Precipitation hardening on mechanical and corrosion properties of extruded Mg10Gd modified with Nd and LaFriday (10.11.2017) 11:55 - 12:15 Part of:
Rare Earth elements are useful in Mg alloys when high strength, creep resistance and moderate corrosion rate are required. To improve mechanical and corrosion properties Nd and La are added to Mg10Gd, on which the influence of precipitation hardening was studied. An increase in strength by decreasing grain size and increasing volume fraction of RE-rich precipitates has been found when increasing the amount of alloying elements. Alloys containing La appear less ductile. Where crack propagation under 3-point bending in Mg10Gd and Mg10Gd1Nd is mostly driven by twinning, the alloys with La show suppressed twinning, but crack initiation and propagation caused by brittle, coarse precipitates. Precipitation hardening (T6) could not improve fracture toughness, mostly based on strong grain growth and low solubility of La in Mg. With adding alloying elements, the grain size is found slightly smaller in T6 condition, precipitates seem to pin grain boundaries and therefore limit grain boundary mobility. Alloys containing Nd show the best precipitation hardening response. Corrosion, investigated by voltammetry and immersion, shows the best behaviour in T6 condition. Corrosion rates and surface morphology are used to discuss corrosion properties.
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