EBSD技术在研究AZ31镁合金挤压织构中的应用

AZ31镁合金挤压棒材在传统正挤压变形过程中易于形成很强的挤压纤维织构。本文利用EBSD技术对AZ31镁合金挤压棒材的挤压组织进行了表征,发现AZ31镁合金挤压棒材在挤压时形成的织构不是均匀的(0002)基面平行于挤压方向的环状纤维织构,而是由(10 10)棱柱面垂直于挤压方向和(11 20)棱柱面垂直于挤压方向的两个不同的纤维织构组分组成的。因此(0002)极图不足以表达该织构的足够信息,必须用沿挤压方向的反极图表示。纤维织构的存在使得挤压样品具有明显的拉伸各向异性。     

平面应变压缩过程中初始取向对AZ31镁合金变形行为的影响

在室温和150℃下对AZ31镁合金进行平面应变压缩试验,应变速率为0.01 s-1,形变量为0.1.试样(切割于强织构的热轧板)的压缩轴c与其基面法向成不同的角度,从而研究初始织构对AZ31镁合金塑性变形行为的影响.利用电子背散射衍射花样(EBSD)采集变形试样的微观结构和织构信息,分析孪生和滑移行为.实验发现AZ31镁合金塑性变形由{10(-12)}<(-10)11>拉伸孪生和基面滑移共同控制,并确定了各种变形模式比例与晶体初始取向的关系,其中拉伸孪生在压缩轴垂直于c轴方向时占主导作用.     

平面应变压缩过程中初始取向对AZ31镁合金变形行为的影响(英文)

在室温和150℃下对AZ31镁合金进行平面应变压缩试验,应变速率为0.01s-1,形变量为0.1。试样（切割于强织构的热轧板）的压缩轴c与其基面法向成不同的角度,从而研究初始织构对AZ31镁合金塑性变形行为的影响。利用电子背散射衍射花样（EBSD）采集变形试样的微观结构和织构信息,分析孪生和滑移行为。实验发现AZ31镁合金塑性变形由{1012} 〈011〉拉伸孪生和基面滑移共同控制,并确定了各种变形模式比例与晶体初始取向的关系,其中拉伸孪生在压缩轴垂直于c轴方向时占主导作用。     

原位背散射电子衍射研究压缩变形过程中AZ31合金的微观组织演变

本文采用原位背散射电子衍射(原位-EBSD)方法研究了AZ31合金在压缩应力下的微观组织演变。结果表明{10 12}[1011]孪生是主要的变形模式。该孪生模式导致了变形后晶体取向发生了明显的转变,由原始取向为其C轴垂直于挤压方向ED的丝织构,转变为其C轴平行于ED及压缩应力方向。同时位错滑移也提供了一定的变形量。AZ31合金中RD和TD织构组分的梯度对于压缩变形条件下的孪生变形没有明显的影响。     

原位背散射电子衍射研究压缩变形过程中AZ31合金的微观组织演变

本文采用原位背散射电子衍射(原位-EBSD)方法研究了AZ31合金在压缩应力下的微观组织演变.结果表明{ 10-12}[-1011]孪生是主要的变形模式.该孪生模式导致了变形后晶体取向发生了明显的转变,由原始取向为其C轴垂直于挤压方向ED的丝织构,转变为其C轴平行于ED及压缩应力方向.同时位错滑移也提供了一定的变形量....     

初始织构对高温轧制AZ31镁合金板显微组织与织构影响的EBSD研究

本文采用EBSD方法表征分析了不同初始取向的AZ31镁合金原料板材经300℃热轧69%后得到的终轧产品的显微组织与织构差异,考察了热轧变形条件下原料的初始织构对热轧成品板材的影响。结果表明,原料的初始织构对终轧板材的显微组织与织构影响不大,但对材料的显微组织界面分布有一定影响。通过高温大变形量变形,不同初始织构的原料均可制得平均晶粒度小于5μm的AZ31镁合金板材。     

激光冲击强化AZ31镁合金摩擦磨损性能的研究

采用高能脉冲激光束对AZ31镁合金进行激光冲击强化(LSP)处理,利用UMT-2摩擦磨损试验机对试样进行磨损实验,通过分析磨痕表面和磨屑形貌及磨屑能谱,得出LSP技术可提高AZ31镁合金的耐磨性能。在相同条件下,LSP AZ31镁合金摩擦系数和磨损量均比未冲击试样小,且磨屑更为细小,表明LSP对AZ31镁合金摩擦磨损性能有一定的改善效果。另外,AZ31镁合金经过LSP后,磨损机理由以剥落磨损为主转变为以磨粒磨损为主。     

AZ31镁合金激光冲击温成形实验研究

为了研究超高应变速率激光冲击对AZ31镁合金温成形性能的影响,采用钕玻璃脉冲激光器(脉冲宽度为20 ns,激光功率密度为1.53 GW/cm2)进行AZ31镁合金薄板室温激光冲击成形(LSF)和200℃时激光冲击温成形(WLSF)实验研究及模拟分析。结果表明:AZ31交叉轧制薄板具有良好的超高应变速率WLSF能力,可实现温成形和改性双重效应,表层形成高幅残余压应力和高密度位错,WLSF表面比LSF具有更稳定的残余压应力,超高应变速率激光冲击和动态再结晶可能是纳米晶形成的主要原因,并分析LSF和WLSF试样表面形貌和粗糙度以及表面残余应力分布。     

AZ80-T6挤压镁合金激光冲击温强化和低周疲劳行为

为了研究激光冲击对AZ80-T6挤压镁合金低周疲劳性能的影响,采用钕玻璃脉冲激光器对疲劳试样进行激光冲击强化(LSP)和激光冲击温强化(WLSP)处理,并进行拉-拉疲劳实验。结果表明:LSP和300℃时WLSP处理后镁合金表面产生的残余压应力分别为-125 MPa和-158 MPa,而其疲劳寿命分别比原始试样提高11.42%和75.74%。WLSP明显地延迟裂纹萌生时间,提高AZ80-T6镁合金的疲劳寿命。另外对激光冲击诱导的镁合金微观结构及其低周疲劳行为进行了分析和讨论。     

激光冲击强化对AZ31镁合金力学性能和组织结构的影响

为了研究激光冲击强化(LSP)对镁合金力学性能的影响,采用电子万能高温拉伸机和钕玻璃脉冲激光(波长1064 nm,脉冲宽度20 ns)研究AZ31镁合金薄板室温和300℃时拉伸应力-应变曲线和力学性能。结果表明,LSP提高了AZ31镁合金室温和高温抗拉强度,而冲击试样的最大热流变应力明显高于未冲击的试样,双面单次LSP导致室温力学性能降低,在激光冲击试样断口发现了沿次表层扩展的层裂现象。讨论和分析了残余压应力、细微结构、表面形貌和粗糙度对激光冲击镁合金力学性能的影响。     

Crystallographic texture of C54 titanium disilicide as a function of deep submicron structure geometry

Detailed analysis of the crystallographic texture of C54 TiSi₂ was performed and showed a strong correlation between the geometry of the silicide structures and preferential crystallographic orientation. The study was undertaken on blanket and patterned TiSi₂ films formed in the reaction between 32 nm of Ti and undoped polycrystalline silicon using both in situ x-ray diffraction during heating and post-anneal four-circle pole figure reflection geometry measurements. Full pole figures were taken to determine the distribution of C54 TiSi₂ grain orientations in narrow (0.2 to 1.1 μm) lines which was compared with similar results obtained from unpatterned (blanket) films. While in blanket films we found the presence of weak <311> C54 TiSi₂ crystallographic orientation perpendicular to the sample surface, the <040> preferential orientation dominated in patterned submicron line structures and increased with decreasing linewidth. Using pole figure analysis, we observed strong <040> fiber texture in narrow lines with a slight variation in the tilt of the (040) planes normal in the direction perpendicular to the line (full width at half maximum [FWHM] ≈6°), but very little along the length of the line (FWHM ≈2°). In addition, a preferred in-plane (azimuthal) orientation of <040> crystals was found which showed that most of the <040> grains had their (004) plane normals oriented parallel with the line direction. These findings support a model of the C49 to C54 TiSi₂ transformation involving rapid growth of certain orientations favored by the one-dimensional geometry imposed by narrow lines.     

多向压缩路径下AZ31镁合金孪生行为的EBSD研究

本文利用EBSD技术研究了室温下AZ31镁合金多向压缩变形中的孪生行为.实验结果表明TD方向预压缩变形以{1012}〈1011〉拉伸孪生为主,导致晶体取向产生86°旋转,{0001}极图中TD附近出现极强的峰值,从而使后续ND方向压缩变形时有利于退孪生行为发生,{0001}极图中ND附近重新出现极强的峰值.     

Microtexture and Chitin/Calcite Orientation Relationship in the Mineralized Exoskeleton of the American Lobster

The exoskeleton of the American lobster Homarus americanus is a hierarchical nanocomposite consisting of chitin–protein fibers, reinforced with amorphous calcium carbonate (ACC) and a small amount of crystalline calcite. Crystallographic pole‐figure analysis reveals two texture components of the crystalline α‐chitin in the exoskeleton. One component represents the well‐known twisted plywood structure of chitin–protein fibers within the cuticle plane, and the second component represents fibers oriented roughly perpendicular to the cuticle surface. These perpendicular fibers interpenetrate the open canals of the planar honeycomblike structure originating from the well‐developed pore‐canal system present in this material. The calcite crystallites reveal fiber texture with the crystallographic c‐axis oriented perpendicular to the cuticle surface, suggesting an orientation relationship between calcite and the organic chitin–protein fibers. Local orientation analysis using X‐ray microdiffraction reveals that the crystalline calcium carbonate fraction is associated with the chitin–protein fibers oriented perpendicular to the surface. Calcite is exclusively found in the exocuticle and is mostly restricted to a thin layer in the outermost region, while the major part of the exocuticle and the whole endocuticle contain ACC exclusively. It is therefore speculated that the most likely function of calcite in the exoskeleton of the American lobster is related to impact‐ and wear‐resistance.     

面向AUV自主回收的单目视觉定位算法

针对自主水下航行器（AUV）自主回收过程中对回收装置的近距相对位置测量问题,提出了一种基于单目视觉的近距定位方法。该方法首先给出AUV与回收装置端面垂直时的单目定位方法,然后提出旋转定位法来解决AUV有俯仰和偏航时AUV与回收装置之间相对位置的精确计算问题,并进行了实验室试验研究,验证了该方法的有效性。     

锆合金准静态压缩变形行为研究

本文以热轧退火态锆合金板材为研究对象,选用两种压缩试验样品,其压缩方向分别平行于原板材的法向(ND样品)和原板材的横向(TD样品),利用Gleeble热模拟试验机和EBSD分析技术,对两种样品准静态压缩变形行为进行了研究.结果表明,热轧退火态锆合金板材的准静态力学性能具有明显的各向异性,TD样品的屈服强度和流变应力均低...     

Cu/Nb微观复合线材中Cu沿径向的织构研究

本文利用电子背散射衍射(EBSD)技术,对含不同铌芯丝数的Cu/Nb微观复合线材中的Cu沿径向的织构进行了表征.结果表明:复合线材在拉拔过程中,各层织构存在差异,织构种类由表及里减少,且主要向平行于拉拔方向的〈111〉丝织构聚集;对于复合不同道次的样品,在相同部位,变形量大的线材内部织构更集中于〈111〉织构组分.     

Relationship between texture and electromigration lifetime in sputtered AI-1% Si thin films

The relationship among the grain structure, texture, and electromigration lifetime of four Al-1% silicon metallizations produced under similar sputtering conditions was explored. The grain sizes and distributions were similar and the grain structure was near-bamboo for all metallizations. All metallizations exhibited a near-(111) fiber texture, as determined by the pole figure technique. Differences in electromigration behavior were noted. Three of the metallizations exhibited a bimodal failure distribution while the fourth was monomodal and had the longest electromigration lifetime. The electromigration lifetime was directly related to the strength of the (111) fiber texture in the metallization as anticipated. However, whereas the grain size distribution has an effect on the electromigration lifetime when metallization lines are several grains wide, the electromigration lifetime of these near-bamboo metallizations appeared independent of the grain structure. It was also observed that a number of failures occurred in the 8 μm interconnect supplying the 5 μm wide test lines. This apparently reflects an increased susceptibility of the wider interconnect lines to electromigration damage.