Structure and Basic Mechanical Properties of Wrought Work-Hardenable Aluminium Alloys

6 Structure and Basic Mechanical Properties of Wrought Work-Hardenable Aluminium Alloys 

Al—Fe—Si contains about 0.6 wt% Fe and 0.8 wt% Si that has been added deliberately. The properties of 

Al—Fe—Si alloys, and of unalloyed aluminium, are strongly influenced by the elements which are in solid solution and the binary and higher phases that form. Increasing amounts of alloying additions lead to a marked increase in strength hut there is a decrease in electrical conductivity since transition elements have a high effective scattering power for electrons. 

Manganese additions increase the strength of unalloyed aluminium (Fig. 3.1-23). The chemical resistance is not impaired. These alloys have very good forming properties, when the Mn content is below the maximum solubility of Mn in the Al-rich a-phase, i. e., practically below 1.5 wt%. At higher Mn content, brittle AlgMn crystals form and impair workability. 

If Al—Mn alloys are rapidly solidified as in continuous casting, considerable supersaturation of Mn occurs. Fe reduces the solubility for Mn and promotes its precipitation in the form of multicomponent phases. Fe is often added to counteract supersaturation and for an increase of the tensile strength (Fig. 3.1-24). Depending on the amount of precipitation, Mn can inhibit recrystallization. 

---