6061铝扁锭铸造防通裂技术研究

结合铝扁锭生产实际,以6061合金特性及铸造工艺为分析重点,研究了6061合金铝扁锭产生通裂缺陷的原因,并针对性的提出了技术措施,预防6061合金铝扁锭通裂缺陷的产生.     

反向挤压时工艺条件对粗晶环的影响

通过对反向挤压6061合金材料时的合金成分、均匀化制度、挤压温度及挤压速度等工艺因素分析入手,总结评述了6061合金粗晶环形成的机理,提出了合理的工艺技术参数,保证了制品的粗晶环在用户要求的范围之内。     

6061合金的热处理特性

探讨了6061合金的热处理特性和不同热处理制度下合金的金相组织和性能。     

连续流变挤压与热处理对6061合金线材组织性能的影响

为探索铝材短流程制备工艺,以及制备高性能的铝合金材料,采用连续流变挤压成形技术制备了直径为9.5 mm的6061合金线材,研究了实验工艺条件及热处理工艺对连续流变挤压成形制得的6061铝合金线材的微观组织和力学性能的影响。结果表明：连续流变挤压制备直径为9.5 mm的6061合金线材最佳浇注温度为720℃,最佳挤压速度为0.157 m·s^-1;当时效温度由160℃升至175℃时,6061合金线材的抗拉强度由270.14 MPa升至274.11 MPa,断后伸长率由18.02%降至16.32%;时效温度继续升至190℃时,抗拉强度由274.11 MPa降至265.12 MPa,断后伸长率由16.32%降至13.16%;连续流变挤压制备的6061合金在535℃固溶3 h,175℃时效4 h后,与时效温度160和190℃相比抗拉强度最高,为274.11 MPa,断后伸长率为16.32%,与一般工业用铝及铝合金挤压型材标准下T6态6061合金线材相比,抗拉强度提高5.43%,断后伸长率提高104%。     

6061气滑铸造圆铸锭表面裂纹及预防措施

分析了6061铝合金圆铸锭表面裂纹产生的原因,通过控制Fe/过剩Si比,优化6061合金成分中Cu、Cr含量,从而降低了裂纹倾向,提高了圆铸锭成型性。     

6082铝合金型材生产工艺探讨

介绍了6082合金的成分、性能、生产工艺及其特点，通过与6063和6061合金比较，说明6082合金具有优良的挤压性能。     

提高6061铝合金塑性生产工艺技术研究

对硬盘用6061铝合金型材损伤开裂样品进行原因分析,从合金成分优化和热处理工艺调整两个方面入手,提高6061铝合金塑性,确保工件在后续机加工和热处理过程中能充分延展而不至于损伤开裂,解决了6061铝合金型材机加工过程中损伤开裂问题,降低工件制造过程质量损失和成本。     

美铝研制MagnaForce新型汽车轮毂合金

美国铝业公司称研制出一种新型汽车轮毂合金，并将在明年年初推出采用此合金生产的首款卡车车轮。此合金被称为MagnaForce，平均强度比美铝6061合金高16．5％。     

6061铝型材双级时效工艺的研究

利用拉伸性能测试、电导率测试、晶间腐蚀试验等手段,研究了双级时效工艺对6061合金组织与性能的影响。结果表明,6061铝型材双级时效后组织和性能良好,满足标准要求,各项性能与峰值时效175℃×8 h相当。其中,170℃×1.5 h+210℃×1.5 h制度下6061合金的综合力学性能优于峰值时效。随着预时效温度的升高,电导率呈上升趋势,180℃×1.5 h+210℃×1.5 h处理后电导率最高,腐蚀形貌由晶间腐蚀变为点蚀,腐蚀深度明显变浅。6061铝型材最优双级时效工艺为170℃×1.5 h+210℃×1.5 h,该制度能有效缩短生产周期,减少能耗,且使型材的力学性能、抗晶间腐蚀性能均优于峰值时效的性能。     

预时效对6061、6005A合金板材力学性能的影响

通过对不同预时效制度下的6061和6005A合金板材进行力学性能、延伸率、加工硬化率、电导率、组织检测等试验,研究了预时效对汽车板材成形性能和烤漆硬化性能的影响。结果表明,180℃×5 min的预时效制度可改善6061-T4和6005A-T4合金板材成形性。热处理状态为T4P+T6的6061和6005A的强度均明显高于T4+T6态。这说明预时效可以解决铝合金板材因自然时效引起的人工时效强化效果不佳的问题,有利于汽车板材的冲压成形和烤漆硬化能力的提高。     

Grain boundary cracking

A chronological summary is given of the various types of grain boundary fracture found in metals. In each case, there is an impurity that adsorbs at the new (fracture) surface being formed. For the case of Fe-P alloys, a quantitative argument can show that adsorption of phosphorous on the free surface greatly reduces the barrier to void nucleation compared to that in the absence of phosphorous. The same or larger reduction would appear for any other element, which adsorbs more strongly than phosphorous and displaces it at the surface. Such an argument is shown to explain a great many cases of dimpled grain boundary fracture in strong alloys undergoing creep or hydrogen attack. The reduction in surface energy can also lead to a smooth grain boundary fracture (no void nucleation), in which diffusion of solute to the new surface limits crack growth. Numerous examples of this are also discussed. Dr. Shewmon studied metallurgical engineering at the University of Illinois (B.S. 1952) and Carnegie Institute of Technology (Ph.D. 1955). His first job was at the Westinghouse Research Laboratory, where he studied thermal diffusion in alloys and surface diffusion. In 1958, he moved to the Carnegie Institute of Technology, where he served as a professor until 1967. The text “Diffusion in Solids” was published in 1963. An NSF Fellowship was used to study at Professor C. Wagner’s Max Planck Institute (Goettingen, Germany) in 1963. From 1968 to 1973, he was at Argonne National Laboratory, serving successively as Associate Director of the Metallurgy Division, Associate Director of the EBR-2 Project, and Director of the Materials Science Division. The text “Transformations in Metals” was published in 1969. Materials behavior in fast breeder reactors was the main theme of his work during this period. He was the director of the Division of Materials Research at the National Science Foundation from 1973 to 1975. From 1975 to 1993, he was Professor at Ohio State University in the Department of Metallurgical Engineering (later Materials Science and Engineering), serving as Chairman from 1975 to 1983. Research interests during this period were hard particle erosion and hydrogen-induced cracking of steel (“hydrogen attack”). From 1977 to 1993 he served on the Advisory Committee on Reactor Safety for the United States Nuclear Regulations Committee, serving as Chair for three of those years. Dr. Shewmon was elected to the National Academy of Engineering in 1979 and has been awarded the standing of Fellow in TMS, ASM, ANS, and AAAS. He has received several outstanding paper awards (Noble-AIME, Raymond—TMS, Mathewson—TMS, and Howe—ASM). He received the Distinguished Alumnus Award of the University of Illinois in 1981 and a Humboldt Foundation Senior Scientist Prize in 1984. The Edward DeMille Campbell Memorial Lecture was established in 1926 as an annual lecture in memory of and in recognition of the outstanding scientific contributions to the metallurgical profession by a distinguished educator who was blind for all but two years of his professional life. It recognizes demonstrated ability in metallurgical science and engineering. The Institute of Metals Lecture was established in 1921, at which time the Institute of Metals Division was the only professional division within the American Institute of Mining and Metallurgical Engineers. It has been given annually since 1922 by distinguished people from this country and abroad. Beginning in 1973 and thereafter, the person selected to deliver the lecture will be known as the “Institute of Metals Division Lecturer and R.F. Mehl Medalist” for that year.     

Grain boundary cracking

A chronological summary is given of the various types of grain boundary fracture found in metals. In each case, there is an impurity that adsorbs at the new (fracture) surface being formed. For the case of Fe-P alloys, a quantitative argument can show that adsorption of phosphorous on the free surface greatly reduces the barrier to void nucleation compared to that in the absence of phosphorous. The same or larger reduction would appear for any other element, which adsorbs more strongly than phosphorous and displaces it at the surface. Such an argument is shown to explain a great many cases of dimpled grain boundary fracture in strong alloys undergoing creep or hydrogen attack. The reduction in surface energy can also lead to a smooth grain boundary fracture (no void nucleation), in which diffusion of solute to the new surface limits crack growth. Numerous examples of this are also discussed. Dr. Shewmon studied metallurgical engineering at the University of Illinois (B.S. 1952) and Carnegie Institute of Technology (Ph.D. 1955). His first job was at the Westinghouse Research Laboratory, where he studied thermal diffusion in alloys and surface diffusion. In 1958, he moved to the Carnegie Institute of Technology, where he served as a professor until 1967. The text “Diffusion in Solids” was published in 1963. An NSF Fellowship was used to study at Professor C. Wagner’s Max Planck Institute (Goettingen, Germany) in 1963. From 1968 to 1973, he was at Argonne National Laboratory, serving successively as Associate Director of the Metallurgy Division, Associate Director of the EBR-2 Project, and Director of the Materials Science Division. The text “Transformations in Metals” was published in 1969. Materials behavior in fast breeder reactors was the main theme of his work during this period. He was the director of the Division of Materials Research at the National Science Foundation from 1973 to 1975. From 1975 to 1993, he was Professor at Ohio State University in the Department of Metallurgical Engineering (later Materials Science and Engineering), serving as Chairman from 1975 to 1983. Research interests during this period were hard particle erosion and hydrogen-induced cracking of steel (“hydrogen attack”). From 1977 to 1993 he served on the Advisory Committee on Reactor Safety for the United States Nuclear Regulations Committee, serving as Chair for three of those years. Dr. Shewmon was elected to the National Academy of Engineering in 1979 and has been awarded the standing of Fellow in TMS, ASM, ANS, and AAAS. He has received several outstanding paper awards (Noble-AIME, Raymond—TMS, Mathewson—TMS, and Howe—ASM). He received the Distinguished Alumnus Award of the University of Illinois in 1981 and a Humboldt Foundation Senior Scientist Prize in 1984. The Edward DeMille Campbell Memorial Lecture was established in 1926 as an annual lecture in memory of and in recognition of the outstanding scientific contributions to the metallurgical profession by a distinguished educator who was blind for all but two years of his professional life. It recognizes demonstrated ability in metallurgical science and engineering.     

Effect of Grain Boundaries and Grain Orientation on Structure and Properties

The evolution of deformation microstructures in metals follows a universal pattern of grain subdivision. However, the structure in the grain boundary region may be different from that in the grain interior, although a characteristic region cannot be identified for polycrystals with medium to high stacking fault energy. In the grain interior, the dislocation structure is predominantly composed of almost planar boundaries (geometrically necessary boundaries) and cell boundaries (incidental dislocation boundaries) forming a cell block structure. For grains with grain sizes reaching down to about 4 μm deformed in tension and by rolling, a clear correlation has been established between the characteristics of the deformation structure and the orientation of the grain in which it evolves. A similar correlation is observed for single crystals of different orientations. Such correlations form the basis for a general analysis of active slip systems and for modeling of the flow stress and flow stress anisotropy of polycrystalline samples.     

Grain Cluster Microstructure and Grain Boundary Character Distribution in Alloy 690

The effects of thermal-mechanical processing (TMP) on microstructure evolution during recrystallization and grain boundary character distribution (GBCD) in aged Alloy 690 were investigated by the electron backscatter diffraction (EBSD) technique and optical microscopy. The original grain boundaries of the deformed microstructure did not play an important role in the manipulation of the proportion of the Σ3 ⁿ (n = 1, 2, 3…) type boundaries. Instead, the grain cluster formed by multiple twinning starting from a single nucleus during recrystallization was the key microstructural feature affecting the GBCD. All of the grains in this kind of cluster had Σ3 ⁿ mutual misorientations regardless of whether they were adjacent. A large grain cluster containing 91 grains was found in the sample after a small-strain (5 pct) and a high-temperature (1100 °C) recrystallization anneal, and twin relationships up to the ninth generation (Σ3⁹) were found in this cluster. The ratio of cluster size over grain size (including all types of boundaries as defining individual grains) dictated the proportion of Σ3 ⁿ boundaries.     

CSP线高强度细晶热轧板的混晶和变形拉长晶粒的成因

对CSP线生产的高强度细晶热轧板的混晶和拉长晶粒的成因进行了分析,用有限元分析法模拟了热轧带钢的变形区的剪切应变场和温度场,用Gleeble实际模拟轧制工艺和组织变化。结果表明,CSP线高强度细晶热轧板的混晶和拉长晶粒的形成与钢板轧制过程中的钢板表层的变形场及温度场有关,也与先析出铁素体的形成后再进行轧制变形的过程有关;采用奥氏体深过冷轧制,既保证得到细晶粒又避免产生混晶和被变形拉长的晶粒。新的CSP轧制工艺,成功地生产了高强度高成形性细晶粒C-Mn热轧板。     

Linear Relationship Between dV/dt and Grain Volume During Grain Growth

Metallurgical and Materials Transactions A - The volumetric growth rate of individual grains has been found empirically to be directly proportional to their individual volume, dV/dt = β(V0...     

Grain Selection During Casting Ni-Base, Single-Crystal Superalloys with Spiral Grain Selector

The behavior of grain selection in a spiral grain selector during investment casting of a Ni-base, single-crystal (SX) superalloy, DD3, has been investigated by electron backscattered diffraction (EBSD) techniques and optical microscopy. The results indicated that the main function of starter block is to optimize the crystal orientation. During the process of grain selection in spiral passage, the grain near the inner wall of spiral passage was usually selected as the final single crystal. It was found that the dendrites near the inner wall could develop new tertiary dendritic arms that paralleled the primary dendrites from the secondary dendritic arms to overgrow the dendrites far away from the inner wall. The crystal orientation that was examined by X-ray diffraction revealed that (1) the crystal orientation did not change obviously with increasing spiral thickness or angle and (2) the crystal orientation could be optimized by increasing the withdrawal rate and ceramic mold temperature. The influence of pouring temperature on crystal orientation was also discussed.     

Phenomenology of Abnormal Grain Growth in Systems with Nonuniform Grain Boundary Mobility

We have investigated the potential for nonuniform grain boundary mobility to act as a persistence mechanism for abnormal grain growth (AGG) using Monte Carlo Potts model simulations. The model system consists of a single initially large candidate grain embedded in a matrix of equiaxed grains, corresponding to the abnormal growth regime before impingement occurs. We assign a mobility advantage to grain boundaries between the candidate grain and a randomly selected subset of the matrix grains. We observe AGG in systems with physically reasonable fractions of fast boundaries; the probability of abnormal growth increases as the density of fast boundaries increases. This abnormal growth occurs by a series of fast, localized growth events that counteract the tendency of abnormally large grains to grow more slowly than the surrounding matrix grains. Resulting abnormal grains are morphologically similar to experimentally observed abnormal grains.