Z.L. Ding
,
Y.C. Fan
,
H.B. Qi
,
D.L. Ren
,
J.B. Guo and Z.Q. Jiang Shijiazhuang Railway Institute
,
Shijiazhuang 050043
,
China
金属学报(英文版)
The SiC_p/Al-alloy composite front broke rotors designed for SHANGHAI SANTANA cars were prepared by semi-solid stirring+liquid for ping process. The properties of the composite rotors were examined. The composite brake rotors were subjected to dynamometer tests on a SCHENCK broke testing system, referring to TLll0 standard of VOLKSWAGEN Company. The friction coefficient and thermal response during fade testing and the wear performance of the composite rotors were studied as the function of various parameters, such as braking pressures, initial speeds, initial temperatures, torque and decelerations, and compared with that of conventional cast iron rotors. The results showed that the properties of SiC_p,/Al-alloy composite rotors can achieve the requirements of commercial cast iron rotor.s. The results also suggested that the friction coefficients of composite rotors under different broking conditions are within the deviation band specified by the TLll0 standard, and the temperature rise of the composite rotors at the cud of each fade stop is lower than that of the cast iron rotors. The wear resistance of composite rotors was higher than that of cast iron rotors. The friction and wear mechanism are analyzed.
关键词:
SiC_p/Al-alloy composite
,
null
,
null
,
null
黄爱华
,
金鸣林
,
李和兴
,
房永征
材料导报
试验是以2种含不同QI的煤沥青为原料,采用变径反应管进行热转化反应制备有序性中间相的研究.试验采用偏光显微镜和扫描电镜(SEM)观察了原料各反应阶段的微观结构,考察了QI对热转化过程中中间相有序生长的影响,分析了热转化过程中软化点及族组分的变化.结果表明:少量的喹啉不溶物含量不会阻碍中间相有序的发展.高QI(2.03%)原料易生成镶嵌结构的中间相体,高温处理后样品呈轴状、短纤维、层片松散的石墨化焦结构;含低QI(0.11%)的原料能生成较好的、大区域的中间相体,域结构的中间相体在外力导向和内部裂解气流的作用下容易生成有序的半焦,高温处理后呈大区域、片层紧密、有序性强的细纤维焦结构.同时研究发现,在热转化过程中可通过测定软化点(SP)和TI含量来确定中间相转化程度.软化点约低于250℃、TI为75%左右时为初始中间相区域体形成阶段、半焦生成的前期.
关键词:
煤沥青
,
热转化反应
,
喹啉不溶物
,
中间相
毕大森
,
武晋
,
张建
,
彭本栋
材料开发与应用
doi:10.3969/j.issn.1003-1545.2009.01.003
高强度烘烤强化(BH)钢是汽车覆盖件用的高强度钢板.本文通过试验对汽车用高强度钢板B180H1的力学性能、成形性能、烘烤硬化性能和抗凹陷性能进行了全面的研究,并与DC04钢板的各项性能进行了比较.使用NADDRG模型对B180H1钢的成形极限进行了预测.试验结果表明,B180H1的力学性能优于DC04,成形性能不低于DC04,且B180H1的烘烤硬化性能及抗凹陷性能方面均优于DC04.B180H1钢板的实冲壳体也具有良好的成形性能.
关键词:
汽车轻量化
,
高强度钢板
,
烘烤硬化
,
成形性能
,
抗凹陷性
Y.L. Chen(Department of Materials Science and Engineering
,
Zhejiang University
,
Hangzhou 310027
,
China)
金属学报(英文版)
Internal friction measurements on binary and ternary α-phase alloys of Pd with hydrogen and boron have been performed with a torsion pendulum and by observing the cttenuation of ultrasonic pulses. A pronounced damping maximum of binary Pd-B alloys at 220K and measuring frequencies of about 4Hz could not be established at a frequency of 15MH. Ternary Pd-B-H alloys show an additional damping maximum besides the hydrogen Zener effect, which is interpreted in terms of a changed jump frequency of hydrogen in the neighborhood of boron atoms.
关键词:
Pd-B-H alioy
,
null
,
null
,
null
Physical Review B
By using a first-principles plane-wave pseudopotential method, the energetics and electronic structure of Sigma5(210) grain boundary (GB) and the (210) surface of undoped as well as B- and/or H-doped Ni3Al are investigated. The geometric structures of the GBs and surfaces are fully relaxed by minimizing the total energy and interatomic force. The results show that B induces a large lattice expansion but H does not. Both B and H "prefer" to occupy the Ni-rich hole at the GB or surface but not the Ni-deficient one. The segregation energies of B and H as well as the interaction energy between them at the GB and surface are calculated. The calculation indicates that B segregates more strongly to the GB than to the surface, which results in an increase in the Griffith work of the GB and, therefore, in agreement with the experiments, improves the ductility of Ni3Al. Contrary to the case of B, H segregates more strongly to the surface than to the GB, which results in a decrease in Griffith work and confirms H as an embrittler for Ni3Al. The calculation of the interaction energy between B and H demonstrates that B and H repel each other. Consequently, B may block the site of occupation of H at the GB, and restrain the H-induced embrittlement. To understand the mechanism of the obtained energetic features, the electronic densities of states (DOSs) are calculated. A comparison of the total DOSs between the B-doped GB and undoped as well as H-doped ones shows that B increases the hybridization of the GB, which contributes to the enhanced binding of the B-doped GB over the undoped and H-doped ones. When the site of B changes from bulk to GB to surface, the hybridization between B and Ni decreases accordingly. It is proposed that the segregation behavior of B at the GB and surface is dominated by the competition between B(p)-Ni(d) bond energy and the strain energy induced by B. The preference of B for the Ni-rich interstice in Ni3Al is explained by the repulsive interaction between B and Al atoms resulting from the hybridization between their electrons when they are close to each other. The repulsion between B and H can also be explained by the same electronic structure mechanism as that for the B-Al interaction. The segregation of B at surface shifts the DOS of its nearest neighbor Ni to lower energy. This may increase the chemisorption potential energy of H2O on Ni3Al surface and, therefore, decrease the reactivity of the surface, inhibiting the environmental embrittlement of Ni3Al.
关键词:
intergranular fracture;environmental embrittlement;polycrystalline;ni3al;water dissociation;first-principles;metal-surfaces;boron;segregation;ductility;hydrogen
张善业
,
高怡斐
物理测试
对马钢生产的耐火H型钢MGFR490B和Q345B H型钢进行了对比试验研究,完成了高温拉伸和高温持久两项力学性能测试和对两种钢微观组织的观察研究.结果表明,耐火H型钢MGFR490B的组织为多边形铁素体+珠光体+少量贝氏体混合多相组织,此种组织在高温下能保持很好的稳定性,并能在高温下析出合金碳化物,这对降低耐火H型钢MGFR490B的室温屈强比和保持高温屈强比小的波动范围有益.耐火H型钢MGFR490B获得了比Q345B H型钢好的高温强度性能,这与耐火钢的混合多相组织及添加合金元素密不可分.耐火H型钢MGFR490B在600℃高温下能保持高的强度,并且其持久断裂时间超过3 h,满足耐火钢的性能指标要求.
关键词:
耐火钢
,
高温拉伸
,
高温持久
,
屈强比
张善业
,
高怡斐
物理测试
对马钢生产的耐火H型钢MGFR490B和Q345B H型钢进行了对比试验研究，完成了高温拉伸和高温持久两项力学性能测试和对两种钢微观组织的观察研究。结果表明，耐火H型钢MGFR490B的组织为多边形铁素体﹢珠光体﹢少量贝氏体混合多相组织，此种组织在高温下能保持很好的稳定性，并能在高温下析出合金碳化物，这对降低耐火H型钢MGFR490B的室温屈强比和保持高温屈强比小的波动范围有益。耐火H型钢MGFR490B获得了比Q345B H型钢好的高温强度性能，这与耐火钢的混合多相组织及添加合金元素密不可分。耐火H型钢MGFR490B在600 ℃高温下能保持高的强度，并且其持久断裂时间超过3 h，满足耐火钢的性能指标要求。
关键词:
耐火钢
,
high temperature tensile high temperature persistent
,
yield ratio
,
null
张蓓
,
张鹏
,
王军
,
朱飞
,
曹兴忠
,
王宝义
,
刘昌龙
原子核物理评论
doi:10.11804/NuclPhysRev.30.04.471
室温下将130 keV，5×1014 cm-2 B离子和55 keV，1×1016 cm-2 H离子单独或顺次注入到单晶Si中，采用横截面试样透射电子显微镜(XTEM)和慢正电子湮没技术(SPAT)研究了离子注入引起的微观缺陷的产生及其热演变。XTEM观测结果显示，B和H离子顺次注入到单晶Si可有效减少(111)取向的H板层缺陷，并促进了(100)取向的H板层缺陷的择优生长。SPAT观测结果显示，在顺次注入的样品中，B离子平均射程处保留了大量的空位型缺陷。以上结果表明，B离子本身及B离子注入所产生的空位型缺陷对板层缺陷的生长起到了促进作用。
关键词:
单晶Si
,
B和H离子注入
,
H板层缺陷
,
XTEM
,
SPAT
Energy & Environmental Science
The Li-Mg-B-H system that is prepared from 2LiH + MgB(2) or 2LiBH(4) + MgH(2) possesses high hydrogen capacity and relatively favorable thermodynamics, but it is greatly restricted in practical hydrogen storage applications by problematic H-exchange kinetics. In the present study, TiF(3) was mechanically milled with a 2LiH + MgB(2) mixture and examined with respect to its effect on reversible dehydrogenation of the Li-Mg-B-H system. Experimental study showed that TiF(3) is highly effective for promoting the two-step dehydrogenation reaction in the Li-Mg-B-H system. Compared to the neat 2LiH + MgB(2) sample, the 2LiH + MgB(2) + 0.01TiF(3) sample exhibits significantly reduced dehydrogenation temperature and markedly enhanced dehydriding rate at both steps. Furthermore, the catalytic enhancement arising upon adding TiF(3) additive was observed to persist well in the hydrogenation/dehydrogenation cycles. Based on the results of phase analysis and a series of designed experiments, the mechanism underlying the observed property improvement is discussed.
关键词:
complex hydrides;libh4;tif3;kinetics;naalh4
