Recrystallized microstructural evolution of UFG copper prepared by asymmetrical accumulative rolling-bonding process

Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.

Enhanced mechanical properties of lamellar Cu/Al composites processed via high-temperature accumulative roll bonding

Cu/Al multilayers were produced by high-temperature accumulative roll bonding(ARB)methods up to three passes.To achieve a high bonding strength,prior to ARB processing,the Cu and Al sheets were heated to 350,400,450 and 500 ℃,respectively.The mechanical properties were evaluated by tensile tests.The microstructure was examined by optical microscopy and scanning electron microscopy equipped with energy dispersive spectrometry.The ultimate tensile stress,the grain size and the thickness of diffusion layer of lamellar composites increase with rolling temperature.When the rolling temperature is 400 ℃,the laminates show the highest ductility,but the yield stress is the lowest.As the rolling temperature further increases,both the yield stress and the ultimate tensile stress increase and the ductility decreases slightly.The mechanical properties of lamellar composites processed by low and high temperature ARB are determined by grain size and the thickness of diffusion layer,respectively.

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.

Improving mechanical properties of Mg-Al-Zn alloy sheets through accumulative roll-bonding

Experiments were conducted to evaluate the potential for improving the mechanical properties of Mg-Al-Zn alloy at room temperature by subjecting to accumulative roll-bonding(ARB).It is shown that ARB may be applied successfully to Mg-Al-Zn alloy at elevated temperatures and it leads to grain refinement and significant improvements in the ductility.The strength of the as-rolled Mg-Al-Zn alloy sheet after ARB processing is slightly decreased and basal texture is weakened by ARB processing.

Microstructural development and its effects on mechanical properties of Al/Cu laminated composite

The microstructural development and its effect on the mechanical properties of Al/Cu laminated composite produced by asymmetrical roll bonding and annealing were studied. The composite characterizations were conducted by transmission electron microscope（TEM）, scanning electron microscope（SEM）, peeling tests and tensile tests. It is found that the ultra-fine grained laminated composites with tight bonding interface are prepared by the roll bonding technique. The annealing prompts the atomic diffusion in the interface between dissimilar matrixes, and even causes the formation of intermetallic compounds. The interfacial bonding strength increases to the maximum value owing to the interfacial solution strengthening at 300 °C annealing, but sharply decreases by the damage effect of intermetallic compounds at elevated temperatures. The composites obtain high tensile strength due to the Al crystallization grains and Cu twins at 300 °C. At 350 °C annealing, however, the composites get high elongation by the interfacial interlayer with submicron thickness.

累积叠轧Al/Cu复合板界面反应层核-壳结构形成机制

采用累积叠轧(ARB)结合多次退火处理制备了Al/Cu复合板,重点研究了Al/Cu界面反应层核-壳结构形成机制.结果表明:Al/Cu界面反应层的形成主要依赖于退火过程中铜原子在界面处的扩散,反应产物包括Al 2Cu、AlCu、Al 4Cu 9.轧制变形致使反应层破碎并在基体中均匀分布,轧后退火处理导致新的反应层不断形成.最终经多次叠轧及退火处理,原始铜板材全部转变为椭球状具有核-壳结构的Al/Cu金属间化合物颗粒.8道次复合板抗拉强度最高,达到176.8 MPa,是退火态1060抗拉强度的1.74倍;0道次复合板延伸率较好,主要是Al/Cu界面分层后铝层均匀塑性变形,应力缓慢释放所致.

累积叠轧制备的Cu/Al/Cu复合板材金属间化合物层演变及其对力学性能影响研究

目的研究在不同温度条件下Cu(商业纯铜)/Al(AA1060)/Cu复合板材累积叠轧过程中界面金属间化合物层对材料性能的强化规律。方法在不同温度条件下(350~500℃)累积叠轧制备Cu/Al/Cu层状复合板材,深入分析其界面金属间化合物层形状、元素分布及其对力学性能的影响规律。结果金属化合物层的厚度随着轧制温度的升高逐渐增加,且随着轧制温度的不同,形貌呈现很大的差异。当轧制温度为350℃和400℃时,金属间化合物相对平整。轧制温度升高到450℃时,金属间化合物层呈现锯齿形,使该工艺条件下加工的材料同时具有较好的强度(273 MPa)和塑性(4.06%)。结论制备Cu/Al/Cu层状复合材料过程中,通过优化轧制温度这一重要轧制参数,能实现强度和塑性的综合提高。

累积叠轧焊制备的Cu-Nb层状复合材料织构演变

层状复合材料的高强度、高硬度、高热机械稳定性以及抗辐照损伤等优良的热力学性能都与材料中的异相界面及其织构密不可分。研究层状复合材料的异相界面结构及织构的演化是目前的研究热点之一。本文利用累积叠轧焊技术制备了单层厚度在微米到亚微米的Cu-Nb层状复合材料。利用电子背散射衍射(EBSD)技术分析了Cu和Nb的织构随轧制道次的演化规律,为更好的理解和设计异相界面,发展高力学性能材料提供了实验依据。

Microstructure and mechanical properties of Al/Cu/Mg laminated composite sheets produced by the ARB proces

In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding(ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.

Improvement of the matrix and the interface quality of a Cu/Al composite by the MARB process

The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.

衬板叠轧Mg/Al复合板基体组织演变优化强塑性机制

Mg/Al复合板兼并了镁合金的轻质性及铝合金的可塑性、耐腐蚀等性能,显著增强了其综合性能,但制造周期长、工艺要求高等不足制约了异质复合板成形技术的快速发展。为此,本文提出一种衬板辅助叠轧成形新方法。研究结果表明:3ARB时Mg/Al复合板抗拉强度可达235 MPa,伸长率为14.7%,镁板中出现明显的韧窝,呈韧性断裂特征,综合性能为最佳。由于此时Mg板基面滑移与非基面滑移同时开动,促进了动态再结晶的生成,此时Mg板再结晶比例为77.21%。随着累积叠轧的进行,大角度晶界增加和晶粒细化明显,原始晶粒已经基本破碎细化成等轴晶,Mg、Al基体硬度波动逐渐减小,复合板内部结构逐渐趋于稳定。本研究可为高性能异质复合板成形制造提供了一种新思路。

Microstructures and Mechanical Properties of Al/Mg Alloy Multilayered Composites Produced by Accumulative Roll Bonding

Al/Mg alloy multilayered composites were produced successfully at the lower temperature（280 C） by accumulative roll bonding（ARB） processing technique.The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy.Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites.It is found that Vickers hardness,bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass.Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load.Strengthening and fracture mechanisms of the composite are analyzed.

Influence of the Accumulative Roll Bonding Process Severity on the Microstructure and Superplastic Behaviour of 7075 Al Alloy

The 7075 Al alloy was processed by accumulative roll bonding （ARB） at 350 ℃ using 2：1, 3：1 and 4：1 thickness reductions per pass （Rp） up to 8, 6 and 3 passes, respectively. Microstructural examinations of the processed samples revealed that ARB leads to a microstructure composed of equiaxed crystallites with a mean size generally lower than 500 nm. It was found that, due to both the stored energy through- out the processing and the particle pinning effect, the alloy is affected by discontinuous recrystallisation during the inter-pass heating stages, the precise microstructural evolution being dependent on Rp. Me- chanical testing of the ARBed samples revealed that the main active deformation mechanism in the ARBed samples in the temperature range from 250 to 350 ℃ at intermediate and high strain rates is grain bound- ary sliding, the superplastic properties being determined by both the microstructure after ARB and its thermal stability.

累积叠轧道次对AZ31镁合金板微观组织和力学性能的影响

开展400℃轧制温度下的累积叠轧试验,并利用光学显微镜、拉伸试验机、显微硬度计、X射线衍射仪、扫描电镜对不同累积叠轧道次板材的微观组织和力学性能进行表征,研究累积叠轧道次对AZ31镁合金板材晶粒尺寸、基面织构、力学性能的影响。结果表明:累积叠轧工艺的晶粒细化主要发生在前3道次,随后的循环道次中晶粒不再明显细化,甚至略微长大。第3道次的综合力学性能最佳。剪切带的存在虽缓解了应力集中,提高了塑性,弱化了基面织构,但该处也易形成裂纹,加速板材的断裂,使伸长率急剧下降。基面织构强度随着轧制道次的增加呈先减弱后增强的趋势。

累积叠轧技术的研究现状与展望

对采用累积叠轧工艺制备超细晶组织的技术进行详细的综述,介绍了累积叠轧技术的原理、ARB材料的组织与力学性能特征,并对ARB变形过程中的剪切变形、晶粒细化机制和强化机制进行分析。采用ARB技术可以制备大尺寸的超细晶组织材料,其室温抗拉强度通常比粗晶材料的高2～4倍。ARB材料的强化源于晶粒细化、位错强化、在大变形轧制时形成的稳定基面织构、表面的氧化膜以及内生原有夹杂物在强烈塑性变形情况下的破碎与弥散分布。分析了ARB技术的优越性,对其在制备超细晶材料领域的应用进行了展望。

累积复合轧制法制备层状超细晶材料的研究现状

综述了累积复合轧制(ARB)的工艺原理及累积复合轧制材料晶粒的细化机理、力学性能、组织与织构演变特征,分析了目前研究中存在的问题,指出累积复合轧制是制备大块体超细晶金属材料最有效的强烈塑性加工工艺。

大变形异步叠轧技术制备高强高导超细晶铜材研究

采用大变形异步叠轧并结合退火处理制备出了超细晶铜材。讨论了大变形异步叠轧的搓轧区、界面以及变形量等技术特征,测试了超细晶铜材的组织及性能。结果表明,搓轧区的存在促进了界面的复合和晶粒的细化;纯铜经过室温六道次AARB变形(累积真应变4.01)后,包含有许多亚结构,之后再经过220℃/35min退火处理,亚结构消失,获得了平均晶粒大小为200nm、抗拉强度、屈服强度分别为424.5MPa,323.1MPa、电导率为76.3 MS.m-1的高强高导超细晶铜;晶界面积的增加提高了超细晶铜的显微硬度;超细晶粒的变形不均匀性小和应力集中小,使得超细晶铜的塑性好、强度高;超细晶铜材的塑性变形机制受晶界行为控制。

深度塑性变形法的研究现状和前景

深度塑性变形加工与传统变形方法相比具有很大的优点,可得到超细晶金属和合金,其微观组织结构和性能也发生很大的变化。通过介绍累积轧合法、等通道角挤压法和高压扭转法等3种目前最主要的深度塑性变形方法,分析了深度塑性变形法的特点和现状,并对其未来进行了展望。

叠轧深变形制备超细晶Al-1%Mg合金

叠轧深变形技术具有商业化生产超细晶材料的潜力. 在叠轧等效应变为4 0的条件下得到了平均晶粒为0 5μm的Al 1%Mg合金超细晶组织; 在热作用下合金组织由亚稳定态向稳定态转化, 在退火温度高于200℃时晶粒变化明显, 在200℃以下, 晶粒生长比较缓慢; 随着退火温度的升高, 合金组织发生静态回复与静态再结晶过程, 静态回复是通过位错的滑移和攀移而进行的, 再结晶是通过亚晶合并生长而进行的.

预退火时间对累积叠轧超细晶铜室温拉伸断裂行为的影响

对采用严重塑性变形方法制备的超细晶金属进行退火处理,是提高该类材料综合性能的常见方法。为保证晶粒不发生明显长大,对累积叠轧(ARB)方法制备的超细晶纯铜在100℃(低于再结晶温度)时进行退火处理,研究保温时间对ARB超细晶铜室温拉伸断裂行为的影响以及样品的微观结构、力学行为、断口形貌,并对其力学性能和断裂机制进行分析。结果表明:当退火时间为30 min时,ARB超细晶铜的屈服强度和抗拉强度都达到退火态的极大值。断口的大量韧窝表明:退火时间30 min时的材料具有一定的塑性变形能力,断裂机制以韧性断裂为主,因此,退火时间为30 min时,ARB超细晶铜的强度与塑性达到最佳匹配。