Effect Of Cross Direction Changing Upsetting Process On Microstructure And Properties Of Rare Earth Magnesium Alloy

When the cylinder blank is upset,the metal expands and flows around the cylinder as the height decreases.The deformation of the cylinder blank is not uniform because of the friction between the blank end face and the die.The non-uniform deformation during upsetting is harmful to the quality of forgings.The circumferential tensile stress on the side of the blank not only causes the longitudinal cracking of the side surface,but also causes the non-uniform grain size of the forgings,which leads to the non-uniform performance of the forgings,especially in the hard deformation zone,the grain size may be coarse due to insufficient deformation,especially for low-plastic alloys such as magnesium alloys.How to improve the non-uniformity of upsetting deformation is always an urgent problem to be solved,and the traditional process method has many limitations.In order to achieve uniform deformation,it is necessary to change the stress state of different deformation zones so that the strain of each deformation zone is as equal as possible.In this paper,a die with a kind of "cross" shaped cavity was designed.The upsetting blank was upset in the die,and the topology-optimized die structure was used,the control of the stress and strain state in different parts of the billet during the deformation process is realized.In addition,in order to ensure that each deformation is upsetting,the transverse channel size of the die cavity is larger than that of the Longitudinal Channel Size,which is beneficial to turning the blank 90 ° to continue the deformation after one upsetting,thus,after repeated deformation,the uniform deformation of the billet can be basically realized.In this paper,DEFORM 3D simulation software is used to simulate the forming process of this process,and the effects of billet temperature and die velocity on streamline shape,stress and strain distribution,forming load and surface folding of billet are analyzed.The research shows that the design of the die with double concave die and punch can control the flow of metal,so that the metal can fill the cavity well and not much metal can flow out of the cavity.The velocity of the die has no obvious influence on the simulation results,but with the increase of temperature,the streamline shape has no obvious change,but the flash is obviously reduced,the distribution of stress and strain is gradually uniform,and the forming load is gradually reduced,the folding phenomenon on the surface of billet is obviously weakened.The effect of this process on the microstructure and mechanical properties of the alloy was analyzed by means of optical microstructure analysis,XRD analysis and micro-hardness test,the microstructure was uniform gradually,no new phase was formed,the texture strength had no significant change,and the hardness increased significantly,but the change of hardness was different in different regions.