The modification effects of ytterbium(Yb), Na_3PO_4 and Yb + Na_3PO_4 on primary Mg_2Si phase in Mg-4Si alloys were investigated by means of X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy...The modification effects of ytterbium(Yb), Na_3PO_4 and Yb + Na_3PO_4 on primary Mg_2Si phase in Mg-4Si alloys were investigated by means of X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) analysis in this work. The results indicate that the morphology of the primary Mg_2Si phase apparently changes from coarse dendrites to fine dispersive polygonal particles and the mean size decreases from 276.6 μm to 7.1 μm, with combined modification of 0.8wt.% Yb and 2.64 wt.% Na_3PO_4. Such a morphological evolution results in improvement in the ultimate tensile strength and elongation of the alloys as compared to the base alloy. This may be attributed to the formation of the YbP particles that acted as the heterogeneous nucleation substrates for the primary Mg_2Si particles, resulting in a refined distribution of these precipitates. The results of XRD examination show that there was no reaction between Si and Yb or Na_3PO_4. Solo addition of Yb or Na_3PO_4 into the melt has no real modification effect on the microstructure, but the primary Mg_2Si particles and α-Mg phases become coarser than that in the unmodified alloy.展开更多
建立了一种用离子色谱法同时测定Na_3PO_4·12H_2O中的Cl^-和SO_4^(2-)的分析方法。该方法采用分离时间20min,分离度为3.02的Metrosep A Supp 4 250/4.0型色谱柱,柱温为35℃,流速为0.8mL/min。两种离子的标准曲线的相关系数达到了0....建立了一种用离子色谱法同时测定Na_3PO_4·12H_2O中的Cl^-和SO_4^(2-)的分析方法。该方法采用分离时间20min,分离度为3.02的Metrosep A Supp 4 250/4.0型色谱柱,柱温为35℃,流速为0.8mL/min。两种离子的标准曲线的相关系数达到了0.9999。Cl^-和SO_4^(2-)的稀释液的测定结果的相对标准偏差分别为1.02%,2.26%;检出限分别为0.010mg/L,0.011mg/L;加标回收率分别96.0%,94.0%。与HG/T 2517-2009中Cl^-和SO_4^(2-)的测定方法相比,该方法的相对误差仅为分别为2.78%和0.00%。因此,该方法具有较高的精密度和准确度,且分析时间短,方法简单,可作为缓蚀阻垢剂Na_3PO_4·12H_2O中的Cl^-和SO_4^(2-)含量分析的常规方法。展开更多
基金financially supported by the Fundamental Research Funds for Central Universities(Grant No.:XDJK2015B001)
文摘The modification effects of ytterbium(Yb), Na_3PO_4 and Yb + Na_3PO_4 on primary Mg_2Si phase in Mg-4Si alloys were investigated by means of X-ray diffraction(XRD), optical microscopy(OM), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) analysis in this work. The results indicate that the morphology of the primary Mg_2Si phase apparently changes from coarse dendrites to fine dispersive polygonal particles and the mean size decreases from 276.6 μm to 7.1 μm, with combined modification of 0.8wt.% Yb and 2.64 wt.% Na_3PO_4. Such a morphological evolution results in improvement in the ultimate tensile strength and elongation of the alloys as compared to the base alloy. This may be attributed to the formation of the YbP particles that acted as the heterogeneous nucleation substrates for the primary Mg_2Si particles, resulting in a refined distribution of these precipitates. The results of XRD examination show that there was no reaction between Si and Yb or Na_3PO_4. Solo addition of Yb or Na_3PO_4 into the melt has no real modification effect on the microstructure, but the primary Mg_2Si particles and α-Mg phases become coarser than that in the unmodified alloy.
