Fabrication Of Fine-grained 5083 Aluminum Alloy By Friction Stir Processing And Its Superplastic Performance Study

Friction stir processing(FSP)can be used to refine the grain,increase the mechanical properties and plasticity of the material.In this paper,5mm thick 5083 aluminum alloy plate was friction stir processed.The orthogonal test method was employed to select the appropriate parameters of rotation speed,feed speed and plunge depth.Tensile test,metallographic test,hardness test and fracture analysis was carried out to get the optimal parameters of friction stir processing.The optimal parameter was used to multi-pass FSP.Multi-pass friction stir processing studied the optimal distance of interval between each pass to fabricate large-size 5083 fine grain material,and the effect of temperature and tool pin shape.Stacking FSP was also tried in this paper to fabricate large thickness fine-grain material.In order to study the superplastic performance of the material,the high temperature tensile test was complemented for fine grain 5083 aluminum alloy.Finite element software was used to simulate the extrusion and stamping forming for both FSP processed plate and unprocessed plate.The main research contents and conclusions are as follows:(1)The optimal process parameters of single pass processing were obtained.For 5mm thick 5083 aluminum alloy,the material had no macroscopic defects at the rotation speed of 1300 r/min,feed speed of 400 mm/min and plunge depth of 0.3 mm.The tensile strength was 214 MPa,93.05% of the base metal,yield strength was 112.4 MPa and elongation was 18.37%.Metallographic test showed that the grain became equiaxial crystal.The hardness decreased in the stirred areas.(2)The optimal interval between each pass was the dimension of the pin end diameter.Due to the contact area of the tool shoulder and plate was larger than the pin surface area,more heat was generate at the upper areas,the grain size was larger at the upper side than the bottom side.The cooling method of spaying water on the plate surface was an effective way to reduce the temperature and control the grain size growth.The grain size processed by cylindrical shape tool was larger than the conical shaped tool.The method of plate stacking FSP was an effective way to produce large thickness fine grain aluminum alloy.(3)The elongation of the stirred material sample produced by multi-pass FSP reached 216% when the initial strain rate was 3×10-3/s and the temperature was 530°C.In comparison,the elongation of unprocessed 5083 aluminum alloy was only 83% at the same test condition.During the plastic forming process,fine grained 5083 aluminum alloy showed good plasticity and metal flowability.It was found from finite element analysis that the press force applied to the punch was smaller.