Songli Zhang

Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles fabricated via magnetochemistry reaction

Abstract Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles are fabricated from A356-Zr(CO3)2 system via magnetochemistry reaction, and the morphologies, sizes and distributions of the in situ particles as well as the microstructures, mechanical mechanisms of the composites are investigated by XRD, SEM, TEM and in situ tensile tests. The results indicate that with the pulsed magnetic field assistance, the morphologies of the in situ particles are mainly with ball-shape, the sizes are in nanometer scale and the distributions in the matrix are uniform. The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed. These are due to the strong vibration induced by the applied magnetic field in the aluminum melt, which in turn, accelerates the melt reactions. The effects of the magnetic field on the above contributions are discussed in detail.

Preparation and microstructure of in-situ (ZrB2+Al2O3+Al3Zr)p/A356 composite synthesized by melt direct reaction

Abstract (ZrB 2 +Al 2 O 3 +Al 3 Zr)/A356 composites were synthesized by melt direct reaction from A356-(K 2 ZrF 6 +KBF 4 +Na 2 B 4 O 7 ) system. The phase compositions and the microstructures of the as-prepared composites were investigated by XRD, SEM and TEM. The results show that the reinforcements are composed of ZrB 2 and Al 2 O 3 ceramic phase particles and Al 3 Zr intermetallic particles. The ZrB 2 particulates are easy to join together to form some particle clusters and distribute along the α(Al) grain boundary. The morphologies of the ZrB 2 particulates are in hexagon-shape with the size of about 50 nm. The TEM investigation results of Al 3 Zr indicate that Al 3 Zr grows in the form of facet with the length-diameter ratio of about 20. The morphologies of Al 2 O 3 particles are in rectangular-shape and ellipsoidal-shape, with the size of about 0.1 μm. In addition, the interfaces of the matrix and particles are net and no interfacial outgrowth is observed.

In situ (Mg2Si+MgO)/Mg composites fabricated from AZ91-Al2(SiO3)3 with assistance of high-energy ultrasonic field

Abstract In situ (Mg 2 Si+MgO)/Mg composites fabricated from AZ91-Al 2 (SiO 3 ) 3 under high-energy ultrasonic field were investigated by XRD, DSC and SEM. The results indicate that the size, morphology and distribution of the in situ Mg 2 Si particles are greatly optimized with the assistance of the high-energy ultrasonic field. The amounts of the in situ Mg 2 Si particles are increased, the sizes are refined, the distributions become uniform, and the morphologies are changed to smooth olive-shape or spherical shape. The amounts of brittle β-Mg 17 Al 12 phases are decreased and the morphologies are granulated. The values of the tensile strength σ b and HB hardness are increased. These are due to the cavitation effects and acoustic streaming effects induced by the high-energy ultrasonic field.

Microstructure and mechanical properties of in situ TiB2/7055 composites synthesized by direct magnetochemistry melt reaction

Abstract In situ TiB2/7055 composites were successfully synthesized via magnetic chemical direct melt reaction from 7055 (Al-3B)-Ti system. The phase composition and the microstructure of the composites were investigated by XRD, OM and SEM technologies, and the mechanical and wear properties were tested. The results indicate that with the pulsed magnetic field assistance, the morphologies of in situ TiB2 particles are mainly hexagonal-shape or nearly spherical, the sizes are less than 1 μm, and the distribution of the matrix is uniform. Compared the microstructures of the 7055 aluminum matrix composites synthesized without pulsed magnetic field, the average size of α(Al) phase with pulsed magnetic field assistance is decreased from 20 to 10 μm, the array of the second phase is changed from continuous net-shape to discontinuous shape. With the pulsed magnetic field, the tensile strengths of the composites are enhanced from 310 to 330 MPa, and the elongations are increased from 7.5% to 8.0%. In addition, compared with matrix alloy, the wear mass loss of the composites is decreased from 111 to 78 mg under a load of 100 N for 120 min.

Preparation and wear properties of TiB2/Al−30Si composites via in-situ melt reactions under high-energy ultrasonic field

Abstract TiB 2 /Al–30Si composites were fabricated via in-situ melt reaction under high-energy ultrasonic field. The microstructure and wear properties of the composite were investigated by XRD, SEM and dry sliding testing. The results indicate that TiB 2 reinforcement particles are uniformly distributed in the aluminum matrix under high-energy ultrasonic field. The morphology of the TiB 2 particles is in circle-shape or quadrangle-shape, and the size of the particles is 0.1–1.5 μm. The primary silicon particles are in quadrangle-shape and the average size of them is about 10 μm. Hardness values of the Al–30Si matrix alloy and the TiB 2 /Al–30Si composites considerably increase as the high energy ultrasonic power increases. In particular, the maximum hardness value of the in-situ composites is about 1.3 times as high as that of the matrix alloy when the ultrasonic power is 1.2 kW, reaching 412 MPa. Meanwhile, the wear resistance of the in-situ TiB 2 /Al–30Si composites prepared under high-energy ultrasonic field is obviously improved and is insensitive to the applied loads of the dry sliding testing.