Enhancing high-temperature mechanical properties and creep resistance of a cast Mg–6Zn–3Cu alloy by minor Cr addition

The influence of 0.4 wt% Cr addition on the microstructural development, elevated-temperature shear strength, softening behavior, and creep resistance of a cast Mg–6Zn–3Cu alloy was studied. The ultimate shear strength (USS) was evaluated through the shear punch test (SPT) over the temperature range of 298–498 K, while creep resistance was measured by impression creep test under stresses of 200 to 400 MPa at 498 K. The as-cast microstructure of the base alloy involves α -Mg, Mg(Zn,Cu) 2 , and Mg(Zn,Cu) intermetallic phases. In the Cr-containing alloy, however, the same phases co-exist with Cr that appears as very fine precipitates, and/or dissolved in Mg to form a solid solution. This led to the enhancement of strength, thermal stability, and creep resistance over the whole testing temperature range, through impeding recovery and recrystallization processes during high-temperature deformation processes.