喷射成形含锰Al-Zn-Mg-Cu合金的显微组织

摘要

为提高Al-Zn-Mg-Cu合金的强度,利用喷射成形的方法制备了含锰Al-Zn-Mg-Cu合金锭,并利用X射线衍射(XRD)、光镜(OP)、扫描电镜(SEM)、透射电镜(TEM)和示差扫描热分析(DSC)研究了其微观组织特征.结果表明:喷射沉积坯主要由晶粒尺寸为5～25 μm的细小等轴晶粒、MgZn2 和Al6Mn相组成.纳米级的MgZn2颗粒弥散分布于基体,而平均尺寸为5 μm的Al6Mn一次相颗粒沿晶界析出.沉积合金中也发现了少量的CuAl2, Al3Zr 和共晶组织.沉积坯中缩孔疏松的体积分数约为12%.DSC分析结果说明大部分溶质原子在喷射成形过程中析出,在450 ℃以下的加热过程中没有明显的热反应发生.随着退火温度的升高,基体晶粒和Al6Mn颗粒单调长大,但Al6Mn颗粒的长大速率显著低于基体晶粒的长大速率.当退火温度高于375 ℃时,基体晶粒迅速长大.%With the aim to improve the strength of Al-Zn-Mg-Cu alloy, the alloy billet containing Mn was produced by spray forming method, and the microstructural features were investigated using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the billet mainly consists of fine equiaxial grains of MgZn2 and Al6Mn with size ranging from 5 μm to 25 μm. Nano-scaled MgZn2 is dispersed in the as-sprayed alloy, primary Al6Mn particles are precipitated at grain boundaries with an average size of 5 μm. A few CuAl2, Al3Zr and eutectic are also found in as-sprayed Al alloy. The volume fraction of the porosity is about 12%. DSC result indicates that most of the solutes are precipitated during spray forming process, and no obviously thermal effects occur below 450 ℃. Both matrix grains and Al6Mn particles grow monotonously with the increase of annealing temperature, but the growth rate of Al6Mn particles is markedly lower than that of Al grains, and the matrix grains grow rapidly when the annealing temperature is above 375 ℃.