Processing, Microstructures and Properties of a Ti-6Al-4V Extrusion Produced by an Industrial Scale Setup

In this paper, a Ti-6Al-4V rectangular bar was successfully produced from a 5kg blended powder mixture using an industrial scale extrusion facility. The elemental hydride-dehydride (HDH) titanium and 60Al-40V master alloy mixture was warm pressed and vacuum sintered prior to β extrusion in air. The as-processed material was characterised for compositional homogeneity, oxygen pickup, microstructure, tensile properties and fracture behavior. Variation in microstructure and properties along the length of the extruded bar were also studied. It was found that oxygen pickup mainly occurred during vacuum sintering of the green billet and consequently the as-extruded material had an oxygen content of 0.55 wt.%. The processed material had a typical lamellar morphology with some evidence of micro-cracks at high magnification. A significant deviation in prior β grain and α colony sizes was observed along the length of the bar, due to variations in extrusion temperature and cooling rate. Both grains and colonies became finer as the location changed from the tip of the extruded bar to the back end. The as-processed material had ultimate tensile strength in the range of 1068-1268 MPa and elongation to fracture of 1.2-4.5%, mainly due to the high oxygen content and non-optimised microstructure. Fractographic analysis was consistent with the variation in mechanical performances obtained.

Microstructures of Spray Formed Superalloy GH742

Microstructures and hot deformation behaviors of spray formed superalloy GH742 have been studied in this paper. The results indicate that the spray formed superalloy GH742 has high relative density, low oxygen pickup, refined microstructure, and good forgeability. The fully inhibited coarsening of microstructure in spray formed superalloy GH742 has also been found in this study. 32wt% γ¢ and 0.5wt% carbonitrides, (Nb,Ti)(C,N) and Ti(C,N) were found in the as-deposited GH742, and most of them are sub-micrometer.

Dynamic modelling of vacuum circulation process for steel decarburization

A dynamic matbematical model of the vacuum circulation process for steel decarburization was developed. [t comprises the process parts of steel circulation decarburization reaction, adjustment of vessel pressure with its influence on the carbon equilibrium content, and the oxygen pickup from the ladle slag. The model allows to simulate the behaviour of all important process values with good accuracy and can be used for optimization of plant construction and operation as well as for improvement of process control.