VGF法GaAs单晶位错分布的数值模拟和Raman光谱研究

采用数值模拟技术和Raman光谱法对4inch垂直梯度凝固(VGF)法GaAs单晶位错进行了研究。运用数值模拟软件计算了GaAs晶体生长过程中的位错分布,模拟计算与实验结果一致。通过Raman光谱测量,定量计算了晶片表面的残余应力分布。Raman测量结果表明,残余应力与位错密度分布基本一致。在VGF法生长的GaAs单晶中观察到了不完整的位错胞状结构,并利用Raman光谱法对其进行了微区分析。     

回火索氏体钢轨钢循环应变行为与位错结构关系的研究

本文用增量步进试验方法，研究了具有不同组织参数的回火索氏体共析钢轨钢的循环应力－应变行为。并通过透射电镜对位错结构的分析，探讨了回火索氏体循环软化机制。试验及分析结果表明，在本试验条件下，回火索氏体组织均发生循环软化。循环应变过程中组织中位错间的交互作用形成位错胞。回火索氏体强烈的循环软化主要是由于位错组态再分布，产生胞状亚结构，使内应力降低所致。     

Nb和Nb-V微合金化钢位错亚结构强化的X射线研究

利用常规X射线线形分析方法,测量了Nb和Nb-V微合金化钢板材的横向(x),纵向(y),和轧面法向(z)三个方向的相干散射区尺寸。证实本实验所用钢种经控轧后的位错胞近似呈椭球形。根据孙福玉等人提出的关于控轧钢屈服强度理论估算公式中所规定的原则,并考虑位错分布组态对强化效果的影响,位错亚结构强化效应可表示为K_DR_ZD(?)~(-1/2)。对本实验钢种,位错亚结构强化系数K_d≈1。     

低碳Ni—Cr—Mo钢中M／A岛及回火特性

采用现代高分辨电子－－光学分析技术及光学显微镜等，对低碳Ｎｉ－Ｃｒ－Ｍｏ碳中Ｍ／Ａ岛及其回火特性进行分析。结果表明，有两种类型的Ｍ／Ａ岛，一种为可聚成团状的小尺寸Ｍ／Ａ岛（即粒状贝氏体中的Ｍ／Ａ岛），它所在的铁素体基体呈胞状结构，位错密度较高，胞状之间为小角度关系；另一种为孤立的块状Ｍ／Ａ岛（类似双相钢中的Ｍ／Ａ岛），它所在的铁素体基休与多边形铁素体类型，位错密度较低，透射电镜下没有看到亚结构。前     

重轨混钢区钢坯碳含量分布及轨性能研究

以包钢5#铸机对称六流中间包结构为研究对象,通过对上下炉成品中间包碳差大于0.03%的中包混钢区部分的钢坯及所轧钢轨横、纵向断面上的碳含量分布情况、波动范围及力学性能的研究,解析了上下炉碳差大于0.03%对重轨钢混钢区钢坯、钢轨的碳含量分布范围及其对钢轨性能的影响。     

细晶强化和位错强化对中锰马氏体钢的强化作用

 研究了碳和锰含量对淬火中锰马氏体钢的位错密度、残余奥氏体含量、晶粒尺寸等组织结构以及室温力学性能的影响。借助于SEM、EBSD、TEM和XRD表征了材料的微观组织,探讨了马氏体钢的强化机制。结果表明:随着碳含量增加,淬火中锰钢的位错密度和残余奥氏体体积分数逐渐增加,板条束和板条块尺寸逐渐细化,大角晶界百分数逐渐增加,强度逐渐升高;增加锰含量能够提高马氏体钢的位错密度和抗拉强度。分析认为,位错强化和细晶强化是淬火中锰马氏体钢的主要强化机制。马氏体板条尺寸是马氏体抗拉强度的结构控制单元,而原奥氏体晶粒尺寸则是马氏体屈服强度的结构控制单元。     

掺杂GaAs单晶中位错的腐蚀观察与探讨

本文阐述水平三温区炉生长的掺杂(Si,Te或Cr)GaAs中位错的腐蚀观察工艺和基本原理。详细探讨了由化学腐蚀所获得的一些结果,诸如位错坑,浅坑或碟坑,沉淀物和夹杂等。     

新型超低碳贝氏体耐大气腐蚀钢

采用增加碳含量和合金含量的方法来提高耐大气腐蚀钢强度，会导致冷裂纹敏感性的增加、焊接热影响区硬度的提高和焊接热影响区韧性的降低。为此，川崎制铁开发了超低碳贝氏体耐大气腐蚀钢，其碳含量约为0．02％。该产品的特点如下：     

TA15钛合金热压缩变形位错演化分析

采用Gleeble—3500热模拟压缩试验机对TA15钛合金进行等温恒应变速率压缩实验,并应用材料分析测试技术(XRD与TEM)和相关定量计算理论(XRD线形傅氏分析法)分析其热压缩变形过程中的位错演化。结果表明,TA15钛合金热压缩变形过程中位错类型主要为柱面(1010)、基面(0002)、锥面(1011)和(110)β面位错,位错密度均在1013~1014 cm-2范围内。当变形温度为950℃且变形量为40%时,随着应变速率的提高,柱面(1010)和(110)β面位错密度几乎不变;当变形量升至60%时,随应变速率的提高,各晶面的位错密度均显著降低。当应变速率为1s-1时,随变形量的增加,平均晶格应变和位错密度均减小;当变形量为60%时,晶格应变降到0.116%~0.138%,位错密度减小到(1.1~1.7)×1014 cm-2。在(α+β)两相区出现了由位错形成的"微观变形带"及位错胞结构;在β单相区板条状马氏体α'相内部位错密度较低,形成位错塞积群,且在位错塞积群和马氏体α'相之间形成高度的应力集中。     

焊接性能优异的新型超低碳贝氏体耐大气腐蚀钢

通过增加碳含量和合金含量来提高耐大气钢的强度的方法会导致冷裂纹敏感性的增加、焊接热影响区硬度的提高和焊接热影响区韧性的降低。为此,川崎制铁开发了超低碳贝氏体耐大气腐蚀钢,其碳含量约为0 0 2 %。该产品的特点有:(1)海岸用耐大气腐蚀用钢的Ni含量不少于2 5 % ,经两年海水喷雾试验表明,其腐蚀失重比常规耐大气腐蚀钢少15 %。(2 )在轧态情况下,田园用新型耐大气腐蚀钢满足5 70MPa级强度和韧性的要求,新型海岸用耐大气用钢也满足4 0 0、4 90、5 70MPa级强度和韧性的要求。(3)在腐蚀失重和铁锈特征方面,田园用新型耐大气腐蚀钢的耐…     

铂丝退火过程中的微观形貌演变和位错密度研究

铂丝的微观形貌和位错密度与退火工艺密切相关,研究铂丝退火过程中微观形貌和位错密度的变化,可以优化退火工艺和提高铂丝电阻性能,为研发高性能铂电阻温度计提供支撑。研究表明:初始铂丝表面有黑色斑驳区域和划痕,有自生颗粒和外来颗粒。随着退火时间的延长,铂丝表面的黑色斑驳区域和划痕消失。退火过程中,铂晶粒晶界处的铂原子很不稳定,逐渐与碳原子形成含Pt和C的颗粒,晶界则变宽边深,产生许多孔隙;随着退火时间的延长,铂丝主体中的杂质元素只剩下C。初始铂丝晶粒的内部和晶界处均存在大量的位错,位错密度达到3.69×10^12 cm^-2,经历退火热处理后晶粒内部和晶界处的位错大量消失。铂丝被充分退火后,位错密度低至无法测出。     

温度和应变速率对FeCrNi合金位错组态的影响

 利用透射电镜观察了不同温度及不同应变速率下FeCrNi合金的位错组态，分析了位错组态与温度及应变速率的关系。结果表明：温度使交滑移频率提高，位错组态从位错墙向位错胞方向发展，而应变速率升高使交滑移频率降低，位错组态从位错胞向位错墙、高密度层错方向发展。     

A microstructural study of dislocation substructures formed in metal foil substrates during ultrasonic wire bonding

A study has been conducted on the deformation mechanisms in metal substrates subject to aluminum ultrasonic wire bonding (UWB). Aluminum wires were bonded to copper, nickel, stainless steel, and aluminum bronze foil substrates and then removed in aqueous sodium hydroxide to permit thin sections of bonded areas to be examined in the transmission electron microscope (TEM). The results showed a variety of dislocation substructures formed during bonding, including dislocation cells, subgrains, and planar arrays. Aluminum and copper showed evidence of thermal effects on microstructural evolution during bonding, such as dislocation annihilation at cell walls in copper and complete recrystallization in aluminum. In the nickel and stainless steel substrates, which have higher recrystallization temperatures, thermal effects on microstructure were not observed. In addition, it was found that low stacking-fault energy (SFE) materials, such as aluminum bronze, were less likely to undergo cell formation, and only planar dislocation arrays formed. In general, it is clear that the process of UWB induces cyclic stresses in the substrates, which exceed the yield strength of the metals examined. In addition, there is some heat generated during the bonding process, which can influence the resultant deformation microstructure.     

Formation of voids and dislocation loops in near-stoichiometric nial by aging at 700° to 900°c,and some effects on alloy properties

Dislocation loops and voids form spontaneously in stoichiometric NiAl annealed between 700° to 900°C. The former probably are formed by a punching mechanism from impurity particles, and the latter are frequently seen to have nucleated on particles. However, it is possible that both loops and voids are nucleated by vacancy/impurity complexes. Some of the loops act as dislocation sources during plastic deformation so that, for example, NiAl annealed at 700° to 900°C is softer and has greater ductility at room temperature, or has poorer creep resistance at higher temperatures, than material annealed at 1300°C. It is probable that small precipitate particles, possibly carbides and/or aluminum oxide form at 700° to 900°C but are in solution at higher temperatures. Their effect on mechanical properties is a form of precipitation softening.     

InP Bulk Crystals Grown from Various Stoichiometric Melt

InP crystal was grown from stoichiometric or non-stoichiometric melt, including P-rich and In-rich condition by the P-injection synthesis LEC method. Owing to the non-stoichiometric condition, there are many pores in the tail of the P-rich ingot. Samples were characterized by high speed photoluminescence mapping and E.P.D. mapping. The perfection (dislocation, stoichiometry and uniformity) of these samples were studied and compared. The PL peak intensity standard deviation of the 4-inch InP wafer is higher. The EPDs around the pores are higher than the other regions. Besides the stress releasing, the pores and the high concentration of dislocations around them are the leading factors causing the inhomogeneity of the wafer. By adjusting the thermal field and ensuring the chemical stoichiometry, InP crystals of larger diameters and better performance can be developed.     

The effect of impurity interstitials on the lattice resistance to dislocation motion

A computer simulation model was developed to determine the nature of the synergistic effect between the lattice resistance and impurity interstitial atoms to dislocation motion. If the interaction between an impurity interstitial and a screw dislocation in a bcc lattice with a large Peierls barrier is treated in an elastic continuum manner, strengthening will occur. This strengthening occurs at all interstitial concentrations and at all temperatures in the low-temperature region.     

The deformation and fracture of Ti3Al at elevated temperatures

The tensile properties of the intermetallic compound Ti₃Al have been determined in air at several temperatures within the range of 25 to 900 °C. The dislocation structures produced by the various testing conditions were studied in the electron microscope and the fracture modes were studied in the scanning electron microscope. These microstructural observations were correlated with the mechanical properties. The results indicate that Ti₃Al has only limited ductility even at 900 °C. The apparent ductile-brittle transition which occurs above 600 °C is due to increasing amounts of intergranular cracking. Some increase in ductility above 600 °C is due to the onset of dislocation cross slipping. The fracture mode up to 600 °C is entirely cleavage. Above 600 °C the fracture shows increasing evidence of plasticity; however, cleavage remains the main fracture mode up to 900 °C. Formerly with the Materials Laboratory Formerly in the Processing and High Temperature Materials Branch     

Microstructural Characterization of Welded Joint in Duplex Stainless Steel by Laser Continuous Heat Treatment

Microstructural characterization in fusion zone of the laser continuous heat treatment welded joint was in vestigated. The results showed that the martensite-like microstructure is the face centered cubic （FCC） crystal structure so that it can be identified as the secondary austenite. The dislocation is observed inside and outside the seconda ry austenite, whereas inclusion is not found in the vicinity of the secondary austenite. In the fusion zone, there is a kind of carbide precipitate which is identified as M23 C6 by the means of transmission electron microscope （TEM）. The carbide precipitate is a representative mode of transformation, which can be generated by the eutectoid reaction. Furthermore, the formation mechanisms of the secondary austenite and chromium carbide are analyzed.     

贝氏体铁素体和残余奥氏体取向关系

 用分析电镜和高分辨电镜确定了贝氏体钢中贝氏体铁素体和残余奥氏体之间存在3种取向关系。其中一种为K-S关系,即［110］γ′//［111］α,（111）γ′//（110）α;一种为N-W取向关系,即［110］γ′//［001］α,（111）γ′//（110）α;还有一种为G-T关系,即［112］γ′//［110］α,（111）γ′//(110)α。高分辨像显示,贝氏体铁素体-奥氏体相界面不平直,α和γ′两相内有系列刃型位错和结构小台阶,两相界面未显示出连续的严格共格关系。