Microstructure And Mechanical Properties Of AM60B Alloy By Friction Stir Processing

AM60B alloy has excellent properties such as low density,high specific strength,strong electromagnetic shielding,and good damping performance.It is widely used in various fields such as transportation,aerospace,and electronic products.Because AM60 B alloy has a close-packed hexagonal crystal structure,its plasticity and wear performance are poor,which limits the scope of application to a certain extent.Friction stir processing(FSP)is a new type of plastic deformation technology,which has broad application prospects in terms of grain refinement,improving the microstructure and mechanical properties of materials.In this paper,AM60 B alloy is used as the research object,and FSP is used as the preparation method.The effects of FSP on the microstructure,hardness,tensile properties and friction and wear properties of AM60 B alloy are studied.At the same time,the distribution level and law of residual stress in FSP processed joints.First,the FSP was performed on an AM60 B alloy plate with a thickness of 3 mm.The effects of the rotation speed,traverse speed,and processing pass of the stirring head on the microstructure and mechanical properties of the stirring zone(SZ)in FSP were studied.The study found that due to the different mechanical agitation and thermal effects in the processing area during FSP processing,the processing area can be divided into stirring zone(SZ),thermo-mechanically affected zone(TMAZ),heat affected zone(HAZ),and base material(BM).The grain refinement and recrystallization of the SZ of the FSP specimens occurred.The average grain size increased with the increase of the rotation speed and decreased with the increase of the traverse speed.Under the condition that the overlapping ratio is 100 %,the microstructure of the AM60 B magnesium alloy SZ is further homogenized in the second pass,which is 16.7 % smaller than the grain size under the 800/100 pass.FSP improves the microhardness of the SZ of the sample and reduces the tensile strength and elongation.The fracture position of the tensile specimen is near the thermo-mechanically affected zone on the advancing side,and a large number of tear edges appear at the fracture,which is a typical brittle fracture.Secondly,it can be obtained through the friction and wear test that the friction coefficient of the sample under high load is higher than that of low load,and the friction coefficient increases with the increase of temperature;the wear rate is higher under high loads and increases with increasing temperature.At room temperature,under the test load of 80 N,all the samples are in the abrasive wear phase;under the test load of 160 N,the base material is in the peeling wear phase,and the FSP sample is in the transition from abrasive wear to peeling wear.At 100℃ and 200℃,all the samples were in a severely broken state,and the effect of temperature on the wear performance was greater than that of FSP.Finally,the residual stress of the FSP joint can be measured.The residual stress of the joint shows an asymmetric distribution,and the rotation speed increases,and the residual stress of the joint increases.Under 800/100 processing parameters,the maximum longitudinal and transverse residual stresses of the joint appear in the heat affected zone and the thermo-mechanically affected zone on the advancing side,and they are all tensile stresses.The stress is 18.0 MPa.The minimum value of joint residual stress appears in the heat affected zone and the thermo-mechanically affected zone on the receding side,which is compressive stress.