Effect of forging on the microstructure and texture of a high Nb containing γ-TiAl alloy

The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.

Maximizing precipitation hardening effect enables ultrahigh strength in a coarse-grained Mg-13Gd forging alloy

In this work,a new strategy for achieving ultrahigh strength in the coarse-grained Mg-Gd binary alloy via utilizing recrystallization texture hardening and maximizing precipitation strengthening has been reported.Forging at a much high temperature suppresses dynamic precipitation,enabling the super-saturation of Gd atoms in Mg matrix.This facilitates the formation of fully recrystallized grains with strong texture and induces an exceptionally high precipitation hardening in the following ageing.Therefore,the forged Mg-13Gd sample exhibited extraordinary tensile yield strength(TYS)of∼430 MPa,in which ageing-induced TYS increment exceeds∼210 MPa,as the highest record so far in precipitation-hardened Mg communities.These results provide important theoretical guidance for fabricating the large section and high-strength Mg components for industrial applications.

白汉共居村落共同体的形塑路径——基于云南大理上村的调查

村落共同体是中华民族共同体形成与发展的现实基础,在构建平等团结互助和谐的社会主义民族关系实践中发挥着基础性作用。云南大理上村白汉共居村落共同体的形成与发展,既有赖于共同地域上的相邻关系和族际通婚实现的血统混合,也是共同的历史记忆、宗教信仰、经济交往、文化基础和党的民族政策产生的趋合力与趋同性共同作用的结果,进而形成了超越宗族意识的村落认同,超越民族边界的深度交融,超越文化差异的文化共享,超越个体利益的经济共生等,为村落共同体的形成与发展奠定了坚实的基础。研究发现,村落主体自觉的内部行动逻辑和国家在场的外部制度逻辑合力形塑了村落共同体的中国化路径。

铸牢中华民族共同体意识学科化再探索——从经济共同体到共同体经济学

建立中国自主的中华民族共同体学科体系是铸牢中华民族共同体意识的基础性研究工作,是解决我国民族学研究中存在的被西方民族理论思想和话语体系所左右的问题的关键所在,需要以中华民族共同体史料体系、话语体系和理论体系为基础,从马克思主义基本原理出发,坚持“两个结合”,对中华民族共同体发展实践进行科学分析。历史实践证明,经济力量在中华民族共同体形成过程中起到了重要作用;同时,中华民族共同体的持续发展与壮大,也对经济活动产生重要影响,推动生产力持续进步。可以说,中华民族是靠文化凝聚的,更是依靠经济一体来推动的。共同体经济学是中华民族共同体形成、发展、完善对经济行为与绩效影响的学科。共同体经济学以中华民族共同体的独特性质和经济行为为研究对象,坚持马克思主义历史唯物主义研究方法,研究经济发展与中华民族共同体形成、发展与完善双向互动的机理与实践。

铸牢中华民族共同体意识的政策文本分析

研析当前我国政府部门发布的铸牢中华民族共同体意识政策文本,可为后续各级政府完善相关政策提供借鉴和参考,进一步健全民族工作政策体系。基于政策工具视角,选用Nvivo 12质性分析软件对政府出台的26份铸牢中华民族共同体意识政策文本进行量化分析,探讨现有政策存在的不足。当前铸牢中华民族共同体意识政策文本在政策工具结构、政策任务分布及政策工具与政策任务协同匹配等方面还存在问题,这极大影响了政策效能的发挥。未来相关政策的制定可从优化政策工具结构、平衡政策任务分布以及调适政策工具与政策任务协同匹配三方面着手,增强铸牢中华民族共同体意识政策的合理性。

Homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging

The homogenization on microstructure and mechanical properties of 2A50 aluminum alloy prepared by liquid forging was investigated.Wheel hubs were produced using direct and compound loading.The results show that the microstructure and mechanical properties are inhomogeneous in direct forged samples.The microstructure of the wall is coarser than that of the base,and the mechanical properties are lower and some defects are detected at the wheel corner.Using compound loading,the microstructure and mechanical properties of the wall are improved evidently.With increasing feeding amount,the microstructure and mechanical properties become more homogeneous.The defects disappear when the feeding amount is 4 mm.The forged wheel hubs could obtain fine and homogeneous microstructure with grain size of 20-30 μm,tensile strength of 355 MPa and elongation of 10% when the feeding amount is 10 mm.The microstructure and mechanical properties of liquid forged workpieces could be controlled and homogenized using compound loading.

Microstructure and mechanical properties of isothermal multi-axial forging formed AZ61 Mg alloy

Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical properties were discussed. The results show that the average grain size decreases with increasing the number of MAF passes. The grains are significantly refined at the 1st and 2nd MAF passes, and gradually refined at higher MAF passes. The initial grain size of 148 lam decreases to about 14 gm after 6 MAF passes. The grain refinement occurs mainly by continuous dynamic recrystallization. With increasing the MAF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.

Structure uniformity and limits of grain refinement of high purity aluminum during multi-directional forging process at room temperature

The effect of forging passes on the refinement of high purity aluminum during multi-forging was investigated. The attention was focused on the structure uniformity due to deformation uniformity and the grain refinement limitation with very high strains. The results show that the fine grain zone in the center of sample expands gradually with the increase of forging passes. When the forging passes reach 6, an X-shape fine grain zone is initially formed. With a further increase of the passes, this X-shape zone tends to spread the whole sample. Limitation in the structural refinement is observed with increasing strains during multi-forging process at the room temperature. The grains size in the center is refined to a certain size （110 μm as forging passes reach 12, and there is no further grain refinement in the center with increasing the forging passes to 24. However, the size of the coarse grains near the surface is continuously decreased with increasing the forging passes to 24.

基于响应面法的TC11钛合金振动热摆辗损伤预测及工艺优化

为有效避免TC11钛合金振动热摆辗过程中出现的材料损伤,获得对摆辗件损伤最小的工艺参数,以TC11钛合金圆柱件作为研究对象,建立基于Lemaitre断裂准则的TC11钛合金圆柱件振动热摆辗有限元模型,通过仿真获得TC11钛合金圆柱件振动热摆辗损伤值,以振动热摆辗损伤值为优化目标,采用响应曲面分析法建立基于TC11钛合金圆柱件的振动热摆辗损伤预测模型,将摆辗成形过程中的加热温度、进给速度、振动频率和振动振幅作为影响因素,分析各影响因素对振动热摆辗损伤值的影响,并进行实验验证。结果表明,各因素对摆辗件损伤值影响显著性按降序排列为:进给速度→加热温度→振动振幅→振动频率;通过对响应面损伤模型进行寻优设计,获得振动热摆辗工艺参数的最优组合为:加热温度为906℃,进给速度为4mm/s,振动频率为49.1Hz,振动振幅为0.066mm。

Microstructure and mechanical properties of TC21 titanium alloy by near-isothermal forging

Microstructure and tensile properties of TC21 titanium alloy after near-isothermal forging with different parameters plus solution treatment and aging were investigated. It is found that the residual β matrix, which was strengthened by fine secondary α platelets forming during aging, exists in all the samples; while primary equiaxed α phase, bent lamellar α phase and α plates are simultaneously or individually present in one sample. The strength of alloy increases proportionally with increasing the content of residual β matrix, which is the result of increasing α/β interphase boundary. The plasticity of alloy has a downward trend as the content of residual β matrix increases. This attributes to the increase of fine secondary α platelets, which are cut by dislocations during the deformation. Additionally, coarse α plates with long axis parallel to the maximum resolved shear stress（MRSS） also reduce the plasticity of TC21 alloy.

Influence of forging process on microstructure and mechanical properties of large section Ti-6.5Al-1Mo-1V-2Zr alloy bars

The mechanical properties, microstructure and tensile fracture of Ti-6.5AI-IMo-IV-2Zr large section bars produced by three diffrent forging processes were investigated. The results show that when billet forging and finish forging were conducted by means of fullering at high and low temperature of r-region, respectively; the microstructure of forged bar is coarse Widmanstaten structure; the mechanical properties, especially the reduction of cross-sectional area, are poor, and the room temperature tensile fracture presents a brittle feature. While billet forging was carried out by upset-fullering at high temperature of the r-region, and finish forging was proceeded through fullering at （a＋fl）-region, the microstructure of forged bar was a duplex structure, the bar has better comprehensive mechanical properties, and the room temperature tensile fracture reveals a ductile feature. In order to obtain qualified Ti-6.SAI-IMo-IV-2Zr alloy bar, it is the key that as-cast microstructure should be completely broken during billet forging, and the forging temperature and deformation are also well controlled upon finishing forging.

Numerical simulation and physical analysis for dynamic behaviors of P/M TiAl alloy in hot-packed forging process

The hot forging of large-scale P/M TiAl alloy billet deformation was investigated based on a joint application of Deform-3D-based numerical simulation and physical simulation techniques.The temperature dependence on the thermal and mechanical properties of the billet was considered and the optimum hot working temperature of packed TiAl alloy was 1150-1200 °C.Based on the simulation,the material flow and thermo mechanical field variables,such as stress,strain,and temperature distribution were obtained and the relationships of load—displacement and load—time were figured out.To verify the validity of the simulation results,the experiments were also carried out in a forging plant,and a pancake with diameter of 150 mm was obtained exhibiting a regular shape.

Comparison of microstructures and mechanical properties between forging and rolling processes for commercially pure titanium

In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated in detail using Gleeble-1500 thermal mechanical simulator, universal testing machine and optical microscope （OM）. The compression deformation experimental data of commercially pure titanium （CP-Ti） were mapped to be a T vs lg diagram in which data fall into three distinct regions, i.e., three-stage work hardening, two-stage work hardening and flow softening, which can be separated by border lines at 17.5 and 15.4 for lg Z, where Z represents the Zener-Hollomon parameter. The deformation twin is found to have higher Z-value corresponding to the work hardening region. The differences in microstructures and mechanical properties for two kinds of billets indicate that forged billet consists of deformation twins and some twin intersections, and many twins cross the grain boundaries. However, nearly no twins can be seen in the microstructure of billet formed by rolling under optical microscope （OM）, but there are equiaxed and platelike grains. Tensile tests and Vickers hardness test indicate that yield strength, tensile strength and microhardness of the samples after forging are higher than those after rolling.

Tensile properties and microstructure of Ti14 alloy after semi-solid forging

Tensile properties of a new α＋Ti2Cu alloy after solid forging at 950 °C and semi-solid forging at 1 000 °C and 1 050 °C were investigated over the temperature range of 20-600 °C. The results reveal that high strength and low ductility are obtained in all semi-solid forged alloys. Tensile properties decrease as the semi-solid forging temperature increases, and cleavage fractures are observed after semi-solid forging at 1 050 °C. The variations in tensile properties are attributed to the coarse microstructures obtained in the semi-solid alloys. It is found that the elevated semi-solid temperatures lead to more liquid precipitates along the prior grain boundaries, which increases the peritectic precipitation and formation of Ti2Cu precipitation zones during re-solidification. Recrystallization heat treatment leads to fine microstructure of semi-solid forged alloys, resulting in improvement of tensile properties.

铸牢中华民族共同体意识理论大众化:内涵、机理与路径

铸牢中华民族共同体意识理论大众化既是科学理论作为改造世界思想武器的必然要求,也是实现中华民族伟大复兴的内在需要。铸牢中华民族共同体意识理论的大众化蕴含群众化、通俗化、生活化的内涵,具有“人民至上”的人本性、“日用不觉”的生活性、“生动呈现”的通俗性、“增同存异”的包容性、“因人制宜”的分众性等内涵特征,其生成机理体现在:认知形塑的理论说服、情感激发的利益认同、行为调适的行动自觉。当前,实现铸牢中华民族共同体意识理论大众化,应着力推进理论建设大众化、利益融入生活化、教育浸润分众化、传播手段创新化、支撑机制长效化,为中华民族伟大复兴凝聚磅礴伟力。

基于Simufact Forging高铁轮毂锻压成形工艺仿真

基于Simufact Forging有限元分析软件对高铁轮毂成形过程进行了仿真,着重研究了轮毂辗扩过程中的等效塑性应变、等效应力及材料流动。结果表明:高铁轮毂在辗扩过程中材料整体变形基本一致,可以获得较好的力学性能;随着锻压成形不断的进行,轮毂内圈塑性应变逐渐变大;成形过程中整个轮毂应力分布较为均匀。

轴类锻件失效分析及其对策

轴类锻件广泛应用于特种设备行业和机械行业中,轴类锻件需要自身的刚性,也需要承受在传递过程中产生的扭矩,再加上生产过程经过热成形,锻件内部的缺陷存在敏感性,极易发生失效。首先,详细介绍了两大容易失效的轴类锻件:离心风机轴和曲轴。其次,通过发现的失效模式进行定位解剖、试验分析,发现钢锭中存在球状氧化物与硫化物,夹杂物在锻压时因破坏钢的连续性而产生裂纹,锻件由于心部白点而报废,是由锻后热处理工艺不当所致。最后,通过分析对原材料控制、锻后热处理工艺、使用中的加固保护三方面来控制此失效模式。

锻态42CrMoA钢热变形软化行为及微观组织演变研究

以锻态42CrMoA钢的热压缩实验为基础,利用光学显微镜(OM)、扫描电镜(SEM)和电子背散射衍射(EBSD)技术对微观组织进行观察和分析。结果表明:当动态再结晶(DRX)完全时,真应力-真应变曲线有明显的峰值应力和软化特征;当DRX不完全时,真应力-真应变曲线没有明显的峰值应力和软化特征。结合EBSD数据可知,母相奥氏体亚结构影响马氏体相变。变形温度越低,应变速率越高,快速冷却后微观组织的中间取向差角晶界(MMAGBs)的比例和平均局部应变越大。由母相奥氏体晶粒和SEM下的微观组织可知,快速冷却后得到的马氏体组织分布与母相奥氏体分布有关,当母相奥氏体晶粒分布均匀时,马氏体组织分布有序和均匀;当母相奥氏体晶粒分布不均匀时,马氏体组织分布无序和不均匀。

CiteSpace软件在铸牢中华民族共同体意识研究文献计量分析中的应用

文章以中国知网2017—2024年公开发表的有关铸牢中华民族共同体意识的1458篇文章为例进行了计量分析研究。数据结果显示:(1)从发文量来看,国内关于“铸牢中华民族共同体意识”的研究自2017年开始呈现显著增长趋势,尤其是在2020年后达到高峰,反映了国家政策的推动和学术界对这一议题的高度关注;(2)关键词共现分析显示,国内研究集中在“中华民族共同体意识”“文化认同”“民族团结”“中华优秀传统文化”等核心概念上,说明通过文化、教育等手段促进民族团结与共同体意识的形成是国内研究重点;(3)在机构合作方面,研究主要集中在民族类高校和研究机构,如中央民族大学、新疆大学和中国社会科学院,这些机构在相关领域具有明显的学术优势与合作趋势;(4)在学者合作层面,研究合作较为分散,缺乏明确的核心学者主导的合作群体,在此领域仍有较大的合作与发展空间;(5)整体来看,国内关于铸牢中华民族共同体意识的研究在理论和应用层面都有显著的进展,未来在国际化合作、文化共融和经济发展等领域仍有进一步拓展的潜力。

铸牢中华民族共同体意识融入高校思政课研究

铸牢中华民族共同体意识是新时代党的民族工作的核心主线,铸牢大学生中华民族共同体意识是高等教育的时代使命和重要任务。思政课作为落实立德树人根本任务的关键课程,将铸牢中华民族共同体意识融入其中既是高校思政课教学的题中应有之义,也是培育大学生中华民族共同体意识的现实需要。为了推动高校思政课有形有感有效开展铸牢中华民族共同体意识教育,需要在思政课的教学实践中挖掘整合教学内容、改革创新教学方法以及提升思政课教师素养等。