Numerical Simulation And Experimental Study On Plastic Forming Of Zinc-Aluminum Based Alloy

Zn-Al-based alloys with ultrafine or even nanocrystalline structure can be obtained at room temperature subjected to certain heat treatment or thermal mechanical treatment,which has the characteristics of good plasticity,low hardness and low flow stress.At the same time,because of the high specific heat of zinc,the heat effect is not obvious during the cold drawing process.So it is expected to replace the toxic industrial detonator delay body where toxic heavy metal lead and antimony alloy was used widely.In this paper,based on the previous research in our laboratory,as well as the available literatures,the alloy was prepared,and the microstructure and mechanical properties were tested at room temperature,the effects of different annealing time on the hardness and microstructure of the extruded tube of Zn-Al-based alloy were studied.The material properties model and the usability of the Deform-3D software package were validated by the thermal compression experiment and the corresponding simulation.Based on the self-defined material performance model,the geometric model of extrusion and drawing process was established.The effects of different extrusion processes on the extrusion force,the temperature rise and average stress of the billet were studied using Deform-3D software package.The effect of die size on the wall thickness of pipe during the drawing process was studied by ANSYS software package.Finally,the Zn-Al-based delay bodies of detonator filled with delay powder were prepared by extrusion and drawing experiments,and the assembly and testing were carried out on-site,the results were compared with those of the traditional lead-antimony delay body.The main results are in the following:The results of thermal compression simulation agree well with the experimental data,which verifies the reliability of the material model.According to the experiment design and results analysis based on L9(34)orthogonal experiment,the change of squeezing force shows that when the billet temperature is 280?,in order to reduce the extrusion force and improve the smoothness of the extrusion process,slow extrusion speed,small extrusion ratio and good lubrication conditions should be applied.When the billet temperature is 250?,the extrusion speed is more sensitive to the extrusion force than the extrusion ratio and the friction condition.And when the billet temperature is 220?,the squeezing force is more stable than that at high temperature.The factors sequence influencing the degree of rising temperature of billet in different extruding process conditions were as follows:extrusion speed>initial billet temperature>extrusion ratio.The average stress of the involved nine single experiments is greater than the yield strength of the material,which meets the requirements of the weld strength.The mean stress of the three-hole and the four-hole die has little difference,but the weld number of the former is less.The influence factors of average stress are as follows:extrusion ratio>friction condition>extrusion speed>billet temperature.Therefore,based on the comprehensive consideration,the better process is:using three holes diverter mold,billet temperature is set at 250?,extrusion speed is set at 1 mm·s-1,friction coefficient is 0.3.The Zn-Al-based alloy extruded tube with excellent properties has been prepared experimentally.In this paper,a series of drawing forming dies were designed.By using the finite element software ANSYS which has high accuracy in the small deformation simulation,the influence of the die aperture on the wall thickness of the alloy tube was studied.By using the hexahedral meshing,setting proper material parameter assignment and multi-pass drawing technique,the experimental drawing process is reproduced in a considerably realistic way,and the simulated wall thickness agrees with the measured variation.It is found that there is a critical die aperture in each pass when decreasing the pore size.When the diameter of the die is larger than the critical value,the wall thickness of the alloy tube is increases after the drawing process.On the contrary,when the die aperture is smaller than this value,the wall thickness of the alloy tube reduces.Therefore,by controlling the size of mold diameter of each pass,the alloy tube wall thickness can be controlled quantitatively.By designing multi-pass drawing experiments,the Zn-Al-based alloys composite tube filled with compact delay powder were prepared successfully,where the wall thickness and diameter were controlled well.The on-site assembly and test of delay detonator show that the Zn-Al based alloy can be applied to replace the lead-antimony alloy initially although some extensive work need to be done further.