Effect of pulse frequency on microstructure and properties of Ti-6Al-4V by ultrahigh-frequency pulse gas tungsten arc welding

An experimental program of welding a titanium alloy, Ti-6Al-4V, was carried out using ultrahigh-frequency pulse gas tungsten arc welding (UHF-GTAW). The characteristics of the welds were investigated, such as the defection, microstructure, and mechanical properties. The experimental results show that the high pulse frequency reduces the heat input from the UHF-GTAW process, while gaining one-side welding with backing as a precondition. Basketweave and long acicular α′ martensite only existed in some areas of the FZ (fusion zone) with both low uniformity and distribution density (8.4 %) as a result of conventional GTAW processes. With a pulsed current, basketweave and short acicular α′ martensite were distributed in the FZ evenly. Short acicular α′ martensite could be detected within the parallel long acicular α′ martensite in the CGR when f?>?30 kHz. Plastic weld joints were characterized by both the elongation, A, and the percentage of the area reduction, Z, and were optimized with a high pulse frequency. Ideal mechanical properties of the joints were achieved with an A of 68 % and a Z of 150 % with f?=?30 kHz. The integrated effects of the pulse frequency and the heat input are the key factors for determining the microstructure morphology and the mechanical properties.     

报纸印刷超色域情况分析

<正>理论上,超过印刷品色域再现范围的色彩,在印刷品上是难以复制的,色彩稳定性也无法保证,印刷时色彩波动明显,易出现粘脏等工艺故障。目前对报纸印刷色彩的投诉中,约90%以上是由于印前     

WTi10合金的高温高压制备及相特征

采用高温高压工艺制备了WTi10合金。使用电子探针、扫描电子显微镜及X射线衍射仪等手段研究制备工艺对合金密度及微观组织的影响,尤其是合金中的相演变特征。评价靶材对合金相的要求,并据此获取优化的制备工艺。研究表明,温度是制备WTi10合金密度的主要影响因素,合金的密度随温度升高而增大;温度高于1250℃的合金中为完全固溶生成的体心立方β相,其中主要包含W颗粒、富钨β(W,Ti)及富钛β1(W,Ti)3种成分;钨钛合金靶材要求其中富钛相β1越少越好,富钨β(W,Ti)相占比也不宜过高,故其加工温度应该在1400和1500℃之间,保压保温时间则与加工温度成反比关系,加压压力≥15 MPa。     

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe_2.85O₄ and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe₂O₃ and hydroxyapatite.     

Accuracy of single-shot autocorrelation measurements of petawatt laser pulses

At the Shen Guang II (SGII) Petawatt Laser Facility, measurements of large-energy, single-shot laser pulses sometimes feature asymmetric autocorrelation signals, causing uncertainty in the measurement of compressed pulses. This study presents a method for defining and describing the asymmetry of autocorrelation signals. We discuss two sources of asymmetry: the nonuniform distribution of the near field excited by a beam, and the rotation of autocorrelator arms from the cylinder lens. The pulsewidth of an asymmetric autocorrelation signal is shorter than its real width. After updating the autocorrelator, the single-shot autocorrelator for the SGII petawatt laser exhibits a measurement uncertainty of below 12.3%. Recommendations on reducing asymmetry in large-energy, single-shot autocorrelation are discussed.     

真空蒸馏法处理铜砷锑合金综合回收铜银的研究

从理论上分析了采用真空蒸馏法处理铜砷锑合金综合回收其中有价金属铜银的可行性,并通过实验探讨了蒸馏温度、保温时间、真空度、元素As,Sb对Cu与Ag分离和富集效果的影响。结果表明:在蒸馏温度1673 K,保温时间150 min,系统残压20~30 Pa条件下,残余物中Cu含量可达82.8%,直收率为92%左右,残余物中Ag含量可降至100×10-6,表明Cu,Ag基本完全分离,挥发物中Ag含量可达0.88%,直收率为93%左右,Cu,Ag分离和富集效果显著。As,Sb因为与Cu的相互作用力很强,容易形成多种不易挥发的化合物,导致其实际挥发性和理论计算结果相差很大。产出的含Ag 0.9%左右的挥发物可以继续采用真空蒸馏法富集Ag,然后把富集Ag得到的残余物投入粗铅精炼环节,和粗铅中原有的Ag一同按传统工艺产出。含Cu80%左右的残余物可以采用改进后的硝酸-硝酸铜电解液电解精炼产出阴极铜。     

真空钙热还原法制备金属钛粉的研究

在真空炉中(30~40 Pa)1273 K下,将物料放入螺纹密封的石墨坩埚中进行不同时间下的还原反应。本文采用热力学分析及X射线衍射、扫描电子显微镜及能量弥散X射线谱等方法与手段,系统研究了金属钙(Ca)与反应器中的氧气(O2)、氮气(N2)、二氧化钛(TiO2)的反应和还原时间及还原产物的预处理对得到金属钛粉(Ti)的影响。通过热力学研究,在温度低于钙的熔点(1115 K)时,密封容器内的O2与Ca的反应及N2与Ca的反应满足反应发生的热力学条件。当温度达到1273K时,Ca的饱和蒸气压p*≈p系,有利于整个气固反应进行。实验研究表明,在还原反应发生前,反应器内的O2,N2与Ca反应完全。将在1273 K下还原时间为4 h得到的还原产物在酸洗前真空挥发处理还原产物表面大量的Ca时,金属单质Ti再次被氧化成低价氧化物,最终得不到金属Ti粉。将反应时间延长至6 h时,酸洗过滤后得到形状不规则、纯度达到98.64%的Ti粉。     

报业CTP成熟期将至

CTP技术是近年来报业印刷技术发展的亮点，也是报业印刷走向数字化的突出表现。但由于技术和成本的原因．报业CTP的应用推进一直较为缓慢．10余年后的今天，CTF工艺还在顽强地占据着报业输出工艺的主流。新型高速照排机仍受追捧，CTF和CTP混合工艺盛行，报业CTP面临尴尬。     

兰州市城区深层地热水的水化学成因及其指示意义

兰州市城区蕴藏有丰富的地热资源,属于沉积盆地大型水热地热田,水质具有独特的理疗价值。从地热水化学和热储矿物成份入手,与地热地质条件紧密结合,首次采用了 Piper 三线图法、Schoeller 图法、主要离子比例系数法和相关分析法,全面系统地揭示了西北黄土高原半干旱区典型山间盆地兰州地热田水文地球化学特征及其主要离子的来源。选取适宜的 K-Mg 地热温标法,解决了热储温度难以准确测量的问题。利用氢氧稳定同位素测试技术,示踪判定了地热水的补给来源、补给区域和循环深度。结果显示: 兰州地热田钻孔揭露出水温度为 35. 5 ～ 74 ℃,总溶解性固体含量( TDS)为 3. 89～22. 04 g /L,阴、阳离子分别以 Cl－和 Na+、Ca2+为主,高矿化水质及特殊组分源于地热流体比较充分的溶滤作用。推测地热水中 Na+、Cl－主要来源于岩盐的溶解,Ca2+、Mg2+除了来源于方解石、白云石、硬石膏等矿物的溶解外,还来源于长石等矿物的溶解。地热水中不存在阳离子交换作用。确定地热田热储温度为 58～90 ℃,属于中低温水热资源。结果表明: 地热水的补给主要来源于城区南部基岩山区的大气降水,经深部循环的加热而成,形成一个 “源、通、储、盖”明了和补径排条件清晰的地热水系统。