Investigation of physical and mechanical characteristics of aluminium alloys 1915T, 1565ch and 6082-T6 at low temperatures

Introduction. Aluminium alloys are characterized by the absence of a cold fracture threshold, have high strength and ductility characteristics at low temperatures. However, the norms do not provide the design of aluminium structures that take cyclic force effects at low temperatures. In this regard, there is a need to study the properties and mechanisms of deformation and destruction of aluminium alloys to assess the possibility of their use in the Far North, as well as well as for the inner shells of isothermal reservoirs.

Materials and methods. The mechanical properties of structural aluminium alloys 1915, 1565ch and 6082 (similar to AD35) were studied. The specimens were tested for uniaxial tensile strength, impact toughness and fatigue strength, and the characteristics of static crack resistance were determined. The tests were carried out using Instron 8802, Instron 1000HDX, LabTex machines and Instron 450 MPX pendulum coper according to the relevant GOST standards of Russia.

Results. Experimental dependences of strength and elastic characteristics (tensile strength, offset yield strength, modulus of elasticity), as well as deformative ones (relative elongation and contraction of the cross-sectional area of specimens) of the studied alloys on the test temperature are obtained. The change of character of deformation of aluminium alloys with decrease in temperature is shown. The results of deformation and fracture resistance under conditions of impact bending and eccentric tension in the temperature range from –104...+20 °C are presented. Fracture toughness (crack resistance) was estimated according to the criteria of fracture mechanics when testing standard specimens with fatigue cracks. The paper also shows the limited limits of endurance based on 2 · 106, 107 cycles of the studied alloys at positive and negative temperatures.

Conclusions. The obtained results make it possible to reasonably select materials, assign loads when designing structures made of aluminium alloys and evaluate their service life.

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