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Your search keyword '"Roven, Hans J."' showing total 37 results
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37 results on '"Roven, Hans J."'

23. Wire and Arc Additive Manufacturing with TiC-Nanoparticle Reinforced AA5183 Alloy

Author

Langelandsvik Geir, Ragnvaldsen Olav, Flåm Jan E., Akselsen Odd M., and Roven Hans J.

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

Wire and arc additive manufacturing of aluminium-ceramic composites shows great potential to produce high strength materials. By incorporation of nanoparticles in the feedstock wire, fine-grained material with low susceptibility for solidification cracking and enhanced strength can be obtained. In fact, this study utilised the novel screw extrusion method to prepare an aluminium alloy containing TiC nanoparticles. The commercial aluminium alloy AA5183 was selected for WAAM to assess and benchmark the effects of screw extrusion and TiC. The materials have been assessed in terms of microstructure, porosity content and mechanical properties. The presence of TiC reduced the average grain diameter by 70%, while Vickers hardness increased with 13%. However, number of pores per unit volume increased by one order of magnitude. The porosity is believed to stem from hydrogen introduced in the AA5183-material through screw extrusion processing, in addition to hydrogen trapping and pore nucleation on TiC nanoparticles.

Published
2020
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37. Microstructure evolution and dislocation configurations in nanostructured Al–Mg alloys processed by high pressure torsion

Author

LIU, Man-ping, JIANG, Ting-hui, XIE, Xue-feng, LIU, Qiang, LI, Xue-feng, and ROVEN, Hans J.

Abstract

Microstructure evolution and dislocation configurations in nanostructured Al–Mg alloys processed by high pressure torsion (HPT) were analyzed by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The results show that the grains less than 100 nm have sharp grain boundaries (GBs) and are completely free of dislocations. In contrast, a high density of dislocation as high as 1017m−2exists within the grains larger than 200 nm and these larger grains are usually separated into subgrains and dislocation cells. The dislocations are 60° full dislocations with Burgers vectors of ½<110> and most of them appear as dipoles and loops. The microtwins and stacking faults (SFs) formed by the Shockley partials from the dissociation of both the 60° mixed dislocation and 0° screw dislocation in ultrafine grains were simultaneously observed by HRTEM in the HPT Al–Mg alloys. These results suggest that partial dislocation emissions, as well as the activation of partial dislocations could also become a deformation mechanism in ultrafine-grained aluminum during severe plastic deformation. The grain refinement mechanism associated with the very high local dislocation density, the dislocation cells and the non-equilibrium GBs, as well as the SFs and microtwins in the HPT Al–Mg alloys were proposed.

Published
2014
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