Effect of thermal ageing on microstructure,mechanical properties,and fracture behaviour of 50 % cold rolled duplex stainless steel (alloy 2507)

The paper deals with cold rolling and ageing on microstructure and mechanical properties of 2507 duplex stainless steel. Microstructure depicts acicular/Widmanstätten austenite and δ-ferrite with dissimilar volume fraction (∼0.55 for ferrite and ∼0.45 for austenite). Cold rolling and ageing at 950 °C, 1000 °C and 1050 °C result in equiaxed austenite for samples solution treated at 1040 °C and elongated at 1300 °C. By lowering ageing temperature from 1050 °C to 950 °C, structure becomes finer from ∼20 μm to <10 μm grain size. The sigma (σ) phase appears after ageing at 950 °C. Micro-hardness reveals maximum hardness for the hot rolled, solutionized (1040 °C) water quenched, and cold rolled (50 %) sample (380 HV_δF 100 and 430 HV_γ 100), whereas the tensile results reveal the hot rolled, solution treated (1300 °C, 1040 °C), cold rolled and aged at 950 °C samples show higher strength (yield strength=625 MPa, 567 MPa and ultimate tensile strength=892 MPa, 826 MPa) and lower ductility (23 %, 32 %) due to the σ-phase. The solution treated (1040 °C), cold rolled, aged at 1050 °C sample exhibits attractive strength and ductility combination (∼30 GPa %). Fractography supports the tensile results.     

高强Ti-IF钢铁素体区热轧和冷轧过程织构演变规律

为了揭示铁素体区热轧、冷轧和退火过程中高强Ti-IF钢中织构的演变过程,采用X射线衍射仪研究了铁素体区热轧及随后的冷轧和退火织构的特点.研究表明,在铁素体区热轧后,表面和中心面的织构类型和强度不尽相同,表面上的主要织构组分是剪切织构{110}<001>,而中心面上的主要织构组分是{001}<110>～{223}<110>和{111}<110>,由于织构的遗传性,冷轧和退火后的织构在表面和中心面上也不相同;经不同压下率冷轧后,织构变化趋势一致,表面上{110}<001>组分消失,{001}<110>成为最强组分,而中心面上最强组分由{001}<110>沿α取向线向{112}<110>偏移,冷轧织构由α织构和γ织构组成;退火后,表面上织构的变化与以往结论有所不同,{001}<110>～{112}<110>组分减弱,而γ取向线上的{111}<123>组分增强,{111}<112>和{111}<110>减弱.     

冷轧Al_(0.3)CoCrFeNi高熵合金退火再结晶组织和织构的演变

利用维氏硬度计(HV)、X射线衍射仪(XRD)、电子背散射衍射(EBSD)和透射电镜(TEM),研究了90%冷轧Al0.3CoCrFeNi高熵合金在900℃退火过程中的微观组织和织构演变规律。结果表明:退火0.5h合金发生完全再结晶,退火孪晶形成于再结晶面心立方(FCC)晶粒内;经退火1h后,富集Al-Ni原子的有序体心立方(BCC)相优先于FCC相的晶界处形核,且FCC相和BCC相均随着退火时间(1h~10h)的延长而发生晶粒长大。再结晶FCC相的织构组分主要为强{123},〈634〉S织构和强α-{110}纤维织构,{001}〈100〉立方织构随着退火时间的延长也逐渐转化为强织构;再结晶过程的进行使无择优取向的初始BCC晶核选择性长大,{111}〈112〉织构从而演变为强BCC相织构。     

Features of austenitic steels' microstructure following plastic deformation

The carried out transmission electron microscopic (TEM) analysis of steels 316L and TWIP, has shown that important mechanisms of plastic deformation are mechanical twinning, shear band formation and deformation martensitic transformations. Mechanical twinning is a characteristic feature of a plastic deformation at ε ≈ (20–50) % deformation degrees. At ε = (20–70) % the basic contribution in plastic deformation of a material brings shear band formation. The contribution deformation martensitic transformations into plastic deformation is defined by level of phase instability of steels.     

酸洗-冷轧联合机组闪光焊接头断带原因分析

采用宏观分析、力学性能测试、金相检验和断口分析等手段对某酸洗-冷轧机组闪光焊低碳Stb35L钢薄板接头在冷轧过程中频繁出现断带的原因进行了分析。结果表明:闪光焊接头发生开裂和断带的主要原因是其热轧原料钢板的头尾板形较差,而闪光焊前又未对其进行校平或剪切,从而导致接头局部出现焊缝搭接错边现象;在冷轧过程中,焊缝搭接处产生折叠和缺口裂纹,裂纹不断扩展最终导致断带;另焊缝中存在未挤压干净的链状氧化物是导致接头开裂和断带的另一个原因。     

微碳深冲钢板中非{111}织构的工序演变

生产试制的微碳深冲钢板出现了偏离常规的非{111}织构特征,通过研究这种织构的工序演变分析其形成特点.选取热轧、冷轧和退火3组试样,检测各试样的织构和金相组织,分析比较各工序试样的织构、金相组织和工艺参数,并与常规的{111}织构的工序演变过程进行比较.结果表明:非{111}织构的工序演变过程与通常的{111}织构的工序演变过程具有显著的不同;非{111}织构在热轧阶段就已经显现,在冷轧阶段形成较强的非{111}织构,在退火过程中遗传到最终钢板产品中.     

冷轧形变量对钛板材再结晶织构形成的影响

采用三维晶体学取向分布函数（ＣＯＤＦ）分析法研究了工业纯钛板材不同冷轧形变量对织构形成的影响。结果表明，冷轧形变量为５０－７０％时，再结晶退火后形成了（２１１８）（０１１０）和（１０１８）（１２１０）的部分纤维织构，而在３０％较低或８６％较高的形变量冷轧时，形成典型的轧制织构（２１１５）（０１１０）和再结晶织构（１０１３）（１２１０）型式。     

退火工艺参数及母材性能对取向硅钢超薄带磁性能的影响EI北大核心CSCD

采用EBSD技术对不同退火工艺处理后的冷轧取向硅钢超薄带样品进行研究,分析退火样品的显微组织、织构与磁性能的关系,讨论母材性能对超薄带性能的影响。结果表明:冷轧超薄带的退火组织均匀、Goss取向度高以及母材磁性能优良均可有效提升磁性能;退火升温速率主要影响晶粒尺寸、Goss取向度及磁性能;再结晶的平均晶粒尺寸改变,会影响最终超薄带的磁感应强度及铁损;在900℃退火5 min以上会明显发生再结晶,10~30 min内退火的超薄带磁性能变化较小,退火15 min获得最佳磁性能。此外,在1000℃及1100℃下退火的时间均不宜超过10 min,否则会恶化磁性能。     

退火温度对GH3600合金箔材组织与性能的影响

目的 探究退火温度对GH3600镍基高温合金箔材微观组织及力学性能的影响。为制备综合性能良好的GH3600箔材提供参考。方法 将厚度为2 mm的铸态板材反复轧制退火得到组织均匀的0.3 mm厚度带材,再利用四辊冷轧机将带材轧制成厚度为0.1 mm和0.05 mm的箔材,然后将2种厚度箔材在950、1 000、1 050 ℃下保温1 h后空冷。通过金相观察、电子探针、EBSD检测及XRD分析来研究箔材的微观组织演变。通过拉伸实验检测箔材的室温拉伸性能。结果 随着变形程度的增大,轧制态箔材晶粒沿轧制方向被拉长得更加明显。在相同热处理参数下,0.05 mm退火态箔材晶粒尺寸更小。退火后,箔材晶粒发生了回复再结晶并析出了细小的碳化物。随着退火温度的升高,晶内碳化物逐渐减少,孪晶界比例增大,再结晶程度及晶粒尺寸增大。0.05 mm箔材在1 050 ℃退火时,其晶粒迅速粗化,在厚度方向上出现单层晶,导致箔材的抗拉强度及延伸率出现异常降低的现象,即“越小越弱”的尺寸效应。结论 适宜的热处理工艺有助于改善箔材的微观组织,进而提高其力学性能。0.05 mm箔材在950 ℃下退火1 h时,其延伸率为19.1%,屈服强度以及抗拉强度分别达到293 MPa和560 MPa,综合力学性能良好。     

热镀锌钢板用冷轧板退火工艺的确定

采用盐浴退火方法分别对牌号为SSGrade40,SSGrade33和SSGrade50的热镀锌钢板的冷轧硬卷进行了不同工艺的退火处理,研究了退火工艺对三种热镀锌钢板用冷轧板显微组织和力学性能的影响,以确定三种冷轧板的再结晶温度及最佳退火温度范围。结果表明：SSGrade40冷轧板的再结晶温度在720℃左右,退火温度在720℃较佳;SSGrade33冷轧板的再结晶温度在680℃左右,考虑到力学性能的稳定性,退火温度选择在720℃左右较佳;SSGrade50冷轧板的再结晶温度在700℃以上,为了保证其强度富余量和性能稳定性,退火温度选择在780℃左右较佳。     

Process Parameter Optimization of the Pulsed Current Argon Tungsten Arc Welding of Titanium Alloyin process parameter selection of pulsed current gas tungsten arc welding of titanium alloy

The selection of process parameters for obtaining optimal tensile properties in the pulsed current gas tungsten arc welding is presented. The tensile properties include ultimate tensile strength, yield strength and notch tensile strength. All these characteristics are considered together in the selection of process parameters by modified taguchi method to analyse the effect of each welding process parameter on tensile properties. Experimental results are furnished to illustrate the approach.     

对称复合板冷轧变形模式的上限分析

应用上限法建立了对称复合板冷轧变形模式的数学模型,在此基础上对软复层复合板在不同条件下冷轧时的变形模式进行了计算,给出了相关计算曲线。计算结果表明,依过程参数的不同,软复层复合板冷轧时存在比例变形、界面撕开及不稳定变形三种可能的变形模式。加工率越大、界面结合强度越高、基体材料的相对强度和复合板轧后的相对厚度越小,则均匀变形区越大,界面撕开区越小。不稳定变形区仅在基体材料的相对厚度和相对强度足够大时才存在。      

Critical current studies on metal clad R1Ba2Cu3O7−x wires

Silver clad wires of R₁Ba₂Cu₃O_7−x (R=Y, Gd, Sm, Dy and Ho) have been fabricated following the powder-in-tube method and cold-rolling. The critical current densityJ _c at 77 K and zero magnetic field is restricted to 66 A.cm⁻². In a separate experiment we have studied the effect of silver sheath thickness onJ _c of the Y₁Ba₂Cu₃O_7−x wires. Interestingly,J _c is higher for larger sheath thickness indicating that large sheath thickness prevents oxygen loss during sintering. Uniaxial pressing of the wires into flat tapes results in an increase of theJ _c . MaximumJ _x is, however, limited to 169 A.cm⁻². No grain alignment is found in the core material of our wires which is essential for highJ _c . Several options are being tried.     

Production scheduling optimization algorithm for the hot rolling processes

The hot rolling production scheduling problem is an extremely difficult and time-consuming process, so it is quite difficult to achieve an optimal solution with traditional optimization methods owing to the high computational complexity. To ensure the feasibility of solutions and improve the efficiency of the scheduling, this paper proposes a vehicle routing problem (VRP) to model the problem and develops an easily implemented hybrid approach (QPSO-SA) to solve the problem. In the hybrid approach, quantum particle swarm optimization (QPSO) combines local search and global search to search the optimal results and simulated annealing (SA) employs certain probability to avoid getting into a local optimum. The computational results from actual production data have shown that the proposed model and algorithm are feasible and effective for the hot rolling scheduling problem.     

混合离散变量模拟退火方法及其应用

基于海洋工程中存在的设计变量为离散型和连续型的混合离散变量的情况,探讨了一种优化设计问题的方法———混合离散模拟退火法.该方法相对常规模拟退火方法有一定改进并且针对混合离散变量进行了特定处理.实际算例计算表明,该方法可用于海洋工程优化设计中,其结果不需圆整,而且其解题可靠性和效率相当高.