Multi-pass hot extrusion was used to prepare the Al2O3/AZ31 composite.The microstru-cture was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and mechanical properties were tested by Vickers hardness tester and electron universal strength tester. The results show that Al2O3 particles are uniformly distributed in AZ31 magnesium matrix by multi-pass hot extrusion. The grain refining effect of Al2O3 particles on the matrix is enhanced, and the grain size of the composite decreases significantly with the increase of the pass. During the hot extrusion process, the dislocation density around the Al2O3 particles increases, and the high-density dislocation region facilitates the dynamic recrystallization nucleation, so that the grains of the Al2O3/AZ31 composite are significantly refined. The Al2O3 particles are gradually distributed into a long strip from the initial island distribution, then distributed in a linear pattern, and finally distributed uniformly in the form of particles in the AZ31 magnesium matrix. After fourth-pass hot extrusion, the mechanical properties of Al2O3/AZ31 composite are significantly improved, and hardness, tensile strength and yield strength are 89HV, 305MPa and 198MPa, respectively. The hardness, tensile strength and yield strength increase by 19.2%, 14.8%, and 14.1%, respectively, compared with the first-pass hot extrusion.
LIU J , ZHANG J L , QU Z B , et al. Effect of rare earth Gd on corrosion resistance of AZ31 magnesium alloy[J]. Journal of Materials Engineering, 2018, 46 (6): 73- 79.
CHELLIAH N M , SINGH H , SURAPPA M K . Processing, microstructural evolution and strength properties of in-situ magnesium matrix composites containing nano-sized polymer derived SiCNO particles[J]. Materials Science and Engineering:A, 2017, 685, 429- 438.
CHANG H , WANG J L , ZHENG M Y , et al. Effect of equal channel angular pressing on the microstructure evolution and mechanical property of the SiCP/AZ91 composite fabricated by stir-casting[J]. Acta Materiae Compositae Sinica, 2017, 34 (3): 611- 618.
LI J M , DENG K K . Effect of heat treatment on microstructure and mechanical properties of particle reinforced magnesium matrix composite[J]. Transactions of Materials and Heat Treatment, 2012, 33 (9): 29- 32.
KARTHICK E , MATHAI J , TONY J M , et al. Processing, microstructure and mechanical properties of Al2O3 and SiC reinforced magnesium metal matrix hybrid composites[J]. Materials Today Proceedings, 2017, 4 (6): 6750- 6756.
FENG Y , CHEN C , PENG C Q , et al. Research progress on magnesium matrix composites[J]. The Chinese Journal of Nonferrous Metals, 2017, 27 (12): 2385- 2407.
WU K , DENG K K , NIE K B , et al. Microstructure and mechanical properties of SiCp/AZ91 composite deformed through a combination of forging and extrusion process[J]. Materials & Design, 2010, 31 (8): 3929- 3932.
PARAMSOTHY M , HASSAN S F , SRIKANTH N , et al. Enhancing tensile/compressive response of magnesium alloy AZ31 by integrating with Al2O3 nanoparticles[J]. Materials Science and Engineering:A, 2009, 527 (1/2): 162- 168.
XIAO P , GAO Y , YANG C , et al. Microstructure, mechanical properties and strengthening mechanisms of Mg matrix composites reinforced with in situ nanosized TiB2 particles[J]. Materials Science and Engineering:A, 2018, 710, 251- 259.
HABIBNEJAD K M , MAHMUDI R , POOLE W J . Work hardening behavior of Mg-based nano-composites strengthened by Al2O3 nano-particles[J]. Materials Science and Engineering:A, 2013, 567 (4): 89- 94.
SRINIVASAN M , LOGANATHAN C , NARAYANASAMY R , et al. Study on hot deformation behavior and microstructure evolution of cast-extruded AZ31B magnesium alloy and nanocomposite using processing map[J]. Materials & Design, 2013, 47, 449- 455.
FAN Y Y , LI Q S , LI Y F . A study on AZ91D Mg matrix compound materials enforced by Al2O3 particles[J]. China Foundry Machinery & Technology, 2011, (1): 16- 19.
WEN L H , JI Z S , LI X L . Effect of extrusion ratio on microstructure and mechanical properties of Mg-Nd-Zn-Zr alloys prepared by a solid recycling process[J]. Materials Characterization, 2008, 59 (11): 1655- 1660.
ZHU Y , HU M L , WANG D J , et al. Microstructure and mechanical properties of AZ31-Ce prepared by multi-pass solid-phase synthesis[J]. Materials Science and Technology, 2018, 34 (7): 876- 884.
DENG K K , WU K , WANG X J , et al. Microstructure evolution and mechanical properties of a particulate reinforced magnesium matrix composites forged at elevated temperatures[J]. Materials Science and Engineering:A, 2010, 527 (6): 1630- 1635.
CAVALIERE P , EVANGELISTA E . Isothermal forging of metal matrix composites:recrystallization behaviour by means of deformation efficiency[J]. Composites Science and Technology, 2006, 66 (2): 357- 362.
HE G J , LI W Z . Influence of nano particle distribution on the strengthening mechanisms of magnesium matrix composites[J]. Acta Materiae Compositae Sinica, 2013, 30 (2): 105- 110.
PARAMSOTHY M , CHAN J , KWOK R , et al. The synergistic ability of Al2O3 nanoparticles to enhance mechanical response of hybrid alloy AZ31/AZ91[J]. Journal of Alloys and Compounds, 2011, 509 (28): 7572- 7578.
HASSAN S F , PARAMSOTHY M , PATEL F , et al. High temperature tensile response of nano-Al2O3 reinforced AZ31 nanocomposites[J]. Materials Science and Engineering:A, 2012, 558, 278- 284.
ALAM M E , HAMOUDA A M S , NGUYEN Q B , et al. Improving microstructural and mechanical response of new AZ41 and AZ51 magnesium alloys through simultaneous addition of nano-sized Al2O3 particulates and Ca[J]. Journal of Alloys and Compounds, 2013, 574, 565- 572.
KOIKE J . Enhanced deformation mechanisms by anisotropic plasticity in polycrystalline Mg alloys at room temperature[J]. Metallurgical and Materials Transactions A, 2005, 36 (7): 1689- 1696.