Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Abstract:

Peculiarities of formation of solid-state joining of the parts for bimetallic heat exchanger are considered. For solid-state activation of the surfaces, being joined, the layer-activator (liquid gallium) is used. Inter-granular segregation of an activator along the grain of the alloy-matrix is rapid and deep, which leads to polygonal structure in the diffusion zone. A negative fact for such joints is the brittleness of materials after intermetallic phase transformation of the chemical elements of alloy-matrix with gallium. The joint formed with an increasing of volume of the diffusion zone after rotation of newly formed phases at growth. Rotation of grains leads to emergence of high local internal stresses. Excess of an activator may be a reason for generation and distribution of main cracks. Indentation allows recording an abnormal decrease of the micro-hardness in grain boundary area. Obtained data of the Young's modulus, micro-hardness and coefficient of plasticity, with spectral mapping of chemical elements and phase analysis are allowed to exactly specify structural components that are the initiators of the materials stress state and are the reason for local cracks.

• Periodical: Materials Science Forum (Volumes 768-769)
• Pages: 321-326
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.768-769.321
• Online since: September 2013
• Authors: Julia Khoklova
• Keywords: Aluminum (Al), Berkovich Indenter, Bi-Metal, Crack, Gallium, Intergranular Diffusion, Local Internal Stress, Magnesium, Micromechanical Test, Nanoindentation

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