晶体学织构对金属板材宏观各向异性影响的模拟

基于多晶体黏塑性自洽方法, 建立了金属板材的Lankford 系数(r值)、屈服应力和屈服面的计算模型. 以fcc多晶体为例, 模拟分析了理想织构组分对宏观各向异性的影响. 模拟结果表明, 具有Cube和Goss织构的板材, 其r值在45°附近最小, Cube织构的r值具有对称性, 而Goss织构90°的r值远大于0°的r值; 具有Cu, Bs和S织构的板材, 其最大r值均出现在45°附近, 0°和90°的r值均具有一定的不对称性. 各理想织构的单轴拉伸屈服应力呈现出与^r值相对应的变化规律, 屈服面的形状也表现出相应的变化. 上述模拟结果与Taylor--Bishop--Hill (TBH) 模型以及唯象方法的计算结果定性符合.     

织构对铝-镁-钪合金板材平面各向异性的影响

采用室温拉伸、X-射线衍射技术(XRD)等方法研究了不同取向条件下铝-镁-钪合金冷轧-退火态板材的织构类型以及拉伸力学性能的各向异性.通过Schmid因子及其倒数的加权计算,初步探讨了织构对合金板材力学性能各向异性的影响.结果表明,经350℃×1h退火后,铝-镁-钪合金板材的织构组分主要为S织构{123}<634>和Brass织构{110}<112>等典型的形变织构;合金板材在纵向(0°方向)和横向(90°方向)的屈服强度较高,在45°拉伸方向的屈服强度较低,并且表现出反常的各向异性,而伸长率则在45°拉伸方向上最高.经分析可知,织构是影响合金板材平面各向异性的主要因素.     

7475-T7351合金板材不同取向条件下的组织与性能

通过室温拉伸性能测试、金相组织观察、透射电镜分析以及取向分布函数测定,研究了25 mm厚时效态7475-T7351合金板材不同取向条件下的显微组织和力学性能,定量分析了织构与平面各向异性的关系。结果表明,7475-T7351合金板材纵向抗拉强度、屈服强度和伸长率分别为501MPa、428MPa、8.4%;横向抗拉强度、屈服强度和伸长率分别为491MPa、416 MPa、8.9%。纵向抗拉强度和屈服强度比横向高约10 MPa,但伸长率变化很小,表明板材具有各向异性。7475-T7351合金板材中的晶体织构主要有Cu织构{112}111、S织构{123}634和Brass织构{110}112,这3种织构是由于铝合金冷轧后受层错能影响产生的。经计算,它们在合金中的体积分数分别为19.95%、16.67%、12.06%。此外,还有相对较弱的立方织构{001}100,为再结晶时形成的织构,体积分数为4.58%。通过对施密特因子的计算,表明不同取向条件下合金板材力学性能的各向异性与合金织构密切相关。     

EFFECT OF STRUCTURE AND TEXTURE ON COLD WORKABILITY OF 3%-AND 4%Si-Fe ALLOYS

采用冷轧和冷弯试验方法研究了热轧显微组织和织构成分对3％和4％Si-Fe合金的冷加工性能的影响。结果表明,细化热轧板的晶粒、改进热轧板组织的均匀性可以提高热轧板的冷轧和反复弯曲性能。特定位向单晶体的冷轧试验结果指出,在热轧板的主要织构组分中,增强{112} <110>和{111} <112>成分同样有助于改善冷轧塑性。     

微量Sr对Al-Mg-Si-Cu合金板材织构的影响

应用取向分布函数(ODF)研究和分析了微量Sr对Al Mg Si Cu合金板材织构的影响。结果表明:Al Mg Si Cu合金板材主要存在{100}<011>旋转立方织构,另还存在{112}<111>铜织构,{111}<110>、{111}<112>黄铜R织构。加入微量Sr可以改变织构组分含量。当加入0.093%Sr时,降低了其旋转立方织构的含量。其原因是Sr的加入引起基体晶格变化,降低铝合金板材的层错能,阻碍了交滑移的进行,造成织构类型的转变。     

基于粘塑性自洽模型6061铝合金厚板轧制过程模拟北大核心CSCD

以厚度为60 mm的6061铝合金板材为研究对象,采用Deform仿真分析技术研究了不同压下率轧制变形过程中板材温度、应变、应力场的变化规律,着重分析了对板材心部、1/4处、表层的影响,并结合粘塑性自洽(VPSC)有限元法研究了板材不同位置处的织构演变规律,为铝合金轧制过程中的变形行为和各向异性研究提供了新的方法。结果表明:多道次轧制过程中,心部与表层区域的最大温差受轧件压下率影响不大,最大温差为10℃,板材表层和1/4处的累积应变均始终大于心部,轧件与轧辊接触导致表层承受较大的应力,轧件局部表现出明显的应力分布不均匀的状态;轧件表层、1/4处以及心部均形成了β取向线上的3种典型织构,即Copper织构{112}<11-1>、Brass织构{011}<21-1>和S织构{123}<63-4>,随着轧制压下率的不断增大,织构的体积分数越来越大,织构强度也逐渐增大,其中,S织构的体积分数和强度上升趋势明显,进一步说明S织构相比其他两种织构对应变变化过程更加敏感。     

铸轧Al-Mn合金板材的各向异性分析

分析了织构、晶界及第二相对铸轧Al-Mn合金板材各向异性的影响。结果表明,铸轧铝板与轧向0°、45°、90°夹角方向上屈服强度分别为158.51、141.78、164.32 MPa,且其屈服强度、抗拉强度、伸长率的平面各向异性指数(IPA)均大于8,表明其力学性能具有各向异性;铸轧铝板的晶粒沿着轧向呈带状,主要含{112}111、{123}634两种织构,第二相呈非等轴状且分布不均匀;织构、晶界及第二相的共同作用导致了铸轧铝板力学性能的各向异性。     

板坯组织类型及热处理对Ti6321合金板材力学性能各向异性的影响

结合力学性能测试和OM、SEM、EBSD分析,研究了Ti6321合金板材力学性能各向异性及其影响因素。结果表明:板坯组织类型对板材平面各向异性具有显著影响,等轴组织板坯和魏氏组织板坯制备的合金板材屈服强度、抗拉强度和冲击功均具有明显的平面各向异性,且等轴组织板坯制备板材的屈服强度、抗拉强度和冲击功平面各向异性指数高于魏氏组织板坯制备板材相应指数。不同板坯组织类型制备的热轧态板材,织构均主要为柱面织构({0002}⊥轧面),织构的方向为c轴倾向于平行于TD方向排布;经(980℃, 80 min)热处理后板材织构主要为基面织构({0002}//轧面),织构方向为c轴倾向于与ND平行。不同组织类型的板坯经相同的热变形和热处理,对应板材的金相组织、织构组分、再结晶程度和裂纹扩展路径存在明显的差异,这综合引起Ti6321合金板材力学性能的各向异性。     

轧制方向对Ni47Ti44Nb9锻造板，热轧板及冷轧板织构影响

采用XRD研究了Ni47Ti44Nb9锻造板坯织构、不同热轧、冷轧方向板材织构。研究表明,锻造板坯有典型的γ取向线织构,锻板心部最强取向在{111}<112>。沿轧向(RD)、交叉方向(CD)、横向(TD)热轧板织构类型相似,主要有3条取向线织构,接近{114}、{223}、{332}（或{221}）,{332}面织构取向密度最强,最强织构分别为{221}<110>、{332}<113>、{332}<023>,不出现γ-织构。沿与轧向成0o、45o、90o方向二次冷轧最强织构近似为{332}<110>。90o方向二次冷轧织构强度最高,有多个强织构组分,γ-织构得到显著加强     

超塑Al-Mg-Li合金的显微组织与织构特性

采用一种新型形变热处理方法制备细晶Al-Mg-Li合金板材,研究静态再结晶退火对合金板材晶粒组织及超塑变形行为的影响。结果表明,晶粒尺寸、形状和织构的分布沿板材法向方向存在明显不同;表面层的晶粒组织细小、等轴,含有旋转cubeND{001}（310）取向;中心层具有粗大、长条状晶粒,含有a取向线的织构组分。随着再结晶温度的升高,整个板材的晶粒尺寸长大,中心层晶粒纵横比减小,表面层织构强化而中心层织构弱化,超塑性伸长率下降。升高再结晶温度导致整个板材内的旋转cubeND{001}（310）织构组分强化而a取向线的织构弱化。分析了不同温度下再结晶织构的形成机制。     

MGH754合金挤压棒材的二次再结晶与织构

研究了ＭＧＨ７５４合金在二次再结晶过程中的组织和结构变化。结果表明，合金大热挤压状态具有细小的等轴晶组织，织构微弱，有利于进行殂变加工；二次再结晶后，组织为粗大的柱状晶，且出现强烈的织构；随着退火时间延长，「１１０」〈００１》和「１００」〈００１〉织构含量明显增加，而「１１０」〈１１１〉，「１１０」〈１１３〉和「１１２」〈１１１〉等织构的含量减少，合金棒材的纵向主要为〈００１〉取向。     

Effect of Sc and Zr on the in-plane anisotropy of Al-Mg-Mn alloy sheets

The Al-Mg-Mn alloy sheets with and without trace Sc and Zr were investigated by means of tensile test, X-ray diffraction, optical microscope, and transmission electron microscope. The indexes of in-plane anisotropy （IIPA） of their tensile mechanical properties were calculated and their inverse pole figures were obtained by Harris method. The two alloy sheets have the same law of in-plane anisotropy and remarkable in-plane anisotropy of mechanical properties, and the IIPA of the alloy sheet with Sc and Zr is bigger than that of the alloy sheet without Sc and Zr. The relationships of the in-plane anisotropy and the anisotropy of the crystallographic texture were analyzed based on the model of monocrystal. It is the common action of the anisotropy of crystallography and microstructures that causes the in-plane anisotropy of their mechanical properties, but the major cause is the { 110 }〈112〉 crystallographic texture. The trace Sc and Zr can promote the formation and stabilization of the { 110 } 〈 112〉 texture, inhibit the formation of the { 100 } 〈001 〉 texture, and increase the in-plane anisotropy of the alloy sheet containing trace Sc and Zr.     

SiCp增强铝基复合板材力学性能与晶粒取向分布

研究了粉末冶金法制备的ＳｉＣｐ增强铝基复合板材在热轧和冷思状态下的力学性能及板材中的晶粒取向分布,结果表明,热轧板材抗拉强度及塑性明显高于冷轧态,屈服强度则氏于冷轧态。冷轧板织构主要包含微弱的剪切织构｛００１｝〈１１０〉和两个常的面心立方金属织构组分｛１１０｝〈１１２〉及｛３３１４｝〈７７３〉;而热轧板织构近乎无规分析,晶粒取向的择优对复合板材的屈服强度有一定影响,与抗拉强度无关。冷轧板抗拉强度的     

Texture evolution of extruded AZ31 magnesium alloy sheets

The evolution of texture during the annealing and hot rolling process of extruded AZ31 magnesium alloy sheets was studied. There are two kinds of texture components in the extruded AZ31 sheets. One is {0002}<1-010> and the other is {1-010}<1-120>. The {0002}<1-010>component predominates. After annealing at 723 K for 3 h, both {0002}<1-010> and {1-010}<1-120> components are strengthened moderately. This indicates that grains with both two components mentioned above grow faster than those with other orientations. The {1-010}<1-120> component disappears and the intensity of {0002}<1-010> component decreases significantly after hot rolling with a 30% reduction at 623 K. This is mainly attributed to rotational dynamic recrystallization (RDX) during the hot rolling.     

拉伸取向控制对AZ31镁合金孪生和织构演化的影响

以室温单轴拉伸实验与晶体塑性有限元相结合的方法,通过拉伸取向控制,研究了AZ31镁合金拉伸变形过程中孪生行为、织构演化规律、塑性各向异性之间的关系。基于率相关晶体塑性本构理论,建立了滑移和孪生机制耦合的具有不同取向的晶体塑性本构模型,引入孪晶体积分数研究孪生对AZ31镁合金塑性变形过程中织构演变和力学性能的影响。结果表明,2种不同取向的样品在塑性变形过程中呈现出明显不同的织构演变规律,表现出明显的各向异性。轴向拉伸时孪生被抑制,孪晶激活体积分数低,径向拉伸时孪晶极易产生,孪晶激活体积分数高。轴向试样在整个塑性变形过程中{0001}极图偏移较小,径向试样因大量拉伸孪晶的开启,使得{0001}棱柱面织构的极密度逐渐向RD的正反方向发生明显偏移。     

润滑对3104铝合金板变形织构的影响

在无润滑(WOL)和润滑(WL)2种轧制条件下,分别对2.3 mm厚的热轧3104铝合金板进行不同压下量的冷轧.应用取向分布函数(ODF)定量计算和分析在不同轧制压下量下润滑对3104铝合金板材沿板厚方向织构演变的影响.结果表明:随着轧制压下量的增加,样品各层的织构组分强度均逐渐增加;无润滑轧制时样品表面层主要织构组分取向密度普遍高于相同压下量下润滑轧制时的取向密度.导致表面层织构组分增强的原因是摩擦引起应变状态改变的结果.     

Recrystallized microstructural evolution of UFG copper prepared by asymmetrical accumulative rolling-bonding process

Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}1ī2+{112}11ī texture component disappears and turns into{122}212cube twin texture component.     

Texture Evolution Behavior and Its Triggered Mechanical Anisotropy of CP Ti During Severe Cold Rolling and Subsequent Annealing

The texture evolution behavior and its triggered mechanical anisotropy of commercially pure titanium(CP Ti) during severe cold rolling and subsequent annealing are discussed based on the optical microscopy and the electron backscattered diffraction analyses. Some enlightening results are found. It is shown that planar textures exist under all treatments, namely the {11–29}10–10 under rolling state, the {11–27}10–10 under 300 °C annealing state and the {11–24}10–10 under 500 °C annealing state. This indicates that the crystal plane indices of planar texture change toward {-12–10} with increasing annealing temperature, which is a result of crystal lattice rotation. Planar texture triggers anisotropy of the mechanical properties for CP Ti sheets under all treatments. In particular, CP Ti sheets exhibit severe and similar anisotropy behavior under rolling and 300 °C annealing states. Generally speaking, the rolling direction(RD) specimens get relatively low yield strength, high ultimate tensile strength and good plasticity, and RD + 45° specimens show relatively high yield strength, low ultimate tensile strength and good plasticity. The transverse direction specimens, however, usually exhibit high yield strength and low plasticity. It is proved that the above anisotropy behavior is mainly determined by the Schmid factor distribution of the(10–10)[11–20] prismatic slip system in different directions. Due to the non-negligible influence exerted by the(0001)[11–20] basal slip system after 500 °C annealing, the anisotropy behavior under this state is obviously different.     

搅拌摩擦焊焊接5083铝合金板材焊核区的晶体取向

采用搅拌摩擦焊焊接了5083铝合金板材,借助电子背散射衍射技术和取向成像分析软件,对比性地分析了母材和焊核区的晶粒形貌、取向差分布、织构组分及取向分布函数,分析了焊核区晶体取向的变化.结果表明,在热-力作用下,焊核区发生动态再结晶,显示等轴晶粒形貌,平均晶粒尺寸约为15.8μm,同时大角度晶界比例明显增加.母材的黄铜织构B{011} <211> 和S织构{123} <634> 的比例分别达到30.6%和13.6%以上;搅拌摩擦焊后,焊核区的B织构和S织构的比例分别降至4%和1.8%,原位再结晶形成的R{124} <211> 织构组分约为7.7%,焊核区其它常见面心立方金属织构组分的比例均低于8%,意味着焊核区由强取向组织转变为弱取向组织.     

CSP卷取温度对冷轧深冲钢板的影响

研究了热轧卷取温度对CSP(compact strip production)冷轧深冲板的性能、组织和织构的影响。CSP热轧板组织主要为多边形铁素体,随卷取温度降低,晶粒尺寸略有减小。660℃和680℃卷取的成品冷轧板组织为等轴晶粒,卷取温度不超过600℃时则以"饼型"晶粒为主。力学性能测试表明,低于600℃卷取的成品板屈服强度和抗拉强度较低,其加权平均塑性应变比(rm)可达到1.80以上,伸长率超过49%。随卷取温度升高,成品板的{001}〈110〉和{110}〈110〉织构的取向分布密度逐渐升高,{111}织构取向分布密度先升高后降低,{111}〈110〉和{111}〈112〉织构取向分布密度差值也是先升后降。