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The damage model parameters for Magnesium AZ61A alloy were fitted using DMGfit_55p_v1p1. The original sources, the fitting procedure and results are detailed below.


Source Data

The source data was based on the digitization of AZ61A stress-strain curves. A compression and a tension stress-strain curves, respectively, were digitized. The environment temperature and strain rate were not specified, on the diagrams, so they were assumed to be 293K and 0.001 1/s respectively.

Mg.009 AZ61A magnesium alloy forging compressive stress-strain curve. [1]

Composition: Mg-6Al-1Zn. UNS M11610
Mg.009 AZ61A magnesium alloy forging tensile stress-strain curve. [1]

Composition: Mg-6Al-1Zn. UNS M11610

Digitized data files:

Material and environmental parameters for Mg AZ61 alloy
Constant Value
Temperature 293K
Strain rate 0.001 1/s
Young's modulus 44.8 GPa
Poisson ratio 0.35

Fitting Procedure

We followed the general outline of the fitting procedure detailed on the DMGfit_55p_v1p1 page with some modifications to accommodate for the types of available data. For example, temperature dependence constants were not fitted because we did not have temperature dependent data.

First we preformed a rough manual fit, by adjusting several of the Cn constants as detailed below, followed by an automatic optimization for the same set of constants. The initial manual fit helped the goal seeking algorithm move in the right direction toward convergence, and also helped the algorithm converge faster.

The following parameters were fitted manually in the order listed below:

  1. Fit C3, which is the yield stress.
  2. Fit C9, C7
  3. Fit C15, C13
  4. Fit Cb
  5. Readjust C9, C7, C15 and C13 after fitting Cb.

Finally, we performed an optimization procedure. To do this we unchecked the parameters mentioned above, while leaving the rest of the parameters checked and hit the 'optimize' button. The results are detailed in the section below.


Screenshot of the DMGfit UI after performing the fitting operations listed in AZ61A#Fitting_Procedure

Estimated constants and their values
Constant Value Meaning
C3 100 MPa Rate independent yield stress
C5 1e-05 1/sec Transition strain rate from rate independent to dependent yield
C7 1/MPa 9.16489 Kinematic recovery constant
C9 19485.5 MPa Kinematic anisotropic hardening modulus
C13 282.43 1/(MPa sec) Isotropic dynamic recovery
C15 109944 MPa Isotropic hardening modulus
Cb 1.49397 Tension/compression asymmetry constant


  1. 1.0 1.1 "Magnesium Design", Dow Chemical Co., 1957. As published in Aerospace Structural Metals Handbook, vol 3, Code 3603, CINDAS/USAF CRDA Handbooks Operation, Purdue University, 1995, p4
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