Texture Development in the Ni47Ti44Nb9 Shape Memory Alloy During Successive Thermomechanical Processing and Its Effect on Shape Memory and Mechanical Properties

For improving the shape memory performance and mechanical properties of shape memory alloys (SMAs), crystallographic texture and second phase are generally induced in SMAs by suitable thermomechanical processing. For this purpose, the development of texture in the Ni₄₇Ti₄₄Nb₉ SMA during successive processing (e.g., hot forging, hot rolling, cold rolling, and heat treatment) and the effects of texture, grain size, and β-Nb particle precipitation on recoverable strains and tensile properties were studied. In the hot-forged and hot-rolled Ni₄₇Ti₄₄Nb₉ alloy rods, intense 〈111〉 fibers are formed, and water quenching from 873 K and 1123 K (600 °C and 850 °C) leads to the decrease in intensity of 〈111〉 fiber in the hot-rolled rod. When the hot-forged rod is hot-rolled into sheet, intense {001} and weak {123} fibers appear, but grain growth leads to the disappearance of {001} fiber and {110}〈001〉 becomes the strongest component. Cold-rolling deformation of the hot-rolled sheet promotes the development of γ-fiber and the convergence of {332} and {123} fibers to {233}〈110〉 and {123}〈121〉 components, respectively, and the intense component is turned into {111}〈110〉; in this case, the recoverable strain (ε _SRS) and tensile yield strength (σ _YS ) exhibit an anisotropy. When the quenching temperature is 1123 K (850 °C), some weaker components appear, the anisotropy of ε _SRS disappears, and the difference level in σ _YS along the rolling direction (RD) and transverse direction (TD) becomes smaller. Therefore, an appropriate heat-treatment temperature should be selected to maintain the deformation texture and also to obtain fine grains for different thermomechanical processing.     

The Formation of the {112}<111> Shear Texture in Hot-Rolled Sheets of Electrical Steels

Due to the friction between rolls and sheet surface, shear texture inevitably occurs in the surface layer of the hot-rolled sheets in electrical steel. The shear texture contains Goss texture {110}<001>, brass texture {110}<112>, and copper texture {112}<111>. The existence of shear texture and its corresponding microstructure affect the texture distribution in the subsequent normalized sheets, cold-rolled sheets, and final sheets. Electron backscattered diffraction and reaction stress model are used herein to study the formation conditions of {112}<111> orientation in the hot-rolled sheets. The results show that initial rotated cube orientation tends to rotate around transverse direction to the copper orientation during hot rolling due to the shear action. Different shear orientations can be formed in different regions of an initial coarse columnar grain during hot rolling, because of the change in surrounding environment reaction and the difference of the shear strain at different thickness positions. The thinner the hot-rolled sheet is, the smaller the dynamic recrystallization region with shear orientation, and there is almost no copper texture in the thinnest hot-rolled sheet. The simulation results show that the copper texture is easy to form under the action of σ₂₃ and σ₂₂ reaction stresses.     

Crystallographic texture and structure of rolled Al-Cu-Li alloy sheets

The crystallographic texture of billets—namely, forgings and a pressed strip made of an Al-Cu-Li alloy—and sheets rolled from them has been studied by X-ray diffraction. The results obtained are used to estimate the structural state of the rolled metal of the sheets fabricated according to various schemes. Pronounced crystallographic orientations {110}〈112〉 and {113}〈332〉 in the sheets rolled from the pressed strip correspond to a homogeneous fine-grained grain structure of the aluminum matrix. This structure provides good ductility (δ = 10%) and small δ anisotropy in the rolled metal. The absence of a symmetrical texture “motif” in the pole figures recorded from the sheets rolled from the forged billets is related to the inhomogeneity of their recrystallized structure. This structure decreases the ductility characteristics of the sheets rolled from the forged billets.     

Effect of Austenite Pancaking on the Microstructure,Texture, and Bendability of an Ultrahigh-Strength Strip Steel

The effect of austenite pancaking in the non-recrystallization regime on microstructure and texture evolution and thereby on bendability was investigated in an ultrahigh-strength strip steel with a martensitic-bainitic microstructure. The results indicate that an increase in rolling reduction (R _tot) below the non-recrystallization temperature, which improves the strength and toughness properties, increases the intensities of the ~{554}〈225〉 _α and ~{112}〈110〉 _α texture components along the strip centerline and of the ~{112}〈111〉 _α component at the surface region. Even with the highest R _tot of 79 pct, the bendability along the rolling direction was good, but the preferred alignment of rod-shaped MA constituents along the rolling direction led to a dramatic decrease in the bendability transverse to the rolling direction, with severe cracking occurring even at small bending angles. The early cracking is attributed to localization of the strain in narrow shear bands. It is concluded that the R_tot value has to be limited to guarantee successful bendability.     

高硅钢近柱状晶初始组织的形变、再结晶行为及磁性能

采用电子背散射衍射技术对高硅钢近柱状晶初始组织直接热轧、温轧、冷轧和退火组织及织构演变进行分析,并测定相应退火板的磁性能.该实验条件下组织与织构演变规律体现了表层剪切细小组织和中心层粗大组织的竞争关系,其中中心层组织与原始立方取向相关或表现为α线取向.柱状晶的影响在最终退火组织中仍存在,少量立方取向区域可遗传到最终退火板中,虽然没有大量出现,仍有效削弱了{111}织构.形变退火过程中与原始立方取向线有关的晶粒尺寸普遍较大,有利于磁性.样品最终的磁感应强度低于文献报导的强{120}〈001〉或{100}〈021〉织构样品,但高于普通无取向高硅钢,且轧向和横向磁感应强度值差异小,所以柱状晶组织有利于无取向高硅钢的制备.      

Crystallographic Reconstruction Study of the Effects of Finish Rolling Temperature on the Variant Selection During Bainite Transformation in C-Mn High-Strength Steels

The effect of finish rolling temperature on the austenite-(γ) to-bainite (α) phase transformation is quantitatively investigated in high-strength C-Mn steels using an alternative crystallographic γ reconstruction procedure, which can be directly applied to experimental electron backscatter diffraction mappings. In particular, the current study aims to clarify the respective contributions of the γ conditioning during the hot rolling and the variant selection during the phase transformation to the inherited texture. The results confirm that the sample finish rolled at the lowest temperature [1102 K (829 °C)] exhibits the sharpest transformation texture. It is shown that this sharp texture is exclusively due to a strong variant selection from parent brass {110} \( \left\langle {1\bar{1}2} \right\rangle \) , S {213} \( \left\langle {\bar{3}\bar{6}4} \right\rangle \) and Goss {110}〈001〉 grains, whereas the variant selection from the copper {112} \( \left\langle {\bar{1}\bar{1}1} \right\rangle \) grains is insensitive to the finish rolling temperature. In addition, a statistical variant selection analysis proves that the habit planes of the selected variants do not systematically correspond to the predicted active γ slip planes using the Taylor model. In contrast, a correlation between the Bain group to which the selected variants belong and the finish rolling temperature is clearly revealed, regardless of the parent orientation. These results are discussed in terms of polygranular accommodation mechanisms, especially in view of the observed development in the hot-rolled samples of high-angle grain boundaries with misorientation axes between 〈111〉γ and 〈110〉γ.     

JSP-双机可逆冷轧条件下IF钢织构研究

针对济钢现场工艺条件下生产的Ti-IF钢,利用X’Pert ProxX射线衍射宏观织构分析方法,研究了中薄板坯热连轧轧制及随后的冷轧、退火工艺过程中织构的变化规律。IF钢冷硬板主要织构类型为{111}〈110〉、{111}〈112〉和{001}〈110〉,其中{111}〈110〉织构强度达到12;再结晶退火后的IF钢退火板,主要织构类型为{111}〈110〉和{111}〈112〉,{111}〈110〉织构强度提高到15.37。济钢生产的Ti-IF钢获得了对板材成形最有利的{111}//ND织构。     

Texture distribution through-the-thickness after cold-rolling of 3% silicon steel

A simple laboratory technique was used to produce cold-rolled specimens with various reductions from 40 to 80% at a 10% interval starting with commercial hot band of 3% silicon steel. The quantitative and sensitive Orientation Distribution Function (ODF) method was applied to analyze the evolution of texture from hot-rolled to cold-rolled through-thickness. The results indicated that there are two different types of texture in hot sheet which are called recrystallization type texture and deformation type texture. The developed texture at each level of cold sheet specimens was inherited from the texture at respective level of hot sheet. The Goss texture memory effect at subsurface level was discussed. The conclusions indicated that it is important to get suitable hot band which has strong recrystallization type texture at its surface level and use appropriate cold rolling reduction for producing cold band which has a texture distribution of strong {111}〈112〉, weak {001}〈110ång; and some {110}〈001〉 components at its subsurface level and is beneficial to forming sharp Goss texture during recrystallization. The appropriate reduction is about 70%.     

Stress-Induced Twinning and Phase Transformations during the Compression of a Ti-10V-3Fe-3Al Alloy

A metastable β Ti-10V-3Al-3Fe (wt pct) alloy containing different α phase fractions after thermo-mechanical processing was compressed to 0.4 strain. Detailed microstructure evaluation was carried out using high-resolution scanning transmission electron microscopy and electron back-scattering diffraction. Stress-induced β → α′′ and β → ω transformation products together with {332}〈113〉β and {112}〈111〉β twinning systems were simultaneously detected. The effects of β phase stability and strain rate on the preferential activation of these reactions were analyzed. With an increase in β phase stability, stress-induced phase transformations were restricted and {112}〈111〉β twinning was dominant. Alternatively, less stable β conditions or higher strain rates resulted in the dominance of the {332}〈113〉β twinning system and formation of secondary α′′ martensite.     

Simulation de la texture de deformation en traction uniaxiale et calcul du coefficient de lankford R(α) de toles d'aciers extra doux—application au cas non orthotrope

Two calculations to simulate the plastic behaviour of b.c.c. materials are presented. The first one allows to calculate the plastic deformation textures and so the O.D.F. F(g) in Euler space G (gϵG). The second one allows to calculate the Lankford factor R(α) of a polycrystalline sheet in all cases of symmetry of the texture. Previous works were principally devoted to orthotropic symmetry. Both calculations use the two slip systems {110}〈111〉 and {112}〈111〉 in the Taylor approximation with variable ration of critical resolved shear stresses for the two slip planes {110} and {112}.     

初次再结晶退火对模拟CSP含Cu Hi-B硅钢组织和织构的影响

在实验室用模拟CSP工艺试制Hi-B高磁感取向硅钢薄板（/%:0.07C,3.02Si,0.13Mn,0.020P,0.006S,0.21Cu,0.025Cr,0.016A1,0.004Sn）,该钢经25kg真空感应炉熔炼,铸成41 mm×120 mm板坯-热轧成2mm板-1 120℃常化-冷轧成0.27mm薄板。研究了830~870℃,3~7min退火对再结晶组织和织构的影响。结果表明,0.27mm含Cu Hi-B高磁感取向硅钢板的合适退火工艺为830℃ 5 min,其平均晶粒尺寸为15.6μm,不利织构{111}〈110〉和{001}〈110〉含量较低,有利织构{111}〈112〉分布合理,有利于在二次再结晶退火过程形成良好的高斯组织。     

Formation of crystallographic texture in titanium nickelide single crystals during rolling

The texture formation in the single crystals of the Ti-48 at % Ni-2 at % Fe alloy rolled at a temperature of 350°C up to a strain of 80% in eleven different initial orientations is examined. There are three stable initial orientations that remain unchanged in rolling: {011}〈011〉, {111}〈011〉, and {111}〈112〉. The TiNi single crystals are shown to be deformed by means of a combined action of slip in systems {011}〈001〉 and twinning in systems {114}〈221〉 and {118}〈441〉. The types of formed rolling texture in the single crystals depend on their initial orientation and strain.     

Correlation Between Pre-annealing Temperature and {110}〈001〉 Annealing Texture in C- and Al-Free Fe-3 Pct Si-0.1 Pct Mn-0.002 Pct S Electrical Steel

In C- and Al-free electrical steel, the increase in primary grain size with increasing pre-annealing temperature causes the transition in annealing texture after final annealing from {110} + {100} to {110}. The strip pre-annealed at 1073 K (800 °C) shows a low magnetic induction B₈(T) of 1.784 T after final annealing. The strip pre-annealed at 1223 K (950 °C) shows a sharp {110}〈001〉 Goss texture, producing a high magnetic induction B₈(T) of 1.914 T comparable to that of the conventional electrical steels.     

卷取温度对深冲DP钢组织性能及织构的影响

为研究深冲织构的演变规律,利用OM、TEM和XRD等技术研究了热轧卷取温度对微碳深冲DP钢组织、性能与织构的影响。结果表明,热轧板主要由铁素体＋珠光体构成,随卷取温度升高,铁素体晶粒略增大,伸长率逐渐上升;热轧板中钼基碳化物的最佳析出温度为700℃;与650和750℃相比,700℃卷取后的退火板能获得较高体积分数（4.0%）马氏体与较细（11.7μm）铁素体的组织特征,同时拥有最强的〈111〉//ND纤维织构和最弱的{001}〈110〉织构,使得其抗拉强度达到455 MPa,塑性应变比r值达1.5。     

Deformation banding and copper-type rolling textures

It is shown by a crystallographic etching technique applicable to copper that deformation banding is an important deformation mode in f.c.c. metals and alloys. In a cold rolled coarse grain copper, deformation banding forms in a three dimensional manner dividing the grain on average into over 600 regions of different orientations. The influence of this important, but long ignored deformation mode, is studied by incorporating it into the Taylor model. The predicted textures from the new model are better than those from other existing models in mainly two respects. Firstly, the DB model predicts the co-existence of the three major f.c.c. rolling texture components, namely {123}〈634〉 or S component, >112>〈111〉 or C and >110>〈112〉 or {f}B{/f}. The existing models are deficient in that they predict either C and S or B, but not their co-existence. The second point is that textures predicted by the existing models are always too sharp compared to the experimental textures. The DB model predicts texture peaks with larger spread and hence more realistic texture sharpness. Another feature of the model is that only two independent slip systems, instead of five, are required to accomodate the imposed shape change, which agrees with experimental observation.     

薄带连铸取向Fe-6.5％Si钢形变热处理过程组织演化

设计并利用双辊薄带连铸工艺制备出取向Fe- 6. 5%Si钢铸带,研究了热处理工艺对铸态、形变和初次再结晶组织、织构及析出物的影响规律。结果表明,铸带退火可以促进铸态组织中的柱状晶长大,同时增加200nm以下MnS- AlN或MnS- NbN复合析出物的面密度。随着铸带退火温度升高,冷轧组织中变形带宽度以及带内剪切带长度增加,初次再结晶织构中{111}〈112〉组分增强,{110}〈001〉晶粒所占比例增大。铸带退火有助于改善冷轧板高温退火过程中的二次再结晶行为,提升产品磁性能。     

薄板坯连铸连轧流程Fe-3%Si钢热轧板和常化板织构

在实验室按照薄板坯连铸连轧工艺流程试制了Fe-3%Si硅钢热轧板,采用EBSD和X射线衍射方法观察了A钢和B钢热轧板和常化板的织构组织,分析了α、ε和γ取向线上织构取向密度变化规律。A和B钢热轧板具有相似的{110}〈112〉和、{001}〈110〉和{001}〈010〉和高斯织构组织,A试样表层的晶粒均匀性较差,B试样具有较强的γ织构取向。采用EBSD观察比较了A钢和B钢热轧板和常化板的垂直TD面的EBSD微观织构组织,A钢和B钢常化退火后基本保留了热轧时形成的中心部位的组织,而次表层和表层晶粒发生了再结晶长大,晶粒组织和织构梯度减小,织构主要集中在{001}〈^-1^-10〉和{001}〈0^10〉和之间以及高斯织构上。常化后织构的总体强度下降,高斯强度减弱。试验研究结果为开发薄板坯连铸连轧短流程生产电工钢技术提供理论依据和参考数据。     

纯铁纯度对其再结晶织构及晶粒Schmid因子的影响

 为了研究纯铁纯度对其再结晶织构及Schmid因子的影响,以商业的2N8、3N5纯铁和实验室制备的4N级公斤级高纯铁为原料,通过退火再结晶和EBSD研究了2N、3N、4N纯度纯铁再结晶织构特征和晶粒的Schmid因子。结果表明,2N8、3N5和4N3纯铁的晶粒组织均为等轴铁素体,残余应力少、位错密度低,样品再结晶完全。其中,2N8和3N5纯铁的织构呈现出相同的分散分布特征,而4N3高纯铁织构特征集中,随机织构较少。ODF图和取向线分布密度进一步表明,2N8和3N5纯铁具有相似的α织构{hkl}〈110〉和γ织构{111}〈uvw〉特征及变化趋势,即两者都在α取向线的{111}〈110〉取向具有较高的分布密度和γ取向线密度随φ₁的增大而有降低;而4N3高纯铁具有〈113〉|X和γ织构特征,且包含利于材料力学性能各向异性的{332}〈113〉织构,另外,其γ取向线密度随φ₁的增大逐渐升高,直至{111}〈112〉取向密度高于2N8和3N5纯铁。晶粒Schmid因子及其频率分布直方图结果表明,2N、3N、4N纯铁均存在低Schmid因子晶粒被高Schmid因子晶粒包围的现象,且在{110}〈111〉、{112}〈111〉和{123}〈111〉这3个滑移系下晶粒Schmid因子总和平均值为0.467(4N3)＞0.461(3N5)＞0.459(2N8),呈现出纯铁晶粒Schmid因子总和平均值随纯度增大的趋势;根据Schmid定律可知,4N3纯铁的织构特征最有利于其变形。综上所述,在本工作中,随着纯铁纯度由2N8提升至4N3,样品中杂质原子减少,促进了4N3高纯铁产生强烈的〈113〉|X和γ织构特征以及利于材料力学性能各向异性的{332}〈113〉织构,增大了其晶粒Schmid因子总和平均值。     

TSCR试制低碳低硅无取向电工钢织构的演变

 研究了模拟TSCR流程生产的低碳低硅无取向电工钢在热轧-冷轧-退火过程中织构的演变。对热轧板采用EBSD技术进行织构的测定,而对冷轧板和退火板采用X射线衍射技术进行了织构的测定。结果表明：热轧板沿板厚方向织构变化比较明显,在1/10处主要织构为α纤维织构和γ纤维织构;在1/4厚度处出现了较强的γ纤维织构;在1/2厚度处主要为较强的{001}〈110〉织构,其他织构分布漫散。冷轧板表面和中心处主要织构均为α纤维织构和γ纤维织构,但是在中心处两织构强度都显著减弱。退火板表面和中心处α纤维织构基本消失,γ纤维织构织构进一步加强,出现了{110}〈001〉高斯织构和{001}〈010〉立方织构。     

Microstructural Changes by Annealing in Ultrafine-Grained Electrodeposited Pure Iron

In situ neutron diffraction during annealing was performed for ultrafine-grained as-deposited and cold-rolled pure iron. Changes in the integrated intensity and full-width at half-maximum in the diffraction profiles during annealing were measured. EBSD measurements were performed before and after annealing to obtain microstructural change. Abnormal grain growth was clearly found at 673 K (400 °C) upon annealing; this observation corresponds to the hydrogen desorption behavior of the as-deposited specimen. The texture changes from {111}〈hkl〉 to {211}〈hkl〉 between 673 K and 873 K (400 °C and 600 °C) upon continuous heating. Such a texture change is postulated to decrease the Lankford value from 7.6 to 2.2. The 40 pct cold-rolled specimen exhibited a complicated textural evolution upon annealing, which was caused by the intrusion of recrystallization at deformation bands.