Re-recognition of the Effects of Phosphorus and Boron on the γ’’ and γ’ Phases in IN718 Alloy

The effects of P and B on the matrix strength and precipitations of γ’ and γ’’ phases in the grain interior were re-recognized in this study. The combination addition of P and B markedly accelerated the precipitations of γ’ and γ’’ phases and strengthened the matrix of IN718 alloy when air-cooled from high temperature, while made no difference when waterquenched from high temperature. The effect of single addition of P on the precipitations of γ’’ and γ’ phases was the same with that of the combination addition of P and B, while the single addition of B had no effect on the precipitations of the two phases. Therefore, it was P rather than B which accelerated the precipitations of γ’ and γ’’ phases. P could take part in the precipitations of γ’ and γ’’ phases, which was revealed by electrochemical extraction and quantitative analysis of chemical composition. It also revealed that P atoms were dissolved in the c matrix to a relatively high degree at the temperature that γ’ and γ’’ phases began to precipitate, and consequently the precipitations of γ’ and γ’’ phases were accelerated. The first-principle calculation indicated that P decreased the formation enthalpies of γ’ and γ’’ phases when it occupied the Ni lattice sites in the two phases, which explained the effect of P on the γ’ and γ’’ phases.     

热处理对Inconel718合金组织及力学性能的影响

针对Inconel 718合金的不同用途,分析研究了4种常用热处理工艺对Inconel 718合金组织和力学性能的影响。结果表明:固溶温度超过1020℃时,奥氏体晶粒显著长大。合金中主要析出相有MC、δ、γ’和γ″相。δ相沿晶界分布,1025℃固溶时呈颗粒状少量析出;950℃固溶时呈块状大量析出;直接时效时呈网状不连续分布。同时,δ相对合金的晶粒度影响较大,且其析出数量和形态决定了合金的韧塑性,γ″、γ’相的析出量和尺寸与晶粒尺寸决定了合金的强度变化。     

一种改型Inconel718合金的组织与性能的研究

采用化学相分析、显微组织分析和显微硬度测试等方法,研究了一种改型镍基高温合金718A在标准热处理状态的显微组织和力学性能。试验结果表明,原型718合金和改型718A合金的主要析出相皆为γ″、γ′、δ、MC相。在标准热处理状态下,改型718A合金中强化相γ′和γ″的量较原型718合金明显增多,而对于组织稳定性不利的8相的析出量则较718合金少。此外,改型718A合金的显微硬度与原型合金相比有了明显的提高,因此具有广阔的应用前景。     

The Effect of δ Phase on the Mechanical Properties of an Inconel 718 Superalloy

The relationship between the δ phase content and the mechanical properties of Inconel 718 superalloy is still uncertain in the scientific literature. This study investigated the effects of the amount of δ phase and of the grain size on the mechanical properties of an aged γ-matrix with γ′ and γ″ precipitates. The material in as-received condition in the form of a forged bar was solution-treated in different conditions and aged according to UNS7718 standard. The microstructures were characterized using optical, scanning, and transmission electron microscopy. Hardness and tensile tests were also conducted. After solution treatment, γ′ and γ″ phases are dissolved and δ phase volume fraction is reduced to a minimum amount only observed by TEM, resulting in an increase of the grain size and a decrease of hardness and strength. After aging, the precipitation of γ′ and γ″ occurs and the amount of δ phase increases. The volume fraction of δ phase varying from 0.30 to 1.38% and the grain size varying from ASTM 7 to 5 do not have a significant effect on the tensile properties and hardness.     

Microstructure and Mechanical Properties of Laser Welded Joints of DZ125L and IN718 Nickel Base Superalloys

The microstructure and mechanical properties of the laser welded joint of DZ125L and IN718 nickel base superalloys were investigated. The results show that the fusion zone (FZ) mainly consists of fine dendrite structure with fine γ′, Laves phases and MC carbides inhomogeneously distributed. The high welding temperature induces the partial dissolution of γ′ in the heat-affected zone (HAZ) of DZ125L and liquation of grain boundaries in both of the HAZs. After post-weld heat treatment (PWHT), fine γ″ and γ′ phases precipitate in the FZ, IN718 HAZ and IN718 base metal (BM), and fine γ′ precipitate in the γ channel of the HAZ and BM of DZ125L. With tensile testing, the joints after PWHT show higher strengths than that of the weaker DZ125L alloy. Plastic deformation mainly concentrates in the weaker DZ125L and the joint finally fails in the DZ125L BM.     

热处理对激光增材制造IN718合金组织及析出相演变的影响

研究了经过固溶+双时效(SA)、均匀化+双时效(HA)、均匀化+固溶+双时效(HSA)3种热处理后IN718合金的微观组织、析出相的演变。结果表明,沉积态试样中的显微组织为柱状晶结构,并贯穿多个沉积层;经过SA热处理后开始发生再结晶;经HA和HSA热处理后再结晶程度显著提高。热处理能够促进沉积态中的柱状晶逐渐向等轴晶转变。沉积态试样中存在γ基体、Laves相和一些碳化物;经过SA热处理后溶解了大部分的Laves偏析相,并在晶界、晶内、枝晶间析出大量的针状δ相,还有部分碳化物残留;经过HA热处理后,Laves偏析相、δ相全部溶解,只有少量的碳化物残留;经过HSA热处理后Laves偏析相全部溶解,在晶界处析出部分δ相,还有少量的碳化物残留。沉积态试样中没有γ′、γ″相析出,3种热处理状态均有大量的γ′、γ″相析出。     

Effect of Zr addition on precipitates in K4169 superalloy

In order to investigate the effect of Zr addition on the precipitations of K4169 superalloy,a manual electric arc furnace was used to prepare the superalloy with different Zr addition from 0.03wt.% to 0.07wt%.After standard heat treatment and long-time aging,the microstructures of the alloys were observed using XRD,SEM and TEM.The results show that Zr not only inhibits the precipitation of Laves phase at the grain boundary,but also significantly promotes the precipitation of earlobe-like γ’ and γ″ phases.After long time aging at 680℃ for 500 h,the γ″ phase grows up obviously and forms a γ’/γ’’ clad microstructure when the Zr addition is 0.03 wt.%.A large number of fine orbed γ’ particles precipitate in the grains and some γ″ phase transforms to disk-like δ phase when the Zr addition increases to 0.05wt.%.The nano-polycrystalline γ’ phase precipitates in the grains and there is a little δ phase when the Zr addition is 0.07wt.%.As the Zr addition increases,the amount of Laves phase at the grain boundary decreases at first,and then increases and forms flaky morphology.     

固溶处理对Ni48Cr21Cu2Mo合金组织与力学性能的影响

采用材料分析模拟软件(JMatPro)、X射线衍射仪(XRD)和扫描电镜(SEM)等研究了Ni48Cr21Cu2Mo合金棒材随不同制度固溶处理后组织性能的演化规律。平衡相图计算结果显示,温度超过990 ℃时,合金基体组织基本已为γ相,在870~1008 ℃存在Laves相,870 ℃以下析出δ、γ′和σ相。合金显微组织研究结果显示,随着固溶温度的升高,晶粒尺寸不断长大、颗粒相逐步回溶,经1010 ℃固溶处理后的显微组织最均匀且其中颗粒相已基本回溶。时效后,合金中析出γ′相和γ″相,晶界出现粒状δ、σ复合相。经1010 ℃×1 h固溶并在718 ℃×8 h+622 ℃×8 h时效处理后的Ni48Cr21Cu2Mo合金具有优良的综合力学性能。     

Tensile Properties of Cast Alloy IN625 in Relation to d Phase Precipitation

The relationship between the tensile properties and δ (delta) phase precipitation in cast alloy IN625 was investigated in this paper. Although the influences of δ phase on the mechanical properties have been pointed out in our previous work, the relationship is still not directly determined due to the coexistence of γ″ (gamma double prime) and δ precipitates. In order to exclude the effect from γ″ phase, various fractions of δ precipitates with few γ″ precipitates were obtained by a set of experimental alloys aging at 750 °C, and tensile tests were conducted in parallel. The results showed that both yield strength and ultimate tensile strength increased nearly in linear with increasing δ phase fraction, while the elongation was relatively and limitedly affected by δ precipitation when the area fraction of δ phase was above 10%.     

热处理对3D打印制备GH4169合金组织与性能的影响

通过选区激光熔化(SLM)技术三维打印(3D priting)制备了GH4169合金板状试样,并对其进行了热处理。采用三维原子探针技术(3DAP)以及附带原位拉伸功能的扫描电镜(SEM)对热处理前后试样的显微组织及力学性能进行了检测。结果表明,打印态GH4169合金中熔池和晶粒内部均为凝固枝晶组织,合金元素分布均匀。经过热处理后,基体中形成了大量细小γ″相和γ′相;拉伸试验结果显示,3D打印GH4169合金热处理后具有更优的力学性能,这归因于枝晶组织的消失、有害δ相的减少以及大量纳米级γ″相和γ′相在基体中的析出。     

扫描间距对选区激光熔化IN718合金微观组织的影响

通过选区激光熔化(SLM)技术制备了IN718合金,利用X射线显微镜、X射线衍射仪、扫描电镜和电子背散射衍射等技术分析了IN718合金的致密性、相组成和晶粒形态以及取向关系。结果表明:SLM成形IN718合金的物相组成为面心立方结构的γ-Ni相与体心四方结构的γ″相,晶粒沿构建方向呈柱状晶。当激光扫描间距为100 μm时合金的致密度达到最高,当激光扫描间距为90 μm时,合金沿构建方向形成强<001>织构。     

二次固溶处理对IN718合金组织性能的影响

对IN718合金进行二次固溶处理,研究了二次固溶处理对其组织及高温拉伸性能的影响。结果表明,经二次固溶处理后,IN718合金组织中δ相含量较一次固溶增加,高温屈服强度降低。随二次固溶温度升高,δ相析出减少,高温屈服强度升高。     

Isolation and determination for δ, γ′ and γ″ phases in Inconel 718 alloy

A method of anode selective electrolysis for phase extracting and isolation of δ-Ni₃Nb, γ′ and γ″ phases in Inconel 718 alloy has been proposed. The ratio of volume fraction of γ″ to γ′ phase is taken as a constant equal to 3.     

Zr对Mg-5Sn合金显微组织与力学性能的影响

研究了含Zr0．4％-1．2％的Mg-5Sn合金（质量分数，％，下同）的显微组织和力学性能。显微组织观察表明，Zr元素能够起到明显的晶粒细化作用。扫描电镜EDS分析和XRD分析验证了这一结果。力学性能测试结果表明：随着合金中Zr含量的增加，抗拉强度及延伸率都有提高，延伸率提高更显著，Zr的晶粒细化起了主要作用；而合金的显微硬度基本不变，其原因是在合金中没有明显数量的硬质相出现。     

回炉料对K441合金性能及杂质元素含量的影响

通过采用真空感应熔炼法,对K441合金回炉料进行了四次熔炼,研究了回炉料对K441合金持久寿命、力学性能、杂质元素含量及微观组织形貌的影响.结果表明,经过四次回炉熔炼后合金的持久性能均满足标准的要求.合金的抗拉强度及塑性与新料合金相比变化幅度不大,但第四次回炉料合金的抗拉强度较高,这主要是由于Si元素的固溶强化作用所致.随回炉料合金回炉次数的增加,合金中的S元素含量降低,Mn含量变化幅度不大,P、Si元素含量增加.合金微观组织形貌观察表明,新料合金与回炉料合金中的碳化物均沿晶界分布,新料合金中晶粒内也存在部分碳化物.回炉料合金中的晶界存在杂质增加的现象.新料合金及回炉料合金中的γ'相数量相当,含量都较少,经多次回炉熔炼后合金中的γ'相尺寸减小.     

热处理对激光选区熔化制备Inconel 718合金组织和拉伸性能的影响

采用激光选区熔化工艺(SLM)制备了Inconel 718合金,并对合金分别进行了1050 ℃×1 h固溶和1050 ℃×1 h固溶+720 ℃×8 h+620 ℃×8 h双级时效热处理。结合微观组织、拉伸性能和断裂特征分析,研究了热处理工艺对SLM制备的Inconel 718合金组织和力学性能的影响。结果表明:固溶处理后合金内Laves相溶解,位错密度显著降低,材料的强塑性匹配较打印态得到良好的改善。经过时效热处理后,γ′和γ″强化相析出使合金强度大幅度提高的同时,保留了一定的塑性。     

IN718合金γ'、γ'、中(Ti+A1)/Nb比值的变化对其相含量的影响

建立了用于计算γ′-Ni3Al和γ′′-Ni3Nb成分及含量的最优化数学模型,证明了通过复相分离法(Multiple Phases Separation Method,以下简称MPSM)计算两相成分及含量的可行性和准确性,利用MPSM法计算了调整(Al+Ti)/Nb比值后析出相的成分、含量及分配量,解释了调整该比值对改型IN718合金高温稳定性影响的原因.     

Precipitation behavior of hot-extruded alloy 718 during isothermal treatment

The precipitation and dissolution behavior of hot-extruded alloy 718 was investigated during isothermal treatment at temperatures from 600°C up to 1150°C at different times from 0.3h to 72h. Analysis was conducted using hardness measurement and an electron microscope. It was observed that the γ/γ′ phases were precipitated further during isothermal exposure at 600°C-700°C. When the isothermal treatment was carried out at 800°C, the δ phase was precipitated at the expense of the γ′ phase, which resulted in a slight decrease of hardness with increasing holding time. Above exposure temperature of 900°C, a rapid decrease in hardness occurred within the holding time of 0.3h, resulting from the dissolution of the γ phase and a sharp decrease in the amount of the γ′ phase. Rapid grain growth also affected the decrease in hardness above 900°C.     

INFLUENCE OF ASSOCIATED AND SEPARATE PRECIPITATION OF γ″ AND γ′ ON STRUCTURE STABILITY IN INCONEL718 AND MODIFIED ALLOYS

The precipitation behavior in Inconel 718 and modified alloys has been studied by means ofTEM.The structure of associated precipitation and compact morphology of γ″+γ′ were ob-tained by modifying the contents of Al,Ti and Nb.Experimental results show that the com-pact morphology of γ″+γ′ has the best structure stability at higher temperatures.Instead ofthe transformation γ″→δ in alloy 718 the dissolution of strengthening phases in modified alloyleads material degradation.     

Effect of Heat Treatment on the Microstructure and Mechanical Properties of the Modified 718 Alloy

M718 alloy with an extra high Mo content of 7.50 wt% which reduced Nb addition and increased Al and Ti additions within the composition specifications of 718 alloy has been designed to increase the service temperature of 718 alloy. And the effect of the heat treatment on the microstructure and mechanical properties of M718 alloy has been investigated in this study. The results showed that Laves phase precipitated on the grain boundaries of M718 alloy instead of d-Ni_3 Nb phase in718 alloy, and y'and y'phases precipitated in the matrix of M718 alloy as that in 718 alloy. Increasing the solution temperature from 960 to 1050 ℃ noticeably reduced the intergranular precipitation of Laves phase. The precipitation of Laves phase was appropriate at 1020 ℃ for improving the grain boundary cohesion. Increasing the two-stage aging temperatures markedly increased the sizes of y' andy'phases. As a result, the strength of M718 alloy increased.