Study On Cold Deformation Of As-cast Az80Magnesium Alloy

Magnesium alloy has been widely concerned for its good performance in different fields.However, being short of the plasticity at room temperature, magnesium alloy is restricted inits industrial applications. The cold shaping of magnesium alloy is a major method in theprocess of surface modification. Thus, the extreme cold sizing of magnesium alloy acts asimportant theoretical evidence in the actual production and experiments. Taking as-cast AZ80magnesium alloy as the research object, This thesis designs a set of die device to measure theextreme cold sizing of magnesium alloy(extrusion speed maintains480mm/min and thelubricant of soybean oil).using the die device to extrude the inner hole diameter of differentcylinder samples at the room temperature. The study shows that the surface of the sample,whose inner hole diameter is14.60mm, is not cracking and its surface roughness is muchlighter after the deformation. It indicates that the quality of the sample surface is improvedafter extrusion. However, the sample of inner hole diameter in14.50mm forms some cracking.Based on studying the limit deformation of as-cast AZ80magnesium alloy, the deformationlimit of the as-cast AZ80is the inner hole diameter of14.60mm and the extreme cold sizingof magnesium alloy is6.24%.Compared with the differences of organization and properties of the samples before andafter the process of deformation, this study analyzes the causes which improve the surfacequality of the samples. Experiment results show that, the sample hardness changed little in thedeformation before and after, but the extrusion specimen surface roughness has greatlyimproved. With the DEFORM simulation software, this study discusses the flow of metal inthe forming process and the strain in the process of extrusion, which represent that theforming of metal has always been affected by tension stress. In that process, the surfacetensile stress rather than the metal of extreme tensile strength is accumulating to a certainextent, until the inner surface of the sample forms cracks out of the metal fracture strength limit. This thesis analyzes the reasons of the surface cracking in as-cast AZ80magnesiumalloy theoretically.