The low specific weight combined with favourable strength values and good machining properties make magnesium alloys particularly interesting. However, the forming and mechanical properties differ significantly from those of other lightweight materials because the hexagonal magnesium exhibits an anisotropic behavior with regard to tensile and compressive load parallel to the direction of extrusion and the compressive yield stress is significantly lower than the tensile yield stress. Therefore, conventional extrusion processes can only be used to a limited extent.
Technical Description
With the counter-pressure extrusion process developed at the TU Berlin, the pressure flow limit of extruded magnesium alloys can be significantly increased. This is achieved by specifically influencing the alloy texture by activating twins. The crystals are rotated by increased counterpressure so that the basal planes after extrusion are no longer parallel to the extrusion axis but perpendicular to the direction of extrusion. By activating tensile twins during extrusion, the resistance of profiles and hollow profiles produced in this way to deformation under subsequent compressive stress is increased by at least 50% (reduction of the Strength Differential Effect from -0.66 to -0.27).
Possible Applications
Automotive industry, aerospace industry, medical technology
A pressure chamber is connected to the die of the conventional extrusion line. The pressure chamber is equipped with an appropriate filling system for the high-pressure liquid and a control and regulating device.
Benefits
specific adjustment of compressive yield stress and tensile yield stress
high strength values despite low-cost standard alloys
also suitable for hollow profiles
Technology Readiness Level
Technology demonstrated in relevant environment (TRL: 6)
