激光快速成形GH4169合金显微组织与力学性能

利用GH4169合金粉末进行激光快速成形实验,制备出GH4169合金块状试样,并进行固溶时效热处理。利用扫描电镜(SEM)及能谱分析(EDS)等方法分别对激光成形沉积态及固溶时效态试样进行显微组织及元素偏析分析,并测试显微硬度、室温及高温拉伸性能。结果表明:沉积态微观组织为生长方向不一的细长柱状树枝晶,组织细小致密;经过固溶时效热处理后晶粒得到细化,晶粒内部仍保留枝晶亚结构;固溶时效态试样较沉积态显微硬度及抗拉强度大幅提高,塑性有所下降,但整体优于锻件技术标准。断口形貌表现为韧性穿晶断裂方式。     

GH4169隔板汽封弹簧片断裂分析

通过化学成分分析、硬度测试、金相检验、断口分析、腐蚀产物及受力情况分析等,对某电厂机组的隔板汽封GH4169弹簧片发生断裂的原因进行了研究。结果表明:弹簧片断裂的性质为应力腐蚀开裂,主要原因为弹簧片运行环境中有大量的腐蚀性介质。     

GH4169合金双锥实验组织模拟与验证研究

建立了综合考虑变形参数、温升、冷速等交互作用的GH4169合金热变形组织演化预测模型及计算流程,同时,采用外廓尺寸约为200mm×160mm的双锥形试样为研究对象,在980,1020,1060,1120℃温度下进行锻造的组织演变模拟计算和验证实验。结果表明:采用的双锥形试样能够较好地符合零件锻造的实际状态,建立的组织预测模型是合理可行的,能够实现合金锻造过程的组织模拟。     

GH4169合金锻造混晶组织的均匀细化机制与工艺

目的 消除GH4169合金锻造混晶组织,获得高品质GH4169合金锻件的制备工艺.方法 对变形后锻件进行后续的热处理退火,探明均匀细化锻造混晶组织的热处理工艺方法与机制.首先,设计并实施不同的单级退火工艺及双级退火工艺.随后,统计不同热处理退火工艺下锻造混晶组织的平均晶粒尺寸.最后,分析不同热处理退火工艺下混晶组织的细...     

激光立体成形GH4169高温合金γ″相的高温粗化行为

采用激光立体成形技术制备GH4169高温合金块体,对其在720~780℃温度区间进行不同保温时间的双级时效处理,采用微观测试分析方法对高温短时时效处理后γ″相的形态、尺寸变化及粗化动力学行为进行研究。结果表明:激光立体成形GH4169合金在不同保温时间双级时效条件下,γ″相形态基本为圆盘形;和保温时间相比,时效温度对γ″相的影响更为显著;γ″相的粗化规律符合Lifshitz-Slyozov-Wagner(LSW)理论,计算获得γ″的粗化激活能Q=281.85kJ/mol,较锻造GH4169合金的γ″粗化激活能略高,表明激光立体成形GH4169合金的组织稳定性优于锻态。     

模拟海洋环境下GH4169合金电化学行为

GH4169合金是一种高温合金,具有优越的耐腐蚀特性,为探究合金在海洋装备上的应用,本课题研究了其在高盐度海洋环境中的电化学行为。利用光学显微镜、扫描电镜和能谱分析研究了GH4169合金的微观结构,利用电化学工作站研究了GH4169合金在2.0 g/ml、2.5 g/ml、3.0 g/ml、3.5 g/ml NaCl溶液中的电化学行为。实验结果表明：GH4169合金经1000℃×1h、水淬,以及780℃×3h固溶处理后微观组织主要为奥氏体γ相,等轴晶粒,晶粒中存在细小弥散的第二相颗粒（γ′相、γ′′相）;随Na Cl溶液浓度的增加,GH4169合金的耐腐蚀性能逐渐降低、自腐蚀电位逐渐变负、自腐蚀电流密度逐渐增大,其中3.5 g/ml NaCl溶液中分别为-0.251 V和9.552e-8A;抗腐蚀性能的降低主要是由于海洋环境中Cl-对金属表面钝化层的破坏导致的。     

GH4169合金的低温冲击试验

对GH4169高温合金边缘和中心部位进行了低温冲击试验,比较晶粒大小对合金冲击功的影响,进一步进行室温冲击试验,比较室温冲击和低温冲击冲击功的大小。同时还对径锻试样和热连轧试样低温冲击所需要的冲击功进行对比,并用SEM观察了冲击断口的表面。结果表明:晶粒越细小,所用的冲击功越大;低温冲击和室温冲击所用的冲击功几乎一样;热连轧试样低温韧性要远远好于径锻试样,冲击端口为韧窝断口。     

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。     

高温合金GH4169铣削力试验

高温合金是材料加工中典型的难加工材料,在加工过程中,铣削力大,刀具破损严重,给加工生产造成很大影响。本次试验主要针对高温合金GH4169的铣削力进行研究,对正交试验所得数据进行线性回归分析,得到了适用于本次试验设备条件的铣削力经验公式;对试验结果进行极差分析,结果表明:各向铣削力随切深和进给量的增加而增大,随切削速度的增加而减小,并且在铣削参数组合为v=400m/min,ap=0.9mm,fz=0.05mm/z时,各向铣削力取得最小值。     

GH4169合金楔横轧加工过程中动态再结晶及织构演变

为研究GH4169合金楔横轧加工过程中动态再结晶及织构演变规律,采用金相显微镜(OM)和电子背散射衍射(EBSD)对30%,50%两种断面收缩率下GH4169合金楔横轧件表层与心部的微观组织、晶体取向及织构进行分析。结果表明:GH4169合金楔横轧加工过程中,随着动态再结晶的发生,晶体取向逐渐变得随机化分布;轧制表层大角度晶界数量较轧件心部多,轧件表层织构强度变化不大,心部织构强度明显增强;经过楔横轧变形后织构发生转动,原始态织构类型为{001}〈110〉,{111}〈110〉,{111}〈011〉,轧制后主要织构类型为{001}〈010〉,{112}〈110〉,{110}〈111〉,{110}〈112〉;GH4169合金楔横轧件动态再结晶及织构演变规律是由楔横轧特殊变形特点决定的。     

A finite element model for thermomechanical analysis of sheet metal forming

A thermal model based on explicit time integration is developed and implemented into the explicit finite element code DYNA3D to model simultaneous forming and quenching of thin‐walled structures. A staggered approach is used for coupling the thermal and mechanical analysis, wherein each analysis is performed with different time step sizes. The implementation includes a thermal shell element with linear temperature approximation in the plane and quadratic in the thickness direction, and contact heat transfer. The material behaviour is described by a temperature‐dependent elastic–plastic model with a non‐linear isotropic hardening law. Transformation plasticity is included in the model. Examples are presented to validate and evaluate the proposed model. The model is evaluated by comparison with a one‐sided forming and quenching experiment. Copyright © 2004 John Wiley & Sons, Ltd.     

Efficient implicit finite element analysis of sheet forming processes

The computation time for implicit finite element analyses tends to increase disproportionally with increasing problem size. This is due to the repeated solution of linear sets of equations, if direct solvers are used. By using iterative linear equation solvers the total analysis time can be reduced for large systems. For plate or shell element models, however, the condition of the matrix is so ill that iterative solvers do not reach the huge time‐savings that are realized with solid elements. By introducing inertial effects into the implicit finite element code the condition number can be improved and iterative solvers perform much better. An additional advantage is that the inertial effects stabilize the Newton–Raphson iterations. This also applies to quasi‐static processes, for which the inertial effects finally do not affect the results. The presented method can readily be implemented in existing implicit finite element codes. Industrial size deep drawing simulations are executed to investigate the performance of the recommended strategy. It is concluded that the computation time is decreased by a factor of 5 to 10. Copyright © 2003 John Wiley & Sons, Ltd.     

Dynamic recrystallization behavior of GH4169G alloy during hot compressive deformation

The microstructure evolutions and nucleation mechanisms of GH4169 G alloy were studied by optical microscope, electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). The hot compression tests were performed different imposed reductions in the range of true strain from 0.12 to 1.2 at the temperatures of 930 ℃-1050 ℃ with strain rates of 0.01 s⁻¹-1 s⁻¹. It is found that cumulative and local misorientation increase firstly and then decrease when the strain is increased due to the progress of dynamic recrystallization (DRX). The low angle boundaries (LAGBs) rapidly develop to high angle boundaries (HAGBs) at relatively high deformation temperature or the low strain rate. There are three DRX mechanisms observed for GH4169 G alloy during hot deformation. Discontinuous dynamic recrystallization (DDRX) as the dominant mechanism for GH4169 G alloy is characterized by typical necklace structures and bulged-original boundaries. Besides, different deformation bands with dislocation cells formed in deformed matrix at low temperature and large strain, which indicates that continuous dynamic recrystallization (CDRX) contributed to the DRX process. The twin boundaries lost their coherent characteristics and provide sites for nucleation, which also accelerates the nucleation of DRX.     

GH4169合金细晶棒材的连轧工艺及其组织与性能

介绍了最新引进的我国第一套高合金钢连轧生产线及其所生产的GH4169合金φ20~φ55mm热轧细晶棒材的组织与性能。与传统的横列式轧机轧制的同规格棒材相比,该连轧工艺更易于获得晶粒均匀、适量δ相合理分布的细晶棒材;在所研究的规格范围内,晶粒度可稳定控制在10级左右,且工艺更稳定可控。因而,其轧棒具有更优良稳定的综合性能。同时产品尺寸精度和成材率均有较大幅度的提高。     

新型熔炼工艺下GH4169合金的凝固组织控制研究

为探求新型熔炼工艺(三联)下GH4169合金大型重熔锭组织调控、元素偏析改善的方法,研究了熔速对氩气保护电渣重熔GH4169合金重熔锭枝晶间距、Laves相的尺寸及分布和显微疏松的影响,定量分析了熔速对组织与成分偏析的影响规律.研究发现:随着熔速的增加,GH4169合金重熔锭边缘处的枝晶间距基本保持不变;中心处二次枝晶间距呈增大趋势.边缘和中心处的疏松尺寸随熔速增加变化平缓,R/2处先增大后减小.心部的Laves相比例较高且随着熔速增加呈上升趋势,而R/2处趋势相反;重熔锭不同部位的偏析区比例随熔速无明显变化.枝晶间距越小,越有利于减轻偏析.     

A finite element analysis of thermal relaxation of residual stress in laser shock processing Ni-based alloy GH4169

The residual stress induced by laser shock processing and the thermal relaxation behaviors of residual stress in Ni-based alloy GH4169 were investigated by means of three-dimensional nonlinear finite element analysis. To study the effect of different given exposure time and different temperatures on residual stress in laser shock processing Ni-based alloy GH4169, Johnson–Cook material model was used in order to account for the nonlinear constitutive behavior. The influence of heating temperature and exposure time on the stress thermal relaxation was studied. It was concluded that stress relaxation mainly occured during the initial period of exposure, and the degree of relaxation increased as the temperature risen. The results would provide a theoretical basis for controlling the laser shock processing and guiding subsequent experiments.     

大口径直缝焊管O成形过程的有限元分析

采用有限元分析方法,研究了焊管UOE成形工艺O成形过程模具载荷、板料变形模式和曲率分布变化,揭示了板料O成形过程变形的机理.结果表明,O成形过程是一个悬弧分段细分弯曲的过程,板料横截面形状曲率峰由单一峰向多峰演变,曲率峰峰间距离均匀.载荷在成形过程产生相应的阶段性交化,各段位移载荷曲线具有相似性,并且载荷随悬弧的细分明显增加.O成形过程分为4个阶段:U形口合扰、直边弯曲、悬弧二次弯曲和悬弧多次弯曲过程.