Formation of Layered Mg/Eutectic Composite Using Diffusional Processes at the Mg-Al Interface

Abstract

A processing technique has been developed to produce a layered magnesium-intermetallic compound light composite from elemental magnesium and aluminium sheets. Structural examination and measurements of transition layer grown at the magnesium-aluminium interface at high annealing temperature were performed. It was found using Mg/Al diffusion couple that solid state diffusion results in development of Al 3 Mg 2 and Mg 17 Al 12 intermetallic compounds, which are separated into two sublayers. The rate of the layer growth substantially increases with the appearance of the liquid phase at the Mg-Al interface. The microstructure resulted from the partial solidification contains an eutectic composed of Mg 17 Al 12 intermetallic compound and solid solution aluminium in magnesium. The structural processes, which transform the magnesium-aluminium interface, can be applied for fabrication of layered magnesium-eutectic composites. Alternately stacked magnesium and aluminium sheets, formed into a packet, were heated until aluminium was exhausted throughout the course of the Mg-Al reaction with the liquid phase contribution. As a result, the composite containing residual magnesium and layers of eutectic mixture (Mg 17 Al 12 and solid solution of aluminium in magnesium) was obtained. Rapid solidification resulted in fine-grained eutectic microstructure development. Using the presented method, composites with required thickness ratio of magnesium and the eutectic layers can be obtained by choosing appropriate thickness ratio of starting magnesium and aluminium sheets.Keywords: metal-matrix composites, layered composite, intermetallicsOpracowano metodę otrzymywania kompozytu zbudowanego z warstw magnezu i warstw zawierających związek między-metaliczny, wykorzystując jako substraty blachę magnezu i blachę aluminium. Stosując złącze dyfuzyjne Mg/Al przeprowadzono badania zmian strukturalnych zachodzących pod wpływem temperatury na granicy międzyfazowej magnez-aluminium oraz badania wzrostu warstwy produktów reakcji. Stwierdzono, że warstwa ta, utworzona w wyniku zachodzących w stanie stałym przemian dyfuzyjnych, składa się z dwu podwarstw o strukturze związków międzymetalicznych: Al 3 Mg 2 i Mg 17 Al 12 . Szybkość wzrostu warstwy zwiększa się znacznie, gdy na granicy Mg-Al pojawia się faza ciekła. Mikrostruktura utworzona podczas krzepnięcia zawiera głównie eutektykę, składającą się ze związku międzymetalicznego Mg 17 Al 12 i roztworu stałego aluminium w magnezie. Zjawiska zachodzące na granicy magnez-aluminium zostały wykorzystane do formowania kompozytu warstwowego magnez-eutektyka. Arkusze blachy magnezu i blachy aluminium ułożone naprzemiennie w pakiet wygrzewa się do momentu wyczerpania się aluminium w reakcji z magnezem zachodzącej z udziałem fazy ciekłej. W wyniku powstaje kompozyt składający się z warstw pozostałego magnezu i warstw eutektyki zbudowanej z Mg 17 Al 12 i roztworu stałego aluminium w magnezie. Gwałtowne krzepnięcie pozwala uzyskać eutektykę o drobnoziarnistej mikrostrukturze. Przez dobór stosunku grubości wyjś...

The Influence of the Asymmetric Arb Process on the Properties of Al-Mg-Al Multi-Layer Sheets / Wpływ Asymetrii W Procesie Arb Na Właściwości Wielowarstwowych Blach Al-Mg-Al

“…No diffusion layer was observed to have been formed at the Mg-Al joint boundary in Al-Mg-Al sheets produced in either the symmetric or asymmetric rolling process. The rolling was conducted at a temperature lower than the eutectic temperature which, for the Mg-Al system, is 437°C [5,41,42]. the test results reported in study [41] demonstrate that it is possible to obtain a diffusion bond between the magnesium layer and the aluminium layer by soaking the package at a temperature of 430 o C for a duration of 20 minutes.…”

“…The rolling was conducted at a temperature lower than the eutectic temperature which, for the Mg-Al system, is 437°C [5,41,42]. the test results reported in study [41] demonstrate that it is possible to obtain a diffusion bond between the magnesium layer and the aluminium layer by soaking the package at a temperature of 430 o C for a duration of 20 minutes. In the study presented herein, the bond between the metals is of the adhesion type; the rolling temperature was too low for reactions to occur between magnesium and aluminium, as a result of which metallurgical bonding of individual layers in the strip would have been obtained.…”

Fabrication and Microstructure of Diffusion Alloyed Layers on Pure Magnesium Substrate/ Wytwarzanie I Struktura Dyfuzyjnych Stopowych Warstw Na Magnezie

“…This indicates that the alloyed layers form during the solidification of the liquid layer, which appears at the interface between magnesium substrate and the Al-Zn powder mixture. In previous work [19] author and co-workers examined the layer growth, which was formed in elevated temperatures at the Mg-Al interface and reported that the rate of the layer growth substantially increases with the appearance of the liquid phase at the interface. Under experiment condition applied in a present work, addition of Zn into the diffusion powder mixture results in the formation of intermetallic phases that exhibit a low melting temperature below 437…”

Microstructure of the Bonding Zone Between AZ91 and AlSi17 Formed by Compound Casting

“…Successful research on the joining of Mg with Al as well as the fabrication of Mg-Al compound parts is expected to further increase the application of these materials in lightweight structures. Different methods have been used to join these two types of materials, for instance, MIG welding [1], laser welding [2], friction stir welding [3], diffusion bonding [4,5], hot rolling [6,7], explosive cladding [8], twin-roll casting [9].…”