| Research Abstract |
Die design considering the elastic deformation of die itself and achieving the sound product without defect in hot extrusion requires detailed and realistic stress analysis. Mechanistic interpretation of run-out direction, which is closely connected with distortion of the cross section of the product and that of peripheral recrystallization in hot extrusion of some aluminum alloys, which causes streaks after anodizing, are also required to optimize the extrusion process and die design. In the present investigation, some uniaxial compressive testings of Al-Mg-Si (6063) aluminum alloy, plane strain hot extrusion experiments of the same alloy using the symmetric and non-symmetric dies and numerical analyses concerning with the above subjects were performed. Those results are summarized below.
1) The work-hardening rate equations proposed by the investigator previously were introduced to predict the distributions of effective stress and temperature rise due to plastic working energy with taking into account the complex distributions of effective strain-rate, effective strain and temperature in the deformation zone in hot extrusion. 2). Run-out direction of the extruded product could be related to the angle between the u=0 line and the extrusion direction. (Velocity component, u, is directed to normal direction to the extrusion direction.) The angle of u=0 line can be controlled by both die configuration and dead metal zone. 3). The peripheral recrystallized grain structure is not generated in hot extruded product when the effective strain, epsilon, is less than 1.55 or the effective strain gradient is less than 0.44epsilon is satisfied. Those values, 1.55 and 0.44, are obtained at 473^ﾟC and become smaller at higher temperature. 4) The metal flow patterns involving thin dead metal zones were observed in extrusion using ceramic dies having smooth surface and low heat conductivity.
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