To clarify the mechanism of the role of Al element in the additive manufacturing of Ni-based superalloys,ATI 718Plus alloys with varying Al contents(1,3,and 5 wt%)were fabricated using the laser additive manufacturing...To clarify the mechanism of the role of Al element in the additive manufacturing of Ni-based superalloys,ATI 718Plus alloys with varying Al contents(1,3,and 5 wt%)were fabricated using the laser additive manufacturing and the effects of Al content on the microstructure and mechanical properties were systematically analyzed.The experimental and CALPHAD simulation results show that with the increase in Al addition,the freezing range of the alloys was lowered,but this has a paradoxical effect on the susceptibility of the alloy to hot-tearing and solid-state cracking.The addition of Al increased theγ′and Laves phase volume fractions and suppressed the precipitation of theηphase.Simultaneously improvingγ/γ′lattice misfits effectively promoted the transformation ofγ′phase from spherical to cubic.The precipitation of NiAl phase in the 5 wt%Al-added alloy was determined,the formation mechanism of NiAl phase was analyzed,and the solidification sequence of the precipitated phase in the alloy was summarized.In addition,with the increase in Al addition,the microhardness of the alloy increased gradually,the tensile strength increased at first and then decreased,but the plasticity deteriorated seriously.The insights gained from this study offer valuable theoretical guidance for the strategic compositional design of additively manufactured Ni-based superalloys destined for deployment under extreme conditions.展开更多
ATI 718Plus(简称718Plus)合金作为一种新型镍基变形高温合金涡轮盘材料,由于在700℃以下具备优异的综合力学性能、良好的热加工和焊接等工艺性能以及适宜的成本,而受到国内外的广泛关注。本文综述了近几年国内718Plus合金的研究进展,...ATI 718Plus(简称718Plus)合金作为一种新型镍基变形高温合金涡轮盘材料,由于在700℃以下具备优异的综合力学性能、良好的热加工和焊接等工艺性能以及适宜的成本,而受到国内外的广泛关注。本文综述了近几年国内718Plus合金的研究进展,主要包括:(1)718Plus合金相组成及合金特点;(2)P对718Plus合金组织及性能的影响规律及机理;(3)Al对718Plus合金组织及性能的影响规律及机理;(4)析出相对718Plus合金性能的影响规律及机理。展开更多
ATI 718Plus(以下简称718Plus)是一种基于IN718高温合金改进的时效强化型镍基变形高温合金,已广泛应用于航空发动机的热端零部件。合金最初以锻造态引入,随着航空航天领域对大型复杂零部件需求的提高,锻造态合金已不能满足实际要求,因...ATI 718Plus(以下简称718Plus)是一种基于IN718高温合金改进的时效强化型镍基变形高温合金,已广泛应用于航空发动机的热端零部件。合金最初以锻造态引入,随着航空航天领域对大型复杂零部件需求的提高,锻造态合金已不能满足实际要求,因此在锻造态合金的基础上通过提高Nb含量开发出了铸造718Plus合金,并对其微观组织、焊接性能和拉伸性能开展了研究。锻造态和铸造态合金的化学成分与成型工艺的差异导致其微观组织及性能不同,因此阐明两种合金微观组织与使役性能之间的内在联系具有重要意义。本文综述了近年来锻造态和铸造态718Plus合金的微观组织调控及性能研究进展,包括:元素含量与分布状态对合金微观组织的影响,热处理制度对γ′相及η相分布状态的影响,热变形工艺与合金微观组织的关系,并得到最优热加工参数,总结了服役环境对合金蠕变、疲劳、焊接及抗氧化性能的作用机制,最后分析了合金研究过程中存在的问题及发展趋势。展开更多
In the precipitation-hardened Ni-based superalloy,typified by ATI 718 Plus,the nano-scaleγandγphase in duplet or triple coprecipitate morphology can provide superior high-temperature strength.Thus,it is of great sen...In the precipitation-hardened Ni-based superalloy,typified by ATI 718 Plus,the nano-scaleγandγphase in duplet or triple coprecipitate morphology can provide superior high-temperature strength.Thus,it is of great sense to study the evolution ofγ’/γ’’coprecipitate during long term service at elevated temperature.In this study,the new-typeγ’/γ’’coprecipitates with a sandwich or compact configuration were found firstly in wrought ATI 718 Plus superalloy during long term thermal exposure at 705℃.These co-structure of theγ’/γ’’precipitates evidently inhibit the coarsening ofγ’phase.The increase of thermal exposure time evidently leads to the increase of the volume fraction ofγ’/γ’’coprecipitate and transformation of sandwich-typeγ’/γ’’coprecipitate to compact-typeγ’/γ’’coprecipitate,which is characterized asγphase precipitate at several faces of theγphase.The main evolution mechanism ofγ’/γ’’coprecipitates is element segregation,especially the composition variations of Al+Ti and Nb and their ratio of Al+Ti/Nb.In addition,the interfacial energy betweenγ’’phase andγmatrix also plays a key role on theγ’/γ’’coprecipitates evolution.The calculated results show that the longer thermal exposure time leads to the higher interfacial energy,which is beneficial for nucleation and precipitation ofγ’’phase on the faces ofγ’phase.展开更多
In this work, the eff ect of microstructure on hot deformation behavior of ATI 718Plus(hereinafter refers to 718Plus) alloy was studied by isothermal compression test. The results showed that when the strain rate was ...In this work, the eff ect of microstructure on hot deformation behavior of ATI 718Plus(hereinafter refers to 718Plus) alloy was studied by isothermal compression test. The results showed that when the strain rate was 0.01–0.1s^(-1) with deformation temperature of 980 and 1030℃, hot deformation behavior was mainly aff ected by dislocation density. Dislocation density of the air-cooling alloy was larger than that of the furnace-cooling alloy, which makes its critical strain smaller and peak stress higher than that of the furnace-cooling alloy. When the strain rate was 1 s^(-1), hot deformation behavior of the alloy was mainly aff ected by twins and γ ′ phase, and high-density deformation twins in air-cooling alloys resulted in higher critical strain. γ ′ phase exists in furnace-cooling alloy, which makes its peak stress higher than that of air-cooling alloy. 718Plus alloy is sensitive to cooling rate;dislocation and γ ′ phase have obvious eff ects on its hot deformation behavior.展开更多
Allvac 718Plus alloy is a compromising Ni-based superalloy at elevated-temperature of 704℃,due to its combination of good mechanical properties and excellent structure stability.The precipitation behaviors during hea...Allvac 718Plus alloy is a compromising Ni-based superalloy at elevated-temperature of 704℃,due to its combination of good mechanical properties and excellent structure stability.The precipitation behaviors during heat treatment in Allvac 718Plus alloy processed by rapid solidification technique were systematically investigated in this work.The evolution of secondary phases in rapidly solidified(RS)718Plus alloy during annealing at 960℃is:η+MC in 1 h,η+MC+Laves(C14)in 6 h,and MC+Laves(C14)in longer duration.The growth and dissolution behaviors ofηphase are evidenced in RS samples and different types of dislocations at theη/γinterface are characterized.Based on these experimental observations,we examine the transformation mechanisms ofγ→ηandη→γ,which are related to the formation of stacking faults(SFs)with a1/6[211]γShockley partial dislocation and the climbing of14[0001]ηedge dislocations at theη/γinterface,respectively.Both MC and Laves(C14)phases are enriched in Nb and Mo,with a higher level of Ti in MC carbides and Cr in the Laves(C14)phase.The precipitation of MC carbides is driven by the high concentration of C atoms inγ-matrix,while the Cr segregation promotes the later nucleation of Laves(C14)phase inγ-matrix around MC carbides,which is due to the Cr atoms rejection from MC carbides into the matrix.展开更多
Solidification behaviors of Pt-containing 718Plus superalloys were studied by scanning electron microscopy(SEM),energy dispersive spectrum(EDS),differential scanning calorimetry(DSC)and simulation calculations.It is f...Solidification behaviors of Pt-containing 718Plus superalloys were studied by scanning electron microscopy(SEM),energy dispersive spectrum(EDS),differential scanning calorimetry(DSC)and simulation calculations.It is found that Pt increases solidification range and decreases solidus temperature of the alloy and precipitation temperature of Laves+ γ eutectic phase since Pt enlarges the region of γ phase by increasing Nb solubility.In addition,Pt segregates to the interdendritic region and increases the segregation of Nb and Ti in the interdendritic region due to the strong attractive interactions between Pt and Nb/Ti.As a result,Pt promotes the precipitation of the Laves+ γ eutectic phase andηphase around eutectic phase.The increase of solidification range and segregation degrees of Nb and Al caused by Pt also promotes the precipitation and growth of γ'+γ" phase around eutectic phase.These results provide experimental bases for understanding the mechanism of Pt in solidification behavior of superalloys.展开更多
基金supported by the National Science and Technology Major Project(J2019-VI-0004-0144).
文摘To clarify the mechanism of the role of Al element in the additive manufacturing of Ni-based superalloys,ATI 718Plus alloys with varying Al contents(1,3,and 5 wt%)were fabricated using the laser additive manufacturing and the effects of Al content on the microstructure and mechanical properties were systematically analyzed.The experimental and CALPHAD simulation results show that with the increase in Al addition,the freezing range of the alloys was lowered,but this has a paradoxical effect on the susceptibility of the alloy to hot-tearing and solid-state cracking.The addition of Al increased theγ′and Laves phase volume fractions and suppressed the precipitation of theηphase.Simultaneously improvingγ/γ′lattice misfits effectively promoted the transformation ofγ′phase from spherical to cubic.The precipitation of NiAl phase in the 5 wt%Al-added alloy was determined,the formation mechanism of NiAl phase was analyzed,and the solidification sequence of the precipitated phase in the alloy was summarized.In addition,with the increase in Al addition,the microhardness of the alloy increased gradually,the tensile strength increased at first and then decreased,but the plasticity deteriorated seriously.The insights gained from this study offer valuable theoretical guidance for the strategic compositional design of additively manufactured Ni-based superalloys destined for deployment under extreme conditions.
基金the National Natural Science Foundation of China(Nos.52034004,51974201 and 52122409)for grant and financial support。
文摘In the precipitation-hardened Ni-based superalloy,typified by ATI 718 Plus,the nano-scaleγandγphase in duplet or triple coprecipitate morphology can provide superior high-temperature strength.Thus,it is of great sense to study the evolution ofγ’/γ’’coprecipitate during long term service at elevated temperature.In this study,the new-typeγ’/γ’’coprecipitates with a sandwich or compact configuration were found firstly in wrought ATI 718 Plus superalloy during long term thermal exposure at 705℃.These co-structure of theγ’/γ’’precipitates evidently inhibit the coarsening ofγ’phase.The increase of thermal exposure time evidently leads to the increase of the volume fraction ofγ’/γ’’coprecipitate and transformation of sandwich-typeγ’/γ’’coprecipitate to compact-typeγ’/γ’’coprecipitate,which is characterized asγphase precipitate at several faces of theγphase.The main evolution mechanism ofγ’/γ’’coprecipitates is element segregation,especially the composition variations of Al+Ti and Nb and their ratio of Al+Ti/Nb.In addition,the interfacial energy betweenγ’’phase andγmatrix also plays a key role on theγ’/γ’’coprecipitates evolution.The calculated results show that the longer thermal exposure time leads to the higher interfacial energy,which is beneficial for nucleation and precipitation ofγ’’phase on the faces ofγ’phase.
基金supported by the National Natural Science Foundation of China(Nos.52175312 and 52122409)the Natural Science Foundation of Hebei Province(Nos.E2019202161 and E2021202091)+1 种基金the High-level Talent Funding Project of Hebei Province(No.A201902008)the Key R&D Program of Hebei Province(No.19251013D)。
文摘In this work, the eff ect of microstructure on hot deformation behavior of ATI 718Plus(hereinafter refers to 718Plus) alloy was studied by isothermal compression test. The results showed that when the strain rate was 0.01–0.1s^(-1) with deformation temperature of 980 and 1030℃, hot deformation behavior was mainly aff ected by dislocation density. Dislocation density of the air-cooling alloy was larger than that of the furnace-cooling alloy, which makes its critical strain smaller and peak stress higher than that of the furnace-cooling alloy. When the strain rate was 1 s^(-1), hot deformation behavior of the alloy was mainly aff ected by twins and γ ′ phase, and high-density deformation twins in air-cooling alloys resulted in higher critical strain. γ ′ phase exists in furnace-cooling alloy, which makes its peak stress higher than that of air-cooling alloy. 718Plus alloy is sensitive to cooling rate;dislocation and γ ′ phase have obvious eff ects on its hot deformation behavior.
基金National Natural Science Foundation of China(Nos.52034004 and 52122409)for grant and financial support。
文摘Allvac 718Plus alloy is a compromising Ni-based superalloy at elevated-temperature of 704℃,due to its combination of good mechanical properties and excellent structure stability.The precipitation behaviors during heat treatment in Allvac 718Plus alloy processed by rapid solidification technique were systematically investigated in this work.The evolution of secondary phases in rapidly solidified(RS)718Plus alloy during annealing at 960℃is:η+MC in 1 h,η+MC+Laves(C14)in 6 h,and MC+Laves(C14)in longer duration.The growth and dissolution behaviors ofηphase are evidenced in RS samples and different types of dislocations at theη/γinterface are characterized.Based on these experimental observations,we examine the transformation mechanisms ofγ→ηandη→γ,which are related to the formation of stacking faults(SFs)with a1/6[211]γShockley partial dislocation and the climbing of14[0001]ηedge dislocations at theη/γinterface,respectively.Both MC and Laves(C14)phases are enriched in Nb and Mo,with a higher level of Ti in MC carbides and Cr in the Laves(C14)phase.The precipitation of MC carbides is driven by the high concentration of C atoms inγ-matrix,while the Cr segregation promotes the later nucleation of Laves(C14)phase inγ-matrix around MC carbides,which is due to the Cr atoms rejection from MC carbides into the matrix.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(Nos.51771018,51871022)the Fundamental Research Funds for the Central Universities(Nos.FRF-GF-19-004B,FRF-GF-20-01A)。
文摘Solidification behaviors of Pt-containing 718Plus superalloys were studied by scanning electron microscopy(SEM),energy dispersive spectrum(EDS),differential scanning calorimetry(DSC)and simulation calculations.It is found that Pt increases solidification range and decreases solidus temperature of the alloy and precipitation temperature of Laves+ γ eutectic phase since Pt enlarges the region of γ phase by increasing Nb solubility.In addition,Pt segregates to the interdendritic region and increases the segregation of Nb and Ti in the interdendritic region due to the strong attractive interactions between Pt and Nb/Ti.As a result,Pt promotes the precipitation of the Laves+ γ eutectic phase andηphase around eutectic phase.The increase of solidification range and segregation degrees of Nb and Al caused by Pt also promotes the precipitation and growth of γ'+γ" phase around eutectic phase.These results provide experimental bases for understanding the mechanism of Pt in solidification behavior of superalloys.
