scholarly journals Modification of the anisotropy and strength differential effect of extruded AZ31 by extrusion-shear

2018 ◽  
Author(s):  
M. Jaehnke ◽  
F. Gensch ◽  
S. Mueller
Keyword(s):  
Differential Effect ◽  
Strength Differential Effect ◽  
Strength Differential

scholarly journals Strength differential effect in age hardened aluminum alloys

2017 ◽  
Vol 99 ◽  
pp. 144-161 ◽  
Author(s):  
Jens Kristian Holmen ◽  
Bjørn Håkon Frodal ◽  
Odd Sture Hopperstad ◽  
Tore Børvik
Keyword(s):  
Aluminum Alloys ◽  
Differential Effect ◽  
Strength Differential Effect ◽  
Strength Differential

Modifications of the Extrusion Process of Magnesium Alloys for Improved Mechanical Properties

2008 ◽  
Vol 367 ◽  
pp. 9-16 ◽  
Author(s):  
Sören Müller ◽  
Klaus Mueller ◽  
Walter Reimers
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloys ◽  
Differential Effect ◽  
Cold Deformation ◽  
Compressive Loading ◽  
Extrusion Process ◽  
Detailed Knowledge ◽  
Strength Differential Effect ◽  
Strength Differential ◽  
Structural Applications

In the course of the increasing discussions about a reduction of the CO2 emissions magnesium has gained importance since it is the lightest metal for structural applications. Currently magnesium alloys are almost exclusively used as cast parts in the automotive industry because due to their microstructure extruded magnesium profiles exhibit a strong asymmetry in the mechanical properties under tensile and compressive loading (strength differential effect). In order to improve the mechanical properties a detailed knowledge about the influence of the different extrusion parameters on the microstructure of the extrudates is necessary. Therefore, the parameters extrusion method, billet temperature, product speed, extrusion ratio and cooling condition were varied for the extrusion of the magnesium alloys AZ31, AZ61 and AZ80. Subsequently the microstructure was analyzed and the mechanical properties determined. With an additional analysis of the deformation modes of the extruded and cold deformed products it could be discovered that an improvement of the mechanical properties can be achieved by a modification of the extrusion process. Since the strength differential effect in caused by twinning which due to the texture of the extrudates is only active under a compressive loading along the extrusion direction the modification of the extrusion process aims at a suppression of this twinning. Because on the one hand compared to that for dislocation glide the Hall-Petch-Constant for twinning is bigger a grain refinement of the extruded products could be achieved by a predeformation using ECAE similar processes. On the other hand a process has been developed where the profiles are extruded into a hydrostatic counter pressure in order to alter the texture during the extrusion. Thereby the twinning is already activated during the extrusion. Both modifications of the extrusion process result in an increase of the critical resolved shear stress for twinning during the subsequent cold deformation and thus in improved mechanical properties.

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