热等静压对单晶高温合金组织和持久性能的影响

在高温度梯度真空定向凝固炉中,采用螺旋选晶法制备了单晶高温合金,再在1180℃/150 MPa条件下对其进行热等静压,然后进行标准热处理,研究了热等静压对单晶高温合金组织和不同条件下持久性能的影响。结果表明,合金热等静压后,铸态组织的共晶含量基本保持不变,γ′相尺寸增加,立方化程度增加,γ基体通道变宽。热处理组织的γ′相尺寸稍有减小,立方化程度增加。在760℃/800 MPa和980℃/250 MPa条件下,合金的持久寿命增加;而在1100℃/140 MPa条件下,粒状碳化物的析出导致持久寿命没有提高,与未热等静压的合金持平。     

Effect of Argon-Induced Porosity on Mechanical Properties of Powder Metallurgy Titanium Alloy Components using Hot Isostatic Pressing

This work reported the Ar-induced porosity in powder metallurgy Ti-5Al-2.5Sn alloy prepared by hot isostatic pressing(HIPing).The obtained microstructures of powder compacts were studied through optical and scanning electron micro-scopes,X-ray tomography,and the mechanical properties evaluated through tensile and impact tests.The results showed that the Ar-induced porosity is related to the hollow powder with gas bubble and the Ar leakage of sealed container during the powder densification.The hollow powder with gas bubble shows no obvious effects on mechanical properties of as-HIPed powder compacts.The Ar content decreases with the increasing shrinkage of encapsulated powder.0.7％ Ar-induced porosity degrades the impact toughness,but no reductions of tensile properties were obtained.Ar content test is an effective method to detect the powder compacts with Ar concentration.     

TiAl合金粉末热等静压技术研究进展

TiAl合金具有高熔点、低密度、高比强度,良好的高温抗氧化、抗蠕变等性能,在航空航天及汽车发动机等领域应用前景广阔。粉末热等静压技术能够实现复杂形状TiAl合金零件的一体化成形,并且获得的零件晶粒尺寸细小、成分均匀、力学性能优异。本文介绍了TiAl合金雾化粉末制备原理与粉末热等静压致密化技术,评述了TiAl合金雾化粉末及经过热等静压和热处理后组织性能的研究进展,分析了TiAl合金粉末热等静压技术当前存在的一些问题,并对该技术的未来发展提出展望。     

Powder Size Influence on Tensile Properties and Porosity for PM Ti_2AlNb Alloy Prepared by Hot Isostatic Pressing

Pre-alloyed powder of Ti_2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti_2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti_2AlNb alloy were tested. Results show that mean grain size of PM Ti_2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti_2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores( 50 μm) are observed in PM Ti_2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti_2AlNb alloy, powder with an average size(～ 100 μm) is suggested.     

热等静压冷速对SLM成形K536合金力学性能的影响

采用激光选区熔化工艺制备K536航空发动机零件,研究了不同冷速的热等静压HIP工艺对制件组织及力学性能的影响。结果表明,激光选区熔化K536高温合金制件经HIP处理后,制件内部产生完全再结晶,金相组织为奥氏体基体及晶内和晶界碳化物,合金强度降低、塑性上升,数据分散性下降;随HIP冷速的增大,组织中晶界碳化物减少,晶内出现少量颗粒状碳化物,有效提升了合金在815℃的高温屈服强度。     

IN783低膨胀高温合金的热变形行为和组织演变

本文通过热压缩试验研究了IN783低膨胀高温合金在温度为1000-1120℃、应变速率为0.01-10 S_-1^条件下的热变形行为,并采用电子背散射衍射( EBSD)研究了不同变形参数下合金的组织演变规律。结果表明,IN783合金的峰值应力随着温度的升高和应变速率的减小而显著降低。基于 Arrhenius 方程和 Zener-Hollomon 参数模型,建立了该合金的本构方程,可以很好地描述热变形过程中峰值应力与变形温度和应变速率的关系。基于动态材料模型绘制了IN783合金的热加工图,并根据热加工图和微观组织分析,确定IN783镍基高温合金的失稳区为：变形温度1095℃-1120℃、应变速率10_0.39814^-10₁ ^S_-1^。此外,在高温低速率条件下(1060-1120℃、0.01 S_-1⁾,尽管合金具有较高的功率耗散值,但会出现混晶组织和晶粒粗化现象,也不适合作为IN783合金的热加工区间。     

粉末粒度对一种新型镍基粉末高温合金热变形行为的影响

利用EBSD、SEM、OM、热模拟试验机等对比研究了不同粉末粒度制备的一种新型镍基粉末高温合金(WZA3)在不同热压缩变形条件下的变形行为和组织差异性。结果表明：相比细粉制备的HIP-01样品而言,粗粉枝晶组织明显,成分偏析严重,其制备的HIP-02样品中残余粗大γ′较多。低温(1050、1080℃)高应变速率(1、0.1s-1)时,HIP-01样品峰值应力值高于HIP-02。热压缩后HIP-01样品边缘开裂情况较HIP-02严重,HIP-01样品保留了大部分原始热等静压组织,裂纹优先在粉末原始颗粒边界(priorparticleboundary,PPB)处产生,HIP-02样品边缘出现了部分再结晶组织。在1080℃/0.001 s^-1时,HIP-02样品峰值应力较HIP-01低约30 MPa,HIP-02样品热压缩过程再结晶现象明显,再结晶晶粒均匀,HIP-01样品出现项链晶组织,再结晶不充分。粗大γ′有利于促进1050和1080℃时HIP-02样品的再结晶。高温(1150℃)、低应变速率(0.001、0.01s^-1)时,γ′全部溶解进基体...     

热等静压成形Ti6Al4V制件的石墨控形精度与Ni耐磨涂层性能的研究

热等静压粉末近净成形技术在航空航天发动机关键零部件制造上有其独特的优势,但采用传统不锈钢或碳钢为控形型芯材料时,往往会造成制件内部变形大、控形不精准,且此类零部件成形后还需后续的表面处理,大大增加了该零部件的加工生产周期。基于此,提出了一种热等静压成形复杂结构同时完成功能层在线制备的成形方法。该方法选用石墨为控形型芯材料,热等静压前在石墨表面沉积一层耐磨涂层,使热等静压过程中预涂层原位扩散到正在成形的制件表面,实现复杂结构与功能涂层一体化成形。以Ni作为预涂层材料、Ti6Al4V为粉末成形材料,研究了石墨的控形效果及致密体成形后表面Ni涂层的耐磨性能,验证了该方法的可行性。     

Using a novel technique to shape a refractory castable by Cold Isostatic Pressing and a study of the effect of pressure on the hydration reaction of high-alumina cement

Calcium aluminate cements are the most hydraulically setting cements used for refractory castables. The anhydrous phases of this type of cements incorporate CA, CA₂ and traces of C₁₂A₇ and alpha-alumina where C and A stand for CaO and Al₂O₃, respectively. Hydration starts to form the hexagonal crystals of CAH₁₀ (H denoting H₂O) and C₂AH₈, which convert to the cubic crystals of C₃AH₆ and AH₃ by the passage of hydration time. In this work, Al₂O₃−C (alumina-graphite) castables were shaped by cold isostatic pressing at 100 to 400 bars (≈100 to 400 Kg/cm²). Hydration and conversion reactions were studied using the Ratio of Slopes Method for quantitative XRD studies after 3 and 28 days. The results showed that by increasing the pressure, the kinetics of the hydration reaction will increase and higher strengths can be obtained, which supports the idea of forming this graphite containing castable by Cold Isostatic Pressing (CIP) in industrial applications for special refractories.     

Combining Aluminum Heat Treat with Hot Isostatic Pressing： A Comparison of Structure, Properties, and Processing Routes for a Cast Al-Si-Mg Alloy

Bodycote researchers have successfully demonstrated that a T6 heat treatment can be integrated with Densal^R, a proprietary, aluminum specific, hot isostatic pressing (HIP) process. In this combined operation, at least a portion of the solution heat treatment is conducted at elevated pressure. During development, two issues, adiabatic cooling during depressurization and a possible variation in the kinetics of homogenization resulting from conducting the solution heat treat at elevated pressure were perceived as factors which could alter the heat treat response from that seen in conventional processing.This paper reviews the results of experiments performed to Al-Si-Mg (A356.0) castings subjected to both combined and conventional processing routes. Results indicate that the combined HIP and heat treat process is an efficient means of achieving a microstructure characteristic of a conventionally T6 processed material while eliminating porosity within the casting. Further, the fatigue life of an A356.0 casting processed using the combined cycle can be improved by more than an order of magnitude over the as-cast and T6 treated component.     

Combining Aluminum Heat Treat with Hot Isostatic Pressing: A Comparison of Structure, Properties, and Processing Routes for a Cast AI-Si-Mg Alloy

WHEN CAST ALUMINUM COMPONENTS are usedin applications which require high strength,a T6heattreatment is often employed to bring the castings to amaximum strength condition.This heat treatmentconsists of three steps:a solution heat treatment,duringwhich the large deleterious phases which have formedduring solidification are dissolved into a solid solution;quenching,to produce a supersaturated solid solution;and an aging treatment which yields a microstructureconsisting of a fine array …     

K418合金车用增压涡轮熔模铸造过程数值模拟及热裂预测

针对K418合金车用增压涡轮铸件极易出现热裂缺陷的现象,结合工厂实际生产条件,应用ProCAST铸造模拟软件对K418合金车用增压涡轮的充型过程、凝固时间以及凝固过程中的温度场、缩孔缩松形成过程和应力场进行了模拟。基于分析的结果,预测了涡轮中存在的热裂缺陷,模拟结果与实际生产情况吻合良好。分析结果表明,涡轮叶梢处容易产生热裂纹的主要原因是凝固过程中热应力不均引起的。     

消失模铸造专用热胶棒与普通胶棒的差别及应用

选取实型(消失模)铸造专用热胶棒与市售普通热胶棒,通过多项性能的研究、比较后发现,市售普通热胶棒不适用于实型(消失模)铸造工艺;专用实型(消失模)铸造热胶棒的研究、生产已经成熟,并市场化;配合热胶枪使用热胶棒,其快捷、灵活的操作方式很受消失模铸造工作者欢迎。     

Electropolishing and electrolytic etching of Ni-based HIP consolidated aerospace forms: a comparison between deep eutectic solvents and aqueous electrolytes

It is reported in this study that the deep eutectic solvent (DES), (Ethylene glycol)₂(Choline chloride), (2Eg:ChCl) is an effective medium in the electrolytic removal of the Fe-rich layer from Ni-based hot isostatic press (HIP) consolidation and that it is capable of sustaining etching at higher rates and at higher current efficiencies than a comparable aqueous electrolyte formulated from methane sulphonic acid/glycolic acid (MSA/GA). At high etch rates, the surface finish is not as good using 2Eg:ChCl, but high etch rates, current efficiency and excellent surface finish can be obtained from a 90%/10% hybrid mixture of 2Eg:ChCl MSA/GA electrolytes. This study has set out to compare the electropolishing and bulk electrolytic etching of HIP-formed bodies fabricated from RR1000 Ni-based superalloys in aqueous methane sulphonic acid/glycolic acid (MSA/GA) electrolyte and in DES-type ionic liquids. It is shown that the HIP alloy can be effectively removed under mild conditions using DES electrolytes that are of low toxicity, environmentally sustainable, relatively low cost and without the use of strong acids or chemical etchants.     

Hot Deformation Behavior and Processing Maps of a High Al-low Si Transformation-Induced Plasticity Steel: Microstructural Evolution and Flow Stress Behavior

Hot deformation behavior of a high Al-low Si transformation-induced plasticity(TRIP) steel was studied by an MMS-300 thermo-simulation machine at the temperature range of 1050–1200℃ and strain rate range of 0.01–10s~(-1). The constitutive equations of the TRIP steel were established at high temperature by fitting the strain factor with a sixth-order polynomial. The instability during hot rolling was discussed using processing maps. The results reveal that two types of flow stress curves(dynamic recrystallization and dynamic recovery) were observed during the hot compression of the high Al-low Si TRIP steel. Flow stress decreased with increasing deformation temperature and decreasing strain rate. The predicted flow stress of experimental TRIP steel is in agreement with the experimental values with an average absolute relative error of 4.49% and a coefficient of determination of 0.9952. According to the obtained processing maps, the TRIP steel exhibits a better workability at strain rate of 0.1s~(-1) and deformation temperature of 1200℃ as compared to other deformation conditions.