Internal Stress during Creep in a Die-Cast AM50 Magnesium Alloy at 473 K

Abstract

The internal stress during high temperature creep was investigated for the die-cast AM50 magnesium alloy at 473 K through the straintransient dip test technique. The microstructure of the alloy is characterized by fine -Mg grains together with the -Mg 17 Al 12 particles located on the grain boundaries. The internal stress is proportional to the applied stress, when the applied stress ranges below the yield stress. The ratio of the internal stress to the applied stress is 0.36 for the alloy, which is about half of those for conventional pure metals such as Cu, -Fe and Ni. The small internal stress is a characteristic feature in the creep for the alloy.

Role of Eutectic Intermetallic Phase on Creep Strength in a Die-Cast Mg-Al-Ca Alloy: Evaluation by Internal Stress Measurement

“…The data for the AM50 (Mg-5.42 mass%Al-0.28 mass%Mn) die-cast alloy at 473 K obtained in our previous paper 22) are reproduced in the figure. The stress-exponent n ¼ 4:6 is detected at the low stress range below 65 MPa.…”

“…A detailed description of the strain transients after stress reductions and an evaluation scheme of the internal stress have been presented in our previous paper. 22) 3. Results and Discussion…”

“…2 Plots of minimum creep rates against stress for the AX52 die-cast alloy at 473 K. The data for the AM50 die-cast alloy are reproduced in the figure. 22) AM50 alloy, which is originated in the dislocation substructures generated during creep deformation. 22) On the contrary, the stress-independent component of the internal stress with the magnitude of 15 MPa would be ascribed to the microstructural features other than the dislocation substructures; typically to the eutectic intermetallic phase of the alloy.…”

“…It is well established for single-phase alloys that the internal stress is originated in the dislocation substructures generated during creep deformation. 21) The internal stress during creep has been investigated for the Mg-Al die-cast alloy AM50 in our previous study, 22) whose microstructure consists of a small number ofMg 17 Al 12 particles in a matrix of -Mg phase.…”

Effect of Calcium Additions on Creep Properties of a Die-Cast AM50 Magnesium Alloy

“…3, accompanied by the results for the AM50 alloy. 14,37,42) Two distinct creep regimes, the low and high stress-exponent regimes, are observed for each alloy. Hereafter, the low and high stress-exponent regimes are designated as Regime I and Regime II, respectively.…”