铸态及快淬态La2Mg(Ni0.85Co0.15)9Crx(x=0～0.4)贮氢合金的电化学性能

为了提高La-Mg-Ni系(PuNi3型)贮氢合金的电化学循环稳定性,在La2Mg(Ni0.85Co0.15)9合金中加入微量Cr,用铸造及快淬工艺制备了La2Mg(Ni0.85Co0.15)9Crx(x=0,0.1,0.2,0.3,0.4)贮氢合金.研究了Cr含量对铸态及快淬态合金微观结构及电化学性能的影响.XRD,SEM及TEM的分析结果表明,铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3型结构)、LaNi5相和一定量的LaNi2相.随Cr含量的增加,铸态合金中LaNi2相的量增加.电化学测试结果表明,Cr的加入提高了铸态及快淬态合金的循环稳定性,但使合金的容量下降.当Cr添加量从0增加到0.4时,铸态合金的容量从396.3 mAh/g下降到355.6 mAh/g,循环寿命从72次增加到97次;快淬态(30 m/s)合金的容量从364.2 mAh/g下降到334.2 mAh/g,循环寿命从100次增加到131次.Cr添加使铸态合金的放电电压特性和活化性能得到改善.     

铸态及快淬态Mm(NiMnSiAlCu)4.3Co0.6-xFex(x=0～0.4)电极合金的电化学性能

用XRD,TEM及SEM测试了稀土基AB5型贮氢合金Mm(NiMnSiAlCu)4.3Co0.6-xFex(x=0～0.4) 的微观结构,并全面测试了合金在铸态及快淬态下的电化学性能.研究结果表明,铸态合金为双相结构,主相为CaCu5型相,还有少量Ce2Ni7相,经快淬处理后,第二相减少.对铸态合金,随Fe含量的增加,合金的容量有所降低,循环稳定性得到改善.对快淬态合金,当铁含量大于0.2时,合金的容量急剧下降,而循环稳定性大幅度增加.这主要是由于铁的加入使合金的微观结构发生了变化.     

硼及快淬工艺对La-Mg-Ni系贮氢合金的微观结构及电化学容量的影响

用铸造及快淬工艺制备了La-Mg-Ni系(PuNi3型)贮氢合金La2Mg(Ni0.85Co0.15)9Bx(x=0,0.05,0.1,0.15,0.2),分析测试了铸态及快淬态合金的微观结构与电化学容量,研究了硼及快淬工艺对合金微观结构及电化学容量的影响.结果表明,铸态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3型)、LaNi5相,一定量的LaNi2相和微量的Ni2B相,经快淬处理后Ni2B相消失.硼的加入对铸态及快淬态合金的容量产生不同的影响,铸态合金的容量随硼含量的增加而单调下降,而快淬态合金的容量随硼含量的增加有一极大值.快淬处理对含硼及不含硼合金的容量也有不同的影响,随淬速的增加,不含硼合金的容量单调下降,而含硼合金的容量可以获得一个极大值.     

快淬对贮氢合金组织和电化学性能的影响

通过XRD、TEM、DTA分析和电化学实验，研究了快淬对贮氢合金组织和电化学性能的影响，研究表明，成分均匀性改善和单胞体积减小是影响快淬氢合金电化学性能的主要因素，其中，前者使充放电循环稳定性提高，后者使放电容量降低，在本研究中，快淬速度为10m/s时，合金成分的均匀性已较铸态有明显改善，更高的快淬速度并不能使成分的均匀性进一步大幅度提高，反而使单胞体积减小，因此，快淬速度为10m/s时，快淬合金的综合电化学性能最佳。     

AB5型储氢合金电极材料的研究

采用熔体旋转(melt-spinning)技术制备的AB5型储氢合金，用扫描电镜观察合金的显微组织并对合金成分进行了EDX分析，用XRD研究合金结构和晶胞参数及吸氢体胀率，对比快淬态与铸态合金的使用性能．结果表明．快淬态合金性能优于铸态合金．     

硼对稀土系AB5型贮氢合金电化学容量及循环寿命的影响

为了提高低钴AB5型贮氢合金的电化学循环稳定性，在MmNi3．8Co0.4Mn0.6Al0．2贮氢合金中加微量的硼．用真空快淬工艺制备了稀土系低钴AB5型MmNi3．8Co0．4Mn0．6Al0．2Bx(x=0，0．1，0．2，0．3，0．4)贮氢合金，分析测试了铸态及快淬态合金的电化学性能及微观结构，研究了硼对铸态及快淬态合金电化学容量及循环寿命的影响．结果表明，硼使铸态及快淬态MmNi3.8Co0.4Mn0．6Al0．2贮氢合金的电化学容量不同程度地降低，但使电化学循环稳定性大幅度提高．硼对电化学性能的影响主要是促进非晶相的形成．     

RE-Mg-Ni系A_2B_7型合金的循环稳定性及电化学贮氢动力学

为了改善La-Mg-Ni系A2B7电极合金的电化学循环稳定性,用Zr部分替代合金中的La,并采用熔体快淬技术制备了La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05,0.1,0.15,0.2)电极合金.用XRD,TEM分析了合金的微观结构,结果表明,快淬不含Zr合金具有完全的纳米晶结构,而快淬含Zr合金中出现明显的非晶相,证明Zr替代有利于提高合金的非晶形成能力.铸态及快淬态合金均具有多相结构,包括两个主相(La,Mg)2Ni7及LaNi5和残余相LaNi2,Zr替代及快淬导致LaNi5相增加和(La,Mg)2Ni7相减少.Zr替代及快淬处理显著提高了合金的电化学循环稳定性,但快淬明显降低Zr0.2合金的电化学贮氢动力学;随Zr替代量的增加,5 m/s快淬合金的电化学贮氢动力学先增加后降低.     

LaxMm1-x(NiCoMnCuAl)5.1贮氢合金的电化学性能

在低钴AB5型贮氢合金LaxMm1-x(NiCoMnCuAl)5．1(x=0．25，0．38，0．56，0．74)中，加入纯La调整富Ce混合稀土中的La含量，测试了合金的电化学性能，研究了La含量的变化对LaxMm1-x(NiCoMnCuAl)5．1合金晶格参数、热力学参数及电化学性能的影响。结果表明，合金的晶格常数、晶胞体积及标准生成焓的绝对值随La含量的增加而增大，La含量的增加对提高铸态及快淬态合金的容量有利，但使得电化学循环稳定性及放电平台压下降，La含量的变化对合金的活化性能基本没有影响，铸态和快淬态合金通过1～2次循环均可完全活化。     

铸态和烧结态AlCoCrFeNi高熵合金模拟海水腐蚀性能研究

为了研究铸态和烧结态AlCoCrFeNi高熵合金在模拟海水介质下的电化学腐蚀性能,采用真空电弧熔炼和放电等离子烧结工艺制备AlCoCrFeNi高熵合金,分别采用X射线衍射仪(XRD)和光学显微镜(OM)分析其相结构和微观组织,采用电化学工作站对其进行电化学试验测试。研究结果表明:AlCoCrFeNi铸态合金组织呈现等轴晶形貌,物相为单一BCC结构;烧结态合金组织呈球形形貌,在900℃的烧结温度下,除了BCC相,还出现极少量的B2相以及FCC相。烧结态和铸态自腐蚀电位分别为-0.535 4V和-0.667 6V,自腐蚀电流密度分别为2.914 9×10~(-5) A·cm~(-2)和2.150 4×10~(-5) A·cm~(-2),铸态合金的钝化区比烧结态宽。2种合金均只出现一个容抗弧,且铸态合金的容抗弧半径远大于烧结态合金,表明铸态合金的耐蚀性优于当前烧结温度下的烧结态合金。     

快凝合金La(NiMn)5.6的贮氢性能

借助X-ray及吸放氢性能测试装置研究了非化学计量比快凝合金La(NiMn)5.6的结构和贮氢性能以及A端、B端元素替代对合金的影响,测试了不同温度下合金的PCT曲线.结果表明,快速凝固(35 m/s)条件下合金La(NiMn)5.6均可获得过饱和CaCu5型单相组织.A端以Ce取代La,使平台压力增大,最大吸氢量减小,但滞后降低;B端以Sn取代Ni,改善了合金的活化特性,并使平台降低,吸放氢滞后减小.     

Melt-spun Al<Subscript>70−<Emphasis Type="Italic">X</Emphasis></Subscript>Si<Subscript>30</Subscript>Mn<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript> (<Emphasis Type="Italic">X</Emphasis>=0, 3, 5, 7, 10) anode in lithium-ion batteries

Al_70−X Si₃₀Mn _X (X=0, 3, 5, 7, 10, mol%) ribbons were prepared by melt spinning. A supersaturated solid solution of Si and Mn in fcc Al and some microstructures consisting of nano grains were obtained. Some alloys with nano-sized grains exhibited high discharge capacities and favorable cycle properties. The capacity of more than 400 mAh/g could be obtained in melt-spun Al₆₇Si₃₀Mn₃ alloy after 20 cycles and more than 300 mAh/g after 40 cycles. Li/Si and Li/Al compounds in the anodes of pure Al and pure Si were not detected in Al-Si-Mn alloys inserted by Li. It is considered that the formation of the supersaturated solid solution and refinement of microstructures have prevented the alloys from the forming the compounds with superfluous Li. As a result, the electrochemical properties have been improved. Supported by the National Natural Science Foundation of China (Grant No. 50371066)     

Melt-spun Al_(70-X)Si_(30)Mn_X (X=0,3,5,7,10) anode in lithium-ion batteries

Al70-XSi30MnX (X=0, 3, 5, 7, 10, mol%) ribbons were prepared by melt spinning. A supersaturated solid solution of Si and Mn in fcc Al and some microstructures consisting of nano grains were obtained. Some alloys with nano-sized grains exhibited high discharge capacities and favorable cycle properties. The capacity of more than 400 mAh/g could be obtained in melt-spun Al67Si30Mn3 alloy after 20 cycles and more than 300 mAh/g after 40 cycles. Li/Si and Li/Al compounds in the anodes of pure Al and pure Si were...     

Microstructure and mechanical properties of ultrafine grained Mg15Al alloy processed by equal-channel angular pressing

An as-cast magnesium alloy with high Al content Mg15Al was subjected to equal-channel angular pressing (ECAP) through a die with an angle of ϕ=90° at 553 K following route B_c. It is found that the network β-Mg₁₇Al₁₂ phases in the as-cast Mg15Al alloy are broken into small blocks and dispersed uniformly with increasing numbers of pressing passes. Moreover, many nano-sized Mg₁₇Al₁₂ particles precipitate in the ultra-fine α-Mg matrix. The grains are obviously refined. However, the grain structure is inhomogeneous in different areas of the alloy. The average size of the primary phase α-Mg is reduced to about 1 μm while grains of around 0.1–0.2 μm are obtained in some two-phase areas. With additional ECAP passes (up to 8), coarsening of the grains occurs by dynamic recovery. Room temperature tensile tests show that the mechanical properties of Mg15Al alloys are markedly improved after 4 ECAP passes. The ultimate tensile strength and elongation to failure increase from 150 MPa to 269.3 MPa and from 0.05% to 7.4%, respectively. Compared with that after 4 passes, the elongation to failure of the alloy increases but the strength of the alloy slightly decreases after 8 ECAP passes. Fracture morphology of the ECAP-processed alloy exhibits dimple-like fracture characteristics while the as-cast alloy shows quasi-cleavage fractures.     

彩色金相技术的浅析与应用

利用"黑白衬度"金相和彩色金相技术研究五种铁碳合金(热轧态37Mn5、中温回火65Mn、铸态QT400-18L、热轧态P92超超临界钢和退火态20钢)和一种钛合金(热锻后淬火)的金相组织。研究结果表明,"黑白衬度"金相仅能用来观察传统碳钢和低合金钢的金相组织,试剂一(40 m L水+1 m L稀硝酸+0.5 g钼酸钠)、试剂二(盐酸(35%)+蒸馏水=1:5体积比(共100 m L)+0.5~1 g的焦亚硫酸钾)和热染法三种彩色金相方法能够清晰地观察球墨铸铁材料QT400-18L的铁素体基体晶界,且三种方法在操作性方面均较容易实现。热染法也可用来观察工业上批量化生产的碳钢和低合金钢的金相组织。     

Mechanical properties and microstructure of as-cast and extruded Mg-（Ce, Nd）-Zn-Zr alloys

1INTRODUCTION Thebeneficialinfluenceofrareearth(RE)metalsontheambientandelevatedtemperature mechanicalpropertiesofmagnesiumalloyhaslongbeenrecognized[13].Recently,Yttriumisaddedto Magnesiumalloytoimproveitstensilestrength andcreepresistance,andsuchinvestigationsatheat resistantmagnesiumalloyhaveledtothede velopmentofWE43andWE54alloys[4,5].Al thoughsuchalloysexhibitgoodpropertiesupto573Kthroughcastingandextruding,therelativelyhighcostofYttriumrestrictstheapplicationof suchalloys.Otherr…     

Structures and Electrochemical Performances of As-spun RE-Mg-Ni-Mn-based Alloys Applied to Ni-MH Battery

The La-Mg-Ni-Mn-based AB₂-type La_1-xCe_xMgNi_3.5Mn_0.5 (x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical hydrogen storage performances of the alloys were studied systematically. The XRD and SEM analyses proved that the experimental alloys consist of a major phase LaMgNi₄ and a secondary phase LaNi₅. The variation of Ce content causes an obvious change in the phase abundance of the alloys without changing the phase composition. Namely, with the increase of Ce content, the LaMgNi₄ phase augments and the LaNi₅ phase declines. The lattice constants and cell volumes of the alloys clearly shrink with increasing Ce content. Moreover, the Ce substitution for La results in the grains of the alloys clearly refined. The electrochemical tests showed that the substitution of Ce for La obviously improves the cycle stability of the as-spun alloys. The analyses on the capacity degradation mechanism demonstrate that the improvement can be attributed to the ameliorated anti-corrosion and anti-oxidation ability originating from substituting partial La with Ce. The as-spun alloys exhibit excellent activation capability, reaching the maximum discharge capacities just at the first cycling without any activation treatment. The substitution of Ce for La evidently improves the discharge potential characteristics of the as-spun alloys. The discharge capacity of the alloys first increases and then decreases with growing Ce content. Furthermore, a similar trend also exists in the electrochemical kinetics of the alloys, including the high rate discharge ability (HRD), hydrogen diffusion coefficient (D), limiting current density (I_L) and charge transfer rate.     

ZM5型铸造镁合金的晶粒细化

以自行铸造的ZM5型镁合金为基,添加多种变质剂C,C2Cl6,FeCl3,TiO2等,以细化镁合金晶粒,并比较其细化效果.实验结果表明,以上变质剂均能显著细化晶粒,且细小等轴的晶粒组织可以改善其力学性能.其中,C2Cl6的细化效果最为明显.     

Sr对Mg-5Sn-5Zn铸造镁合金组织的影响

通过光学显微镜、扫描电镜和X射线衍射仪研究了Mg-5Sn-5Zn-xSr（x=0,0.5,1,2）4种铸造镁合金的显微组织和相组成.结果表明：在Mg-5Sn-5Zn合金中加入质量分数为0.5%～2%的Sr元素后,不但能够缩小α-Mg枝晶间距,而且还能形成三元相MgSnSr.随着Sr含量的增加,在晶界析出的Mg2Sn相减少,晶内的MgSnSr相增加。合金中的MgZn相与Mg2Sn相依附在一起,大多数的MgZn相以α-Mg＋MgZn相的共晶方式存在.