稀土Y对挤压态7075铝合金微观组织和力学性能的影响

Effect of Rare Earth Yttrium on Mechanical Properties and Microstructure of Extruded 7075 Aluminum Alloy

通过在7075铝合金中添加质量分数为0.2%的稀土Y,利用扫描电子显微镜(SEM)、电子背散射衍射(EBSD)、透射电子显微镜(TEM)和拉伸试验等方法,研究了Y元素在反向挤压过程中对7075铝合金微观组织和力学性能的影响及其作用机理。力学性能测试表明,经过反向挤压的7075-0.2Y铝合金的硬度、极限拉伸强度、伸长率都得到了提高,分别为106.2 HV、444.53 MPa和14.9%。微观组织分析表明,稀土Y的添加,可以促进合金在挤压过程中发生动态再结晶,并使7075铝合金基体中的合金元素Zn、Mg、Cu、Mn和杂质元素Fe、Si等发生偏析聚集,形成大尺寸的含Y夹杂物和含Y共晶相,如AlFeMnY、AlZnY、(AlaZnbMgcCudFeeMnfCrgTihZriAgjCokMolY)等。这些含Y颗粒会在挤压过程中,改变尺寸大小和分布状态,形成硬脆相,减少基体中的杂质元素,影响合金的力学性能,并通过对富Fe相的影响进一步改变合金中各织构的含量和分布。

By adding 0.2%Y to 7075 Al alloy,the effect and mechanism of Y on the microstructure and mechanical properties of 7075 Al alloy during indirect extrusion was studied by using SEM,EBSD,TEM and tensile testing,The mechanical properties test shows that the hardness,ultimate tensile strength and elongation of the indirect-extruded 7075-0.2Y Al alloy were increased to 106.2 HV,444.53 MPa and 14.9%,respectively.The microstructure analysis shows that the addition of Y can promote the dynamic recrystallization of the alloy during the extrusion process,cause segregation and aggregation of alloying elements like Zn,Mg,Cu,Mn and impurity elements Fe,Si in 7075 Al alloy matrix,forming large-size Y-containing inclusions and Y-containing eutectic phases,such as AlFeMnY,AlZnY,(Al a Zn b Mg c Cu d Fe e Mn f Cr g Ti h Zr i Ag j Co k Mo l Y).These Y-containing particles will change the size and distribution during the extrusion process to form hard-brittle phases,reduce the impurity elements in the matrix,affect the mechanical properties of the alloy,and further change the contents and distribution of textures in the alloy by affecting the Fe-rich phases.