Properties of Graphite‐Strengthened Magnesium

Abstract Mg was dispersion‐strengthened with graphite by powder metallurgy. The material was produced by ball milling Mg micropowder (median particle diameter 40 μm) with 3 vol.‐% graphite powder (median particle diameter 1–2 μm). After 8 h ball milling the product was consolidated by hot extrusion. Structural analysis revealed that a submicrocrystalline structure developed during ball milling. Tensile tests showed that the material was brittle even up to 300 °C and, therefore, most mechanical tests were carried out under compression. Under those conditions the reinforced material showed yield stresses of 270 MPa at ambient temperature, 170 MPa at 150 °C, and 125 MPa at 300 °C. Mg processed under the same conditions, but without graphite addition, had significantly lower yield stresses. The dispersion‐strengthened Mg showed a marked increase in creep resistance: at 200 °C and a stress, σ_c, of 100 MPa, the secondary creep rate, ϵ_s, was in the lower 10^–9 s^–1 range and at 300 °C and σ_c of 80 MPa, ϵ_s values of up to 1 × 10^–8 s^–1 were measured. The results are discussed.