A Comparative Microstructure Evolution of AISI H21 and Inconel 718 in Cyclic Heating

Abstract

The AISI H21 steel used for dies in copper hot extrusion softened only after several runs. To improve production parameters a new material was necessary for the die, and, as a first choice, Inconel 718 was preferred. Prior to adopting this material for new extrusion dies an experimental program with temperature exposure cycles was performed so as to study microstructure evolution within AISI H21 and Inconel 718. The samples were studied by optic and scanning electron microscopy (SEM) and were also submitted to X-ray diffraction (XRD) and microhardness tests. The results showed carbide coalescence, which led to softening, followed by a re-precipitation in the steel, while, in Inconel 718, the precipitation (in small amounts) of delta (ä) phase was observed.Using these results and combining them with practical experience with steel, we could predict that the Inconel 718 die performance is such that at least a double quantity of copper could be extruded per die.

Effect of Heat Treatment on Magnetic Properties of Bulk Amorphous Alloys Fe63+xCo10Y7-xB20 (x=0, 2)

“…In amorphous materials, defects of the structure can be distinguished, which can be divided into free volumes and pseudolocation dipoles [10][11][12].These defects are examined using an indirect method based on the analysis of the primary magnetization curve carried out in accordance with the assumptions of H. Kronmüller's theory [10][11][12]. It has been shown in numerous works that the change in the shape of Ewing's knee gives the possibility to assess the impact of structural defects on magnetic properties [10][11][12][13][14][15][16][17][18][19][20][21][22].…”