累积叠轧焊制备超细晶IF钢微观组织与力学性能

采用累积叠轧焊方法制备了超细晶IF钢，对其微观组织和力学性能进行了分析。实验结果表明，累积叠轧后IF钢的平均晶粒尺寸为700nm；抗拉强度为621．3MPa，达到冷轧IF钢抗拉强度的2．02倍，屈强比σ0.2/σb为0．81。在累积叠轧过程中产生的氧化物夹杂导致超细晶IF钢的脆化。     

叠轧无氧纯铜制备超细晶材料的EBSD分析

主要对不同条件下叠轧并退火处理的无氧铜试样进行扫描背散射电子衍射(EBSD)分析。EBSD反极图表明，试样内晶粒分布比较均匀，晶体学择优取向不是特别明显，但在局部仍存在微小的取向；EBSD晶粒图分析表明低道次叠轧后材料局部出现细小晶粒和小区域小角度晶界；晶粒度图表明低道次叠轧后大晶粒和小晶粒并存。结果表明利用叠轧法制备超细晶材料可以达到一定的细化目的。     

超细晶铜带材的制备及其力学性能研究

采用常规的四辊冷轧设备对厚度为2．5mm的紫铜板经大变形多道次冷轧，最终轧成厚度为20μm的超细晶薄带材，并对其组织结构、抗拉强度和硬度等进行了检测分析．实验结果表明：铜材的晶粒尺寸由原始材料的30μm减小到250nm；与组织转变相对应，其抗拉强度和显微硬度随着变形量的增大而增加，最终抗拉强度比原始材料提高了约130MPa，显微硬度值提高了约30．     

7075铝合金累积叠轧焊组织与性能

为了提高7075铝合金的力学性能,7075铝合金在350℃无润滑条件下进行了5道次的累积叠轧焊实验,通过X射线衍射(XRD)与透射电镜(TEM)分析,研究了7075铝合金在叠轧过程中微观组织的演化规律,利用室温拉伸实验,研究了叠轧道次对7075铝合金力学性能的影响规律,并且采用扫描电镜(SEM)对拉伸断口形貌进行了分析。结果表明:7075铝合金在叠轧过程中材料的组成相η相发生回溶,数量减少;微观组织经历由位错缠结/位错胞状结构向形变亚晶结构转变的过程,5道次后,形成了尺寸小于1μm的亚晶组织;材料的强度随道次的增加而增加,5道次后,其抗拉强度与屈服强度分别达到373.52,315.84 MPa,约为原始合金的1.8倍和3.2倍,同时,延伸率则随着叠轧道次的增加而下降,5道次后,延伸率仅为原始合金的1/3,并且拉伸断裂由韧性断裂转变为脆性断裂。     

累积叠轧焊制备Al／AZ31多层复合材料及其强度

采用累积叠轧焊法制备了Al/AZ31多层复合材料,并通过扫描电镜、X射线能谱仪和显微硬度计对所制备的Al/AZ31多层复合材料进行了横截面形貌观察、能谱分析以及显微硬度测试.结果表明,经过三道次的累积叠轧焊之后可制备Al/AZ31多层复合材料.能谱分析表明,在Al层和AZ31层的界面处产生了扩散层.随着轧制道次的增加扩散层的厚度逐渐增加.显微硬度测试表明,随着轧制道次的增加,Al/AZ31多层复合材料的层组元的强度也随之增加,但Al层的强度较AZ31增加得快,并且形成的界面扩散层具有一定的硬度梯度.     

室温ECAP变形纯钛孪生行为研究

室温下对纯钛进行多道次等径弯曲通道变形（ECAP）,分别采用光学显微镜（OM）、透射电镜（TEM）、电子背散射衍射仪（EBSD）、室温拉伸和显微硬度观察,测试纯钛变形过程组织演变和力学性能变化规律,探讨纯钛室温变形机制和孪生行为。结果表明,纯钛ECAP变形过程中出现■拉伸孪晶和■压缩孪晶,随着挤压道次的增大,孪晶数量先增大后减小。孪晶的出现有效改变晶格取向,激发进一步位错滑移,辅助塑性变形过程,使纯钛显微组织有效细化,经过4道次ECAP变形,平均晶粒尺寸由约63.79μm细化至约2.81μm。1道次变形后晶粒细化效果最显著,平均晶粒尺寸比变形前减小约94%;随着变形道次的增加,晶粒细化效果减弱,4道次变形后平均晶粒尺寸累积减小约95.6%。同时,大量位错、孪晶和亚晶的形成,使得位错、孪晶以及亚晶之间的相互作用加强,显著提高了纯钛的屈服强度和显微硬度,4道次变形后,屈服强度从215 MPa增加到600 MPa,增幅为179%;显微硬度从HV 129增加到HV 200。由于1道次变形后晶粒细化效果最显著,并且出现大量孪晶和位错,屈服强度与硬度的增幅也最大。     

用等径角挤压变形法制备纳米晶金属结构材料的组织演变

用实验方法研究了工业纯铁在等径角挤压变形(路径C)过程中晶粒细化过程。实验结果表明，经4道次剪切变形后开始出现纳米级晶粒。晶粒细化过程为：原始粗晶粒→晶粒被剪切变形带分割→位错线分割滑移带→位错线发展为位错墙，把变形带分割成细小的亚晶→亚晶界的位错密度增加→形成大角度晶界的纳米晶粒。测试了不同变形道次下材料的显微硬度值。     

ARB工艺对1060工业纯铝组织和性能的影响

采用ARB技术中两种轧制工艺, 研究变形后1060工业纯铝的显微组织和力学性能变化. 结果显示, 在两种ARB轧制工艺中, 单向轧制工艺的晶粒细化效果明显好于换向轧制. ARB7道次后, 采用单向轧制工艺试样的显微组织由拉长的细小纤维状晶粒组成, 平均晶粒尺寸是470 nm;采用换向轧制工艺试样由等轴状晶粒组成, 平均晶粒尺寸是680 nm. 同时, 单向轧制后, 材料的抗拉强度和显微硬度提高程度大于换向轧制, 但延伸率却不如换向轧制. 分析了ARB过程材料的变形规律和细小晶粒的形成机制.     

微量元素和变形条件对超细晶中厚板显微组织的影响

通过对3种不同铌、钒含量的低碳钢进行多道次热压缩变形以模拟中厚板的超细晶轧制工艺，考察了显微组织演变过程、微合金元素和变形条件对组织演变的影响。结果表明：变形过程中有部分奥氏体通过形变诱导相变转变为铁素体；变形并快速冷却后得到平均晶粒尺寸为3～6μm的超细晶组织．铌促进、钒抑制形变诱导铁素体相变，铌、钒微合金化均有较好的细化作用，铌的作用优于钒．再结晶温度以上进行的粗轧有利于精轧时形变诱导铁素体的形成；在精轧温度范围内，增加变形道次、降低道次应变率有利于获得细化的显微组织；降低终轧变形温度对组织细化是最有效的．     

工艺参数对CVCE变形工业纯铝组织和性能的影响

采用连续变断面循环挤压(CVCE)工艺制备细晶工业纯铝,结合金属流动规律研究挤压角度和变形道次对变形工业纯铝组织和性能的影响。结果表明:随着挤压角度的增加,网格畸变程度和变形不均匀程度随之增加,θ=7°试样的晶粒细化程度远大于6°,但晶粒尺寸和晶粒分布不及6°均匀;随着变形道次的增加,累积变形量增大,晶粒被充分细化,θ=7°试样经3个循环变形后的晶粒尺寸被细化至10μm,是原始晶粒尺寸的1/10; CVCE变形工业纯铝由表面至芯部的网格畸变决定了硬度的分布是沿表面到芯部逐渐减小,并且随着变形道次的增加,θ=7°试样的硬度呈显著增加趋势,3个循环的显微硬度可达HV 105. 62,相比于原始试样提高了4倍。经CVCE变形后试样,横截面与纵截面上晶粒的形状和取向性完全不同,纵截面上原始等轴晶粒取向性逐渐削弱,横截面上原始粗大的柱状晶经过变形后,晶粒的取向性几乎消失。     

Effect of CVCE passes on the microstructure and properties of the as-cast commercially pure aluminum 1A85

In this study, the as-cast commercially pure aluminum 1A85 was prepared through continuous variable cross-section recycled extrusion (CVCE) technique at room temperature(300?K) to investigate the effect of number of CVCE passes on its microstructure and mechanical properties. The results showed that the ultrafine-grained pure Al with the average grain size of 0.4 μm could be obtained after 3 passes, which was 1/210 of the original grain size. Besides, the grain size of specimen was gradually decreased when the number of CVCE passes was increased from 1 to 3 passes, while the dislocation density was elevated. As a result, the highest average microhardness, yield strength and ultimate tensile strength could be obtained after 3 passes. However, the mechanical properties of the as-prepared specimen were substantially reduced after 4 passes. Moreover, differences in mechanical properties between the cross and longitudinal sections could be attributed to the grain size and dislocation substructures. Taken together, the grain refinement and dislocation strengthening had significant effect on the mechanical properties of the CVCE-prepared pure Al.     

超声滚压处理7B85合金的显微组织和力学性能

采用不同压下量（0、0.1、0.2、0.3、0.4 mm）对7B85合金进行超声滚压处理，利用光学显微镜、表面粗糙度测量仪、显微维氏硬度计、拉伸实验、扫描电镜、X射线衍射和电子背散射衍射对经过超声滚压处理的7B85合金的微观组织和力学性能进行研究。结果表明，当下压量为0.2 mm时，超声表面滚压处理后7B85合金的表面粗糙度、显微硬度以及抗拉强度达到较优值。滚压处理后合金的断口形貌呈现出大量较深的韧窝，其主要以韧性断裂形式为主。同时，超声表面滚压处理后合金中大部分η析出相溶解到铝基体中，其表层晶粒的平均晶粒尺寸约为（25.22 ± 6.46）nm。滚压后合金力学性能的提高主要归因于合金表面细晶强化和应力强化的共同作用。      

异步轧制工业纯钛的组织与力学性能

采用异步轧制方式在室温下轧制TA1工业纯钛,获得平均晶粒尺寸小于300nm的超细晶组织,显著提升了材料的强度,并探讨了超细晶的形成和强化机制。经轧下量为87％的异步轧制后,材料内部形成均匀分布的狭长剪切带,组织中主要为等轴超细晶,亦存在少量拉长晶粒和小角度晶界;材料的显微硬度比原始热轧态提高了60％,抗拉强度提高至740MPa以上。     

异步轧制AZ31镁合金板材的晶粒细化及性能

采用上下轧辊速比1.125的异径异步轧制方法对AZ31镁合金板材进行轧制。采用光学显微镜、X射线衍射仪和电子拉伸机等设备分析轧制前后AZ31镁合金板材的微观组织和力学性能。结果表明:AZ31镁合金热挤压板坯在加热到350℃后,经一道次38%压下率的异步轧制,可获得平均晶粒尺寸为2.8μm的等轴晶粒,板材轧制方向的伸长率和抗拉强度显著增加;轧制过程中形成了非基面晶粒取向;伸长率的增大与晶粒细化和非基面织构的形成有关,抗拉强度的增大归因于晶粒的显著细化效应。     

Recrystallization kinetics of an austenitic high-manganese steel subjected to severe plastic deformation

The evolution of the microstructure and the properties of an austenitic high-manganese steel subjected to severe deformation by cold rolling and subsequent recrystallization annealing is investigated. Cold rolling is accompanied by mechanical structural twinning and shear banding. The microhardness and microstructural analysis of annealed samples are used to study the recrystallization kinetics of the high-manganese steel. It is shown that large plastic deformation and subsequent annealing result in rapid development of recrystallization processes and the formation of an ultrafine-grained structure. A completely recrystallized structure with an average grain size of 0.64 μm forms after 30-min annealing at a temperature of 550°C. No significant structural changes are observed when the annealing time increases to 18 h, which indicates stability of the recrystallized microstructure. The steel cold rolled to 90% and annealed at 550°C for 30 min demonstrates very high strength properties: the yield strength and the tensile strength achieve 650 and 850MPa, respectively. The dependence of the strength properties of the steel on the grain size formed after rolling and recrystallization annealing is described by the Hall–Petch relation.     

Mechanical properties of iron processed by severe plastic deformation

In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time. The grain size of annealed Fe, with an initial grain size of about 200 μm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization, an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe. The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms and softening behavior are discussed.     

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The stainless steel/iron chips core cladding bar was hot-rolled by using recycling iron scrap. The interface of the metals and the influence of rolling pass, rolling temperature, graphite additive on properties of stainless steel/iron chips core cladding bar were analyzed by optical microscope, SEM, EDS and micro hardness tester. The experimental results show that element diffusion occurs at the interface after six passes rolling and the width of diffusion zone is about 70-80??m. The Fe of carbon steel diffuses into stainless steel and the Cr, Ni, Mn of stainless steel diffuse into carbon steel which makes micro hardness of carbon steel near the interface increase obviously. The bonding strength between stainless steel and iron chips core increases with increasing of rolling passes and it is 355MPa after six passes rolling. The tensile strength and elongation of the cladding bar increase with increasing of rolling temperature and they are 470MPa and 32% at 1150??, 500MPa and 35% at 1250??. The composition of iron chips core is improved by adding graphite powder. With the increasing of the graphite in iron chips, the tensile strength of cladding bar increase, but decrease for elongation. White reticular secondary cementite is appearing when the graphite is 1. 0% and the tensile strength is up to 736. 5MPa, the elongation decrease to 16%. The tensile fracture shows brittle fracture morphology.     

Strain Effect on the Microstructure,Mechanical Properties and Fracture Characteristics of a TWIP Steel Sheet

Twinning-induced plasticity (TWIP) steels are a highly promising group of steels for the production of complex structural components in cold forming operations for car body manufacturing. In this work, the effect of cold rolling strain on the microstructure, mechanical properties and fracture characteristics of a TWIP steel sheet used for automobile body structure was studied by means of optical microscopy, scanning electron microscopy, electron back-scattered diffraction technique, microhardness measurement, tensile test and fractography. TWIP steel sheets were cold rolled with reductions of 0, 15 and 30%. An increase of the cold rolling strain led to an increase of deformation twinning activity in certain favourably oriented grains and resulted in significant increase in ultimate tensile strength and hardness of TWIP steel. However, the ductility of TWIP steel significantly decreased with increasing degree of cold rolling strain. The increase in the ultimate tensile strength was almost linear with the increase in cold rolling strain. After cold rolling reduction of 30%, the ultimate tensile strength increased by approximately 50%, whereas the elongation decreased by approximately 85%. The size and depth of the dimples in the fracture surface decreased with the increase of the twin boundaries at 30% cold rolling strain, leading to highly limited plasticity through the tensile testing.     

铸态304L奥氏体不锈钢等径角挤压变形的力学性能

 研究了经1~4道次等径角挤压变形(ECAP)后,铸态304L奥氏体不锈钢微观结构的演变,同时测定了ECAP变形后的力学性能。结果表明,经4道次变形后,铸态粗大晶粒破碎形成细小的大角度晶粒,平均晶粒尺寸约202 nm;抗拉强度和屈服强度大大提高(Rp02=1 002 MPa,Rm=1 100 MPa),但均匀塑性变形能力(A＜3%)和加工硬化指数(n=0060)却显著下降。     

精轧工艺对30 mm厚X65管线钢板组织和性能的影响

Nb-Ti微合金化X65管线钢(/%:0.07C、1.60Mn、0.35Mo)的生产工艺流程为130 t顶底复吹转炉-钢包吹氩-LF-RH-250 mm×1500 mm板坯连铸-连轧至30 mm板-控冷工艺。研究了第Ⅱ阶段开轧(890～940℃)轧后冷却温度(780～850℃)和冷却速度(8～20℃/s)对X65钢厚板拉伸、落锤性能和组织的影响。结果表明,Ⅱ阶段开轧温度为940℃,轧后冷却速度为20℃/s可以使X65钢厚板得到以针状铁素体和粒状贝氏体为主的组织,钢板抗拉强度665～695 MPa,屈服强度495～520 MPa,落锤纤维组织率约为92%,满足标准要求。