Twist Deformation And Recrystallization Analysis Of Magnesium Alloy Extrusion Through Rotating Container

With the ever-increasing technology development and productionrequirements, extruded profiles are headed in the direction of large scaleintegration, high precision size, complex and diversity. The fields of manufactureand application are developed, and already extended to the fields of aerospace,equip manufacturing and military industry. But currently, some problems such ashigher extrusion energy, relative lower material utilization and productionefficiency become the internal causes that constraint the extrusion techologyimprovement.For the above problems, extrusion through rotating container(ERC) whichhas rotating container was proposed. This extrusion techology can not only avoidthe problems that high requirements in stem structure and perfomance, but alsoslove the bottleneck that rotating die cannot apply on the profiles extrusion.For the above problems, extrusion through rotating container whichextrusion tooling system included a rotating container was proposed. Thisextrusion techology can not only avoid the problems that high requirements instem structure and perfomance, but also slove the bottleneck that rotating diecannot apply on the profiles extrusion. This paper focused researched interactiveinfluence between twist deformation behavior (include twisting length andtwisting degree) and key processing parameters were researched. The AZ31magnesium alloy was employed in the research and the micostrucure evolutionrule was also analyzed.First of all, the billet in the cavity of the extrusion tooling was divided intothree zones. Ths upper bound and slab analysis were respectively employed in the theoretical analysis of deformation behavior and the twisting length andrelative extrusion pressure calculation models were also derived. The researchresult indicated, when the rotating speed of container lies in a specific range (0~1rad/s), the average extrusion pressure applied by the punch decreases apparentlywith the friction increasing. Unlike the traditional extrusion which usuallydecreases the friction factor in order to improve the properties of the material.Although the relative slippage inevitably occurred between the billet and thecontainer, the optimum results could be obtained by optimization of the slippageparameters.The calculation models of twist angle along the circumferential direction areobtained on account of the theory derivation. From the analysis, with the samecondition of rotating speed, the circumferential twist angle presented anincreasing tendency. With the increasing of the container angular velocity, theaxial twist angle on the outer space of the billet presents an increasing tendencyunder the effect of the constant friction factor. But the increasing magnitudebecomes small. The change rule of radial twist angle was in-depth analyzed byusing of the numerical simulation. The research results showed, the radial twistangle changed with the increasing of rotating speed when other conditions keepconstant. But the increasing magnitude decreased with the rotating speed grown.The influence of processing parameters that imposes on the twisting deformationbehavior can be analyzed through the distribution characteristic of radialintersecting lines.Then, through the data of hot compression experiment of AZ31magnesiumalloy, the dynamic recrystallization empirical model was built. The empiricalmodel was used for the AZ31magnesium alloy microstructure prediction andevaluation that processed by extrusion through rotating container. The researchindicated, comparing with the convebtional extrusion in the same conditions,imposing torque on the container can facilitate the dynamic recrystllizationbehavior and enhance the recrystallization volume fraction. The average grainsize obviously decreased and distribution uniformity improved at the same time.These characteristics provided the theoretical basis for the comprehensivemechanical performance enhancement during the extrusion through rotatingcontainer.