Development of high-strength pure magnesium and wrought magnesium alloys AZ31, AZ61, and AZ91 processed by hydrostatic extrusion with back pressure

Abstract

Abstract Cold hydrostatic extrusion with and without back pressure of commercial Mg 99.5+% and AZ31, AZ61, and AZ91 wrought magnesium alloys has been performed on a press operating up to 2000 MPa with a back pressure reaching up to 700 MPa. Application of back pressure extended the formability of Mg, and AZ-type magnesium alloys, which decreases with the increase in the Al content. Fibrous and elongated grains above 1 micrometre and nanometre scale sub-grains and grains were observed. The strength of all materials was significantly higher in comparison to materials conventionally and hydrostatically hot-extruded, hot ECAP-ed or after hot wire drawing. In comparison to materials processed by traditional methods the ultimate tensile strength increment after hydrostatic extrusion with back pressure increases gradually with an increase in Al content reaching for AZ91 almost 40%. The potential application of AZ-type magnesium alloys as semi-products for degradable medical implants or high strength structural components is indicated.