The amorphous Fe 67.5 Ni 32.5 alloy particles have been prepared by mechanical alloying (MA) process of elemental powders. The crystallization is observed at temperature around 405°C by means of differen...The amorphous Fe 67.5 Ni 32.5 alloy particles have been prepared by mechanical alloying (MA) process of elemental powders. The crystallization is observed at temperature around 405°C by means of differential thermal analyzer. It is found that the coercivity H C and the effective magnetic anisotropy value of amorphous phase are not far from that of crystal phase. The magnetization behavior of amorphous and nanocrystalline samples prepared by mechanical alloying and milling process are quite similar, they obey 1/H law at middle high field and 1/H 2 at higher field. The 1/H field dependence is attributed to a large number of dislocations created during MA process. The studies on the 1/H 2 field dependence reveals that magnetization of Fe Ni ultrafine particles are governed predominantly by internal stress fields induced by MA process.展开更多
Al-Zn-Mg-Cu alloy is a favorable choice for aerospace applications requiring good combination of strength and toughness, which is greatly influenced by the coarse intermetallic particles. The evolution of intermetalli...Al-Zn-Mg-Cu alloy is a favorable choice for aerospace applications requiring good combination of strength and toughness, which is greatly influenced by the coarse intermetallic particles. The evolution of intermetallic particles in an Al-Zn-Mg-Cu alloy during heat treatment was studied by field emission gun scanning electron microscopy (FEG-SEM) and X-ray diffractometry(XRD). The results show that there are lamellar eutectic structure (α(Al)+Mg(Zn,Al,Cu)2) and Al7Cu2Fe particles in the solidified structure. The Al7Cu2Fe particles are embedded in the eutectic structure. The content of eutectic structure decreases with the increase of holding time and disappears after 24 h. The size and morphology of Al7Cu2Fe particles exhibit no change during the heat treatment. It is found that the Al2CuMg phase is formed during the treatment at 460℃. A transformation process from the primary eutectic phase Mg(Zn,Al,Cu)2 to Al2CuMg is observed, and the transformation mechanism and kinetics are analyzed. The Al2CuMg constituents form in the primary Mg(Zn,Al,Cu)2 phase, and grow along the eutectic microstructure.展开更多
The size,crystal structure and phase transformation of Ni49.8Mn28.5Ga21.7 alloy particles prepared by planetary ball milling(PBM) and vibration ball milling(VBM) were investigated by SEM,XRD and DSC. The results show ...The size,crystal structure and phase transformation of Ni49.8Mn28.5Ga21.7 alloy particles prepared by planetary ball milling(PBM) and vibration ball milling(VBM) were investigated by SEM,XRD and DSC. The results show that the particles milled by PBM for 4 h exhibit irregular polyhedron,with the size distribution between 5 μm and 40 μm. These particles present disordered fct structure with no phase transformation behaviour. When annealed at 600 ℃ for 1 h,the crystal structure of the particles evolves from disordered fct to Heusler completely. The particles milled by VBM for 4 h exhibit flaky shape,with the size distribution from 3 μm to 30 μm. The particles present disordered fcc structure with no phase transformation behaviour. However the crystal structure of these particles doesn't transform from disordered fcc to Heusler completely after annealing at 600 ℃ for 1 h,for the severe lattice distortion induced in the VBM process is not eliminated entirely.展开更多
文摘The amorphous Fe 67.5 Ni 32.5 alloy particles have been prepared by mechanical alloying (MA) process of elemental powders. The crystallization is observed at temperature around 405°C by means of differential thermal analyzer. It is found that the coercivity H C and the effective magnetic anisotropy value of amorphous phase are not far from that of crystal phase. The magnetization behavior of amorphous and nanocrystalline samples prepared by mechanical alloying and milling process are quite similar, they obey 1/H law at middle high field and 1/H 2 at higher field. The 1/H field dependence is attributed to a large number of dislocations created during MA process. The studies on the 1/H 2 field dependence reveals that magnetization of Fe Ni ultrafine particles are governed predominantly by internal stress fields induced by MA process.
基金Project(2004AA5BG018) supported by the Science and Technology Development Fund of Harbin, China
文摘Al-Zn-Mg-Cu alloy is a favorable choice for aerospace applications requiring good combination of strength and toughness, which is greatly influenced by the coarse intermetallic particles. The evolution of intermetallic particles in an Al-Zn-Mg-Cu alloy during heat treatment was studied by field emission gun scanning electron microscopy (FEG-SEM) and X-ray diffractometry(XRD). The results show that there are lamellar eutectic structure (α(Al)+Mg(Zn,Al,Cu)2) and Al7Cu2Fe particles in the solidified structure. The Al7Cu2Fe particles are embedded in the eutectic structure. The content of eutectic structure decreases with the increase of holding time and disappears after 24 h. The size and morphology of Al7Cu2Fe particles exhibit no change during the heat treatment. It is found that the Al2CuMg phase is formed during the treatment at 460℃. A transformation process from the primary eutectic phase Mg(Zn,Al,Cu)2 to Al2CuMg is observed, and the transformation mechanism and kinetics are analyzed. The Al2CuMg constituents form in the primary Mg(Zn,Al,Cu)2 phase, and grow along the eutectic microstructure.
文摘The size,crystal structure and phase transformation of Ni49.8Mn28.5Ga21.7 alloy particles prepared by planetary ball milling(PBM) and vibration ball milling(VBM) were investigated by SEM,XRD and DSC. The results show that the particles milled by PBM for 4 h exhibit irregular polyhedron,with the size distribution between 5 μm and 40 μm. These particles present disordered fct structure with no phase transformation behaviour. When annealed at 600 ℃ for 1 h,the crystal structure of the particles evolves from disordered fct to Heusler completely. The particles milled by VBM for 4 h exhibit flaky shape,with the size distribution from 3 μm to 30 μm. The particles present disordered fcc structure with no phase transformation behaviour. However the crystal structure of these particles doesn't transform from disordered fcc to Heusler completely after annealing at 600 ℃ for 1 h,for the severe lattice distortion induced in the VBM process is not eliminated entirely.