Express control of aluminum alloys mechanical properties by instrumented indentation

A technique for determining the mechanical properties of aluminum alloys by instrumented indentation with a ball indenter was developed. The technique is based on the correlation between the maximum equal strain during specimen tension and the indentation strain hardening parameter in the plastic region. This made it possible to obtain a formula for calculating the ratio of yield strength to ultimate strength using the strain hardening parameter. The values of the loading ratio necessary to achieve the maximum Brinell hardness, which is proportional to the ultimate tensile strength with a constant conversion factor for the tested aluminum alloys, were established. The ultimate tensile strength value and the ratio of yield strength to ultimate tensile strength allow calculating the yield strength of the alloy, which is usually determined quite difficult by indentation according to other known methods. Given the unambiguous correlation between the ratio of yield strength to ultimate tensile strength and the strain hardening parameter, it is proposed to use it as a diagnostic parameter in the estimation the degree of fragility of structural materials. The higher this parameter, the more prone the material is to brittle fracture. The proposed method for determining mechanical properties by instrumented indentation is quite simple and easily responds to automation, which increases the productivity of monitoring the mechanical properties of aluminum alloys.

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