture using selective laser melting. Dimensionally accurate frameworks were manufactured in 316L stainless steel and chromium‐cobalt alloy. These were assessed for accuracy of fit and function on the patient cast and on the patient in clinic.

This successful case study demonstrates that an RM approach can produce fully functional, precisely fitting RPD frameworks for specific individual patients.

The study was based on a single design produced using two materials. Further studies are in progress to show that the results can be achieved on a regular and predictable basis.

This study provides some practical guidance for the application described and suggests that similar success may be achieved in related custom‐fitting applications.

The paper demonstrates the successful application of a novel approach to the design and manufacture of custom‐fitting dental devices.

The purpose of this paper is to explore an application of computer‐aided design and manufacture (CAD/CAM) to a process of electronically surveying a scanned dental cast as a prior stage to producing a sacrificial pattern for a removable partial denture (RPD) metal alloy framework.

With the introduction of laser scan technology and commercial reverse engineering software, a standard plaster maxillary dental cast with dentition defect was successfully scanned and created as a STL‐formatted digital cast. With the software, the unwanted undercuts were eliminated based on the desired path of insertion. Parts of the RPD framework were then successfully custom‐designed and combined as a whole.

A sacrificial pattern was produced by rapid prototyping (RP) method and finally casted with chromium cobalt alloy. With suitable finishing process, both the sacrificial pattern and the casted framework fitted the cast well.

The research indicated the feasibility of creating a library of RPD framework components. It is believed that, in the future, with the advance of the techniques, a totally new platform can be developed for the design and fabrication of custom‐fit RPD framework based on the CAD/CAM/RP system.

The aim of this paper is to analyse the recent changes in the role played by Africa as a traditional natural resources supplier for the world economy in a multipolar context. We highlight, on the one hand, how Africa remains a prominent supplier of critical minerals needed for information and communication technologies (ICT), including platinum, vanadium, coltan, chromium, manganese, zirconium, etc., and how the boomerang effect results in Africa also importing electronic waste. On the other hand, we show how the BRICS’ growth model, based on a very intensive use of natural resources acquired through international trade, is now being fuelled by Africa too. BRICS countries (especially China and India) are making foreign direct investments in Africa using their state companies to ensure the supply of natural resources under favourable economic terms. Thus, Africa appears as a disputed territory between the old domination of the advanced capitalist countries and emerging powers like the BRICS. However, this should not mask the fact that the European Union and North America are still the dominant foreign powers in the continent. Finally, we discuss which scenarios are open to further this multipolar moment, particularly in the wake of the great crisis.

THE rules for the 1935 Deutsch de la Meurthe Cup Race remained almost identical with those of 1933 and 1934. Briefly, the contest was open to all types of land “aerodynes”; the only limitation being that the total capacity of the engine (or engines) remained under 8 litres (488·20 cu. in.). In other directions, designers were left with an absolutely free hand—the usual Certificate of Airworthiness even being dispensed with. To avoid the participation of machines of doubtful characteristics, each competitor had to qualify between April 2 and May 2 by passing successfully the following tests: a flight of 500 km. (311 miles) in a closed circuit at a speed exceeding 300 k.p.h. (186·5 m.p.h.)—against 250 k.p.h. (155·5 m.p.h.) last year. In addition, take‐off and landing had to be performed in less than 500 metres (1,640 ft.) over a “screen” 1 metre (3·28 ft.) high—against 550 metres (1,801 ft.) last year. Actually, the “screen” took the form of two parallel ropes set at the required height and separated by an interval of 50 metres (164 ft.), so as to ensure correct execution of the test. The wind velocity had to be under 6 metres per second (19·7 f.p.s.) during the take‐off and landing tests.

In this paper, the mechanical properties and corrosion resistance of CoCr alloy fabricated by selective laser melting (SLM) were studied, and the changes of performance after porcelain sintering process were also analysed. This study is to point out the relationship between the microstructure, mechanical properties and corrosion resistance of CoCr alloys prepared by SLM after porcelain sintering process. In addition, the biosafety of the sintered CoCr alloy was evaluated.

The microscopic feature changes of CoCr alloy samples after porcelain sintering process were observed by DMI 5000 M inverted metallographic microscope and Nova Nano430 FE-SEM. Moreover, phase identification and determination were conducted by X-ray diffraction (XRD) using Smartlab X-ray diffractometer. The Vickers microhardness was measured on the HVS-30 microhardness tester, and tensile tests were carried out on a CM3505 electronic universal testing machine. The corrosion resistance was tested by a classical three-point electrode system electrochemical method, then the ion precipitation was measured by using an atomic absorption spectrometer of Z2000 7JQ8024.

The XRD results indicate that the transition of γ phase (FCC) to e phase (HCP) occurs during the porcelain sintering processing of CoCr alloy. Moreover, the Vickers microhardness of the upper surface and the side surface of the CoCr alloy sample was improved by more than 36%. In addition, the ultimate strength of CoCr alloy via porcelain sintering treatment was increase to 1,395.3 ± 53.0 MPa compared to 1,282.7 ± 10.1 MPa of unprocessed CoCr alloy. However, the corrosion resistance of CoCr alloy samples decreases after porcelain sintering process.

There are few studies on the relationship of microstructure, mechanical properties and corrosion resistance of CoCr alloys prepared by SLM after porcelain sintering process. In this study, the microstructure, mechanical properties and corrosion resistance of CoCr alloy after porcelain sintering process were studied, and the biosafety of the alloy was evaluated. The research found that it is feasible to apply CoCr alloy fabricated by SLM to dental medicine after porcelain sintering process.

GERMANY Metals in contact with aqueous solutions. When metals are brought into contact with aqueous solutions at room temperature there is said to be an initial or ‘incubation’ period which may be of extremely short duration, almost a transient. After this period corrosion may increase rapidly to a thousand times its initial value or more, or may decrease even more rapidly. The latter process can be followed only with a cathode ray oscilloscope. The formation of local elements is assumed to be the cause of the processes observed. The effect on corrosion is shown at the instance of aluminium of different degrees of purity. Dissolution speeds are 6 g./sq.m./day for Al 99.998% rising to 190,000 g./sq.m./day for Al 99.2%.— (F. Tödt, Werkstoffe & Korrosion, 1954, 5, (11), 430–433).

THE Glacier Metal Co Ltd manufacturers three dry bearing materials, namely Glacier DU, DQ and Deva Metal.