Influence of the electric field strength and hydrogen on the rate of removal of iron atom impurities in refining remelting of tantalum

A comparison of the results of electron beam remelting (EBR) of tantalum and plasma arc remelting (PAR) of tantalum in a hydrogen atmosphere shows that some impurity elements are removed better during PAR with hydrogen than during EBR. The refining mechanism, the role of hydrogen, and the change in the electric field strength during the removal of impurity elements from tantalum are analyzed by molecular dynamic simulation.     

Change of critical events of cleavage fracture with variation of microscopic features of low-alloy steels

Two steels with different contents of carbon and impurity elements are heat treated to produce various ferrite grain sizes. Four-point-bend (4PB) tests of specimens are carried out at low temperatures. Microscopic observations of metallographic sections and fracture surfaces combined with finite-element model (FEM) calculations are made in detail. Results of the investigation reveal that the critical event for cleavage fracture changes from a crack-propagation-controlling model to a crack-nucleation-controlling model with increasing grain sizes to very large ones and decreasing carbon and impurity element contents. The cleavage initiation sites also move closer to notch roots, which in the case of fine grains locate around the positions where the peak tensile stresses are reached. The mechanism of changes of critical events and the cleavage initiation sites are analyzed.     

Effect of sulfur removal on scale adhesion to PWA 1480

A commercial superalloy, PWA 1480, was annealed in hydrogen at 1000 ° to 1300 ° in order to remove a 10 ppmw sulfur impurity. This treatment was very successful above 1200 °, resulting in residual sulfur contents below 0.1 ppmw. The degree of scale adhesion in subse-quent 1100 ° cyclic oxidation tests was inversely related to residual sulfur content. Control of adhesion by desulfurization in the absence of reactive elements supports an adhesion mechanism based on oxide-metal bonding weakened by sulfur segregation. Attempts at sulfur purging and improving adhesion by repeated oxidation/polishing were not successful, in contrast to previous studies on NiCrAl. Formerly student, Case Western Reserve University.     

90W-7Ni-3Cu重合金真空热处理的研究

研究了真空热处理温度和时间对90W-7Ni-3Cu重合金机械性能的影响以及合金氢含量与机械性能的关系。表明:真空热处理可以降低合金的氢含量,改善其性能,当合金氢含量由7.3ppm降至3.6ppm时,其极限抗拉强度提高18%,延伸率提高近3倍。     

冷加工T91钢制管热处理工艺探讨

T91生产成功与否除了控制钢中S、Al、Ti等杂质元素的含量，取得最好的化学成分配比外，选择合理的热加工和热处理制度也是关键。本次试验采用了两套方案，将相同规格的丰成品分别在26M2大炉和RODR2000连续炉内进行热处理，寻找最佳的半成品热处理工艺，解决半成品和成品管子表面贯穿性裂纹、应力开裂等问题。     

高纯铝旋转偏析行为研究

采用自主研制的高纯铝的旋转偏析设备、 Element GD型辉光放电质谱仪（GDMS），结合界面稳定性理论，研究了偏析速度和旋转速度对高纯铝提纯效果的影响以及杂质元素在偏析锭上的分布特征。结果显示：晶体以平界面生长的临界速度为52 mm/h。偏析速度增加，导致杂质元素在晶体中的浓度明显增加，提纯率显著降低，偏析速度增加破坏原有稳定扩散状态，改变了杂质元素分凝能力。旋转速度增加，诱发杂质元素在晶体中的浓度明显降低，提纯率显著增加，旋转偏析有效提高熔体温度梯度，降低有效分配系数（Ke），改善晶体提纯效果。平衡分配系数（K0）<1的杂质元素含量从偏析锭心部到表面逐渐增加，K0>1的杂质元素正好相反，杂质元素浓度极差表明偏析锭底部均匀性最好。     

铝液凝固过程中显微组织对溶质元素偏析的影响

以溶质元素分配系数小于1的元素Fe、Si、Ga、Zn为研究对象,通过分析工业试验条件下铝液凝固过程中杂质元素含量变化,以及对应的显微组织(包括晶粒形貌、尺寸和金属间化合物),并与热力学计算软件Factsage计算的Scheil-Gulliver冷却条件下杂质元素含量和析出相进行了比较。研究发现,铝液凝固初期固相中杂质元素含量最低,且均大于理论计算值,随着凝固的进行,杂质元素含量逐渐增高且与理论值偏差越来越大,出现以上现象的原因包括：1)铝液实际凝固过程中存在边界层效应,即从固相中排出的杂质元素没有完全扩散到液相中;2)铝液实际凝固过程中存在微观偏析现象,即沿着晶界处有Al-Fe-Si中间相析出。另外,发现本研究试验条件下铝液凝固组织有粗大柱状晶、细小柱状晶、等轴晶,粗大的柱状晶更有利于提高部分杂质元素的偏析提纯效率,通过控制提高强制冷却可以促进粗大柱状晶的形成。     

高温合金母合金真空冶炼中炉前快速分析的取制样方法探讨

高温合金母合金的成分范围控制较窄,应用综合检测手段,建立了高温合金母合金中主量、微量及痕量元素的炉前快速分析方法.使用φ30 mm的铝刚玉材质取样杯,在真空感应炉中采用二次浸没法取高温合金母合金熔液,凝固后快速冷却完成取样.在样品的尾部切割厚约8 mm的第1试样,用于辉光放电质谱仪(GDMS)测试其痕量元素含量;在剩下...     

钢试样中Na、K类杂质元素来源的新发现

对钢试样制备过程和加工钢试样时机床所用切割液的组成进行了分析,切割液中的Na含量接近15％,K含量接近9％。对同一断口试样的能谱分析结果表明,无切割液残留物时断口处未见Na、K类杂质元素,有切割液残留物时断口处发现了含Na、K类杂质元素,而且其它成分也与切割液的成分相近。确定机床所用切割液是钢试样中的Na、K类杂质元素的来源之一。建议在分析钢试样时,应做断口能谱分析,排除留在钢试样上的机床切割液残留物对分析结果的影响。     

辉光放电质谱法测定高纯钨中10种杂质元素

高纯钨广泛应用于电子信息行业,其电子特性很大程度上取决于其杂质含量,因此,有必要对高纯钨中杂质元素进行测定。通过优化辉光放电工艺参数、选择合适的同位素及分辨率,建立了辉光放电质谱法(GDMS)测定高纯钨中10种痕量杂质元素的分析方法。优化后的放电条件为:放电电流3.0 mA,放电气体流量500 mL/min,预溅射时间20 min。为提高痕量杂质元素的检测准确度,利用高纯钨标准样品对10种元素的相对灵敏度因子(RSF)进行了校正,获得了与基体匹配的RSF。方法中10种元素的检出限为0.005~0.019 μg/g,定量限为0.017~0.064 μg/g。按照实验方法测定高纯钨中10种杂质元素,并用电感耦合等离子体质谱法(ICP-MS)的测定结果作为比较以验证准确性。结果表明:样品中杂质元素的含量为0.027~155.07 μg/g,质量分数小于100 μg/g的杂质元素,其结果相对标准偏差(RSD,n=6)均小于30%;质量分数大于100 μg/g的杂质元素,其结果RSD(n=6)小于10%。除Mg、Sn、Pb低于ICP-MS的检出限外,其余各杂质元素的测试结果与ICP-MS结果基本一致。     

硼化物的形成以及在电工铝硼化处理中的作用

对电工铝进行硼化处理,研究了硼降低铝中Ti、V微量杂质元素的作用。结果表明,利用硼化处理能够使Ti、V含量大幅度降低,适宜的硼化处理工艺可以将Ti、V含量降低到0.002%以下;通过化学反应热力学计算和扫描电镜观察及分析,证实了硼能够与Ti、V等元素化学反应生成硼化物,硼化物的下沉去除导致了Ti、V含量的降低。     

V、Ti、Cr、Mn对电工圆铝杆导电性能的影响

试验研究了V、Ti、Cr、Mn等杂质元素之和对电工圆铝杆电阻率的影响,对杂质元素的影响机理、B合金化处理降低杂质元素危害性进行了分析和探讨,提出了杂质元素的控制范围。     

辉光放电质谱法测定高纯铬中杂质元素

高纯铬作为钢铁的添加材料,其杂质含量关系到材料的性能,高效、准确测定其杂质元素的含量至关重要。试验将粒度为150μm的高纯铬粉压制成片,建立了辉光放电质谱法(GD-MS)测定高纯铬中Na、Mg、Al、Si等68种杂质元素的方法。试验表明:通过优化仪器工作条件,铬压片放电信号稳定且强度可满足测试要求;高分辨模式下测定K、Zn、Ga、Ge、Se、Mo、Ru、Rh、Pd、Ag、Sn元素,其余元素则在中分辨模式下消除质谱干扰。Na、Al、Si、P、S等13个元素采用校正后的相对灵敏度因子(RSF)进行测定,其余元素则采用仪器预设标准RSF(std-RSF)进行测定。方法检出限为0.001~0.50μg/g。按照实验方法测定两个高纯铬中杂质元素,其中56种常见元素的测定结果与采用电感耦合等离子体质谱法(ICP-MS)、电感耦合等离子体原子发射光谱法(ICP-AES)、原子吸收光谱法(AAS)、原子荧光光谱法(AFS)、红外光谱法(IR)的测定结果相一致;其余12种元素的测定结果也与ICP-MS半定量参考值相吻合。     

小西南岔金铜矿床石英的成因矿物学研究

通过对矿床内石英的杂质元素，包裹体成分，稀土元素和氢氧同位素组成研究，得出石英系岩浆热液的产物，并具有浅成矿床石英之特点。     

辉光放电质谱法测定高纯金靶材中42种杂质元素

高纯金靶材广泛应用于电子信息行业,靶材产品对其所含杂质元素含量有着极高要求,杂质元素含量偏高将影响其使用性能.对辉光放电质谱法(GDMS)放电电流、放电气体(氢气)流量和样品预溅射时间进行了优化,以丰度高、无干扰或干扰小为原则来选择待测同位素,同时通过选择分辨率来克服可能存在的质谱干扰,建立了GDMS测定高纯金靶材中A...     

The effect of small amounts of ag,se, and sn on the recrystallization of copper

This study is a laboratory investigation of the effects of small amounts of Ag, Se, and Sn singly and in combination on the recrystallization of copper. Pre-anneal solution heat treatments were given to copper wires to establish various amounts of the impurity element in solid solution in the wires. The wires were then cold drawn in tungsten carbide dies and given recrystallization anneals in low temperature salt baths. Degree of re-crystallization was determined by yield point measurements. The recrystallization behavior was found to obey the Avrami equation with the exponent in the Avrami equation indicating unidirectional recrystallization. Yield points did not vary with impurity concentration in the concentration ranges studied. The greatest increase in recrystallization temperature was found for tin additions. Activation energies and recrystallization temperatures for the various concentrations of impurity elements are given in the paper. Increased amounts of second phase precipitates had little effect on the recrystallization temperature with the greatest effect occurring for the impurity elements in solid solution. This paper is based on a presentation made at a symposium on “Recovery Recrystallization and Grain Growth in Materials” held at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy Committee.     

Segregation to interphase boundaries in liquid-phase sintered tungsten alloys

Scanning Auger electron spectroscopy has been used to examine the distribution of impurity elements on the fracture surfaces of liquid-phase sintered W-Ni-Cu and W-Ni-Fe alloys. On the interphase boundaries between the fcc Ni-based matrix phase and the tungsten particles, segregation levels of ~0.4 and ~0.2 monolayers of phosphorus have been observed in as-sintered, furnace-cooled specimens of W-Ni-Cu and W-Ni-Fe, respectively. The phosphorus is homogeneously distributed but at fracture adheres preferentially to the matrix phase. High temperature heat treatment (1350 °C) followed by water quenching reduces significantly the phosphorus segregation and improves the degree of cohesion across these boundaries. Segregated sulfur is detected on both sides of the interphase boundaries after fracture. The sulfur is much less uniformly distributed than the phosphorus, and its segregation level increases in the heat treated specimens. Copper also segregates to the interphase boundaries during the heat treatment of W-Ni-Cu specimens, but no equivalent segregation of iron was observed in the W-Ni-Fe system. The boundaries developed between adjacent tungsten particles are free of impurity contamination in both alloy systems but have a segregated layer of nickel.     

超纯氧化铁制备及其在电感耦合等离子体原子发射光谱法测定高纯铁化合物中杂质元素的应用研究

用电感耦合等离子体原子发射光谱法(ICP-AES)准确测定高纯铁化合物中的痕量杂质元素,需要更高纯度的铁作为基体,以研究它对测定杂质元素的干扰。为此,以分析纯硫酸亚铁为原料制备了高纯氧化铁,制得的高纯氧化铁中杂质元素Al、Cd、Co、Cr、Cu、Mg、Mn、Ni和Zn等的含量低于方法检出限。用制备的高纯氧化铁作为标准系列溶液的基体,得到了基体匹配的标准系列溶液,用此标准系列溶液绘制的校准曲线测定了GBW01402d高纯铁标准物质中杂质元素的含量,其测定值与认定值一致。研究了用无基体匹配标准溶液测定高纯铁及铁化合物中Al、Cd、Co、Cr、Cu、Mg、Mn、Ni和Zn等杂质时的干扰校正方法,结果表明:Al、Co、Cr、Cu、Mg和Zn受到的光谱干扰仅需采用离峰法校正即可,而Cd、Mn和Ni受到的光谱干扰则必需采用多元光谱拟合法校正。用拟定的校正方法测定高纯铁化合物中的痕量杂质元素,准确度高的元素有Al、Cd、Cr和Cu,准确度稍差的元素有Co、Mg、Mn、Ni和Zn。     

Si、Fe对电工圆铝杆导电性能的影响

试验研究了Si、Fe等杂质元素对电工圆铝杆电阻率的影响,分析了对杂质元素进行RE合金化处理降低杂质元素危害的有效性,提出了杂质元素的控制范围。     

Microstructure and properties of high strength aluminium alloys for structural applications

This article discusses the fundamental basis of high strength Al alloy design and describes the role of alloying elements, mechanical processing parameters and heat treatments toward the evolution of microstructure that controls the desired properties i.e. strength, fracture toughness, stress corrosion cracking (SCC) resistance, fatigue crack initiation and propagation resistance, and weldability in 7xxx series Al alloys. The beneficial effects of suitable micro/trace alloying elements, and deleterious effects of certain impurity elements on a variety of properties are further discussed within the present context.