Investigation of secondary phase particles in spray deposited 7000 series aluminium alloys

Abstract

Three 7000 series aluminium alloys, namely SS70, N707, and 7075, were produced by rapid solidification using the spray deposition process, which yields massive preforms directly from the liquid state. Optical and electron microscopy, along with energy dispersive X-ray and microprobe analysis, revealed the presence of coarse constituent phases and dispersoid particles. Constituent phases of the N707 alloy were (Al,Cu)₆(Fe,Cu), Al₆Fe (modified), Mg(Zn,Cu,Al)₂, and amorphous silicon oxide. The same phases were present in the SS70 alloy; however, this alloy also contained an additional zirconium rich phase. In the 7075 alloy, (Al,Cu)₆(Fe,Cu), (Fe,Cr,Mn)₃SiAl₁₂, Al₁₈Mg₃Cr₂, an Mg-Si rich compound, and amorphous silicon oxide were observed. The dispersoid phase present in the SS70 and N707 alloys was identified as Al₃Zr.