固溶温度对激光增材制造Inconel 718合金组织和性能的影响

目的探索激光增材制造Inconel718高温合金最理想的固溶处理制度。方法利用激光增材制造技术制备了Inconel 718合金,通过组织观察(光学显微镜和扫描电镜)、能谱分析和维氏硬度测试等方法,研究了固溶温度对其组织、析出相及硬度的影响。结果不同固溶温度对Inconel 718的晶粒尺寸有很大影响。在固溶温度1000℃下保温1 h,沉积层开始出现再结晶现象。当固溶温度继续增加到1080℃时,与沉积态的组织相比,晶粒明显细化且再结晶过程基本完成。此外,不同固溶温度条件下,Inconel718的相析出和溶解行为也有所差异。固溶温度为940℃时,在未溶解的Laves相周围存在明显的δ相,当固溶温度继续提高时,δ相由于固溶作用而数量减少。另外,不同固溶温度处理后的合金显微硬度也表现出规律变化。当固溶温度为940℃时,试样硬度高于沉积态硬度,但是随着固溶温度持续升高,合金的显微硬度开始迅速下降并低于沉积态硬度,1050℃时保持稳定;当温度高于1150℃时,显微硬度继续迅速下降。结论激光增材制造Inconel718合金的热处理制度不同于铸造和锻造的热处理制度,其较为理想的固溶制度为1080～1150℃保温1 h。     

热处理对SLM成形的Inconel 718合金组织的影响

研究了固溶+双级时效处理对激光选区熔化(SLM)工艺制备的Inconel 718高温合金微观组织形态和析出相的影响。结果表明,SLM沉积态合金为椭圆状晶组织,其由细小柱状晶组成。沉积态合金经固溶处理后转变成等轴细晶组织,且随固溶温度升高,晶粒尺寸增大。经固溶+双级时效处理后,合金会在晶界和晶内析出多种析出相,在940~1 020℃固溶过程中晶界析出短棒状δ相(Ni3Nb),在620~720℃时效过程中晶内析出针状δ、圆盘状γ″(Ni3Nb)和黑点状γ′相(Ni3Al,Ti)。     

热处理态激光立体成形Inconel 718高温合金的组织及力学性能

研究了经过高温均匀化固溶处理+中间δ时效处理+双级时效处理的激光立体成形Inconel 718合金的组织及力学性能,并考察了热处理后合金的位错组态.结果表明,由于热处理过程中的再结晶行为,合金组织由沉积态的初始柱状晶转化为等轴晶.Laves相完全固溶,针状δ相以及γ″强化相分别在晶界处以及γ基体上大量弥散析出.激光立体成形Inconel 718合金热处理态的抗拉强度、屈服强度、延伸率以及断面收缩率均达到锻件标准.位错与γ″相的相互作用为位错切割γ″相以及位错绕过γ″相,在位错绕过γ″相的区域,位错密度比位错切割γ″相区域高.由于热处理态δ相尺寸大于锻件,位错会在δ相中发生塞积.碳化物和位错之间也存在强烈的相互作用,通过钉扎和拖曳作用来阻碍位错运动.     

热处理制度对IN718变形合金组织和性能的影响

考察了热处理工艺和长时时效对IN718变形合金组织性能的影响。结果表明:固溶时间为1 h时,960℃固溶处理对合金的晶粒度和δ相特征均无明显影响,然而固溶时间延长至2 h,晶内开始析出δ相,且δ相含量急剧增加。经1040℃固溶处理1 h,δ相完全溶入基体且晶粒显著粗化。在720℃直接时效8 h对合金的组织特征无明显影响,但680℃,100 h长时时效过程中δ相含量随时效时间增加明显增加。合金的性能与析出相特征显著相关,晶界少量δ相的析出提高合金强度和塑性,然而晶内的γ″相转变成针状δ相使屈服强度和晶界调节塑性变形能力下降。经960℃,保温1 h的固溶热处理使合金的晶内强度和晶界强度达到良好的匹配,可以在保持塑性的同时提高合金强度。     

应变诱发Inconel 718合金γ″相析出和γ″→δ转变

采用X射线衍射技术测定了冷轧Inconel 718合金在810℃时效温度下γ"相和δ相的含量,研究了冷轧变形对γ″相析出和γ″→δ转变的影响.结果表明,在810℃时效,γ″相的析出达到饱和状态此时γ"→δ的转变即将发生;应变可诱发γ″相析出以及γ″→δ转变;δ相的数量与时间的关系符合Avrami方程,随冷轧变形量增加,时间指数减小,δ相析出速率增加;γ"→δ转变的数量与时间的关系也可以用Avrami方程描述.     

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。     

应变诱发Inconel718合金γ〃相析出和γ〃→δ转变

采用X射线衍射技术测定了冷轧Inconel 718合金在810℃时效温度下γ"相和δ相的含量,研究了冷轧变形对γ″相析出和γ″→δ转变的影响.结果表明,在810℃时效,γ″相的析出达到饱和状态此时γ"→δ的转变即将发生;应变可诱发γ″相析出以及γ″→δ转变;δ相的数量与时间的关系符合Avrami方程,随冷轧变形量增加,时间指数减小,δ相析出速率增加;γ"→δ转变的数量与时间的关系也可以用Avrami方程描述.     

低温形变热处理对Inconel718合金组织的影响

利用透射电子显微镜(TEM)和X射线衍射仪研究了低温形变热处理时冷轧变形道次及不同变形量对Inconel 718合金中金属间化合物γ″相和δ相的分布﹑形貌和数量的影响。结果表明:随着变形量的增加,析出相由晶内和晶界析出逐渐转变到形变带及位错墙处析出,δ相形状由针状过渡到短棒状或颗粒状,γ″相的尺寸逐渐减小。形变既促进γ″相的析出又促进γ″相向δ相的转变。γ″﹑δ相的含量随变形量的增加而增加,两道次冷轧的低温形变热处理工艺提高了δ相的含量,却减少了γ″相的量。     

INFLUENCES OF ASSOCIATED AND SEPARATE PRECIPITATION OFγ′WITH γ" ON THERMAL STRUCTURE STABILITY IN INCONEL718 TYPE ALLOYS

用透射电镜观察了Inconel718及其改型合金中的时效析出组织调整Nb,Ti,Al的含量及比例,可以得到与通常合金中γ′和γ″单独析出有所不同的γ′和γ″的复合组织及包覆组织两类析出形态、其中γ″在γ′上析出的包覆组织具有较好的高温长期时效组织稳定性过时效试验结果表明.改型合金不同于Inconel718合金γ″致δ的相转变,却以强化相溶解而使材料软化     

热处理对粉末冶金Inconel 718高温合金组织及性能的影响

以超高转速等离子旋转电极法(SS-PREP法)制备的高球形度Inconel 718高温合金粉末为原料,采用热等静压(HIP)工艺制备了Inconel 718粉末高温合金,重点研究了热处理制度对合金组织和力学性能的影响。实验结果表明:采用SS-PREP法制得的Inconel 718高温合金粉末粒度分布均匀,球形度良好,具有优异的HIP工艺性能;随着固溶温度的提高,合金晶界逐渐变浅,说明晶界析出相数量逐渐减少。时效热处理后,沿晶界析出大量针状δ相,同时还有少量MC碳化物相。在1210℃、120MPa条件下保温保压4h的HIP工艺下,经1020℃固溶热处理后,合金室温抗拉强度可达1404MPa;经980℃固溶处理后,合金在650℃的高温抗拉强度为1153MPa,固溶处理温度为980℃的合金综合性能较好。     

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.     

Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy

The effect of phosphorus on the precipitations of γ",γ' and δ phases and associated tensile properties in IN718C alloy are investigated in this study.It is revealed that P atoms are dissolved in the grain interior to a relatively high degree and hence influence the precipitation behaviors in the grain interior and improve the tensile strength of IN718C alloy.γ" and γ' phases did not precipitate in the alloy without P addition during air cooling,while γ" and γ' phases precipitated in the grain interior during air cooling in the alloys with P addition,and the amounts of γ" and γ' phases increased with increasing P content.Therefore,the Vickers micro-hardness in the as-cast state increased gradually with increasing P content.In double-aging state,the sizes of γ" and γ' phases in the alloys with P addition were larger than that in the alloy without P addition,while the sizes were invariable when the P content(wt%)was higher than 0.015.Therefore,the micro-hardness and tensile strength of IN718C alloy treated by double aging increased first and then kept invariable with increasing P content.The precipitations of δ phases both in the grain interior and on grain boundaries were inhibited by P markedly.The inhibitory effect of P on δ phase enhanced gradually with increasing content of P,but the plasticity increased first and then decreased.What is more,the crack tended to propagate into the matrix around the particles(Laves phases and NbC carbides)in the alloys without P addition at the beginning of the tensile fracture,while it tended to propagate along the interfaces between the matrix and those particles in the alloys with P addition,which resulted from the synthetical effect of P on γ" γ' and δ phases.     

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。     

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.     

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.     

GH4096合金在长期热暴露过程中的组织演化

基于粉末冶金René88DT合金的成分,采用新型定向凝固铸锭变形工艺研制了GH4096合金,并研究了其固溶时效热处理后在700~900 ℃长期热暴露过程中γ′相的粗化和晶界析出相的析出行为。结果表明:GH4096合金在700 ℃热暴露时具有良好的组织稳定性,晶内γ′相的尺寸稳定在70 nm左右,未发现明显的长大行为,晶界上未发现析出相;750 ℃热暴露500 h以上时,二次γ′相开始出现聚集长大现象,晶界开始出现不连续析出相,但γ′相的长大速度和晶界析出相的析出速度均比较低;800 ℃以上长期热暴露时,γ′相的粗化速度和晶界析出相的析出长大速度明显加快。长期热暴露后晶内二次γ′相的尺寸与Larsen-Miller参数近似呈线性关系,晶界析出相以M₃B₂和μ相为主。     

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.