Evaluation of Elastoplasticity-Dependent Creep Property of Magnesium Alloy With Indentation Method: A Reverse Numerical Algorithm and Experimental Validation

Abstract

Magnesium (Mg) alloys have been widely used in automotive and aerospace industries due to its merits of exceptional lightweight, super strong specific strength, and high corrosion-resistance, where intermetallic compounds with a small volume are very critical to achieve these excellent performance. This study proposes a reverse analysis that can be employed to extract elastoplasticity-dependent creep property of commercial die-cast Mg alloys and their intermetallic compounds from instrumented indentation with two sharp indenters. First, the creep deformation that obeys the Norton's law (ε˙ = Aσn) is studied, and the parameters of A and n are determined from two indentation experiments conducted with different sharp indenters. Then, a numerical algorithm and dimensional function developed is extended to extract the elastoplasticity of various metallic materials by focusing on the loading stage of indentation experiments. By considering the full loading history with both linear increase and holding stages of loads, we propose a framework of reverse analysis to determine both elastoplasticity and creep properties simultaneously. Parallel indentation experiments on pure magnesium and aluminum and Mg alloys are performed, and the results agree well with the numerical predictions.

Numerical Investigation on Precipitation Hardening of Mg-Gd Alloys

“…To describe the plastic behavior of the matrix, a two-dimensional axisymmetric finite element model (see Figure 6 b) is built for reverse analysis [ 45 ], which refers to calculating the elastic–plastic properties of the matrix from the given indentation data. The standard Berkovich indenter [ 45 ] used in experiments is equivalently modeled as a rigid conical indenter with the same projected area (half cone angle of 70.3°). The Ludwick hardening model is applied to characterize the plastic behavior of the matrix material during quasi-static uniaxial deformation [ 46 ].…”

“…The resultant plastic stress-strain curve of the matrix is illustrated in Figure 7b. To describe the plastic behavior of the matrix, a two-dimensional axisymmetric finite element model (see Figure 6b) is built for reverse analysis [45], which refers to calculating the elastic-plastic properties of the matrix from the given indentation data. The standard Berkovich indenter [45] used in experiments is equivalently modeled as a rigid conical indenter with the same projected area (half cone angle of 70.3 • ).…”