Transformation textures in new ultrahigh strength hot rolled microalloyed steel

Abstract

Texture development during thermomechanical processing of a newly developed ultrahigh strength microalloyed steel was investigated, with particular attention to through thickness texture gradient. A considerable texture gradient was evident, particularly in the 1/2 depth compared to the other three positions (surface, 1/8 depth, 1/4 depth). The most intense deformation texture at all depths was {113}〈110〉, which was also more prevalent at the centre than elsewhere, implying an overall dominance of {112}〈111〉 in the deformed austenite during hot rolling. The recrystallisation texture of austenite, {100}〈001〉, transformed into {100}〈011〉 component in the ferrite indicated an increase in intensity with increase in depth. The {100}〈011〉 type of texture has an undesirable effect on the delamination behaviour of steels. However, the centre and 1/4 depth contained considerable intensity of the desired texture, {332}〈113〉, which offsets the undesired {100}〈011〉 texture.     

A study of recrystallisation textures in hot band of a continuous cast Al–Mn–Mg alloy

Abstract

The hot band of a commercial continuous cast (CC) Al–Mg–Mn alloy was annealed at different temperatures ranging from room temperature to 510°C for 3 h. The evolution of microstructure and crystallographic texture was investigated during the annealing treatment. It was found that the recrystallised alloy exhibited a severely elongated grain structure and a texture that consisted of a new type of component ({113}〈110〉) and two fibre components (〈100〉//ND and 〈110〉//ND), the axes of which were along the normal direction of the rolling plane (ND) in 〈100〉 and 〈110〉 respectively. The 〈100〉//ND fibre was dominated by a ND rotated cube orientation {001}〈310〉, while the 〈110〉//ND fibre was mainly composed of Goss and P orientation ({011}〈566〉). The formation of the {113}〈110〉 texture and two fibre textures was likely to be attributed to the concurrent precipitation effect taking place upon heating in annealing treatment of the alloy.     

P、Ti对高强IF钢{=111}面织构的影响

借助电子背散射衍射（EBSD）技术测量和计算了高强IF钢退火试样的取向分布函数（ODF）、织构组分的含量和7取向线强度。研究了{111}（112）和{111}010）织构组分的变化,分析了P、Ti对{111}面织构的影响机理。P的存在阻碍了位错的运动和晶界的迁移,进而使再结晶晶粒取向趋于一致,形成较尖锐的{111}面织...     

GH4169合金楔横轧加工过程中动态再结晶及织构演变

为研究GH4169合金楔横轧加工过程中动态再结晶及织构演变规律,采用金相显微镜(OM)和电子背散射衍射(EBSD)对30%,50%两种断面收缩率下GH4169合金楔横轧件表层与心部的微观组织、晶体取向及织构进行分析。结果表明:GH4169合金楔横轧加工过程中,随着动态再结晶的发生,晶体取向逐渐变得随机化分布;轧制表层大角度晶界数量较轧件心部多,轧件表层织构强度变化不大,心部织构强度明显增强;经过楔横轧变形后织构发生转动,原始态织构类型为{001}〈110〉,{111}〈110〉,{111}〈011〉,轧制后主要织构类型为{001}〈010〉,{112}〈110〉,{110}〈111〉,{110}〈112〉;GH4169合金楔横轧件动态再结晶及织构演变规律是由楔横轧特殊变形特点决定的。     

Rolling and annealing textures of a SiCw/Al composite

A SiC whisker reinforced pure aluminum composite (SiC_w/Al) was fabricated using a squeeze casting route and cold-rolled to 50% reduction in thickness. Some cold-rolled composites were then annealed at 500 °C for 1 h. The pure aluminum was also cold-rolled and annealed in the above way for comparison purpose. The textures of the cold-rolled and annealed materials were examined using XRD technique. It was found that the dominant texture components in the cold-rolled composites consisted of {112}〈111〉, {100}〈011〉 and {123}〈634〉. They were much weaker than those in the cold-rolled aluminum. When the cold-rolled composites were annealed, the new texture components {211}〈213〉, {013}〈131〉 and {011}〈211〉 occurred and had the similar intensity as the texture components remained from the deformation state. This indicated that the recovery reaction and recrystallization occurred simultaneously when the cold-rolled composite was annealed 1 h at 500 °C. Like the situation of the deformed materials, the annealing texture was also much weaker in the composite than in the aluminum. The weaker deformation and annealing textures in the composites can be attributed to the introduction of the whiskers.     

Mechanical properties of Ti–Nb biomedical shape memory alloys containing Ge or Ga

Mechanical properties of Ti–24 mol% Nb-based shape memory alloys (SMA) containing 3 mol% Ga or Ge were characterized in this paper as a part of our systematic work for the development of β-Ti based biomedical shape memory alloys. The alloys, called TiNbGa and TiNbGe, were produced by severe cold-rolling followed by a solution treatment at 1273 K for 1.8 ks. The apparent phase was β (bcc) at RT in both the alloys. It was revealed by X-ray diffraction pole figure analysis that a {112}_β〈110〉_β recrystallization texture was well developed in TiNbGa. However, a {001}_β〈110〉_β deformation texture still remained in TiNbGe even after the solution treatment. Martensite transformation temperatures were significantly lowered by the addition of Ge, compared to Ga and Al additions. TEM-EDX observation revealed that (Ti, Nb)₅Ge₃ particles are formed in TiNbGe regardless of the solution treatment. The (Ti, Nb)₅Ge₃ particles were judged to be an ineffective strengthener, because significant hardening was not recognized in the flow-stress of TiNbGe. TiNbGa exhibited a large shape recovery of about 2% above RT in the strain–temperature curves during thermal cycles under external stress. The TiNbGe alloy exhibited superelasticity of 3.5% at RT.     

Effect of austenite deformation on crystallographic texture during transformations in microalloyed bainitic steel

Abstract

The evolution of the texture of ferrite as a function of the coiling temperature has been studied in a hot rolled Nb alloyed CMnMoCrB complex phase steel by means of electron backscatter diffraction. Coiling that steel at 720 ° C led to ferrite and pearlite, and coiling at 550 ° C produced a bainite-martensite microstructure. The presence of residual austenite in the steels coiled at 680 and 550 ° C allowed for texture measurements in γ. Analyses of texture gave fundamental information on the decomposition of γ in both the recrystallised state and the deformed state. It was found that austenite, initially deformed below the non-recrystallisation temperature T_nr, recrystallised statically d partially during the γ α and the γ ^d α _b transformations. In the specimen coiled at 680 ° C, primary ferrite and bainite could be distinguished based on the confidence indexof the diffraction pattern. A clear variant selection was observed for the γ ^d α _b transformation, as arotation of ? ₁ = 30 ° occurred inthe austenite between the ferrite and the bainite formations. The bainite was found to result mainly from the decomposition of the brass {110} 〈 112 〉 and Goss {110} 〈 001 〉 orientations of deformed austenite. The residual austenite was found to be recrystallised γ γ austenite with the cube{001} 〈 100 〉 orientation. Coiling simulations were performed in a dilatometer starting from different austenite grains sizes and deformation states. In the most deformed specimens, the deformation state of the austenite and the combined effects between the different alloying elements presentin the steel were responsible for a solute drag like effect.     

Significant effect of as-cast microstructure on texture evolution and magnetic properties of strip cast non-oriented silicon steel

In this study, two types of as-cast microstructure produced by strip casting were cold rolled and annealed to investigate the effect of initial microstructure on the textural evolution and magnetic properties of non-oriented silicon steel. The results indicated that the cold-rolled sheets of coarse-grained strip with pronounced {100} components exhibited stronger λ fiber (〈100〉//ND) and weaker γ fiber (〈111〉//ND) texture as composed to the fine-grained strip with strong Goss ({110}〈001〉) texture. After annealing, the former was dominated by η fiber (〈001〉//RD) texture with a peak at {110}〈001〉 orientation, while the latter consisted of strong {111}〈112〉 and relatively weak {110}〈001〉 texture. In addition, a number of precipitates of size ～30–150?nm restricted the grain growth during annealing, resulting in recrystallization of grain size of ～46?μm in the coarse-grained specimen and ～41?μm in the fine-grained specimen. Ultimately, higher magnetic induction (～1.72?T) and lower core loss (～4.04?W/kg) were obtained in the final annealed sheets of coarse-grained strip with strong {100} texture.     

Texture mechanism in some fcc-type soft magnetic materials

The authors have studied the mechanism for recrystallization texture in some soft magnetic materials with fcc crystal structure. The alloys used were 77% Ni-14% Fe-5% Cu-4 wt% Mo permalloys. Thin foils selected area electron diffraction (SAD) and X-ray diffraction techniques were employed using a Philips 300 Electron Microscope (EM 300) and an X-ray diffractometer, respectively. Investigations were carried out on deformed, recovered and recrystallized states of the alloys. The various results show that the cold-rolled (deformed) and recovered states of the alloys possess copper-type of rolling texture with {110} 〈112〉 texture as the predominant deformation texture though other minor components such as {112} 〈111〉, {110} 〈001〉 and {123} 〈420〉 textures were detected. No cube texture, {100} 〈001〉 was detected in any of the deformed and recovered materials though the recrystallization texture in these alloys is the cube texture, {100} 〈001〉 which forms over 80% of the annealing texture in these alloys. It is concluded here that the detection of cube texture in the deformed and recovered materials is not a prerequisite for the detection of cube texture in these alloys. The present work is not conclusive about the mechanism for recrystallization texture, but it is proposed here that recrystallization texture, in these alloys is attributed to the growth-oriented mechanism based on the following model. (1) The lattice domains which form the recrystallization texture are present in the cold-rolled matrix. (2) The favoured site for nucleation are the grain boundaries and deformation band boundaries. (3) For the nucleus to be able to grow and form the recrystallization texture it must possess the necessary free energy. (4) Grains must be capable of growth into two or more orientations between which it forms, i.e. the nuclei which form the cube texture should have a [111] pole in common with the matrix in which they grow and a rotation of about 30° around this pole.     

Recrystallisation textures in cold rolled low carbon steel containing ferritic and bainitic microstructures

Abstract

Low carbon steel strip was heat treated to generate four different starting microstructures (fine and coarse polygonal ferrite, acicular ferrite and bainite) for investigating their influence on texture development during cold rolling and annealing. The starting materials were cold rolled to 50–90% reduction and annealed for various times in the temperature range 853–953 K. The resultant microstructures and textures were examined mainly by electron backscatter diffraction and X-ray diffraction. The initial microstructure strongly influenced the crystallographic rotation paths during cold rolling, whereby high strain deformation generated strong {223}〈110〉 texture components in the polygonal ferritic microstructures, whereas a strong {001}〈110〉 texture was produced in the acicular/bainitic microstructures. Subsequent annealing generated, to varying degrees, the classic {111}〈uvw〉 (γ-fibre) recrystallisation texture in all materials. Unexpectedly, coarse polygonal ferrite produced the strongest γ-fibre recrystallisation texture after 70–90% cold rolling reduction. Based on arguments involving the effect of carbon in solution, initial grain size and deformation textures on recrystallisation texture development, it was shown that a strong γ-fibre texture can indeed be generated in coarse polygonal ferrite.     

Ubhi

Abstract

A number of approaches for graphically representing electron backscattered diffraction grain orientation measurements are presented, using as examples the distributions and variations of texture in two 8090 AI–Li alloys. In this manner the component orientations constituting the overall texture can be illustrated readily and their relative volume fractions calculated. The locations of texture components can be represented by texture distribution plots. The power of Mackenzian plots is illustrated by demonstrating their capacity to represent the degree of scatter about an ideal orientation, show differences in distribution that may be either real or due to specimen preparation, and highlight when two ideal orientations that are very close to each other, namely, {110} 〈112〉 and {110} 〈335〉 in this work, may be present.

MST/3465     

Al-Zn-Mg-Cu系铝合金厚板冷轧过程中的织构演变

利用电子背散射衍射技术研究了Al-Zn-Mg-Cu系铝合金厚板冷轧过程中不同厚度处的织构演变.结果表明:厚板近表面处的剪切型织构{001}<110>,随着冷轧变形量的增加逐渐向轧制型织构Bs,S,Cu组分转变;厚板1/4厚度和中心厚度处的轧制型织构Bs,S,Cu组分,随着冷轧变形量的增加逐渐流向剪切型织构{001}<1...     

Textures of tantalum metal sheets by neutron diffraction

The orientation distributions of six tantalum samples, TaPA, TaG1, TaG2, TaQ2-S1, TaQ2-S2 and TaQ2-S4, were studied by neutron diffraction and ODF analysis. The TaPA specimen is a commercial tantalum sheet with an unknown fabrication history. The TaG1 and TaG2 were fabricated from a powder metallurgical ingot by uniaxial compression, and the TaQ2 type samples were fabricated from commercial stock by similar uniaxial forging. TaQ2-S1 is the section closest to the centre of the forged disc, S2 is the intermediate section, and S4 is the section adjacent to the periphery. The texture of TaPA consisted of many components, including {014}〈100〉, {111}〈ˉ321〉, {100}〈010〉, and [111]/[100] double-fibre textures with the fibre axes oriented parallel to the normal direction. The two TaG-type specimens were dominated by the [111]/[100] double-fibre texture, accompanied by a weak {100}〈010〉 cube texture. The three sections of TaQ2 had much higher degrees of texture than the TaG-type samples, with an extremely strong (111) peak, which consists of (111)〈11ˉ2〉, (111) 〈ˉ1ˉ12〉, and [111] fibre texture. The average pole density of the three equivalent orientations of (111)〈11ˉ2〉 was the strongest for the S1 with over 150 multiples of random distribution (mrd), and gradually decreased with increasing radial distance to about 100 mrd for the S4 section. On the other hand, the average intensity of (111)〈ˉ1ˉ12〉 type orientations was increased from about 40 mrd at S1 to about 100 mrd for the S4 section.     

Comparison of simulated and experimental strain ratio R for different grain shapes in sheet metal

Abstract

Predicting mechanical properties by means of a simple indicator is of great importance to sheet metal forming. An important parameter characterising the formability of a rolled sheet is the plastic strain ratio R which is strongly determined by the texture. The angular variation of R value in the rolling plane has been calculated from the orientation distribution function using the Bunge method. The following grain interaction models have been tested: two Taylor full constraint models ({hkl}〈111〉 and {110}〈111〉 plus {112}〈111〉), three relaxed constraints models (RC₄ , RC₃ , RC₂ ), and the Sachs–Kochendörfer model. The shapes of the grains were investigated by means of the secant method which allowed the spatial parameters of the two- dimensional structure image to be measured. The comparison of simulated and experimental data has proved that in the case of aluminium killed steels, the relaxed constraints model RC₄ is the best predictor of the plastic strain ratio. Good results were also obtained using the Sachs-Kochendörfer model.     

Grain boundary migration in Fe-3mass%Si alloy bicrystals with twist boundary

The characteristics of grain boundary migration in Fe-3mass%Si alloy bicrystals with Σ3〈011〉, Σ5〈001〉 and Σ9〈011〉 coincidence twist boundaries and random twist boundaries were examined to obtain an information on the development of {110}〈001〉 (Goss) texture. The bicrystals were annealed at 1223 K for an appropriate time and the grain boundary migration speed was evaluated.The Σ5〈001〉 and Σ9〈011〉 twist boundaries showed higher migration speed than Σ3〈011〉 twist boundaries, and the random twist boundaries migrated faster than other boundaries. The migration speed decreased with increasing annealing time due to an increase in the edge components of the lattice misfits in the migrated boundaries. The grain boundary migration was also sensitive to the deviation angle (Δθ) from the ideal orientation relationship for a coincidence boundary. The increase of Δθ accelerated the boundary migration. The motion of the grain boundary was influenced by plastic strain. Migration of the Σ9 twist boundary was more suppressed by plastic strain than that of the random boundary. On the basis of characteristics of the grain boundary migration, the effect of inhibitor on the Goss texture was discussed.     

Texture gradient,average texture,and plastic anisotropy in various AI–Li sheet alloys

Abstract

The variation of texture through the thickness and the average texture of sheet material of recrystallised AA 8090 and unrecrystallised AA 8090 (crossrolled) and AA 2090 AI–Li alloys have been investigated. Conventional (lithium free) AA 2024 alloy in the annealed condition was used as a reference material. The quantitative orientation distribution functions were determined via X -ray diffraction and neutron diffraction techniques. Using X -ray diffraction, textures of layers at various distances from the surface to the centre of the sheets were examined to achieve the texture gradients. The average textures were determined either via neutron diffraction using cylindrical stacked specimens or by summing the texture results obtained via the X-ray techniquefor the various layers. It is shown that the intensity of the common rolling textures, i.e. {112} <111>, {123} <634>, {110} <112>, and shear texture {100} <011> markedly varied through the thickness of unrecrystallised AA 8090 and AA 2090 AI–Li sheets. Also, in recrystallised AA 8090 AI–Li and AA 2024, a variation of the recrystallisation texture components {001} <100> and {011} <100> through the thickness was found. The quantitative texture data in conjunction with Taylor theory were used to predict the plastic anisotropy in terms of the plastic strain ratio as afunction of the angle a between the rolling and tensile directions. This prediction shows that the effects of texture can explain well the anisotropy in recrystallised AI–Li material (AA 8090). For unrecrystallised materials (AA 8090, AA 2090), a correct trend in plastic anisotropy is predicted; however, the calculated values in the 45° direction are larger than those determined experimentally.

MST/1910     

Deformation induced Nanostructure and texture in MP35N alloys

The macro-texture was related to the nano-platelets formed during the rolling deformation of a Co-Ni-Cr-Mo alloy (MP35N) with low stacking fault energy. The deformed materials showed {011}(533) texture but also had {011}(211) and {011}(100) texture components. The {011}(533) component reached the maximum at 74% reduction-in-area. Further deformation of the material to 80% decreased the intensity of the {011}(533) component. The cold deformation introduced platelets of a few atomic layer in thickness and less than 100 nm in diameters. The habit planes of the platelets were identified to be {111}, which were perpendicular to both the rolling and {011} crystallographic plane. Therefore, the tensile strain in the rolling direction assisted formation of the platelets, which were identified as stacking faults. A high density of nano-platelets and dislocations strengthened materials and influenced the plastic deformation behaviors and texture evolution. Thus, the MP35N developed slightly different textures from other low stacking fault energy materials. The maximum at {011}(533) was related the nanoplatelets and stacking fault energy. The {011}(112) and {110}(001)components could be linked to the low stacking fault energy.     

高温多向异步轧制对LZ91镁锂合金组织和力学性能的影响EI北大核心CSCD

采用异步轧制、多向异步轧制、高温异步轧制、高温多向异步轧制四种不同的方式轧制双相镁锂合金板材。通过光学显微镜、MTS E43拉伸试验机和X射线衍射仪观察不同工艺轧制后合金的显微组织、力学性能以及织构特征,综合分析温度和轧制方向条件耦合对镁锂合金组织和力学性能的影响。结果表明:四种轧制工艺可以使α-Mg相沿轧制方向伸长,同时沿着轧制方向法向细化。高温多向异步轧制后α相厚度最低为2.6μm。多向异步轧制后材料的屈服强度、抗拉强度、伸长率分别为149,167 MPa,14.5%,其综合力学性能最优。多向轧制使双峰织构沿ND方向45°偏转,高温轧制使双峰织构由基极向RD方向偏转的角度降低。轧制后样品R-cube织构组分最强,高温多向异步轧制使β-Li相轧制织构转变成为{001}〈100〉织构,有利于{011}〈111〉滑移系发生多滑移。     

亚稳β型钛合金中的{332}〈113〉变形孪晶

{332}113变形孪晶是亚稳β型钛合金变形过程中的一种独特变形机制。该类型孪晶具有特殊性质并且对亚稳β型钛合金力学性能具有显著影响。本文总结了{332}113变形孪晶的研究状况和特性,重点介绍了{332}113变形孪晶形成的几种代表性模型。通过分别对这些模型的假设条件以及需要进一步解释和验证的科学问题进行分析,旨在为理解和揭示{332}113变形孪晶的变形机制提供有用的参考信息。     

Through-thickness texture gradient in AA 7055 aluminum alloy

Through-thickness texture gradient in AA 7055 aluminum alloy rolled plate has been investigated using the electron back-scattered diffraction (EBSD) technique. Quantitative analyses of texture in five layers from the surface to the center of the plate were performed. A pronounced texture variation through the plate thickness was found. In the center layer, a typical β fiber texture running from {112} <111> orientation through {123} <634> orientation to {011} <211> orientation was found. Near the surface, in contrast, shear type textures including {001} <110> orientation, {112} <110> orientation and {111} <110> orientation were dominating. In particularly, when the shear type textures reached the maximum in both intensity and content, the β fiber became minimums.