Daihong Xiao

Effect of VC and NbC additions on microstructure and properties of ultrafine WC-10Co cemented carbides

The nanocomposite WC-Co powders were prepared through planetary ball milling method. Effects of grain growth inhibitor addition and the vacuum sintering parameters on the microstructure and properties of ultrafine WC-10Co cemented carbides were investigated using X-ray diffractometer, scanning electron microscope and mechanical property tester. The results show that VC and NbC additions can refine the WC grains, decrease the volume fraction of Co3W3C phase in ultrafine WC-10Co cemented carbides, and increase the hardness and fracture toughness of the base alloys. After sintering for 60 min at 1400 °C, the average grain size and hardness of ultrafine-grained WC-10Co-1VC cemented carbide are 470 nm and HRA 91.5, respectively. The fracture toughness of cemented carbide WC-10Co-1NbC alloy is over 7 MN·m−3/2.

Effect of Yb addition on precipitation and microstructure of Al-Cu-Mg-Ag alloys

Abstract Al-Cu-Mg-Ag alloys with different Yb contents were prepared by ingot metallurgy and thermomechanical treatment. The effect of Yb addition on the precipitation and microstructure of the alloys was investigated using mechanical properties testing, optical microscopy, differential scanning calorimetry(DSC), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that adding 0.10%-0.35% Yb accelerates the aging hardening process, increases the maximum hardness and the tensile strength of the extruded alloys from room temperature to 300 °C. Trace Yb element addition refines the grains of the casting alloys from 85 μm to 30 μm, decreases the precipitation temperature of Ω phase. Moreover, the addition of Yb into Al-Cu-Mg-Ag alloy decreases the precipitates size, and improves the density and the thermal stability of Ω phase between 200 °C and 300 °C.

Microstructure and mechanical properties of powder metallurgy Ti-Al-Mo-V-Ag alloy

Abstract The Ti-Al-Mo-V-Ag α+β alloys were processed by powder metallurgy (PM) using the blended elemental (BE) technique. The effects of Ag addition and sintering temperature on microstructure and properties of the Ti-5Al-4Mo-4V alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscope and mechanical properties tests. The results show that adding Ag element increases the relative density and improves the mechanical properties of PM Ti-5Al-4Mo-4V alloy. After sintering at 1 250 °C for 4 h, the relative density and compression strength of Ti-5Al-4Mo-4V-5Ag alloy are 96.3% and 1 656 MPa, respectively.

Effects of Cu/Mg ratio on microstructure and properties of AA7085 alloys

AA7085 aluminum alloys with different Cu/Mg ratios (0.67, 1.0, 1.06, 1.6) were prepared by ingot metallurgy method. The effects of Cu/Mg ratio on the microstructure, mechanical properties and corrosion behavior of the AA7085 alloys were investigated by optical microscope, scanning electron microscope (SEM), mechanical properties and corrosion testing. The results indicate that a better recrystallization inhibition and corrosion resistance can be achieved when Cu/Mg ratio is 1.6. When Cu/Mg ratio is 0.67, the alloy reveals better mechanical properties, and the tensile strength and yield strength of AA7085 alloys are 586 and 550 MPa, respectively. Moreover, both the mechanical properties and corrosion resistance of the alloy are reduced when Cu/Mg ratio is equal to 1.0.

Effect of Minor Silver Addition on Microstructure and Properties of Al-8Zn-1.Cu-1.3Mg-0.1Zr Alloys

Effects of minor silver addition on microstructure, mechanical properties and corrosion resistances of Al-8Zn-1.Cu-1.3Mg-0.1Zr alloys were investigated using optical microscope (OM), scanning electron microscopy (SEM), mechanical properties and corrosion testing. The results show that minor silver addition decreases the recrystallization and corrosion resistance of the t77-tempered alloys.Tensile strength of the based alloy was increased by the 0.1 wt% silver addition.