A novel concept for self-healing metallic structural materials: Internal soldering of damage using low melting eutectics

Materials & Design, vol. 252, pp. 113821

Abstract

• Proof of concept to close internal defects by melting eutectic constituents. • More than 120 % regained ductility in Al-Sn model alloy system over pure Al. • Polymorphy of Sn can be exploited to optimize dispersion of the healing phase. • Discussion of transferring the approach to industrial Al alloys and other metals. A novel self-healing concept for metallic structural materials based on internal soldering using low-melting constituents is presented. The proof-of-principle study is based on a binary Al–4.28 wt%-Sn alloy, where a Sn-rich eutectic with a liquidus temperature of 228 °C acts as a self-assembling healing agent, and validated by a two-pronged approach: (i) A bulk sample with artificial damage is exploited to evaluate the healing effect on large cracks open to the sample surface and to gauge its mechanical effectiveness, whereas (ii) a 3.5 µm-thick Al 2 O 3 -Al-Sn-Al thin film multilayer architecture was used as a model system to study the healing mechanisms of small-scale internal damage induced by bending of the brittle Al 2 O 3 layer. A crack length of ∼1.6 mm could be successfully re-filled by the low-melting eutectic with a simple annealing treatment at 400 °C for 30 min, which increased the bulk tensile ductility to more than 120 % compared to a similarly damaged pure Al sample. Furthermore, it is shown that the dispersion of the Sn-rich eutectic can be effectively controlled by utilising the polymorphy of Sn during material production. Alloy design perspectives for translating these findings towards industrial materials and applications are outlined and discussed.

Authors 8

1. L. Tanure Aachen Chair of Sustainable Ferrous Metallurgy

   Max-Planck-Institut für Nachhaltige Materialien · RWTH Aachen University

   Affiliation as printed

   Chair of Sustainable Ferrous Metallurgy, RWTH Aachen University, Intzestr. 1, 52072 Aachen, Germany

   Max-Planck-Institute for Sustainable Materials, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

2. Lena Patterer Aachen Chair of Sustainable Ferrous Metallurgy

   Max-Planck-Institut für Nachhaltige Materialien · RWTH Aachen University

   Affiliation as printed

   Chair of Sustainable Ferrous Metallurgy, RWTH Aachen University, Intzestr. 1, 52072 Aachen, Germany

   Max-Planck-Institute for Sustainable Materials, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

3. Matej Fekete Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

4. Stanislav Mráz Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

5. Soheil Karimi Aghda Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

6. M. Hans Aachen Materials Chemistry

   RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

7. Jochen M. Schneider Aachen Materials Chemistry

   Max-Planck-Institut für Nachhaltige Materialien · RWTH Aachen University

   Affiliation as printed

   Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, 52074 Aachen, Germany

   Max-Planck-Institute for Sustainable Materials, Max-Planck-Str. 1, 40237 Düsseldorf, Germany

8. Hauke Springer corresponding Aachen Chair of Sustainable Ferrous Metallurgy

   Max-Planck-Institut für Nachhaltige Materialien · RWTH Aachen University

   Affiliation as printed

   Chair of Sustainable Ferrous Metallurgy, RWTH Aachen University, Intzestr. 1, 52072 Aachen, Germany

   Max-Planck-Institute for Sustainable Materials, Max-Planck-Str. 1, 40237 Düsseldorf, Germany