Homogeneity of Magnetostriction of Tb--Dy--Fe—Co<110> Oriented Alloy Rod

采用区熔定向凝固方法,先以30 mm/h低速生长,再以480 mm/h高速生长,制备了磁致伸缩性能较为均匀的《110》取向Tb0.36Dy0.64(Fel-xCox)2(x=0,0.1,0.15)合金棒.研究了不同晶体生长阶段的轴向择优取向和微观组织对磁致伸缩性能的影响.结果表明,轴向择优取向度主要影响样品在无预压应力条件下的磁致伸缩性能;富稀土相分布主要影响样品在施加预压应力条件下的磁致伸缩性能.沿合金棒轴向,从底部到顶部择优取向度逐渐增高,富稀土相由网状分布变为平行排列,造成合金棒顶部和中部的磁致伸缩性能较底部更高.磁化场为240 kA/m时磁致伸缩不均匀度小于6%,显示了良好的均匀性.     

定向凝固Tb-Dy-Fe合金的热处理组织与性能

采用区熔定向凝固的方法,制备〈110〉取向Tb-Dy-Fe超磁致伸缩合金晶体.用管式炉氩气保护,在900-1100℃进行4和48 h的均匀化热处理,研究了热处理对Tb-Dy-Fe合金取向、组织、磁致伸缩性能和力学性能的影响.结果表明,热处理不改变Tb-Dy-Fe合金的轴向择优取向;热处理4 h后,网状富稀土相明显退化,向颗粒状转变;热处理48 h后,网状富稀土相基本消失,形成大量颗粒状富稀土相.热处理明显提高了Tb-Dy-Fe合金样品的磁致伸缩性能,特别是提高低场磁致伸缩性能,但力学性能下降.经4 h热处理,本实验条件下制备的〈110〉取向Tb-Dy-Fe合金样品综合性能最好.     

定向凝固铁磁形状记忆合金Co-Ni-Ga的择优取向及其组织演化

采用液态金属冷却定向凝固方法制备出Co-Ni-Ga取向晶体,并研究了不同晶体生长速度下,晶体的轴向择优取向及其定向凝固组织的变化.结果表明:在温度梯度为250 K/cm、晶体生长速度为0.9 mm/min时,柱晶具有完全的〈110〉取向,存在单变体马氏体并有麦穗状γ'相析出;当生长速度提高至9 mm/min时,合金试样为〈111〉 〈001〉 〈110〉混合取向,凝固组织转变为单一的马氏体板条.EDS表明,定向晶体沿稳定生长区轴向成分比较均匀,无明显宏观偏析存在.采用此方法能够获得比较长的稳定的马氏体单变体区,为制备铁磁形状记忆合金取向多晶材料提供了新思路.     

无取向硅钢退火织构的演变与磁性能关系的研究

运用取向分布函数(ODF)分析了50W600电工钢不同退火工艺退火织构的演变及织构对电磁性能的影响,利用织构数据计算了无取向硅钢的磁晶各向异性能.研究表明,较高的退火温度或较长的保温时间,再结晶织构α线的取向密度下降,{100}〈011〉和{211}〈011〉取向密度急剧降低,γ线{111}〈112〉密度显著增加,晶粒取向绝大多数聚集在γ线{111}〈112〉取向附近;低温退火有助于提高无取向硅钢有利织构{100}〈UVW〉的占有率.磁晶各向异性能计算结果表明无取向硅钢也存在磁各向异性.     

定向凝固TbDyFe合金的取向,组织和磁致伸缩性能

采用ＪＳＬ－５００区域熔化真空定向凝固装置,对ＴｂＤｙＦｅ超磁致伸缩合金定向凝固轴向择优取向、组织和磁致伸缩性能的研究表明：温度梯度ＧＬ≈７００Ｋ／ｃｍ基本不变的条件下,当昌体生长速度Ｖ≤１ｍｍ／ｍｉｎ时,晶体以平面晶方式生长;１〈Ｖ≤６ｍｍ／ｍｉｎ时,以胞状昌方式生长;Ｖ＝８－１２ｍｍ／ｍｉｎ时,晶体按胞枝晶方式生长（胞状晶树枝晶转变的初始阶段）;当Ｖ〉１５ｍｍ／ｍｉｎ时,晶体按发达的树枝晶方式     

(110)[110]Fe-Si单晶体的冷轧和再结晶

研究了(110)[110]Fe-Si单晶体的冷轧和再结晶。经过70—90%冷轧后,得到了强的{111}〈110〉和弱的{111}〈112〉加工织构,退火后得到了集中的{111}〈112〉再结晶织构。冷轧变形后,{111}〈112〉取向的地区比{111}〈110〉取向的地区先发生回复,{111}〈112〉取向的亚晶吞并滞后回复的地区而长大,成为再结晶晶核。这种再结晶织构的形成过程,可以概括地称为同位成核-选择生长。     

冷轧板再结晶退火中组织和织构演变的研究

薄板坯连铸连轧(CSP)热轧板料经热处理来适当调整组织后进行冷轧及退火,并运用电子背散射衍射(EBSD)技术研究了再结晶退火中组织和织构的演变.结果表明:发生再结晶的温度范围是530℃～590℃,590℃为完全再结晶温度;再结晶发生时冷轧变形基体和新晶粒取向的晶界角度差大约为25°～55°;{111}〈110〉、{111}〈112〉取向在再结晶初期和中期发生很大的变化,而{001}〈110〉、{112}〈110〉取向在再结晶后期才发生很大的变化;EBSD检测的结果分析可得{001}〈110〉、{112}〈110〉、{111}面取向储存的变形能依次增加.     

Tb0．27Dy0．73Fe1．95合金定向凝固时的固液界面形貌与择优取向

在自制的超高温度梯度定向凝固装置中,通过对Tb0.27Dy0.73Fe1.95合金定向凝固条件和固液界面形貌及晶体生长取向间的关系进行分析,发现Tb0.27Dy0.73Fe1.95合金定向凝固时发生胞枝转变的的凝固条件为GL/V值介于9.60×102K.s/mm2～10.45×102K·s/mm2之间.固液界面形貌与晶体取向间有明显的对应关系,固液界面形貌为胞状晶或无侧向分枝的树枝晶时其择优取向为〈110〉,结晶形貌为树枝晶时其择优生长方向为〈112〉,而在胞-枝转变区晶体为〈110〉,〈112〉,〈113〉等多种取向的混合.当Tb0.27Dy0.73Fe1.95合金以较低的晶体生长速率定向凝固时易产生〈110〉择优生长方向,并且产生〈110〉择优生长方向时的晶体生长速率范围随温度梯度的增加而扩大.     

Fe81Ga19合金<001>取向单晶生长及磁致伸缩性能

采用悬浮区熔法,加入籽晶控制生长取向,以4 mm/h的生长速度,制备了轴向〈001〉择优取向的Fe81Ga19单晶.极图测试结果发现,采用偏离轴向〈001〉方向约5°的籽晶生长得到的单晶,生长始端和生长末端轴向取向分别偏离〈001〉取向5°和4°,上下取向差仅为1°.另一单晶采用轴向〈001〉取向籽晶生长得到,当施加6...     

取向Galfenol合金的结构与磁致伸缩应变

采用非自耗真空电弧熔炼方式制备了不同Ga含量的Fe100-XGaX(X=17、19)合金铸锭,利用定向凝固的方法试验研究了取向多晶Fe-Ga合金的结构与磁致伸缩应变。研究发现,采用定向凝固工艺制备的Fe83Ga17合金试样沿轴向呈现出明显的{110}织构特征。在低场下不同成分两种试样的磁致伸缩随磁场的增加迅速增大,在磁场强度大约为40 kA/m时Fe83Ga17合金的磁致伸缩λ达到饱和,为55×10-6。Ga含量为19%的定向凝固试样沿轴向取向性有所降低,晶粒中存在很多的亚晶界。富Ga相的析出和亚晶界的出现不利于磁致伸缩性能的提高。     

Texture and magnetostriction in rolled Fe-Ga based alloy

添加Nb改善了Fe81Ga19合金的塑性, 采用热轧和冷轧相结合的轧制工艺制备出厚度 为0.6 mm的(Fe81Ga19)+ 1%Nb(原子分数)合金薄板. 研究了(Fe81Ga19)+1%Nb合金轧态和退 火态薄板的织构及磁致伸缩效应. 结果表明: 合金的磁致伸缩与样品的织构密切相关, 再结 晶织构取决于热处理工艺. 轧态织构以{111}面织构和近似的{001}<110>旋转立方织构为主, 样品轧向的磁致伸缩系数λ∥=26×10-6. 在1250和1300 ℃保温2 h后水淬样品的织构分别呈现为近似的{011}<100>Gauss织构和单一{001}<100>立方织构, 其磁致伸缩 (3/2)λRD分别达到106×106和134×10-6     

B2结构Fe3Al单晶在室温拉伸过程中的取向转动

借助于ＥＢＳＤ方法，研究了８个位向Ｂ２结构Ｆｅ３Ａｌ单晶室温拉伸变形时晶体取向的转动。结果表明，无论原始取向如何，在拉伸过程中晶体拉伸轴总会向着〈１１０〉方向转动，也即〈１１０〉为稳定取向。当晶体拉伸轴转向取向三角形中部的软取向时，晶体表现为几何软化，相应的加工硬化率较低。反之，当晶体拉伸轴转向〈００１〉－〈１０１〉对称线时，晶体表现为几何硬化，相应的加工硬化率较高。当拉伸轴处于软取向时，单晶试样     

高磁感取向硅钢轧制及热处理过程中的晶界和织构演化

采用电子背散射衍射(EBSD)对不同轧制和热处理态的高磁感取向硅钢的重合位置点阵(CSL)晶界和织构进行了研究。结果表明,热轧态取向硅钢截面织构呈层状分布,表层主要为{110}<001>Goss织构,1/4厚度主要为{001}<110>立方织构、{112}<111>铜型织构和{110}<001>Goss织构,而心部则形成较强的{112}<111>铜型织构、{111}<110>形变织构和{110}<001>Goss织构;常化处理后截面织构梯度变化不明显,但中心位置{112}<111>织构向{110}<001>Goss织构转变。冷轧退火态主要织构为{110}<001>Goss织构、{112}<111>织构和{111}<110>形变织构。二次再结晶后,则生成强烈的{110}<001>Goss织构。随着织构的变化,CSL晶界也发生了明显的转变。热轧态CSL重位晶界中∑3~∑29均有出现,但比例较低;常化处理后CSL重位晶界比例增加,冷轧退火后CSL晶界比例大幅提高,特别是∑3、∑7、∑9和∑15等晶界;二次再结晶后,由于CSL晶界发生了转化,CSL晶界类型减少,∑3、∑13等晶界比例增加,∑9晶界消失。     

Dendrite growth morphologies in aluminium alloys

Different aluminium alloys, in particular Al–Cu, Al–Mg and Al–Si, have been directionally solidified under well-controlled thermal and convection conditions. For relatively high solidification rates, particular growth morphologies were observed. The most common is linked with the formation of feathery grains: these are constituted by series of twinned lamellae, in which the dendrites have 110 trunks cut through by {111} twin planes. These grains undergo a selection mechanism which is similar to that occurring for regular 100 dendritic grains. The dendritic growth along 110 crystallographic directions is supposed to be due to a change in the anisotropy of certain properties of the alloy, such as the solid/liquid interfacial energy and/or the atom attachment kinetics. When solidification conditions become less favourable to 110 growth morphologies, a mixed dendritic form containing 110 trunks and 100 arms may be obtained. In the case of the 5182 Al–Mg type alloy, 110 columnar grains which were not twinned could be observed together with feathery crystals. The possibility of such changes in the growth direction of aluminium alloys was further demonstrated by the observation of dendrites of Al–Cu–Mg solidified in a Bridgman device. In this case, 112 dendrites grow and progressively change their growth direction, thus showing curved shapes.     

退火温度对6.5%Si极薄带织构及磁性能的影响

采用单辊甩带法制备了厚度为0.03 mm的6.5%Si极薄带,并在真空炉中进行了880 ℃和920 ℃的退火处理。利用XRD和EBSD研究了其在退火后的宏观和微观织构演变规律。结果表明:经单辊甩带制得的6.5%Si极薄带织构主要由{001}<100>立方织构、{110}<001> Goss织构和{112}<111>织构组成。随着退火温度的升高,λ纤维仍占主导地位,且晶粒尺寸逐渐增大。特别是在920 ℃退火时,{001}<120>和{001}<100>晶粒的尺寸优势逐渐增大,不利织构{111}<110>和{111}<112>逐渐减弱,且最终的磁感应强度B₅₀=1.644 T,铁损耗P_10/400=5.896 W/kg。     

衬底温度对CVD金刚石薄膜织构的影响

利用扫描电镜观察了CVD自支撑金刚石薄膜的表面形貌组织,利用X射线衍射技术检测了薄膜织构。研究表明,不同衬底温度条件下制备的金刚石薄膜形成不同的织构和表面形貌组织,衬底温度升高使生长速率参数α减小,金刚石晶体最快生长晶向由〈100〉晶向向〈011〉和〈111〉晶向转变,使得薄膜中{011}和{111}织构随温度提高不断...     

磁场预退火对取向硅钢二次再结晶组织及织构的影响

对二次冷轧后高温退火前3.2%Si取向硅钢在实验室自主设计研发的脉冲磁场预退火管式炉内进行不同温度的预退火处理,通过光学显微镜与XRD对其组织织构进行分析,利用硅钢片磁性能测试系统对高温退火后的试样进行磁性能分析。结果表明,经脉冲磁场预退火处理后,整体上取向硅钢平均晶粒尺寸随预退火温度升高略微减小,晶粒尺寸主要集中在10~25 μm范围内;通过ODF图及{200}极图分析可知,经脉冲磁场预退火后,最强织构随预退火温度的升高从{112}<110>织构变化到{223}<110>织构和{111}<110>织构;随着预退火温度的升高,高温退火后试样的磁性能反而降低。     

PLASTIC DEFORMATION AND DISLOCATION STRUCTURE IN γ'-PHASE OF A DIRECTIONALLY SOLIDIFIED Ni-BASE SUPERALLOY

The dislocation structure of directionally solidified(DS)Rene 80 superalloy during tensileand creep deformation has been studied by TEM.In tensile deformation,γ'shearing occurs byslip of APB-coupled(1/2)<110>dislocation pairs on{111}planes at temperatures below760℃.and by slip of SISF-seperated(1/3)<112>superpartials which have dissociated on{111}planes into a(1/2)<110>screw superpartial and a(1/6)<112>edgesuperpartial with an APB in between at temperatures equal to or above 760℃.In creepdeformation,γ'shearing occurs again by slip of SISF-seperated(1/3)<112>superpartialswhich have not dissociated on{111}planes and by diffusive slip of APB-coupled(1/2)<110>dislocation pairs at 760℃,618 MPa.However,no γ'shearing occurs at 980℃,190MPa.During secondary creep at 760℃,618 MPa or at 980℃,190 MPa,2-dimensional net-works have formed at γ/γ'interfaces,and the strain is mainly the result of diffusion control-led climb of dislocation networks at γ/γ'interfaces.The dependence of secondary creep rate εupon size a and volume fraction v_■ of cubic γ' has been found to be ■∝α/v_f~(2/3).     

Twin formation during the atomic deposition of copper

Vapor deposited copper films with 〈111〉 growth texture usually contain twin plates stacked normal to the growth direction. However, twins are rarely seen when growth occurs in other principle crystallographic directions. Atomistic modeling indicated that during 〈111〉 growth, adatoms occupied either parent or twin surface lattice sites with almost equal probability, resulting in a high nucleation density of twin domains. During growth on either {110} or {100} surfaces, adatoms were only able to occupy parent lattice sites, and no twin nucleation occurred. A phase field method was used to model the twin domain evolution during 〈111〉 growth as a function of deposition rate and temperature. Simulation results indicated that twin domains evolved by rapid lateral expansion with very little vertical thickening. The lateral expansion was found to be fast compared with the deposition rate, and as a result twin domains usually grew to occupy the entire width of a growth column, in good agreement with experimental observations. The model indicated that the twin structures formed during the 〈111〉 growth of copper are not directly controllable by either the processing temperature or the deposition rate.