Sigma phase in tungsten-rhenium alloys .2.

This second part of the paper on sigma (sigma) phase in tungsten-rhenium alloys deals with experimental evaluation of the influence of sigma phase development on microstructure and mechanical properties during processing of powder metallurgy sintered bars of W-25%Re alloys into various shapes. The processing steps may include warm rolling, forging, swaging and drawing when producing sheet, rod and wire products. In addition, intermediate heat treatments have a decisive influence on the structure and hence the properties of the final product. The characteristics of the products at different stages in the processing route have been evaluated using optical microscopy, electron probe microanalysis and hardness testing to determine the effect of the presence of sigma phase in varying quantities. By controlling the appearance and minimizing the quantity of sigma phase in the microstructure the product quality can be greatly improved.