The effect of additions of Mn and Cr and the applied solidification technique on the structure of an Al-2.2 at% Zn-1.4 at% Mg alloy

Abstract

a) Dedicated to Prof. Dr. E. GUTSCHE on the occasion of his 60th birthdayThe structure and hardness of two AI-2.2 at74 211-1.4 atoh Mg alloys with additions of &In and Cr are investigated in dependence of the applied production technique, viz. classical processing method or rapid solidification (RSP). The RSP samples reveal the following main features : (i) Metastable supersaturation of Mn and Cr atoms, (ii) finely distributed precipitates of intermetallic phases (Al,Mn, AI,Cr) in the grain interior and in the boundaries, (iii) the low as well as high angle boundaries of the very fine grains are pinned by precipitates, and (iv) the formation of small precipitates during the ageing a t elevated temperatures. All these effects contribute t o the fact that the RSP samples have in many respects significantly better properties than the classically produced ones. Die Struktur und Harte von zwei AIZn(2,2 At%)Mg(l,4 At?(,)-Legierungen mit Zugaben von Mn und Cr werden in Abhangigkeit vom Herstellungsverfahren, namlich klassisches GieBen und Schnellerstarrung (RSP), untersucht. Die RSP-Proben zeigen folgende Hauptmerkmale : (i) Metastabile tfbersattigung der Mn-und Cr-Atome, (ii) fein verteilte Ausscheidungen intermetallischer Phasen (AI,Mn, Al,Cr) im Korninnern und in den Korngrenzen, (iii) die Kleinals auch die GroBwinkelkorngrenzen der sehr kleinen Korner werden von Ausscheidungen festgehalten und (iv) die Bildung kleiner Ausscheidungen wahrend der Alterung bei erhohten Temperaturen. Alle diese Effekte tragen dazu bei, daB die RSP-Proben in vielen Beziehungen bessere Eigenschaften besitzen als die dber das klassische GieRverfahren hergestellten.

Microstructure of 7N01 Aluminum Alloy Microalloyed with Er and Zr in the Homogenization Process

“…For example, at 490 ℃, the solid solubility of Mn in the aluminum matrix is 0.2 at%, and at 400℃ the solid solubility is only 0.1 at%. So the Mn-containing particles were formed during the annealing process [11]. The single-stage homogenization of 7xxx series aluminum alloys focuses on eliminating primary phases and the dendritic segregation of main elements, while neglecting the segregation of microalloying elements at the dendrites.…”