Effect of extrusion ratio on microstructure and mechanical properties of AZ91D magnesium alloy recycled from scraps by hot extrusion

A method for recycling AZ91D magnesium alloy scraps directly by hot extrusion was studied.Various microstructural analyses were performed using the techniques of optical microscopy,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).Microstructural observations revealed that all the recycled specimens consisted of fine grains due to the dynamic recrystallization.The main strengthening mechanism of the recycled specimen was grain refinement strengthening and homogeneous distribution of oxide precipitates.The interfaces of individual scraps of extruded materials were not identified when the scraps were extruded with the extrusion ratio of 40-1.Oxidation layers of the scraps were broken into pieces by high compressive and shear forces under the extrusion ratio of 40-1.The ultimate tensile strength and elongation to failure increased with increasing the extrusion ratio.Recycled specimens with the extrusion ratio of 40:1 showed higher ultimate tensile strength of 342.61 MPa and higher elongation to failure of 11.32%,compared with those of the cast specimen.

Microstructure and Mechanical Properties of AZ91D Magnesium Alloy Recycled from Scraps by Hot-press/extrusion

A large number of scraps are produced in the fabrication process of magnesium alloy products. It is necessary to recycle these scraps for the development and scale application of magnesium alloys. In this research,a method for recycling AZ91D magnesium alloy scraps fabricated by hot-press / extrusion was studied. Mechanical properties and microstructure of the recycled specimens were investigated. Microstructural analyses were performed by using the techniques of optical microscopy and scanning electron microscopy. Microstructural observations reveal that the recycled specimens consisted of fine grains when adopting the extrusion temperature of 400- 450 ℃,the extrusion ratio of( 25- 100) ∶ 1 and the extrusion rate of 0. 10- 0. 20 mm / s. Ultimate tensile strength and elongation to failure increased with the increase of the extrusion temperature,the extrusion ratio and the extrusion rate,respectively. Recycled specimens reached the highest ultimate tensile strength of average 361. 47 MPa and the highest elongation to failure of average 11. 55% when adopting the hot-press,the extrusion temperature of 400± 5 ℃,the extrusion ratio of 100 ∶ 1 and the extrusion rate of 0. 15 mm / s. The shape of bonding interface was tightly relation with the ultimate tensile strength. When the bonding interface formed continuous curves,the ultimate tensile strength decreased almost linearly with increasing the average width of the bonding interface. When the bonding interface formed discontinuous curves,the ultimate tensile strength increased almost linearly with the increase the proportion of the fine bonding length accounting for the measured interface length. Ultimate tensile strength of the recycled specimens could be calculated by using the forecastable equation.

Effect of additives on anode passivation in direct electrolysis process of copper–nickel based alloy scraps

Effects of nickel component,thiourea,glue and chloride ions and their interactions on the passivation of copper–nickel based alloy scrap anodes were investigated by combining conventional electrochemical techniques.Results obtained from chronopotentiometry and linear voltammetry curves showed that the Ni component made electrochemical stability of the anode strong and difficult to be corroded,caused by the adsorption of generated Cu2O,NiO or copper powder to the anode surface.The Ni2+reducing Cu2+to Cu+or copper powder aggravated the anode passivation.In a certain range of the glue concentration≤8×10–6 or thiourea concentration≤4×10–6,the increase of glue or thiourea concentration increases the anode passivation time.Over this range,glue and thiourea played an adverse effect.The increase of chloride ions concentration led to the increase in passivation time.

Recovery of Co(Ⅱ) and Ni(Ⅱ) from hydrochloric acid solution of alloy scrap

A hydrometallurgical process was developed for recovery of nickel and cobalt from the hydrochloric acid leaching solution of alloy scraps.The process consists of five major unit operations: 1) leaching with 6 mol/L hydrochloric acid under the L/S ratio of 10:1 at 95 ℃ for 3 h; 2) copper replacement by iron scraps under pH value of 2.0 at 80 ℃,and stirring for 1 h; 3) removal of iron and chromium by chemical precipitation: iron removal under pH value of 2.0 at 90 ℃ by dropwise addition of sodium chlorate and 18% sodium carbonate solution,then chromium removal under pH value of 4.0 at 70 ℃ by addition of nickel carbonate solution,stirred by air flow for 2 h; 4) selective separation of cobalt from nickel by extraction using 30% trialkyl amine+50% kerosene (volume fraction) and tri-n-butylphosphate (TBP) as a phase modifier with the O/A ratio of 2:1,and stripping of cobalt with 0.01 mol/L HCl; 5) crystallization of nickel chloride and electrodeposition of cobalt.It is found that the nickel recovery of 95% and the cobalt recovery of approximately 60% with purity over 99.9% are obtained by this process.

电解法回收银铟合金废料中的银

银铟合金废料的综合回收具有重要的意义,采用电解法在实现分离的同时可得到高纯度的银。考察了电流密度、电解液初始银浓度、pH值对电解效率的影响,溶液和银粉中含铟量随电解时间的变化,以及电解废液中银的回收。获得的最佳电解工艺条件为初始电解液初始Ag+浓度100g/L,电解液pH为1,初始温度25℃,电流密度350A/m^(2),电解周期控制在6天内,银回收率大于99%,得到的银粉符合IC-Ag99.99的要求。工艺操作简单,回收率高,适用于银铟合金废料中银的回收。

Na_(2)CO_(3)-Na_(2)SO_(4)复盐熔炼法从碱溶渣中高效分离钨的工艺研究

钨合金废料资源化利用过程中容易产生含钨碱溶渣,且该部分含钨碱溶渣中钨品位较高。本文开发了一种复盐(Na_(2)CO_(3)-Na_(2)SO_(4))熔炼工艺,以对含钨碱溶渣中的钨进行高效分离;探究Na_(2)CO_(3)和Na_(2)SO_(4)的添加量、复盐熔炼温度、熔炼时间以及水浸液固比、水浸温度对钨回收率的影响。结果表明:从含钨碱溶渣中高效分离钨的最优条件为n(W)∶n(Na_(2)CO_(3))∶n(Na_(2)SO_(4))=1∶1.25∶0.54,复盐熔炼温度为800℃,熔炼时间为3 h,水浸液固比为2.5,水浸温度为75℃,在该最优条件下可将含钨碱溶渣中99.93%的钨分离出来。同时,本文通过XRD分析以及热力学分析对复盐熔炼的反应机理进行了探讨,复盐体系的构建有助于降低体系共熔点,降低能耗,同时有助于促进碱溶渣与反应介质的充分接触,提高反应效率。

Cu_(54-56)Zn_(40-44)再生铜合金棒材成形工艺及性能研究

目的促进多杂质元素的废杂铜低成本高效回收,实现二次资源的绿色循环利用。方法基于现有废杂铜直接利用法生产再生黄铜合金棒材,通过废杂铜原料→依成分配料→熔铸合金化→挤压成形→无心车床处理→去应力退火工艺路线,得到了稳定合格的低铜精密棒材成品。结果废杂铜原料的搭配使用是控制杂质元素含量超标的关键环节,需要结合经验值进行合理配方。熔炼工序,在助熔剂、清渣剂、精炼剂和覆盖剂等的作用下,皆可有效减少熔体中的杂质元素,制备出高品质水平连铸铸锭;加工工序,在微量元素的有益范围内,生产的精密再生黄铜棒材抗拉强度≥560 MPa,延伸率≥22%。结论在制备低铜精密再生黄铜合金棒材过程中,开发了一条生产稳定低铜再生黄铜合金产品的工艺路线,实现了废杂铜原料高品质再生。

铝合金压铸件切边废料回收熔融装置研究

针对铝合金压铸件切边废料高效回收利用难的问题,对熔融装置进行设计和优化,能达成废料高效熔融和质量控制的目的。这需要利用结构创新和技术提升明显提高熔融效率,保障操作安全。试验数据证明,优化熔融装置能显著提高废料回收率,对铝合金压铸行业绿色生产具有强大的技术支撑。熔融装置应用于铝合金压铸行业的巨大潜力,能对该产业的可持续发展起到积极的推动作用。

银氧化锡合金废料电解综合回收工艺研究

采用直流电解法和化学法回收银氧化锡(AgSnO_(2))合金废料中的银和锡。优化得到的电解银工艺参数为:槽电压1.5~3.0 V,电解周期为24 h,电解液中Ag^(+)浓度为150~260 g/L,HNO3浓度为15~20 g/L,同极距120~140 mm,极板排布为六阴极五阳极间隔交替排列。一个周期银氧化锡废料电解银直收率接近95%,主体纯银粉在阴极析出。富含氧化锡的阳极泥和残极用硝酸浸出少量残余银,不溶渣还原熔炼回收锡,硝酸浸出的含银溶液中加入氢氧化钠调节pH值到10,沉淀得氧化银,500℃焙烧得到单质银。废料中的银和锡均得到有效回收。全流程银的回收率不低于99%。

超重力分步分离废铝合金中杂质元素的研究

高效去除杂质元素是材料回收领域的核心问题,文中介绍了一种用超重力技术分离废铝合金中杂质元素的新工艺,采用两步分离的方法:第一步用超重力技术从废铝合金中分离Cu、Mg等低熔点杂质元素,第二步用超重力技术分离第一步所得目标样品中的高熔点固体杂质(富铁相)。经过两步分离,废铝合金中杂质元素Fe、Mg、Cu、Zn和Si的杂质去除率分别为62.6%、43.3%、32.4%、16.2%和12.4%,Al收得率为80.1%,回收Al纯度为95.52%。

钨合金废料的资源再生利用技术

钨是一种稀有金属 ,钨合金具有高的强度、硬度 ,较好的耐高温性、耐磨性和良好的电性能 ,广泛应用于航空航天工业、兵器工业、核工业、信息产业、汽车工业和钢铁工业等行业。目前 ,钨资源短缺 ,钨合金价格高、用量大 ,因此各国都把废弃的钨合金作为宝贵的第二钨资源加以再生利用。本文综述了钨合金的再生利用现状 ,分别总结了硬质合金、高比重合金、钨铜合金和钨材的再生利用技术 ,并利用生态环境材料的观点 。

从铂-铱合金废料中回收铂铱的新工艺

首次提出用铂铱不分离的方法处理铂-铱合金废料。工艺包括铝碎化活化,离子交换除贱金属杂质,氯化铵共沉淀铂铱等过程。铂的直收率达到98.64%,铱的直收率达到95.02%。得到的铂铱混合粉经过配料制造新的铂-铱合金材料。

丁苯橡胶/废胶粉弹性体合金的结构与性能

利用反应性增容方法制备了丁苯橡胶(SBR)/废胶粉(SRP)弹性体合金,并研究了反应性增容剂对SBR/SRP弹性体合金的结构与性能的影响。结果表明,当丁苯橡胶100份、增容剂用量9份、废胶粉(粒径80 m esh)用量45份时,弹性体合金的力学性能最佳。差示扫描量热仪和动态力学分析的结果显示,加入增容剂后,弹性体合金的玻璃化转变温度发生位移,SBR与SRP的相容性提高。扫描电镜和透射电镜的结果揭示,加入增容剂后,废胶粉的粒子被丁苯橡胶基体包覆,两相间粘合力大大增强。

从铜钴合金及含钴废料中提取钴的研究现状与展望

分析了钴资源与钴市场现状,提出了综合处理铜钴合金及含钴废料的必要性,介绍了从铜钴合金和含钴废料中浸出铜、钴及回收钴的方法,指出传统的火法工艺不能处理铜含量高的物料,而采用一般的酸法工艺,钴浸出率不高(只能达到95%左右);利用液膜法和微生物浸出法,钴的浸出率最高只能达到96%,而如果采用氧化剂加低酸(酸浓度小于2 mol/L)浸出,则可大大提高浸出速度和浸出率。

镁合金废料回收技术的现状及进展

镁合金废料回收对于镁合金的规模应用和镁工业的可持续发展具有非常重要的理论意义和实际价值。首先简单介绍了镁合金废料的分类及回收方式,然后重点回顾了镁合金废料的回收方法和质量控制措施,最后指出了目前还存在的问题,并对今后的发展方向进行了展望。

从含硒废料中回收制备高纯硒

介绍从含硒废料回收制备高纯硒的工艺过程,首先采用氧气燃烧法将废料氧化为各自的氧化物,然后于溶剂中分离、升华提纯、再还原处理纯净含硒溶液,制备出的硒粉,采用ICP-AES法对其中杂质元素进行测定,硒粉纯度达到5N(99.999%)。

镁合金废料再生技术现状及发展趋势

随着镁合金产品应用范围逐渐扩大,生产过程中产生的废料以及使用后报废的镁合金零件逐渐增多,镁废料回收及再生以及相关环保问题愈来愈受到人们的重视。本文介绍了镁合金废料的分类、再生技术的现状及发展趋势,并讨论了再生过程中的质量要求与检测手段。

AZ91D镁合金中的夹杂物

就镁合金铸件中夹杂物的形成过程以及它们对镁合金铸件质量的影响进行了分析。试验研究表明,在镁合金中,主要存在有氧化物夹杂、熔剂夹杂和外来夹杂等几种夹杂物,其中最主要的夹杂物是氧化物夹杂。通过适当工艺可以去除大部分夹杂物。

报废镁合金零部件表面涂层去除机理研究

采用以氢氧化钠、乙醇和三乙醇胺为主的碱性溶液去除废镁合金表面涂层,并通过金相、SEM和XRD等研究去除机理。结果表明,镁合金基材通过氢键与表面涂层结合,氢键在适宜的温度和时间下易被碱性溶液破坏,使涂层从基材上剥离;通过正交实验测定可证明,当NaOH溶液与乙醇体积比为1,NaOH摩尔浓度为10mol/L时,试样在温度为70℃的电热恒温水浴槽中处理70min,废镁合金表面涂层的起皱率可达到100%。

热挤压AZ91D镁合金边角料组织和性能的研究

采用热挤压工艺直接热挤出AZ91D镁合金边角料,研究挤压温度对挤压成形镁合金组织和性能的影响,并讨论其断裂行为。结果表明：在450℃热挤压时,晶粒尺寸均匀,组织中已不存在原始边角料之间未打碎的结合面,边角料之间结合较好;在350~450℃之间热挤出时,AZ91D镁合金随挤压温度的升高,抗拉强度和延伸率均增加,当挤压温度达到450℃时抗拉强度和延伸率分别达到336.56MPa和11.02%,原始边角料之间结合状态主要影响镁合金的力学性能。