C.L. Mo
,
Y.T. Zhang
,
D.Z. Li
,
Y.Y. Li
金属学报(英文版)
The microstructural banding in steels is often found in hot rolling strips, which plays a very important role in mechanical properties. Much work has been done to investigate how the microstructural banding is formed during hot rolling. In the present study, the microstructure of hot rolling strips was examined in term of optical microscopy and transmission electron microscopy. Electron probe microanalysis ｗａs also used to decide the distribution of microchemical bands, by this means, the phases in these strips were found to be ferrite and pearlite. The average distance between the carbon lamellas in pearlite is about 0.06-0.1μm. It is also shown that microstructural banding in hot rolled carbon steel ｗａs closely related to the segregation of manganese and silicon into those bands. Based on the transformation kinetic, the simulated results pointｅｄ out that the thermodynamic stability of austenite would increase with the increasing of Mn, which led to a decrease of ferrite growth rate. The effect of Mn on the decomposition of austenite is attributed to segregation of Mn atoms along the ferrite/austenite phase boundary which causes a strong solute drag effect. The addition of Mn to steel decreases the activity of austenite, thereby it is beneficial to the formation of non-equilibrium phase, such as degenerate pearlite. The formation of banded structure on the hot rolled process was discussed.
关键词:
pearlite
,
null
,
null
Y.T. Zhang
,
C.Z. Wang
,
D.Z. Li
,
Y.Y. Li
金属学报(英文版)
A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot rolling strip mill. In this model, the parameter k in Avrami equation was developed for carbon steels. The wide range of chemical composition, the primary austenite grain size, and the retained strain were taken into account. It can be used to predict the ferrite volume fraction and the carbon concentration in austenite of hot-rolled steel strip during laminar cooling on run-out table. The coiling temperature controlling model was also presented to calculate the temperature of steel strip. The transformation kinetics of austenite to ferrite and the evolution of carbon concentration in austenite at different temperatures during cooling were investigated in the hot rolled Q235B strip for thickness of 9.35, 6.4, and 3.2mm. The ferrite volume fraction along the length of the strip was also calculated. The calculated ferrite volume fraction was compared with the log data from hot strip mill and the calculated results were in agreement with the experimental ones. The present study is a part of the prediction of the mechanical properties of hot-rolled steel strip, and it has already been used on-line and off-line in the hot strip mill.
关键词:
carbon concentration
,
null
,
null
桂全红
,
马禄铭
,
蒋晓军
,
梁国军
,
李依依
材料研究学报
研究了两种不同Y 含量对8090Al-Li 合金拉伸性能及断裂行为的影响。实验表明:加入0.1wt-%Y 可在不降低强度的情况下提高合金的塑性,加入0.5wt-%Y 可在不降低塑性的情况下提高合金的强度。在峰值时效条件下,不加Y 的合金断裂为穿晶韧窝型和沿晶塑性混合方式,并伴有沿晶二次裂纹,加0.1%Y 不改变合金断裂模式,但使沿晶成分减少;加0.5%Y 合金则发生快速剪切断裂。本文从晶粒结构角度对断裂行为提出了解释。
关键词:
A—Li 合金
,
rare earth element Y
,
tensile properties
,
intergranular fracture
,
transgranular fracture
刘成
,
杨毅
,
韩正玉
,
武晓雅
,
翁景霞
,
林璐
中国稀土学报
doi:10.11785/S1000-4343.20130408
采用溶胶-凝胶法制备Li+掺杂改性的Y2SiO5:Pr3+上转换发光材料,考察了Li+掺杂对样品晶型及发光性能的影响.采用XRD,DSC-TGA,FS对所制备的材料进行表征,结果表明Li+掺入浓度在7％～ 8％(摩尔分数)之间会引起Y2SiO5晶体类型由X型转变为X2型,且Li+掺入后样品转晶型温度由950℃降至800℃;样品经800℃煅烧处理后以X1型Y2SiO5为主相,850℃煅烧处理后以X2型Y2SiO5为主相;Li+掺入同时会提高Y2SiO5:Pr3+材料的上转换发光强度,Li+最佳掺杂浓度为10％,对于双掺杂pr3+,Li+:Y2SiO5体系中pr3+最佳掺杂浓度为1.2％.
关键词:
溶胶-凝胶法
,
上转换
,
晶相转变
,
锂掺杂
,
稀土
沙桂英
,
刘翠云
,
刘腾
,
孙晓光
,
李根
材料工程
doi:10.3969/j.issn.1001-4381.2010.07.014
利用Hopkinson压杆技术对Mg-3.5%Li及Mg-3.5%Li-0.77%Y合金在不同应变率下进行了冲击压缩实验,分析了两种合金的动态应力-应变行为及其应变率效应.结果表明,随应变率提高,Mg-3.5%Li合金的应力-应变行为表现出应变率强化效应与应变率弱化效应的双重特性.添加稀土元素Y后,合金有所强化,但其应力-应变行为仍具有应变率弱化效应,随应变率提高产生的微裂纹引起的内部损伤是导致合金应变率弱化效应的主要原因.
关键词:
Mg-Li合金
,
Mg-Li-Y合金
,
应变率
,
微裂纹
冯剑
,
黄金亮
,
贾玉鑫
兵器材料科学与工程
为改善铸态Mg-12Li-3Gd-3Y-0.6Zr合金的力学特性，对铸锭进行均匀退火处理。采用金相显微镜、SEM、XRD、显微硬度测试和拉伸力学特性测试，观察和研究了试验合金的微观组织和力学特性。结果表明：最佳的均匀化退火工艺为500℃×8 h，均匀化退火后合金的抗拉强度由铸态的114 MPa提高到133 MPa。第二相形态及分布的改变是Mg-12Li-3Gd-3Y-0.6Zr合金力学特性改变的主要原因。
关键词:
镁锂合金
,
均匀化
,
微观组织
,
力学特性
彭晓东
,
李俊辰
,
李文娟
,
杨艳
,
魏群义
稀有金属材料与工程
采用光学显微镜、SEM扫描电镜、XRD以及力学性能和电化学测试等手段,研究了不同Y含量对Mg-9Li-3Al合金组织、力学性能和腐蚀性能的影响.结果表明:随着Y的添加,α相的形貌逐渐发生变化,其体积分数也逐渐减少,并形成新的Al2Y相,Al2Y主要分布在β相和α相内部.当Y的添加量为1.6％(质量分数)时,材料的抗拉强度达到最大190.2 MPa;当Y含量为2.0％时,材料的最大延伸率为19.3％.在Y含量低于1.2％时,材料的抗腐蚀性能随Y含量的增加而减小,超过1.2％后,随着Y含量的增加而增加.
关键词:
镁合金
,
组织
,
力学性能
,
抗腐蚀性能
稀土学报(英文版)
Er(3+) and Li(+) codoped Y(3)Al(5)O(12) (YAG) powders were prepared for a systematic investigation of their upconversion emissions. X-ray diffraction (XRD), upconversion emission spectra, pump power dependence, FT-IR spectra and decay time were studied to characterize the samples. With Li+ doping, the upconversion emission intensity of Er(3+) doped YAG powders was obviously enhanced, accompanied with an increase in the ratio of green to red intensity. The enhancement of emission intensity could be attributed to two mechanisms: one was the distortion of local crystal field around Er(3+), and the other was the decrease in the amount of CO(3)(2-) and OH(-) groups. Our results revealed that the latter was the dominant mechanism of the upconversion intensity enhancement in the YAG:Er(3+)/Li(+) powders.
关键词:
luminescence;optical materials and properties;sol-gel preparation;nanomaterials;rare earths;nanocrystals;nanophosphors;li+
曲涛
,
田彦文
,
钟参云
,
翟玉春
功能材料
橄榄石型LiFePO4是近年发展起来的一种锂离子电池正极材料,它的理论容量为170mAh/g.具有价格便宜、环境友好、无毒、无吸湿性、热稳定性好等优点,越来越受到人们的重视.但是由于LiFePO4的室温电导率低,影响了它的实际应用,为改善其电导率低的问题,本文采用固相法掺杂稀土元素Y合成Li0.99Y0.01FePO4,结果表明,掺杂后材料具有良好的电化学性能,其室温初始放电容量为129.9mAh/g,循环15次后几乎没有衰减.
关键词:
锂离子电池
,
正极材料
,
Li0.99Y0.01FePO4
,
稀土
冯剑
,
黄金亮
,
贾玉鑫
稀土
为了提高Mg-8Li-3Gd-3Y-0.6Al合金铸锭的力学性能,对合金进行了均匀化退火处理.通过金相显微镜、扫描电镜、显微硬度测试、X射线衍射、拉伸力学性能测试等手段,研究了均匀化条件对Mg-8Li-3Gd-3Y-0.6Al合金的显微组织和力学性能的影响.结果表明,铸态合金经773K 8h的均匀化处理后,铸态时的网状相完全溶解到基体中,第二相弥散分布在基体中,同时退火态合金的抗拉强度达到了154 MPa,比铸态合金提高了23％.合金最佳的均匀化退火工艺是773K 8h,此时该合金具有较好的综合力学性能.
关键词:
Mg-8Li-3Gd-3Y-0.6Al合金
,
显微组织
,
均匀化
,
力学性能
