Papers by Keyword: Y

Abstract: By the scanning electron microscopy, the microstructure and mechanical properties testing, the effect of Ca and Y on the microstructure and mechanical properties of magnesium alloy AZ81 are investigated in this paper. The results show that with Ca and Y addition, the grain size is refined. And with the β-Mg₁₇Al₁₂ phase reducing significantly, there will be the precipitation of Al₂Ca and Al₂Y. Meanwhile, the mechanical properties of AZ81 magnesium alloy are enhanced at room temperature and 150°C.

Abstract: Y and Gd are vital alloying elements to the AZ magnesium alloys. It is due to their functions mainly on solid solution strengthening and age strengthening. This paper reviews effect of Y, Gd on mechanical properties of AZ-series magnesium alloys. The future development direction is pointed.

Abstract: The effects of Y and Gd on the microstructure and mechanical properties of AZ81 magnesium alloy were studied by alloy preparation, microstructure analysis and mechanical property testing. The results show that moderate addition of Y and Gd to AZ61 magnesium alloy can obviously refine grains of AZ61 alloy, and decrease the amount of Mg₁₇Al₁₂ phase. With the increase of alloying elements, the tensile strength and elongation of aged AZ61 magnesium alloy at the temperature ranging of 25°C～175°C rise at first and then drop.When content of Y and Gd is up to 2.7%，the values of tensile strength of the alloy at room temperature and 175°C are up to their maximums, 254MPa and 164MPa respectively, while the elongation of the alloy are 22.9%,18.7% respectively. Y and Gd improve the mechanical properties of AZ61 alloy because of the grain refining strengthening, solution strengthening and the dispersion strengthening.

Abstract: The grain refinement of 2-8 wt.% Y addition in as-cast Mg-Y binary alloys has been investigated. The results show that the microstructure of as-cast Mg-Y alloys consists of α-Mg matrix and Mg₂₄Y₅ phase. Mg₂₄Y₅ can become the effective nucleation core of α-Mg, and refine the grain size of the alloys. The ultimate tensile strength of as-cast Mg-5Y alloy is 180MPa at room temperature. Mg-5Y alloy can be a basis for developing light structural materials.

Abstract: In this paper, the microstructure and properties of AZ91D-xCa-ySr were studied by adding alloying elements. The mechanical properties were investigated by WDT-10 micro-electric universal testing machine and WD-T low cycle fatigue testing machine. The OLYMPUS-GX71 Optical electronic microscope, XRD and SEM were employed to investigate the microstructure of AZ91D. The results showed that the grains were refined by adding Ca,Sr,Gd and Y. Low cycle fatigue (LCF) behavior of AZ91D-0.4Ca-0.3Sr was improved obviously by adding 3.0%Gd and 3.0%Y into material, the tensile strengthen was up to 299Mpa, the elongation was 0.78%.

Abstract: There is a great attention to the usage rate of Al-Cu alloys due to the largely use of Al-5%Cu based alloys in the aerospace industry in the past decades. The improvement of microstructure and properties of Al-5%Cu based alloy by refinement and modification. Specially, the refinement and modification of Al-Cu alloy can be achieved by addition of rare earth. In this paper, the effect of Y on the microstructure and properties of Al-5%Cu based alloy was investigated. The results show that θ (Al₂Cu) phases change from mesh structure into fish-bone shape and grains are refined. Y additions promoted the end-solidification temperature and decreased the quantity of eutectic in grain boundaries, and narrowed the crystallization range and increased the hot-tearing resistance and decreased the hot-tearing susceptibility significantly.

Abstract: The effect of Y addition on the microstructure of AZ61 alloy was investigated by optical microscopy (OM), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The corrosion behavior of AZ61 alloy with Y addition in 3.5 % NaCl solution was studied by static weight loss and polarization curves corrosion tests. The results show that AZ61 alloy with Y addition can refine grain size of the matrix and alter the distribution of the phase β-Mg₁₇Al₁₂ from continuous network morphology transition to small and dispersive distribution along the grain boundary by forming the second phase Al₂Y which has a high melting point. In addition, the addition of Y can decrease the corrosion current density of AZ61 magnesium alloy in 3.5% NaCl solution, thereby improving the corrosion resistance of AZ61 magnesium alloy. Results show that AZ61 magnesium alloy with 1.0% Y has the most refined microstructure and the best corrosion resistance.

Abstract: The formation energy, structure relaxation and electronic structure of Mg₂Si and Y-doped Mg₂Si are investigated using first-principle calculations based the density functional theory. The general gradient approximation was used to treat the exchange and correlation potential. The calculated electronic structure shows that Mg₂Si is a semiconductor with a direct gap of 0.27eV at G point. The preferential substitution site of Y inside Mg₂Si is determined to be Mg. Y-doping makes the Si atoms around the impurity outward relaxation and increases the Seebeck coefficient, electrical conductivity and thermal conductivity of Mg₂Si crystals simultaneously.

Abstract: The effects of 2-12 wt.% Y addition on the microstructure and mechanical properties of as-cast Mg-Y binary alloys have been investigated. The results show that proper content of rare earth Y addition can obviously refine the grains and form high melting point Mg₂₄Y₅ phases in the matrix, and improve the microstructure and mechanical properties of the alloys. At room temperature, the optimum combination of ultimate tensile strength and elongation, 195MPa and 7.5%, is obtained in Mg-10 wt.% Y alloy.

Abstract: Three studies on the oxidation behaviour of austenitic stainless steels were described in the present paper. (1) High temperature oxidation behaviour and its mechanism in austenitic stainless steels with high silicon: Sulfur contained as impurity in steel showed a harmful influence to the oxidation resistance of 19Cr-13Ni-3.5Si stainless steels. It was found that the abnormal oxidation was caused from the surroundings of MnS inclusions. (2) Effect of a small addition of yttrium on high temperature oxidation resistance of Si-containing austenitic stain less steels: The oxidation resistance of 19Cr-10Ni-1.5Si steels was improved remarkably even with only 0.01%Y addition, which is the same concentration as added for de-oxygenation. Y was enriched at the grain boundary of oxide scale and metal-oxide interface. It was suggested that Y-containing steels shoed good oxidation resistance, because the enriched Y at the grain boundary and metal-oxide interface prevented the diffusion of iron and oxygen ions through the oxide scale. (3) Effect of grain size on the oxidation behaviour of austenitic stainless steels: Type 304, 316 and 310 steels with finer grain size showed better oxidation resistance than those with coarser grain size at 850°C. The oxide scale of steels with coarser grain size easily spalled during the cooling process.