Ultrafine grain structure features in spray-formed AZ31 magnesium alloy

• Spray forming of Mg alloy was carried out with different delivery tube orifice.
• ∅2.25 mm delivery tube orifice promoted the formation of ultrafine grains.
• A significant refinement of grain size ∼1 μm in ultrafine level was achieved.
• The enhancement in mechanical strength of spray-formed Mg alloy was observed.
• The fracture surface evidences mixed ductile and brittle fracture.

The ultrafine grain structure was developed in spray-formed AZ31 magnesium alloy by optimizing delivery tube orifice diameter. A significant refinement of grain size ∼1 μm in ultrafine level was achieved by using 2.25 mm delivery tube orifice diameter. The tensile strength value was increased from 145 MPa of as-cast alloy to 250 MPa of spray-formed alloy, registering an enhancement of ∼72%. On the other hand, elongation was increased from 6% to 13% using 2.25 mm orifice, registering more than onefold increase in elongation. Also, hardness enhancement of ∼49% was observed in spray-formed AZ31 alloy compared to as-cast alloy. The fracture surface of spray-formed AZ31 Mg alloy evidences the mixed type of ductile and brittle fracture.