高温合金叶片精密成形技术研究

采用挤杆、镦头制坯、预锻、终锻成形的工艺方法,实现了叶片单面余量(0.5±0.2)mm的精密成形.通过变形温度、变形程度对锻件组织性能影响的研究,确定了最佳热工艺参数;通过热处理工艺试验、锻件的表面状态及硬度的检测,确定了热处理工艺参数和冷却方式.锻件的首批试制结果表明,试制出的叶片锻件,金相组织和机械性能均符合锻件技术条件要求,与国外原件的组织状态基本一致.通过了振动疲劳2×107循环考核和发动机的长期试车考核.     

GH4169合金精锻叶片腐蚀条带组织的成因分析及预防措施

目的 分析精锻工艺成形的GH4169合金压气机转子叶片出现腐蚀条带组织的原因,以制定相应的预防措施。方法 对精锻叶片用GH4169合金开展锻造热过程模拟试验,采用电镜观察其显微组织,以判断叶片锻件异常组织与原材料组织的关联。采用数值模拟方法对锻造工艺参数,尤其是锻造变形量进行分析与验证,找出锻造工艺方案的不足之处。结果 当原材料存在δ相偏聚时,容易导致叶身及榫头部位出现纵向腐蚀条带组织;当叶片锻造变形设计不合理,盆弧侧、背弧侧的预锻件与终锻件的变形体积比超出1.1~1.4时,会导致榫头部位出现金属流动异常的现象,进而产生应变剪切带、导致叶片榫头部位出现异常组织。结论 在叶片精密锻造生产前要确保原材料组织均匀,不能出现δ相偏聚,同时采用数值模拟方法来合理控制锻造各阶段的变形量与应变场,确保叶片预锻件与终锻件的变形体积比合理、金属变形均匀,这样才能保证叶片叶身和榫头部位不出现腐蚀条带组织。     

TC17合金β锻管形件近等温挤压成形工艺研究

目的 研究β锻管形件近等温挤压成形工艺对TC17合金显微组织和力学性能的影响。方法 采用DEFORM–3D软件模拟分析了实心挤压和空心挤压成形TC17合金管形件的变形特征,模拟分析2种挤压方式成形下TC17合金管形件在固溶处理过程中的冷却效果。对空心挤压成形的锻件进行金相组织表征和力学性能测试。结果 模拟结果表明,相较于实心挤压的方式,空心挤压方案整体应变较大、变形均匀、材料利用率高、固溶冷速较快且均匀性较好。试验结果表明,空心挤压成形的锻件质量良好,整体的宏观/微观组织均匀,室温拉伸性能和断裂韧性一致性好,且满足相关指标要求。结论 空心挤压方案满足该管形锻件研制要求,研究结果可以为类似管形件制备提供依据。     

TC8合金转子叶片锻造工艺研究

为研制一项TC8合金转子叶片,并达到提高锻造生产效率、降低生产成本的目的,进行了锻造工艺性试验、工艺参数试验,研究了TC8合金锻造工艺适应性以及加热温度、变形程度对低倍组织、显微组织及力学性能的影响.结果表明,TC8合金十分适合锻造工艺,采用较低的锻造加热温度能够获得初生α相含量更高的等轴组织,变形程度在40%以内所获得的组织均匀性较好.在此基础上,依据TC8合金转子叶片单榫头、小尺寸的结构特点,采用了高效的挤压制坯+终锻成形工艺,通过叶片锻造成形试验,试制出了具有均匀且状态理想的金相组织、良好表面质量的TC8合金转子叶片锻件,表明了所制定的叶片成形工艺及工艺参数合理可行.     

Ti150合金离心叶轮锻件工艺优化

目的 解决Ti150合金离心叶轮锻件低倍组织不均匀和锻件力学性能离散性较大的问题。方法 通过对锻件进行金相组织分析,再利用EBSD、DEFORM等工具分析锻件成形时应变分布及组织特点,探索低倍组织不均匀和锻件力学性能离散性较大的原因及解决方法。通过对棒材进行六方拔长、倒棱、平头和滚圆等处理,实现从圆棒到六方形再到圆棒的变形过程(改锻),使棒材各部位的变形均匀,达到消除微织构的目的。结果 对棒材进行反复镦拔(改锻),可有效消除棒材中的微织构并改善低倍组织的不均匀,是控制锻件力学性能离散性的重要措施。结论 中间坯组织的均匀性是影响低倍组织不均匀和锻件力学性能离散性的主要因素,通过对棒材进行改锻,Ti150合金离心叶轮锻件的组织及力学性能优异,满足相应的技术要求。     

轿车左转向节锻造工艺的模拟研究

针对轿车左转向节是带细杆的叉形件,同时兼有叉类、盘类和杆类零件的外形特点,分析其成形的工艺特点,进行工艺计算,确定工艺方案为头部镦粗—杆部拔长—预锻—终锻.利用有限元软件对成形过程进行模拟,得到飞边均匀的终锻成形件,并对模拟得到的应力场、应变场和载荷等信息进行分析.结果表明,各工序变形较为均匀,应力变化正常,没有出现破坏现象;最终锻件完全充满终锻模膛,没有出现缺料、折叠等缺陷,而且飞边均匀.     

阀盖模锻成形模拟分析与试验验证

目的 某型号不锈钢阀盖是一种典型的长肋条内空型零件,在模锻制造过程中,阀盖锻件容易出现不同程度的折叠和裂纹缺陷,亟需改进成形工艺以提升合格率.方法 采用有限元方法分析坯料在制坯/预锻/终锻全流程的金属流动规律和终锻件成形质量,得到最佳成形工艺方案.结果 方坯在后续成形时易产生横向流动,且局部充型不饱满;六边型坯在预成形和终成形时流动均匀、横向流动小,且有效抑制了充型不饱满缺陷;预制坯在过渡区长度过短,产生了折叠缺陷;采用六边形坯料和增加过渡区长度可以获得无缺陷阀体锻件.结论 采用新工艺制备的阀盖锻件合格率达到了100％,通过全流程工艺分析,能够得到金属流线规律,进而优化模锻成形方案,改善成形质量.     

大型薄壁壳类件等温精密锻造成形研究

为了克服某雷达用关键大型薄壁壳类件传统加工方法中存在的材料利用率低,生产效率低,零件强度低等缺陷,提出采用等温精密模锻工艺成形,设计了预、终两步成形工艺方案.有限元模拟结果表明:预锻能够合理分配坯料体积,使得终锻充填均匀;终锻成形栽荷大,采用分流思想使成形载荷下降了20.4%.     

航空接头锻件等温锻压成形工艺

为了提高航空锻件的综合性能,通过等温锻压工艺研究了航空接头锻件的成形过程,采用Deform3D有限元软件对高筋薄壁铝合金航空接头锻件的锻压成形工艺进行了仿真研究,在实验室油压机上开展了缩比(1∶5)锻件的成形工艺实验.研究结果表明:在坯料与模具温度均为450℃、成形速度为0.1 mm/s的等温模锻工艺下,材料变形抗力比常规热模锻降低70%,材料在模腔中的流动性提高,锻件充填完好,锻件变形均匀,应力集中降低;等温锻造工艺可使锻件获得流线顺畅、晶粒细小、力学性能优良的纤维组织,避免了热模锻易出现的涡流、折叠、穿流、充填不满等锻造缺陷;仿真与实验结果吻合,为航空接头锻件锻压成形工艺的制订提供了依据.     

叶片精锻过程刚粘塑性有限元模拟

生产叶片通常采用精锻工艺,以便提高质量和降低成本。高的尺寸精度和组织性能的要求,使工艺和模具设计复杂化。了解成形过程中的金属流动、应力应变和载荷分布规律,才便于综合考虑各工艺参数的影响;特别是预锻件的大小和形状以及它在终锻模上的初始位     

变形程度对复杂铝合金锻件组织性能的影响

为确定最佳成形工艺,通过拉伸试验、金相观察、TEM和SEM观察等方法,研究了不同制坯变形程度对7A09铝合金复杂筋板类锻件组织性能的影响.实验结果表明:随着制坯变形量的增加,所得锻件的强度和硬度升高,而塑性和抗应力腐蚀性能下降;随制坯变形程度的增加,热变形时储存的变形能增多,可以得到更加细小的晶粒,而且储存变形能的增多有利于固溶程度的提高和强化相的析出,因而可以提高锻件的强度和硬度.晶粒细化使晶界面积增加是造成电导率降低的主要因素.因此,在设计成形工艺时,应根据零件按上述规律来调整变形程度.     

Study on isothermal precision forging process of rare earth intensifying magnesium alloy

A three dimensional rigid-plastic finite element model is established to simulate the isothermal precision forging process of the magnesium alloy bracket based on DEFORM 3D in order to analyze the material flow rule and determine the forging process scheme. Some problems such as underfilling and too large forging pressure are predicted and resolved through optimizing the shapes of the billet successfully. Compared to the initial microstructure, the isothermal-forged microstructure of the alloy refines obviously and amounts of secondary phases precipitate on the matrix during isothermal forging process. In subsequent ageing process, large quantities of secondary phases precipitate from α-Mg matrix with increasing ageing time. The optimal comprehensive mechanical properties of the alloy have been obtained after aged at 473 K, 63 h with the ultimate tensile strength, tensile yield strength and elongation 380 MPa, 243 MPa and 4.07% respectively, which shows good potential for application of isothermal forging process of rare earth intensifying magnesium alloy.     

Development of microstructure in isothermally forged Nimonic alloy AP1

Abstract

The development of microstructure in the nickel alloy Nimonic AP1 owing to isothermal forging and subsequent heat treatment has been investigated. The microstructure initially consisted of coarse grains, which corresponded to the prior powder particles; these were surrounded by a coarse dispersion of γ′. On deformation, the volume fraction of material with a coarse γ′ dispersion increased, and this was associated with localised grain refinement following heat treatment. High volume fractions of this structural type gave some increase in tensile strength but reduced stress rupture life and increased fatigue crack growth rates. High temperature compression tests were used to develop a constitutive equation for the material which was then applied, via a finite element model, to simulate the isothermal forging process. The relationships between deformation and structural development, the modelling, and the mechanical properties are discussed. The approach is potentially useful for the design of forging operations for turbine disc production.     

Effect of texture on high temperature deformation behavior at high strain rates in a Mg–3Al–1Zn alloy

A microstructure optimization design method of the forging process is proposed. The optimization goal is a small grain size and a homogeneous grain distribution of the forgings. The optimization object is the preforming die shape. The microstructure optimization code is developed using the micro-genetic algorithm and the finite element method. The two forming steps including the preforming process and the final forging process of H-shape forgings are analyzed using the self-developed code. The optimization results show that small grain size and homogeneous grain distribution can be achieved by controlling the shape of the preforming die. Samples of the same size as in the optimization are preformed and then forged to the desired H-shape forgings under the same deformation conditions as in the optimization. Micrographs in the symmetry section of samples show that the grain sizes of the forgings almost coincide with the optimization results.     

Microstructure evolution of different loading zones during TA15 alloy multi-cycle isothermal local forging

The microstructure evolution of the TA15 Ti-alloy in different loading zones under two kinds of multi-cycle isothermal local forging (multi-cycle local near-β forging and multi-cycle conventional forging combined with near-β heat treatment) was investigated and the mechanical properties predicted. Under the first processing route, a microstructure with small grain size was obtained with a significant difference in morphology and composition between the first and second loading zones. An equiaxial microstructure with larger size and more α-phase was obtained in the first loading zone. In the second loading zone when cooled by water after multiple forging cycles and a tri-modal microstructure (finely interlaced and disordered lamellar α, transformed β matrix, and a few equiaxed α) was obtained. The second loading zone possesses excellent room and high temperature mechanical properties. Under the second processing route, the relatively large bimodal microstructures in both loading zones are almost identical. When treated using a vacuum annealing furnace after forging, a coarse clustered lamellar secondary α-phase appeared, which has poor mechanical properties.     

锻造技术在轻金属中的应用

随着社会的发展,材料的研发与设计向着轻量化、高强化发展,轻金属在航空航天以及汽车工业上表现出了良好的应用潜力,同时也对材料加工成形方式,如锻造技术等提出了更高的要求。简要介绍了金属锻造技术,如自由锻造、等温锻造和多向锻造技术,分析了锻造技术在轻量化金属如钛合金、铝合金以及镁合金上的应用,经过锻造处理后,金属的微观组织及力学性能得到了提升,锻件质量得到了改善。还介绍了数值模拟在锻造过程中模具设计及工艺优化上的研究及应用现状,同时对金属锻造未来向精密化、复杂化以及智能化的发展趋势进行了分析与展望。     

Mg-13Gd-4Y-0. 5Zr 镁合金多向锻造组织和性能研究

由于锻坯的组织和力学性能对其后续成形过程具有重要的影响,研究锻坯的组织和力学性能均匀性具有重要实用价值。利用实验的方法,对比研究了Mg-13Gd-4Y-0.5Zr合金材料的三次多向锻造后的组织演变和力学性能的不同。实验结果表明:随着锻造次数的增加,动态再结晶明显,Mg-13Gd-4Y-0.5Zr镁合金晶粒逐渐细化,析出相逐渐增多;并且,随着锻造次数的增多,硬度变化呈小幅波动的趋势,且第一次多向锻造后的硬度最大。