Experimental and computational study on the load-jump tests of Al–Mg solid–solution alloy using instrumented indentation technique

Constant-load tests and load-jump tests were carried out using a microindenter in Al–5.3 mol% Mg solid–solution alloy. When the representative stress σ ¯ beneath the indenter decreases to a critical stress level, σ ¯ c ≅ 61   MPa , during indentation creep at 573 K, the stress exponent n for creep changes from 5 ( σ ¯ > σ ¯ c ) to 3 ( σ ¯ < σ ¯ c ). With load-jump tests in the stress range of n = 3, instantaneous plastic deformation (IPD) is initiated at stresses of σ ¯   >   54   MPa or more. When IPD does not occur, the n value obtained from load-jump tests agrees fairly well with that of constant-load tests. The experimental results are supported by finite-element simulations on load-jump tests. In order to evaluate the n value robustly by the load-jump test, the test should be conducted under a loading condition at which only elastic deformation takes place or no IPD occurs.