Study on the Microstructure and Mechanical Properties of As-Extruded AZ Magnesium Alloys by Micro-Adding La Rare-Earth Element

Changes of precipitates, dynamic recrystallization, texture, and properties at room temperature in the as-extruded AZ alloys (Al = 0, 3, 6, 8, wt.%) with 0.3% La addition were systematically investigated in this work. The analysis results suggest that new Mg12La with lamellar-structure precipitates in AZ01-0.3La alloy and new Al11La3 with needlelike structure precipitates in AZ-0.3La alloy with 3%–8% Al. Crashed Mg17Al12 could decrease the recrystallization temperature. Proper-sized Mg12La and Al11La3 could promote the dynamic recrystallization nucleation, leading to the reduction of grains in the as-extruded AZ-0.3La alloy, except for 6% Al. At room temperature, the strength of as-extruded AZ-0.3La alloys increases as Al increases, and the elongation first increases and then decreases, while the elongation is greater than 20% with 3%–8% Al. Due to the refined average grain size of 12.2 μm, the scattered and wakened 0002 base texture, the as-extruded AZ31-0.3La shows the best comprehensive tensile property compared with other AZ-0.3La alloys and AZ alloys, of which the Rp0.2 is 162 MPa, the Rm is 252 MPa, and the A is 21.7%.