The first reported tensile semi-solid stress/strain data for as-cast magnesium alloy Mg Al3 Zn1 are provided. The results show that the maximum tensile stress at the solidus temperature (460 degrees C) was 13 MPa. Furthermore, this alloy has no ductility above 540 degrees C. and cannot sustain tensile stresses above 560 degrees C. Based on these tests, an equation relating the maximum tensile stress with temperature was derived. The microstructure of the tested specimens was also examined to link the tensile properties to fraction Solid and microstructure. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.