Manganese metal was evaluated as a fuel for slow-burning delay compositions pressfilled in aluminium or compaction-rolled in lead tubes. Oxides of antimony, bismuth, copper, manganese and vanadium were considered as oxidants. Measured burn rates for binary mixtures varied between 5 and 22 mm/s but slower burning ternary and quaternary compositions were also found. The addition of fumed silica to the Mn/MnO 2 system had little effect on the propagation rate but a low level addition of hollow glass sphere significantly reduced the burn rate. Mn -MnO 2 mixtures showed reliable burning over a wide stoichiometric range. In this system the fuel and the oxidant share a common metal. They combine to form the more stable intermediate oxide (MnO) releasing considerable quantities of heat in the process.

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Ever-leaner compositions are targeted for nominal type 16-8-2 weld metals in attempts to limit sigma phase formation during elevated-temperature operation. Three variants of type 16-8-2 weld metals were exposed to aging at 750°C for up to 3500 h. Evaluation of the resultant structures by magnetic measurements, neutron diffraction (at ambient and cryogenic temperatures), and electron backscatter diffraction established that the leaner variants were susceptible to forming martensite after aging. This is ascribed to a local increase in the martensite start temperature due to sensitization taking place during elevated-temperature aging. The extent of martensite formation diminished during aging treatments exceeding 1000 h owing to diffusion of solute elements from the austenitic matrix to the sensitized regions (recovery). Subsequent elevated-temperature aging of the microstructures containing martensite also resulted in a decrease in martensite content: the mechanism, however, differs from that for single-cycle exposure. This observation is explained by martensite reversion to austenite. Martensite formation was completely absent from the higher-alloyed variant. This variant experienced intergranular carbide precipitation and delta ferrite decomposition into secondary austenite and carbides. This work demonstrates significantly different aging responses for composition variants within the allowed ranges for type 16-8-2 weld metals.

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