Er、Zr微合金化5083铝合金的超塑性

Superplasticity of 5083 aluminum alloy containing Er and Zr

针对5E83合金(Er、Zr微合金化5083合金),采用超塑性拉伸试验、扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM),探究了Er、Zr微合金元素、晶粒尺寸、变形温度、应变速率对合金超塑性的影响。通过再结晶退火、空冷和水冷的搅拌摩擦加工(FSP),分别获得了晶粒尺寸为7.4、5.2、3.4μm的完全再结晶组织,作为初始状态进行超塑性拉伸。结果表明,初始晶粒尺寸越细小,超塑性伸长率越高。当晶粒尺寸>5μm时,超塑性变形过程晶粒粗化缓慢,细化初始晶粒可显著提高超塑性;而当晶粒尺寸<5μm时,超塑性变形过程晶粒粗化严重,进一步细化初始晶粒对超塑性的提高有限。不同变形温度、应变速率的超塑性拉伸结果显示在变形温度为450~540℃、应变速率为1.67×10^(-4)~1.67×10^(-1)s^(-1),超塑性伸长率随变形温度和应变速率的提高呈现先上升后下降再上升的趋势;变形温度为520℃、应变速率为1.67×10^(-3)s^(-1)条件下,水冷FSP态合金获得最大伸长率330%,对应的超塑性变形机理主要是晶界滑移。相比于5083合金,Er、Zr的添加显著提高了超塑性,这主要是由于Er、Zr在Al基体中形成了纳米级弥散的Al3(Er, Zr)相,在超塑性拉伸时能够钉扎晶界,阻碍晶界迁移,在晶粒尺寸>5μm时,有效地抑制了晶粒长大,从而提高了超塑性。

Taking 5E83 alloy(Er and Zr microalloyed 5083 alloy)as tested material,the effects of Er and Zr microalloying elements,grain size,deformation temperature and strain rate on superplasticity of the alloy were investigated by means of superplastic tensile test,scanning electron microscope(SEM),electron backscatter diffraction(EBSD)and transmission electron microscope(TEM).Through recrystallization annealing,air cooling and water cooling friction stir processing(FSP),the grain sizes of 7.4,5.2 and 3.4μm were obtained,respectively,and used as the initial state for superplastic stretching.The results show that the smaller the initial grain size,the higher the superplastic elongation.When the grain size is greater than 5μm,the grain coarsening is slow during superplastic deformation,and refining the initial grain can significantly improve superplasticity.However,when the grain size is less than 5μm,grain coarsening is serious during superplastic deformation,and further refinement of initial grain has limited effect on superplasticity.The superplastic tensile results at different temperatures and strain rates show that when the temperature is in range of 450-540℃and the strain rate is in range of 1.67×10^(-4)-1.67×10^(-1) s^(-1),the superplastic elongation first increases,then decreases and then increases with the increase of temperature and strain rate.Under the condition of temperature of 520℃and strain rate of 1.67×10^(-3) s^(-1),the water-cooled FSP alloy obtains the largest elongation of 330%corresponding to grain boundary slip superplastic deformation mechanism.The addition of Er and Zr significantly improves the superplasticity,which is mainly due to the formation of nano-dispersed Al3(Er,Zr)phase in Al matrix that can pin the grain boundary and hinder the migration of the grain boundary during superplastic stretching.When the grain size is greater than 5μm,the Al3(Er,Zr)phase effectively inhibits the grain growth thus improving the superplasticity.