Experimental And Numerical Studies On The Temperature Field During Friction Stir Welding Of 5005 Aluminum Alloy

Friction stir welding(FSW)is an advanced solid-state joining technology,which has advantages of low energy consumption,environmental friendliness and excellent welding performance.The technology is especially suitable for the welding of light alloys such as magnesium alloys and aluminum alloys.In FSW studies,temperature field is one of main research areas.Determining temperature distribution during the welding process is helpful to optimize process parameters,prevent weld defects and improve welding quality.This paper focuses on the study of temperature field during FSW of 5005 aluminum alloy with experimental and numerical methods.In the paper,material property tests of 5005 aluminum alloy were conducted,and mechanical and thermophysical properties at elevated temperatures are obtained.FSW experiments of 4 mm-thick 5005 aluminum alloy plate are designed and performed with different welding parameters.The data of welding temperature field are measured by embedding thermocouples.The characteristics of temperature distribution were analyzed.The finite element model for calculating FSW temperature field was established,and different heat source models were compared.A general expression was derived to describe the heat generation for a tool with cylindrical pin.Three heat source models were obtained by calculating frictional stresses in the expression according to sliding friction,sticking friction and the combination of them.FEM simulation of temperature field during FSW of 6061-T6 aluminum alloy were carried out with these heat source models.Numerical results were compared with experimental ones.It is found that heat source models based on sticking friction and combination of sliding and sticking friction can predict temperature field well and produces nearly the same results for steady state of welding,while the model based on sliding friction gives higher temperature than experimental results.In terms of practicability and effectiveness,the model based on sticking friction is a good option for the simulation of temperature field since it is relatively simple and reasonable.Based on the obtained material properties and the validated heat source model,a FEM model for simulating temperature field during FSW of 4 mm-thick 5005 aluminum alloy plate was established.Numerical results were found to be in good agreement with experimental ones,which demonstrates the validity of the FEM model.By using the validated model,we systematically studied the influences on temperature field,heat generation rate and torque exerted on the tool for many factors,which include boundary conditions,preheating time,welding process parameters and structural parameters of the tool.A series of rules and some detailed indices were obtained.These rules and indices were valuable in the selection and optimization of FSW process parameters and welding tools for 5005 aluminum alloy.