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.

Structural superlight porous metals (Review)

“…Department of Physico-Metallurgical Processes of Welding Light Metals and Alloys of the E.O. Paton Electric Welding Institute of the NAS of Ukraine made experimental bimetal joints of PA from V95 and AK7 alloys with monolithic aluminium (AD1, AK12, AMg6) and magnesium (ML4, MA2-1) alloys (Figure 11) by the method of activation of the surfaces being joined at 140-300 °C for fabrication of superlight blocks for encapsulation of microelectronics for aero- space applications [11][12][13][14][15][16][17]. Such joints can also be used for fastening the granules-semi-finished product in fabrication of composite armour plates of combined arms assault bulletproof vest (Figure 12), built by the modular principle that ensures all-round protection of the torso from fragments, cold and small arms.…”