Interfacial study of semi-solid aluminum alloy and stainless steel sheathed extrusion

Using sheathed extrusion technique, the bonding and forming of semi solid aluminum alloy with stainless steel sheath are successfully realized. The relationship between the interfacial shear strength and the solid fraction of semi solid aluminum alloy at different extrusion ratios is analyzed; the interfacial and fracture structure of the sheath material are studied by optical mieroseopy（OM） and scanning electric microscopy（SEM）. The result shows that interfacial shear strength increases with the increase of extrusion ratio, the maximum value of the interracial shear strength is obtained when solid fraction of aluminum alloy is 30%, solid phase and liquid phase of the semi solid aluminum alloy are bonded with stainless steel by turns along the interface, and the aluminum alloy can not be peeled from the stainless steel completely, which means nicer bonding occurs at the interface.