Critical Assessment 36: Assessing differences between the use of cerium and scandium in aluminium alloying

ABSTRACT

Key factors affecting an application of two rare-earth metals cerium and scandium as alloying elements in aluminium are critically assessed. Having similar abundance in the Earth’s crust, their cost and consumption differ by three to four orders of magnitude. The spectacular increment of alloy strength, achieved by scandium through the coherent, nano-scale, L1₂-ordered Al₃Sc precipitates is faced by the prohibitive cost barrier. For cerium, the low cost is accompanied by rather limited strengthening effects: negligible solid-state solubility of cerium in aluminium makes age hardening ineffective so the alloy strength depends on the Al₁₁Ce₃ eutectic phase, formed during solidification. As a result, there are still no commercial aluminium alloys with large-scale applications that take advantage of cerium, scandium or their combination.     

四川某黏土矿中钪和钛的焙烧浸出试验研究

以四川某地含钪、钛、稀土黏土矿为研究对象,进行钠盐焙烧-酸浸、直接酸浸、硫酸化焙烧-水浸、空白焙烧-酸浸探索试验。结果表明,直接酸浸、空白焙烧-酸浸对钪和钛的回收效果均不好。硫酸化焙烧-水浸对钛的回收效果很好,但钪的浸出率较低。钠盐焙烧-酸浸试验结果表明,适宜的焙烧条件为:碳酸钠用量80%,焙烧温度800℃,焙烧时间1h；适宜的浸出条件为:10v.%硫酸,液固比20:1,浸出温度60℃,搅拌浸出时间2h；钪的浸出率为89.98%,钛的浸出率为80.55%。液固比对钪和钛的浸出率有显著影响,增大液固比可以暂时解决硅酸造成的过滤困难的问题。      

Scandium recovery from raffinate copper leach solution as potential new source with ion exchange method

Raffinate copper leach solution of the Iran Sarcheshmeh copper complex has up to 3 mg/L scandium (Sc), which is significantly better than many existing sources, making it a possible source for the recovery of Sc using the ion exchange method. Visual Minteq software was employed to ascertain the ionic species likely to be formed under operational conditions in the mine and for selecting the suitable ion exchange resin. The cationic resin thus chosen was employed statically with ions-bearing synthesized solutions and statically/dynamically for actual copper mining raffinate solution. Room temperature and pH of 1.5 showed the highest Sc adsorption. The dynamic tests established the full saturation of the resin at 450 BV of the raffinate solution flow. Using sodium carbonate for elution, desorption of Sc, Y and Ce from the resin during static elution tests at constant duration was higher than that of Fe, Al and Cu. The results from the dynamic tests followed similar trends for the priority and the extent of the elution process. Desorption results from specimens of dynamic tests show a 60:1 concentration ratio leading to a 186 mg/L Sc-rich solution.     

选钛尾矿分选钪实验研究

研究了选钛尾矿的物质特性，进行了选钛尾矿提钪的实验研究     

电感耦合等离子体原子发射光谱法测定氟化钪中铁

氟化钪是钪生产的主要原料之一,测定氟化钪中铁元素对节约生产资源、保证钪产品品质十分重要。钪作为稀土元素之一,若采用溶解氟化稀土常用的硝酸、高氯酸,则难以溶解完全。实验以硝酸-高氯酸-硫酸(1+1)溶解氟化钪,待测液中硝酸体积分数为10%,采用Fe 238.204 nm为分析谱线,利用两点法进行背景校正,建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定氟化钪中铁的方法。钪基体对铁测定的基体效应影响可以忽略,因此不需要钪基体匹配,只需在标准溶液系列中加入与待测液相同浓度的酸进行酸基体匹配绘制校准曲线。校准曲线线性相关系数为0.999;方法检出限为0.001 0%,定量限为0.003 3%。方法用于测定氟化钪样品中铁,测定结果的相对标准偏差(RSD,n=11)为2.2%;同时采用碱熔-分光光度法测定,结果相一致。     

赤泥-钛白废酸浸出液中微量钪的检测

研究了在赤泥-钛白废酸浸出液中微量钪(Ⅲ)的测定,采用铬天青S作显色剂,考察了反应条件对检测结果的影响,确定了酸浸液中钪的最佳检测条件。实验结果表明,有色溶液的最大吸收波长为615nm,表观摩尔吸光系数为1.57×105L·mol-1·cm-1。钪(Ⅲ)的质量浓度在0~14 g/50mL范围内符合比耳定律,分光光度法应用于赤泥-钛白废酸浸出液中微量钪的测定,结果满意。     

Effects of scandium on hypoeutectic aluminium copper microstructures under low solidification rate conditions

This work addresses the microstructures and mechanical properties of Al-4.5 wt-% Cu alloys containing 0.1, 0.2 and 0.4 wt-% Sc that were solidified under low cooling rate conditions (0.01, 0.08, 0.3 and 0.8°C s^?1) and then heat treated. The solidification and heat treatment processes were carried out in a differential scanning calorimeter. Two different approaches were used for heat treatment. The first approach, involved the traditional heat treatment sequences including solutionising for 18.5 h at 535°C then quenching, followed by aging at 240°C for 2 h. The second approach consisted of direct aging of the as-solidified samples. Under low solidification rate conditions, Sc is found to modify the grain morphology from elongated dendrites to equiaxed structures but is neither a grain refiner nor a strengthener. Indeed, much of it is tied up with Cu in the form of the intermetallic W-phase. Consequently, there appears to be no benefit to adding Sc, in the hypoeutectic composition, to Al-4.5 wt-% Cu if the traditional heat treatment route is followed. However, a minor improvement in hardness is observed upon aging immediately after solidification when 0.4 wt-% Sc is added, owing to excess Sc dissolved in the matrix and not precipitating as the W-phase.     

Effects of scandium and zirconium combination alloying on as-cast microstructure and mechanical properties of Al-4Cu-1.5Mg alloy

The influences of minor scandium and zirconium combination alloying on the as-cast microstructure and mechanical properties of Al-4Cu-1.5Mg alloy have been experimentally investigated.The experimental results show that when the minor elements of scandium and zirconium are simultaneously added into the Al-4Cu-1.5Mg alloy,the as-cast microstructure of the alloy is effectively modified and the grains of the alloy are greatly refined.The coarse dendrites in the microstructure of the alloy without Sc and Zr additions are refined to the uniform and fine equiaxed grains.As the additions of Sc and Zr are 0.4% and 0.2%,respectively,the tensile strength,yield strength and elongation of the alloy are relatively better,which are 275.0 MPa,176.0 MPa and 8.0% respectively.The tensile strength is increased by 55.3%,and the elongation is nearly raised three times,compared with those of the alloy without Sc and Zr additions.     

铝厂赤泥中提钪技术的研究

根据赤泥的基本性质和综合处理的现状,研究提高赤泥中稀有金属钪回收率。采用逆流循环浸出赤泥,通过调节浸出过程中各影响因素,最佳工艺条件为：硫酸浓度900～1000g／L,浸出温度90℃以上,液固比5：1,浸出时间4h,钪的综合回收率达到85％以上。     

The influence of Sc/Lu ratio on the phase transformation and luminescence of cerium-doped lutetium scandium orthoborate solid solutions

The dependence of structural characteristics of cerium-doped lutetium scandium orthoborate (Lu_1−xSc_x)BO₃:Ce solid solutions on Sc/Lu ratio was investigated. It was found that the calcite phase of LuBO₃ can be stabilized up to 1550 °C at least when the n(Sc)/n(Lu + Sc) ratio was ≥10 at.%. The closed correlations between Sc³⁺ or Ce³⁺ molar ratio in the host and luminescence mechanism were discussed in detail. Based on the requirements of steady phase structure, better luminescence efficiency and higher density, the reasonable n(Sc)/n(Lu + Sc) and n(Ce)/n(RE) ratio should be in the range of 30-50 at.% and 0.3-0.5 at.%, respectively. A modified composition, (Lu_0.5Sc_0.5)_0.995Ce_0.005BO₃ solid solution, was selected to grow single crystal. Its X-ray excited luminescence intensity can be as high as about 27% of LYSO:Ce standard crystal and the effective lifetime is round 20.1 ns. Hence, the cerium-doped lutetium scandium orthoborate crystal is a promising scintillator for X-ray detection or γ-ray detection.