EFFECT OF Mn-ADDITION ON MICROSTRUCTURE, THERMAL AND MECHANICAL PROPERTIES OF CAST Al-Sc-Zr-BASED ALLOYS
Abstract
The effect of Mn content on microstructure, thermal and mechanical properties of cast Al-Sc-Zr alloy during isochronal annealing was studied. Specimens of three as-cast Al-Sc-based alloys with a various content of Mn and Zr were annealed up to ~ 570 oC.
Precipitation reaction was studied by elec trical resistometry, microhardness (HV0.3) and differential scanning calorimetry measurements. The microstructure development was investigated by transmission electron microscopy and electron diffraction.
The distinct microhardness increase observed after annealing above 270 oC corresponds excellently to the fastest resistivity changes as well as the heat flow changes. These changes are due to the precipitation of the Al3Sc particles.
The apparent activation energy for precipitation of Al3Sc particles was determined. The phases of the Al-Sc-Zr system and also of the Al-Mn system were observed.