轧制复合法制备硅浓度梯度高硅钢薄带的织构演变

采用"热轧复合+冷轧减薄+退火"方法成功制备了0.20mm厚的硅浓度梯度高硅钢薄带,并采用SEM和X射线衍射技术对制备过程中组织和织构演变进行了研究。热轧复合板微观组织呈明显层状分布,复合界面为紧密冶金结合且经过83%的大冷轧变形未开裂。热轧和冷轧复合板带中均形成强α和γ织构,再结晶退火后形成强γ织构。冷轧和退火织构沿板厚呈显著的梯度分布特征,其主要来自于复合界面两侧硅浓度和初始热轧织构的差异性以及冷变形的不均匀性。     

包铝镁合金复合板轧制制备新工艺

本研究采用浇铸预复合+热轧新工艺成功地制备了包铝镁合金复合板。借助金相显微镜和显微硬度测试仪分析了浇铸预复合+热轧新工艺对包铝镁合金复合板的微观组织形貌特征和显微硬度的变化情况。研究表明:由于浇铸预复合的铝液温度较高,使得Mg/Al复合界面上形成较多数量的"熔池",有效地提高了轧前Mg/Al金属预复合的结合强度;热轧制复合工艺下的大压下量有效地细化了Mg/Al结合层的组织,增强了复合界面的结合强度。     

316L-Q345R不锈钢复合板性能评价

从微观组织和显微硬度两方面对真空热轧316L-Q345R不锈钢复合板试样性能进行评价。采用电子显微和能谱分析技术,对试样进行微观组织特征观察和成分含量测定,研究相结构及成分变化规律。通过硬度测试仪对复合板界面附近硬度进行测量,研究微观组织与硬度关系。结果表明:热轧后复合板Q345R侧显微组织以铁素体和珠光体为主,316L侧显微组织为单一奥氏体,一部分晶粒呈孪晶状态,Q345R低合金钢和316L不锈钢经过热轧可良好复合,复合界面平直;界面两侧元素存在扩散现象,不锈钢中Cr,Ni元素向低合金钢侧扩散,在界面形成富Cr,Ni薄层,低合金钢中C向不锈钢侧产生少量迁移;在复合界面处的硬度值较大,低合金钢侧远离界面位置复合板硬度与Q345R本身硬度值接近,而从界面到不锈钢侧硬度呈现先下降后上升至稳定的趋势。     

珠光体钢(α+θ)微复相组织的形成与力学性能

系统研究了珠光体钢在冷轧与随后退火及温变形(温楔横轧)过程中的组织演变规律、力学性能变化、合金元素添加的影响等,发现共析珠光体钢经大冷变形及随后适当温度退火可以形成铁素体晶粒与渗碳体颗粒尺寸均在亚微米量级的(α+θ)微复相组织.冷轧变形后的珠光体组织非常不均匀,主要由不规则弯曲片层、带有剪切带的粗大片层以及精细片层组成.大冷变形能明显提高共析珠光体钢的屈强比和加工硬化指数,随轧制压下率的增大,共析珠光体钢冷轧态试样的强度提高,延性在冷轧压下率小于60%时出现急剧下降后又几乎保持不变.合金元素的添加使冷轧态试样的强度提高,但对延性的影响几乎可以忽略.实际温楔横轧后高碳钢棒件表层也具有超微细(α+θ)复相组织,温楔横轧过程中靠近表层的铁素体基体发生了动态连续再结晶,铁素体晶粒及渗碳体颗粒尺寸分别在0.4μm和0.2μm左右.温楔横轧后硬度与抗拉强度沿高碳钢棒件截面分布不均匀,心部略高于表层,但是在屈服强度方面.表层最高(约600MPa),心部次之(580MPa),其余部位介于二者之间.     

退火制度对钎焊用热轧复合铝板组织与性能的影响

采用金相显微镜、扫描电镜、透射电镜、X射线衍射仪、拉伸试验机、硬度计等研究了4343/3003/4343铝合金轧制复合板在100~500℃退火15min~10h后的微观组织和力学性能。结果表明:芯层合金300℃退火1h后开始再结晶,370℃以上退火1h后已完全再结晶且伴随有弥散相析出,弥散相析出后通过钉扎晶界阻碍再结晶晶粒长大;1h退火时,随退火温度升高,芯层合金晶粒先增大后减小,复合板的拉伸强度与硬度先降低后升高;370℃退火时,随退火时间延长,芯层合金再结晶程度增加,晶粒缓慢长大,复合板的拉伸强度与硬度下降;复合板最佳退火工艺为370℃/1h。     

1Cr17/9Cr18MoV多层复合钢板的组织与性能

采用包覆浇铸方法,经热锻、热轧后制备出各层钢板厚度较均匀分布的1Cr17/9Cr18MoV多层复合板。不同热处理工艺下的试验结果表明,采取加热温度950℃,保温0.5h后空冷的热处理工艺,可使复合板中9Cr18MoV钢获得较高的硬度,1Cr17钢获得较低的硬度,同时满足各层界面两侧附近的组织基本相同,硬度比较接近的要求。     

多层金属复合板的热轧制备方法

提高成材率和复合界面质量是制备多层复合板的难题。本工作提出一种多层复合板的高成材率热轧制备方法,即采用氩弧焊固定各层原料板组成坯料,坯料放入金属套后抽真空,再加热到1000~1200℃进行多道次轧制,成功制备出2.5mm厚的67层复合板。通过金相显微镜及电子显微镜观察和分析了界面组织及元素扩散行为,采用拉伸、剪切实验测定复合板的力学性能,并分析其剪切断口。结果表明:采用两步组坯复合和工艺优化,多层复合板的轧制成材率达90%以上。多层复合板具有良好的结合界面,其抗剪强度达到241MPa。9Cr18和1Cr17镍中间层可以较为有效地阻碍界面附近的碳扩散并改善复合板的组织特征。     

钛网添加对镁/铝复合板微观组织和力学性能影响研究

目的 有效抑制镁/铝复合板界面处金属间化合物的形成。以钛网为中间金属夹层,研究它对镁/铝复合板微观组织和力学性能的影响。方法 利用复合轧制技术制备以钛网为中间金属夹层的镁/铝-钛复合板,采用扫描电子显微镜(SEM)、电子背散射衍射仪(EBSD)、万能试验机等对复合板退火前后的微观组织和力学性能进行表征和分析,系统研究中间层钛网对轧制态和退火态复合板微观组织、织构、拉伸性能、界面结合强度的影响规律。结果 中间层钛网均匀分布在镁/铝-钛复合板界面处,钛网的添加能有效抑制复合板退火过程中镁-铝金属间化合物的连续生长,减少金属间化合物的数量。与镁/铝复合板相比,钛网的添加对轧制态和退火态复合板中镁层和铝层的平均晶粒尺寸和织构类型的影响较小。与镁/铝复合板相比,钛网的添加降低了轧制态复合板的界面剪切强度和延伸率,但极大提升了退火态复合板的界面剪切强度、拉伸强度和延伸率。结论 中间层钛网的添加可有效减少复合板界面处金属间化合物的数量,提升退火态复合板的综合力学性能。     

T6热处理对A356/6082铝合金复合板界面组织及力学性能的影响!

采用液-固轧制复合技术制备A356/6082层状复合板,并对其进行T6热处理。通过光学显微镜(OM)、扫描电镜(SEM)、剪切试验、显微硬度测试等表征手段对比分析了T6热处理前后复合板显微组织变化、界面元素扩散规律以及剪切强度和硬度等力学性能特征。结果表明:T6热处理后,层片状共晶硅形态发生球化,界面附近的共晶硅团聚现象消失且组织更为均匀;界面区Mg元素明显扩散,结合线消失;复合板剪切强度从91. 6 MPa提高到139. 2 MPa,界面区域和基体的显微硬度均得到明显改善,A356侧的平均硬度值达到1102. 5 MPa左右,6082侧的平均硬度值达到851. 6 MPa左右,且沿A356至6082垂直界面方向其显微硬度值逐渐下降。     

固溶处理冷却方式对Cu/Al复合板界面微观组织的影响

利用光学显微镜、扫描电镜、X射线衍射等手段研究了冷却方式(水冷、空冷和炉冷)对Cu/Al复合板界面微观组织的影响,利用显微硬度仪测试了冷却方式对铸轧Cu/Al复合板力学性能的影响。实验结果表明:铸轧复合板界面形成Al_2Cu、AlCu、Cu_9Al_4、AlCu_3四种金属间化合物,经500℃×2 h固溶处理后,界面扩散层厚度增加,形成Al_2Cu、AlCu、Al_2Cu_3、Cu_9Al_4、AlCu_3五种金属间化合物。水冷和空冷界面扩散层产生孔洞,炉冷孔洞基本消失,解释了孔洞形成原因及变化过程,孔洞等缺陷会削弱界面层的结合强度。铸轧复合板界面扩散层厚度小、硬度低;经固溶处理后,界面扩散层厚度和硬度均增加,并随冷却速度的减小,厚度和硬度进一步增加。剥离过程中,铸轧复合板靠近Al基体断裂,而经固溶处理后的复合板断裂在界面扩散层。随冷却速度的下降,裂纹扩展能力减弱,过厚的金属间化合物不利于复合板的结合。     

Zn层添加AZ31/7075合金复合成形工艺及组织与性能研究EI北大核心CSCD

通过在异种材料界面添加厚度为100μm的Zn箔,采用预挤压与孔型轧制复合工艺成功制备出AZ31/7075复合材料,并利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)对复合界面进行表征及显微硬度测试,探究Zn过渡层在挤压复合孔型轧制过程中对产品的影响。结果表明:7075硬质铝合金芯部可细化AZ31镁合金,引入Zn过渡层可减少或者避免镁铝系金属间化合物生成;挤压及变形温升使Mg-Zn互扩散形成的低熔点共晶相熔化,同时加速元素自固相向液相扩散;然而降温冷却使Mg-Zn扩散层易出现不连续裂缝,但后续孔型轧制可显著改善;Mg-Zn扩散层经变形生成的MgZn_(2)金属间化合物具备较高的显微硬度(161HV),但Mg-Zn扩散层变形后厚度则较薄,结合层整体硬度变化不明显。     

Formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed aluminum alloy 1100 sheets

The formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed AA 1100 sheets was investigated. The asymmetrical rolling procedure in this experiment was performed in a rolling mill with different roll velocities (roll velocity ratio of 1.5/1.0). In order to enhance the shear deformation, asymmetrical rolling was performed by a large reduction per pass and without lubrication. Asymmetrical rolling led to the formation of strong shear textures. The evolution of asymmetrically cold rolled textures was analyzed by FEM simulations. After recrystallization annealing, pronounced {111}//ND orientations prevailed in all thickness layers. Intensified shear deformations by asymmetrical rolling also led to the formation of ultra-fine grains after recrystallization annealing.     

Investigation on formability of three-layer joined Al/Cu/Al sheets annealed at different temperature

ABSTRACT

Today, the use of multi-layer sheets has expanded widely in various industries. The determination of the forming limit curve for sheets is essential. In this project, three-layer aluminium1100-copper10100-aluminium1100 sheet was produced using an explosive welding method and cold rolling up to 85% strain. Then to eliminate the rolling microstructure and create the isotropic properties and to investigate the effect of annealing temperature on formability, three-layer sheets were annealed at 350°C, 400°C, and 450°C for one hour. Afterward, the numerical and experimental forming limits for these sheets are obtained at room temperature. ABAQUS finite element software and Freudenthal, Cockcroft, and Brozzo ductile fracture criteria were used in numerical method, and punch stretching test was used in the experimental method.     

铝/钛/铝三层复合板热轧工艺及微观组织研究

钛/铝层状复合材料具有两种材料优异的特性,能够满足一些特殊工程需要。开发了热轧复合技术,成功制备了铝(1100)/钛(TA2)/铝(1100)三层复合板。研究了复合板轧制过程中的关键轧制技术参数(临界压下率和轧制复合工艺条件)。利用光学显微镜和SEM观察了钛/铝复合板及结合界面形貌,分析了不同退火温度对复合板力学性能的影响。基于实验结果,描述了影响复合板质量和有助于提高复合板结合强度的关键工艺过程。     

Proposal of bond criterion for hot roll bonding and its application

The aim of this work was to develop a bond criterion for laminated composites prepared by hot rolling. 7075 Al/AZ31B Mg/7075 Al laminated composites were fabricated by hot rolling at different reduction ratios and temperatures, and the hot rolling process was also simulated by finite element methods (FEM). The FEM results show that two stages existed for an option position of the interface during hot rolling, viz. the bonded interface forming period and the post-bonded period. Bonded interface would be damaged during the latter due to second tensile stress and tear stress (due to the sticking friction between the Al plates and the rollers during the rolling). A bond criterion for laminated composites fabricated by hot rolling was proposed, which includes a strain threshold and a critical bonding strength. The predicted bond results of the 7075 Al/AZ31B Mg/7075 Al laminated composite fabricated by hot rolling from the proposed bond criterion agreed with the experimental data.     

磁屏Cu-Fe-Cu叠层材料的轧制复合

选用电工纯铁与无氧铜两种组元材料, 采用轧制复合工艺制备了Cu-Fe-Cu磁屏叠层材料, 对轧合件进行力学性能分析, 并运用金相显微镜、 扫描电镜、 能谱仪等手段分析复合件界面形貌及复合机制。结果表明: 采用50%热轧压下率可使铜、 铁板有效复合, 轧合件内各叠层厚度尺寸稳定、 叠层间平行度良好, 经简单退火后其叠层间无明显扩散发生, 叠层间抗剪切强度达167 MPa, 此时热轧的主要复合机制为机械啮合。     

Effect of friction,annealing conditions and hardness on the bond strength of Al/Al strips produced by cold roll bonding process

Layered materials have become an increasingly interesting topic in industrial development. Cold roll bonding (CRB) process, as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing process. In this paper, characteristics such as bond strength and threshold deformation of as-received commercial pure aluminum (AA1100) strips prepared by the cold roll bonding process are investigated. Bond strength is evaluated by the peeling test. The main factors evaluated included effects of different annealing time, annealing temperature, hardness, and the effect of friction coefficient on bond strength. It is found that bond strength is enhanced by increasing annealing time, friction coefficient, and annealing temperature but that it is inversely proportional to hardness.     

Bonding strength of Al/Mg/Al alloy tri-metallic laminates fabricated by hot rolling

One of major drawbacks of magnesium alloy is its low corrosion resistance, which can be improved by using an aluminized coating. In this paper, 7075 Al/Mg-12Gd-3Y-0·5Zr/7075 Al laminated composites were produced by a hot roll bonding method. The rolling temperature was determined based on the flow stresses of Mg-12Gd-3Y-0·5Zr magnesium alloy and 7075 Al alloy at elevated temperature. The bonding strength of the laminate composites and their mechanism were studied. The effects of the reduction ratio (single pass), the rolling temperature, and the subsequent annealing on the bonding strength were also investigated. It was observed that the bonding strength increased rapidly with the reduction ratio and slightly with the rolling temperature. The bonding strength increases with the annealing time until the annealing time reaches 2 h and then decreases. The mechanical bond plays a major role in the bonding strength.     

Corrosion study and quantitative measurement of crystallite size of high strength aluminum hybrid composite developed via friction stir processing

This present study is centered on the corrosion behaviors and structural integrity of high strength aluminum-alloy 7075-T651 hybridized with carbonaceous coconut shell ash (CSA) and α+β titanium alloy powder in ratio of 50 : 50, fabricated during friction stir processing (FSP). The study examined the base metal – AA7075-T651 as well as the friction stir processed AA7075-T651 as control experiments. The Processing parameters used were plunge depth of 0.3 mm, travel speed of 20 mm/min, the tilt angle of 3° and rotational speed of 1500 min⁻¹. The corrosion characteristics were examined with the Potentiodynamic Polarization method in 3.5 % NaCl medium while crystalline phases were studied with x-ray diffraction (XRD). Results show that fabricated aluminum hybrid composite (AHC) AA7075-T651/coconut shell ash (CSA)/titanium-alloy has the highest percentage of inhibition performance efficiency (IPE) of 84.81 % resulting to 0.76938 mm/year corrosion rate and 356.51 Ω polarization resistance, whereas inhibition performance efficiency (IPE) for friction stir processed (FSPed) AA7075-T651 was 63.99 % while the base metal – AA7075-T651 was taken as the reference point. It was also revealed that the hybridized coconut shell ash (CSA)/titanium-alloy powder on AA7075-T651 enhanced the structural integrity, producing 38.5 nm crystallite size over friction stir processing (FSP) AA7075-T651 with 41.2 nm and the base metal with 48.7 nm crystallite size.