【作者】 张宇；

【导师】 董闯； 王清；

【作者基本信息】 大连理工大学 ， 材料物理与化学， 2018， 博士

【摘要】 本文基于“团簇加连接原子”模型建立了镍基高温合金成分式,实施了对现有牌号合金的成分解析和性能分析,并进行了实验验证和性能预测。首先,通过分析现有成熟牌号合金成分,揭示了镍基高温合金的成分规律和发展趋势,提出了镍基单晶高温合金的理想模型和相应成分式。其次,借助镍基高温合金的成分式,确定了合金中键的种类和数量,并利用键焓表征键强,建立了承温能力与成分式之间的关联,并实现对承温能力的预测。最后,利用理想模型对第1代镍基单晶高温合金进行了实验验证,所设计合金的1000 ℃/219 MPa持久寿命达到第1代单晶合金的平均水平,并且所设计合金的初熔温度在第1代单晶合金中处于较高水平。具体内容包括以下3方面:(1)基于“合金化元素与溶剂Ni”的混合焓,将合金化元素分为4类:1类Ni元素Ni(含Ni、Co、Fe、Re、Ru和Ir),与Ni呈弱混合焓,范围在-2～+2kJ/mol;2促进γ形成的类Cr元素Crγ(含Cr、Mo和W),与Ni的混合焓在-7～-3 kJ/mol;3促进γ’形成的类Cr元素Crγ’(含Ti、V、Nb和Ta),与Ni的混合焓在-35～-18kJ/mol;4与Ni呈强负混合焓的主要合金化元素Al(-22 kJ/mol)。基于元素分类,本文对272个广泛应用或具有代表性的典型镍基高温合金牌号进行成分分析,发现镍基高温合金落于狭窄的成分区间60～80 at.%Ni,对应连接原子个数为2～7。镍基高温合金的发展过程,就是在Ni-Cr二元体系基础上添加γ’形成元素(Al,Crγ’)的过程。定向凝固柱晶合金和单晶高温合金位于[(Al,Crγ’)1-Ni12](Al,Crγ’)1.5Crγx-1.5成分线。高代次单晶合金最终趋近于符合Friedel振荡和团簇共振模型的理想成分式[(Al,Crγ’)1-Ni12](Al,Crγ’)1.5Crγ1.5=Ni75Al12.5Crγ’9.375Crγ3.125 at.%。通过元素分类还可以获得γ’体积分数。(2)本文基于所获得的成分式,进而确定镍基高温合金中键的种类和数量。对于配位数为12的面心立方固溶体结构,属于每个原子的键为6个,因此含有x个连接原子的成分式有6×(13+x)个键,包括12个中心-壳层键、12x个连接-壳层键和(66-6x)个壳层-壳层键。利用键焓表征键强,本文发现,平均键焓可以反应承温能力的变化趋势,弱键键焓可以反映持久寿命的变化趋势。高承温能力和长持久寿命的高代次单晶合金同样指向理想成分式[Al-Ni12]Al1Cr’0.5Crγ1.5。(3)本文基于镍基高温合金的理想模型[Al-Ni12]Al1Crγ’0.5Crγ1.5,结合已经实际应用的的第1代镍基单晶高温合金DD407(AM3)的成分,设计出3组(A组、B组和C组)团簇高温合金:A 组合金成分式为[Al-Ni11Co1](Al1TaxTi0.5-xCr1Mo0.25 W0.25),x=0、0.25 和 0.5,因此以 Ta 和 Ti 的质量分数命名,“0Ta-2.65Ti”、“4.82Ta-1.28Ti”和“9.32Ta-0Ti”;B 组合金成分式为[Al-Ni12-yCoy](AllTi0.25Ta0.25Cr1MO0.25W0.25),y=1.5、1.75、2 和 2.5,因此以 Co 的质量分数命名,“9.43Co”、“11Co”、“12.57Co”和“15.71Co”。C 组合金成分式为[Al-Ni12-zCoz](Al1Ta0.25Ti0.25Cr1Mo0.25W0.25),z=1.25、2、2.5 和 3,还有[A1-Ni11Co1](Al1Ti0.5Cr1Mo0.25W0.25),命名为“7.86Co”、“12.57Co”、“15.71Co”、“18.85Co”和“0Ta-2.65Ti”。其中,7.86CO 合金和 12.57Co合金的 1000 ℃/219 MPa持久寿命超过DD407的46h,达到了第1代单晶合金的平均水平。同时,所有团簇高温合金的初熔温度在第1代单晶合金中处于较高水平,均超过Nasair 100的初熔温度(1330 ℃)。A组合金中,Ta元素的增加(Ti元素的降低),合金的负错配度ε从-0.262%减小到-0.247%,但在900 ℃长期时效的过程中,合金的负错配度ε能够保持稳定,从而抑制γ’的粗化。同样,Ta增加(Ti降低),A组合金的1050 ℃/120 MPa持久寿命呈现升高趋势。对于B组合金,Co元素的加入并不增加合金在900 ℃C长期时效过程中γ’的粗化速率。因此B组合金在900 ℃C长期时效的过程中,粗化速率与第3代镍基单晶高温合金处于同一数量级(10-5μMm3/h)。此外,Co元素的加入减弱了原子间交互作用(混合焓和键焓),同时也降低了合金的1050 ℃/120 MPa持久寿命。在1050 ℃/120 MPa持久过程中,A组合金和B组合金的γ’均呈现N型筏化。对于C组合金,持久寿命同样可以用键焓表征。此外,在1100℃/137MPa持久实验和1000℃/219MPa持久实验中,C组合金的γ’呈现N型筏化。但在760 ℃/780 MPa持久实验中,C组合金的γ’没有出现筏化。同时,C组合金的7.86Co合金和12.57Co合金的1000 ℃/219 MPa持久寿命优于DD407。承温能力与平均键焓存在明显的对应关系,TC(K)=-4071.852XIave-1867.180,其中Iave为平均键焓(eV/bond),可以利用平均键焓对承温能力进行预测。成分式设计方法的确能够有效指导高温合金的研发。更多还原

【Abstract】 With the cluster-plus-glue-atom model,this paper puts forward the composition formula of nickel-based superalloys,analyzes available compositions,probes performance,experimental tests and predicts performance.First,this paper discovers composition rule and development tendency,presents the ideal model with corresponding composition formula for nickel-based single crystal superalloys by analyzing composition.Secondly,in virtue of composition formula of nickel-based superalloys,both the kinds and the number are clearly for bonds.Meanwhile,this paper also built the relationship between composition formula and temperature capability with bond strength being measured by condensed bond enthalpy.At the same time,this paper also built the relationship between composition formula and temperature capability with bond strength being measured by condensed bond enthalpy.Temperature capability are predict by the composition formula.At last,the first generation single crystal superalloys have been validated by experiments about the ideal model.Compared to the first generation single crystal superalloys,the creep rupture life at 1000 ℃/219 MPa are at the average level and the incipient melting temperature are at higher level for design superalloys.Specifically,this paper covers the following three aspects:(1)According to the enthalpy of mixture with the based nickel solvent,the alloying elements are classified into four groups:1 Ni-like(Ni:Ni,Co,Fe,Re,Ru and Ir)elements,weaker enthalpy of mixture with Ni,ranging between-2～-+2 kJ/mol;2 y-forming Cr-like(Crγ:Cr,Mo and W)elements,enthalpy of mixture with Ni ranging between-7～-3 kJ/mol;3γ’-forming Cr-like(Crγ’:Ti,Ta,Nb and V)elements,enthalpy of mixture with Ni ranging between-35～-18 kJ/mol;4 larger negative enthalpy of mixture with Ni,Al,-22 kJ/mol.As a result of alloying elements classification,compositions of 272 available nickel-based superalloys fall within narrow composition ranges(Ni,60 at.%～80at.%;glue atoms,2～7).Adding y’-forming elements(Al,Crγ’)into Ni-Crγ alloys is the development progress of nickel based superalloys.Especially,the formula of directionally solidified and single crystal superalloys evolutes along a composition line[(Al,Cr γ’),-Ni,2](Al,Crγ’)1.5Crγx-1.5).For the high generation single crystal superalloys,the compositions finally converge towards to the ideal model,[(Al,Crγ’)1-Ni12](Al,Crγ’)1.5Crγ1.5=Ni75Al12.5Crvγ9.375Crγ’3.125 at.%,and the ideal model conforms to the Fried el Oscillation and cluster-resonance model.Alloying elements classification also predicts volume fraction of γ’.(2)Because of the composition formula of nickel based superalloys,both the kinds of bonds and the number of bonds are clearly.For face-centered-cubic solid solution,every atom has 6 own bonds resulting from the coordinate number being 12.As a result,every composition formula with x glue atoms has 6×(13+x)bonds,containing 12 Center-Shell bonds,12x Glue-Shell bonds and(66-6x)Shell-Shell bonds.Bond strength being measured by condensed bond enthalpy,this paper discovers that the average bond enthalpy and the weak bond enthalpy can reflect temperature capability and creep rupture life respectively.The composition formula is also moving towards the ideal composition formula[Al-Ni12]Al1Crγ’0.5、Crγ1.5.for high generation single crystal superalloys with higher temperature capability and longer creep rupture life.(3)With the ideal model of nickel-based superalloys([Al-Ni12]Al1Crγ’0.5Crγ1.5),on the basis of the 1st generation single crystal superalloys DD407(AM3)which are used in the aero-engine of the helicopter,this paper raises three Group Cluster Superalloys:Group A,[Al-Ni11Co1](Al1TaxTi0.5-xCr1Mo0.25W0.25),x=0,0.25 and 0.5(the corresponding mass fractions of Ta and Ti are respectively 0Ta-2.65Ti,4.82Ta-1.28Ti and 9.32Ta-0Ti);Group B,[Al-Ni12-yCoy](Al1Ti0.25Ta0.25Cr1Mo0.25W0.25),y=1.5,1.75,2 and 2.5(the corresponding mass fractions of Co are respectively 9.43Co,11Co,12.57Co and 15.71Co);Group C,[Al-Ni12xCox](Al1Ta0.25Ti0.25Cr1Mo0.25W0.25),z=1.25,2,2.5 and 3,[Al-Ni11Co1]Al1Ti0.5Cr1 Mo0.25W0.25),(the corresponding mass fractions of Co,Ta and Ti are respectively 7.86Co,12.57Co,15.71Co,18.86Co and 0Ta-2.65Ti).Compared to DD407(46h),both 7.86 Co and 12.75 Co alloys have longer creep rupture life at 1000 ℃/219 Mpa which is in the average level of first generation single crystal superalloys.Meanwhile,all the incipient melting temperatures of Cluster Superalloys,at higher level of first generation single crytstal superalloys,are higher than that of Nasair 100(1330 ℃).For Group A,with increasing Ta(decreasing Ti),the γ’/γ lattice negative misfits δ shrinks from-0.262%to-0.247%.Although reduced,the lattice negative misfits δ,maintaining at 900 ℃ long-term aging,reduce coarsening rate.Meanwhile,creep rupture life at 1050 ℃/120 MPa are increasing with increasing Ta(decreasing Ti)for Group A.For Group B,the addition of Co does not increase the coarsening rate and the coarsening rate is of the same order of magnitudes(10-5 μm3/h)with the third generation single crystal superalloys.Moreover,Co is able to cripple atomic interaction(enthalpy of mixture and bond enthalpy),resulting in reducing creep rupture life at 1050 ℃/120 MPa.Furthermore,after creep at 1050 ℃/120 MPa,the coarsening of y’ is N-type raft for Group A and B.For Group C,the bond enthalpy is also able to reflect the creep rupture life tendency.For Group C,this paper also finds N-type raft at 1100 ℃/137 MPa and 1000 ℃/219 MPa,but no No raft at 760 ℃/780 MPa.At the same time,both 7.86Co and 12.57 Co have longer creep rupture life at 1000 ℃/219 MPa than that of DD407(46h).The obvious congruent relationship between temperature capability and average bond enthalpy are discovered,TTC(K)=-4071.852×Iave-1867.180,Iave is average bond enthalpy(eV/bond).The average bond enthalpy is able to predict temperature capability.The composition formula is able to design new nickel-based superalloys effectively.更多还原