In this paper, high-strength brass (Cu-40% Zn) alloy with magnesium (Mg) element was fabricated via powder technology process, and the effect of the additive Mg element on microstructural and mechanical properties of extruded brass alloys with alpha-beta duplex phases was investigated. Pre-mixed Cu -40% Zn alloy powder with 0.5-1.5 mass% pure Mg powder (Cu-40% Zn + Mg) was consolidated using a spark plasma sintering (SPS) equipment. SPSed Cu-40% Zn + Mg specimens consisted of alpha-beta duplex phases containing Mg(Cu1-xZnx)(2) intermetallic compounds (IMCs) with a mean particle size of 10 -30 mu m in diameter. The IMCs were completely dissolved in the alpha-beta duplex phases by a heat-treatment at 973 K for 15 min; thus, in order to disperse fine IMCs on alpha-beta duplex phase matrix, the SPSed Cu-40% Zn + Mg specimens were pre-heated at the solid solutionizing condition, and immediately extruded. The extruded specimen exhibited fine alpha-beta duplex phases, containing very fine precipitates of the above Mg(Cu1-xZnx)(2) IMCs with 0.5-3.0 pm in diameter. In particular, a mean grain size of the extruded Cu -40% Zn + 1.0% Mg specimen was 3.32 mu m analyzed using an electron back-scattered diffraction. Tensile properties of the extruded Cu-40% Zn + 1.0% Mg specimen were an average value of yield strength (YS): 328 MPa, ultimate tensile strength (UTS): 553 MPa, and 25% elongation. This indicated that the extruded Cu-40% Zn + 1.0% Mg specimen revealed the significantly high-strength properties compared to a conventional binary brass alloy with 229 MPa YS and 464 MPa UTS. A high strengthening mechanism of this wrought brass alloy was mainly due to the grain refinement because of a pinning effect by the fine Mg(Cu1-xZnx)(2) precipitates at the boundaries of each phase. (C) 2012 Elsevier B.V. All rights reserved.