Zr-Sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为〈1010〉方向平行于轧向(〈1010〉//RD),而退火后转变为〈1210〉方向平行于轧向(〈1210〉//RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C//ND)的取向;最终退火板材的大晶粒多为〈1210〉//RD的基面织构,小晶粒则以〈1010〉//RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.     

Zr-sn-Nb新型锆合金板材加工过程中不均匀组织与织构演变

利用XRD,SEM-ECC,TEM和EBSD技术,研究了Zr-Sn-Nb系新型锆合金板材加工过程的微观组织及织构演变.结果表明,β相淬火得到的随机织构经热轧后形成沿横向倾斜的基面织构,随后的加工过程均保留该织构;热轧及两次冷轧后的基面织构都为(1010)方向平行于轧向((1010)∥RD),而退火后转变为(1210)方向平行于轧向((1210)∥RD).淬火形成的网状魏氏组织经热轧转变为不均匀形变组织,两次冷轧使组织的不均匀性更显著,最终退火得到完全再结晶组织;轧制形成的难变形晶粒多为晶粒C轴平行于轧板法向(C∥ND)的取向;最终退火板材的大晶粒多为(1210)∥RD的基面织构,小晶粒则以(1010)∥RD为主.结合锆合金的变形及再结晶机制对轧制时产生的不均匀组织及再结晶过程的织构转变进行了分析.     

Cu-Mg-Te-Y合金退火工艺研究

研究了退火温度和退火时间对冷轧变形后的Cu-Mg-Te-Y合金组织及性能的影响。结果表明:Cu-Mg-Te-Y合金在冷轧变形后,显微组织呈纤维状,内部晶粒取向改变,硬度提高,导电率降低;经过退火处理后,铜合金硬度下降,导电率回升,提高退火温度可明显提高合金伸长率;随退火时间延长,Mg原子从晶格中脱出,通过位错等扩散通道,在Cu2Te相周围偏聚,使导电率提高,但再结晶新晶粒的出现,晶界增多,使导电率降低,综合作用使合金的导电率明显提高;退火温度在360~390℃,退火时间1 h以内时,Cu-Mg-Te-Y合金可以得到最佳的综合性能。     

Microstructural Evolution in Hot and Cold-Rolled Ti-Nb Alloy

Phase transformations, morphology, and crystallographic texture evolution in hot and cold-rolled Ti-25.51 wt.% Nb alloys are investigated. The experimental procedure involves synthesis of the alloy by arc melting followed by cold or hot rolling with intermediate prior and postheat treatments. Composition and phase analysis of all alloys are conducted using x-ray diffraction techniques and microstructural observations are conducted using an optical microscope. These examinations reveal that the as-melted alloy possesses large millimeter size grains with no stored strain energy and a two phase β ? α′ microstructure. Direct cold rolling followed by a short homogenization leads to a β ? α′′ mixture with ω precipitates. Two hour annealing before cold rolling leads to an α′ ? α′′ mixture with a characteristic triangular martensitic microstructure evidencing the act of shear on formation of the phase. Hot rolling followed by a water quench results in a β ? α′′ mixture, while annealing prior to hot rolling transforms the arc-melted material to a α′ ? α′′ mixture. The crystallographic textures of similar microstructure mixtures in hot and cold-rolled samples are distinctively different. The analysis shows that the microstructure serves as an identifying characteristic of the processing paths and is highly dependent on the mode of processing.     

Texture Evolution,Formability and Ridging Resistance of a Sn-bearing Ferritic Stainless Steel Under Different Hot Band Annealing Temperatures

The microstructure, texture evolution and spatial orientation distribution during cold rolling and the subsequent annealing as well as formability and ridging of a Sn-bearing ferritic stainless steel under different hot band annealing temperatures were investigated. The four hot bands with annealing temperatures of 900, 950, 1000 and 1050 °C were all cold-rolled to 80% reductions and then were annealed at the same temperature of 900 °C. The results show that optimizing hot band annealing process is benefi cial to reduce the amount of {001} 110 grains and weaken the texture intensity, and thus, to reduce ridging and improve formability. In the present study, the fi nal sheets with hot band annealing temperature of 900 °C possess small and inhomogeneous grains with a large amount of {001} 110 orientations, which deteriorates the formability and increases the ridging. In comparison, the fi nal sheets with hot band annealing temperature of 950 °C are comprised of uniform and equiaxed 111//ND(ND: normal direction) recrystallized grains with a high texture intensity favorable for the improvement in r value and surface quality. However, when hot band annealing temperature further increases to 1000 and 1050 °C, it shows a sharp decrease in r value and a remarkable increase in ridging as a result of a reduction in γ-fi ber texture intensity and an increase in grain size in the fi nal sheets. Suitable controlling and optimizing hot band annealing process is essential to improve the formability and reduce the ridging.     

冷轧不同微量化学状态Al-Mn-Fe-Si铝合金的等温退火

通过3种不同热处理工艺使一种Al-Mn-Fe-Si合金获得了不同固溶液和不同尺寸及数量的弥散析出相,包括铸造态,一种富含高密度、细小、弥散相的状态,另外一种状态则仅有少量、相对粗大的弥散相。采用EBSD技术系统研究冷轧后退火过程中微观组织的演变以及初始组织状态对再结晶动力学、再结晶晶粒形貌和织构的影响。结果表明,再结晶动力学、最终微观组织和织构由加工条件和合金的初始组织和固溶度决定。高密度弥散析出相阻止形核,显著阻碍软化过程,最终得到粗大的狭长晶粒以及P和ND-rotated cube织构。在没有预先存在的细小、稠密的弥散相并且在退火过程中弥散相析出数量很少的时候则能更快完成再结晶并得到均匀、细小的等轴晶以及显著的立方织构。     

Correlating microstructure and texture in cold-rolled Ta ingot

An analysis of tantalum ingot cold-rolled and annealed under different conditions reveals several correlations between the microstructure, developed textures and thermomechanical processing parameters. For example, the hardness of rolled sheet is not significantly affected by the amount of reduction prior to the final anneal, while the final grain size decreases with an increasing number of intermediate annealing steps. Four classes of texture are found in the cold-rolled tantalum, but the finer-grained classes can only be produced via a 70 percent reduction in thickness prior to the final anneal. Although ample dislocation debris is produced by the rolling operation, clearly defined line dislocations and dislocation networks are absent, indicating that full recrystallization is not achieved in the finished sheets. A large concentration of ledge dislocations at the grain boundary regions is considered an important contributor to the good formability of tantalum.     

同步和异步轧制AZ31镁合金板材的织构及力学性能

采用同步轧制(NR)和异步轧制(AR)工艺对AZ31镁合金挤压板材进行了轧制,研究了轧制过程中组织和织构的演化,以及总压下量和异步比对轧材组织、织构和力学性能的影响。结果表明,在压下量为3%～15%的范围内,同步轧制与异步轧制板材在晶粒尺寸以及均匀性上有相似的变化趋势。轧制过程中,在变形初期,随压下量的增加,孪晶数量不断增加,孪晶使同步轧制与异步轧制板材中晶粒取向都发生偏转,即C轴趋向于垂直于法向(ND),从而使初始挤压板材的丝织构强度减弱;而当压下量达到24%时,孪晶大量减少或消失。在压下量为3%～24%的范围内,同步轧制对板材力学性能的影响并不明显,峰值应变呈交替变化;异步轧制板材在压下量达到24%左右时,表现出了良好的塑性变形能力,抗拉强度达到309MPa,峰值应变达到0.163。     

脉冲电流轧制对AZ31镁合金微观组织与力学性能的影响

对比研究脉冲电流轧制工艺与温轧工艺对AZ31镁合金板材的力学性能、织构、微观组织与沉淀相等方面的影响。结果表明：脉冲电流具有促进冷轧AZ31镁合金低温再结晶能力的作用。脉冲电流轧制后的镁合金板材组织由细小的等轴再结晶粒与析出相构成,没有发现孪晶组织,并且完全再结晶,原始晶粒均被细小的再结晶晶粒取代,再结晶晶粒内的位错密度低。而温轧镁合金组织则由稍拉长变形孪晶、粗大的再结晶晶粒和析出相构成,再结晶的晶粒内位错密度高。两种轧制方式下的镁合金析出相均为Mg17Al12。脉冲电流轧制后镁合金的织构具有典型基面织构的特征,而脉冲电流轧制镁合金的织构则出现横向偏转;脉冲电流轧制后镁合金的屈服强度与伸长率均比温轧镁合金的大,但抗拉强度正好相反。     

冷轧薄板再结晶温度研究

在冷轧薄板的生产过程中,金属晶粒将沿着变形方向被拉长.这种变化将导致力学性能等的变化.再结晶退火是冷轧薄板生产过程中的一个重要过程.因此研究冷轧薄板再结晶温度以及压下率对再结晶温度的影响,对冷轧薄板生产具有重要的实际意义,能够为冷轧薄板生产时退火工艺制度的制定提供理论依据.     

AZ31镁合金挤出板降温热轧的组织和织构的演变

研究AZ31镁合金挤出板坯在降温热轧过程中的组织和织构的演变规律.结果表明:退火前滑移和孪生是主要的变形机制和取向硬化机制;退火后长条晶的滑移和细小等轴晶晶界扩散迁移的共同作用成为主要的变形机制;随着压下量的增大,析出物开始破碎和分散,压下量在70%～80%之间时,基面织构组分的取向密度存在突变最大值,形成硬取向较强的{0001}基面织构,软化退火能大幅减弱硬取向;通过一道67%大压下量和一次软化退火可顺利地将AZ31镁合金轧制成厚0.5 mm的薄板.     

AZ31镁合金轧制板材退火后的组织与力学性能

采用单向轧制和交叉轧制工艺分别进行了AZ31镁合金板材轧制实验,分析了轧制板材经退火处理后的组织与力学性能。结果表明:采用单向轧制工艺,当板材最终变形量相等时,经退火处理后的板材大压下量比小压下量得到的微观组织更为细小;交叉轧制得到轧制板材可以缓解镁合金轧制板材在室温下的各向异性,其微观组织较单向轧制均匀,具有更好的冲压成形性能;交叉轧制和单向轧制两种工艺得到的板材微观组织细化效果相似。     

特殊成形工艺下AZ31镁合金的织构及变形机制

通过组织观察以及宏观和微观织构测定、分析了异步轧制及等径角轧制的AZ31镁合金形变机制,确定了在这两种工艺下{0001}基面织构的改善效果.结果表明:异步轧制产牛的平行于轧面的剪切力促进了与普通轧制状态下相反的基面滑移,使基面织构连续地弱化为倾转的基面织构;而等径角轧制通过产生与轧向成122.5°的剪切力,使基面取向的晶粒产生拉伸孪晶,形成与基面织构共存的柱面织构.因此这两种特殊工艺都可能改善镁合金的塑性.还分析了形变量和退火对织构的影响.     

Effect of reverse bending on texture,structure, and mechanical properties of sheets of magnesium alloys with zinc and zirconium

Effect of low-cycle room-temperature reverse bending on the crystallographic texture, metallo-graphic structure, and mechanical properties of sheets of ZE10 magnesium alloy after hot rolling and annealing has been studied. The initial texture is characterized by a wide scatter of basal poles in the transverse direction. In the process of reverse bending, the changes in the initial texture and structure (which is represented by equiaxed grains containing twins) lead to regular changes in the anisotropy of mechanical properties.     

Effect of Laser Texturing on the Microstructure and Textures of 1050 Aluminum Alloy

To improve the surface morphology, formability, and deep drawing properties of 1050 aluminum alloy sheets, laser-textured rolls were used in cold rolling process. Effects of laser-textured rolls, comparing with conventional ones, on microstructure and texture of aluminum alloys after rolling and following recrystallization were studied. In aluminum sheets processed by laser-textured rolls and conventional rolls, microstructure and texture were similar after rolling, but significantly different after recrystallization. Laser texturing process results in finer and inhomogeneous recrystallized grains. The recrystallization texture of the specimen rolled with conventional roll has a major cube component and a minor R component. The intensity of cube component increases with increasing annealing temperature. However, recrystallization texture of the specimen rolled with laser-textured roller is much more random. The specimen shows that recrystallization texture has only a weak cube orientation but strong rotated-cube orientation as well as a much higher fraction of random orientation.     

Influence of Finish Rolling Temperature on Microstructure and Mechanical Properties of a 19Cr1.5Mo0.5W Ferritic Stainless Steel

A 444-type heat-resistant ferritic stainless steel containing 0.05 wt% Ce(rare earth element) and 2 wt%(Mo+W) was adopted as an experimental material to study the effect of finish rolling temperature on microstructure and texture evolution as well as on mechanical properties and formability.The rolling processes contain hot rolling at two different finish rolling temperatures(860℃ and 770℃) and annealing,cold rolling and subsequent annealing.It was found that the microstructures after hot rolling and annealing could be refined by lowering finish rolling temperature.The resultant microstructures after cold rolling and annealing were hereditarily refined.Lowering finish rolling temperature can weaken α-fiber texture in hotrolled or cold-rolled ferritic stainless steel strip,while γ-fiber texture in the final product was homogeneously strengthened.Additionally,enhanced mechanical property and formability in terms of strength and average plastic strain ratio could be obtained via decreasing finish rolling temperature.     

Influence of rolling route on microstructure and mechanical properties of AZ31 magnesium alloy during asymmetric reduction rolling

Four different routes of asymmetric reduction rolling were conducted on AZ31 magnesium alloy to investigate their effect on the microstructure evolution and mechanical properties. Route A is the forward rolling; while during routes B and C the sheets are rotated 180° in rolling direction and normal direction, respectively; route D is the unidirectional rolling. The strain states of rolled sheets were analyzed by the finite element method, while the microstructure and texture were observed using optical microscopy, X-ray diffraction and electron back-scattered diffraction techniques, and the mechanical properties were measured by tensile test. The results show that route D produced the largest effective strain. Compared with other samples, sample D exhibited a homogeneous microstructure with fine grains as well as a weak and tilted texture, in corresponding, it performed excellent tensile properties, which suggested that route D was an effective way to enhance the strength and plasticity of AZ31 sheet.     

摩擦轧压表面处理及退火处理中纯钛的微观组织与织构演化(英文)

通过一种新的摩擦轧压表面处理工艺(FRSP)对纯钛板材表面进行加工,引入的应变沿材料厚度方向成梯度分布。采用光学显微镜、X射线衍射对FRSP加工后的纯钛的微观组织进行观察发现在钛材表面形成了超微细晶粒,且具有明显织构,其方向与FRSP的加工方向有关。另外,对FRSP处理后的钛材在不同温度和时间下进行退火处理,通过EBSD研究织构的形成及其在退火过程中的演变规律。结果表明:在低温退火过程中,钛板材表层主要存在FRSP后形成的织构,而原有的典型轧制织构减少,可见,通过FRSP及后续退火可有效地控制钛材表面的微观组织与织构。     

Effect of Cold-rolling on Mechanical Properties and Microstructure of an Al-12%Si-0.2%Mg Alloy

Effect of multi-pass cold-rolling on the mechanical properties and microstructure of a near-eutectic Al-12%Si-0.2%Mg casting alloy was investigated. Optical microscopy, SEM, and TEM were employed to resolve the as-rolled microstructure, and the microstructure of samples after aging treatment. It has been found that Brinell hardness increases considerably with rolling reduction ratio; and further annealing leads to a remarkable drop in hardness. Two mechanisms, namely precipitation hardening and recovery softening, were found to develop simultaneously in the subsequent aging treatment following cold rolling. In contrast, recovery softening dominated the aging of cold-rolled specimen with prior intermediate annealing. Tensile properties were also performed to measure the effect of cold rolling and subsequent aging treatment.     

Effect of rolling reduction and annealing process on microstructure and corrosion behavior of LZ91 alloy sheet

The effect of rolling reduction and annealing process on the microstructure and corrosion behavior of Mg−9Li−1Zn (LZ91) alloy was investigated. The test alloy sheets were cold rolled with the reduction of 50% and 75%, respectively, and then were annealed at 200 °C for 1 h. The microstructure of test alloys was observed by OM and SEM while the phase composition was determined by XRD. The corrosion property was evaluated by electrochemical measurements and immersion tests. The results show that LZ91 alloy sheet consists of α-Mg, β-Li and precipitated Mg−Li−Zn compounds (MgLi₂Zn and MgLiZn phases). Dynamic recrystallization grains appear in β-Li phase during annealing process, leading to grain refinement. The results indicate that the increasing rolling reduction and performing the annealing process can enhance the corrosion resistance of LZ91 alloy. The 75% cold-rolled and annealed LZ91 alloy shows the best corrosion resistance.