6061T6铝合金流动摩擦挤压成形性能及微观组织

Formability and Microstructure of 6061T6 Aluminum Alloy by Flow Friction Extrusion

通过单点流动摩擦挤压成形试验,研究了工具头转速(ω)、下压量(?l)、下压速度(v)、工具头直径(D)对6061T6铝合金成形性能的影响规律,获得了最佳的成形工艺参数:D=20 mm,ω=950 r?min-1,v=0.6 mm·min-1,?l=3.0 mm,在该参数条件下材料的成形高度最大,达到15mm。利用光学显微镜(OM)和电子背散射衍射(EBSD)对最佳条件成形后不同区域材料的组织进行观察和分析,结果表明:单点流动摩擦挤压成形后的试样由热影响区(HAZ)和变形区(DZ)组成,与母材相比,热影响区晶粒尺寸和形态并未发生明显变化,平均晶粒尺寸为26.5μm;变形区组织分布不均匀,搅拌区(Ⅱ(A)区)材料在工具头带动下发生三维搅动,组织细化不明显,平均晶粒尺寸为23.8μm,大角度晶界比例为45.1%。搅拌挤压复合变形区(Ⅱ(B)区)在搅拌挤压复合力作用下形成了细小等轴组织,平均晶粒尺寸仅为6.54μm。凹模拐角处(Ⅱ(C)区)组织最为细小,平均晶粒尺寸仅为3.75μm,该区域大角度晶界比例明显增加,达到81.8%,材料在变形过程中发生了动态再结晶,形成了稳定的再结晶组织。

The effects of tool head rotation rate(ω),reduction amount(?l),downlink speed(v)and tool head diameter(D)on the formability of 6061 T6 aluminum alloy were studied by experiments on single point flow friction extrusion forming.The optimum forming parameters were obtained as follows:D=20 mm,ω=950 r·min-1,v=0.6 mm·min-1,?l=3.0 mm,under which the maximum forming height was 15 mm.The microstructures of different deformation zone were studied by optical microscope(OM)and electron backscatter diffraction(EBSD),and the results showed that the samples formed by single point flow friction extrusion were composed of two parts:heat affected zone(HAZ)and deformation zone(DZ).Compared with the parent material,the grain size and morphology of HAZ did not change significantly.The average grain size was 26.5μm.The structure distribution in DZ was not uniform,and the material in II(A)zone stirred three-dimensional under tool head,the structure refinement was not obvious,the average grain size was 23.8μm,and the large angle boundaries ratio was 45.1%.The fine equiaxed structure was formed in the II(B)region under the combined stirring and extrusion force,and the average grain size was only 6.54μm.The corner of concave die(II(C)zone)had the smallest structure with average grain size of only 3.75μm.The proportion of large angle grain boundaries in the region increased significantly to81.8%.Dynamic recrystallization occurred during deformation and stable recrystallization structure was formed.