Ni 基高温合金中 MC 碳化物生长的理论形貌

本文应用 PBC 理论证实了 MC 碳化物从 Ni 基高温合金熔体中生长的理想形貌是以{111}面为外表面的八面体.认为 MC 的一种生长基元为由金属原子和周围六个碳原子组成的八面体配位体,在近平衡条件下MC 碳化物的晶体生长机制是该配位体沿晶体的{111}面层状生长.     

快速凝固对Ni基高温合金中碳化物的影响

对常规铸态凝固和快速凝固高温合金中 MC 型碳化物的观察、分析表明,快速凝固后碳化物的形态、尺寸、成分和分布都发生了明显变化,这些变化对合金的高温力学性能有可能产生重要影响。     

Ni3Al基高温合金添加碳化物质点的探索研究

在较成熟的Ｎｉ３Ａｌ基高温合金成分的基础上，探索了研究了用特殊的方法添国了ＴｉＣ质点的工艺方法，并观察了组织变化及Ｔｉ质点的分布特征。结果表明，通过对工艺及合金成分的调整，ＴｉＣ质点能够均匀地分布在ＩＣ６合金的组织中，这为提高ＩＣ６合金的性能提供了可能性，同时还讨论了工艺实施过程中所暴露出的主要问题。     

Ni 基高温合金中 MC 碳化物的 Raman 光谱及键能计算

根据激光 Raman 探针所测定的 Raman 光谱,用简正振动模型计算b Ni 基高温合金中的 MC 碳化物各键的振动力常数和键能近似值。结果表明,〔MC_6〕八面体配位体是 MC 碳化物的主要结构单元,MC 碳化物中最强的键是金属与最近邻碳原子之间的共价键。本文还根据 Raman 光谱确定了 Lennard-Jones势中的 m 和 n 值.     

热轧态Inconel690合金中碳化物的溶解和析出

研究了热轧态690合金中碳化物的溶解和析出行为及其结构,结果表明:在热轧态合金中存在的碳化物多数沿晶界长条状分布,少量呈颗粒状分布于晶内,类型为M_(23)C_6.热轧态合金的晶界和晶内碳化物的完全固溶温度分别为1050℃、1080℃,在低固溶温度下未完全溶解的残余晶界碳化物直接导致后续TT处理晶界不再析出碳化物;将合金完全固溶处理后,在后续TT处理的晶界上会重新析出细小、半连续的碳化物.     

Ni基单晶高温合金的强化特点

本文研究一种在热腐蚀环境下工作的 Ni 基单晶高温合金错配度以及γ′筏状形成与性能的关系;通过蠕变和持久试验,研究合金的变形组织和强化特点。在变形过程中,基体运动位错遇γ′相受阻而在γ′相表面形成位错网络,这种位错结构在变形中形成了新的强化机制,提高了合金的蠕变抗力。     

Characteristics of High Temperature Rupture of a Cast Ni-Based Superalloy M963

The rupture behavior of a cast Ni-base superalloy M963 at high temperature has been investigated. The microstructure examination shows that there exists a large amount of the carbide and     

Low ductility at intermediate temperature of Ni–base superalloy M963

Tensile behavior of a cast Ni–base superalloy M963 under solution treatment and age treatment was studied in the temperature range from 20 to 1100 °C. Extensive TEM investigations were performed after tensile test to fracture. Furthermore, the fracture surfaces were studied in the SEM. The yield and tensile strengths under the two conditions initially increase with temperature and reach a peak at around 800 °C. Beyond this temperature, a sharp decrease of both yield and tensile strengths was observed. A ductility minimum was observed at 800 °C under solution treatment and disappeared under age treatment. With the increment of temperature, the following sequence of deformed substructure features was observed: dislocation pairs → connected slip bands within matrix channel under solution treatment and homogeneous interface dislocations under age treatment → homogeneous dislocation network within matrix channel. The fracture surface observation indicated that localized slip which leading to glide plane decohesion caused the poor ductility of M963 alloy.     

一种低成本镍基铸造高温合金的高温力学行为

研究了一种无钴镍基铸造高温合金K46的高温拉伸、蠕变和持久性能,并与K412合金进行了比较.结果表明,K46合金的高温拉伸和高温持久强度均高于K412合金,但前者成本低于后者.K46合金在950℃高温下仍具有强度和塑性,足以保证K46合金的安全使用.K46合金的高温拉伸蠕变曲线表现出非常长的稳态蠕变阶段,而较高的蠕变塑性来自于加速蠕变阶段.K46合金的蠕变机制受位错通过γ′沉淀相的攀移过程所控制.K46合金的拉伸、蠕变和持久断裂都表现出沿晶(枝晶间)特征.     

Development of a Nickel-base Cast Superalloy with High Strength and Superior Creep Properties

Derived from Russian alloy CHS88U, six experimental Ni-base alloys named as A to F in the Ni-Cr-Co-W-Ti-Al-Hf system are designed, evaluated and processed. One of these alloys, F, shows excellent high temperature tensile strength and ductility with superior creep rupture properties. As predicted by using modeling tools such as PHACOM and NEW PHACOMP, there is hardly the tendency for formation of topologically close-packed phase (TCP) phase in alloy F. Furthermore, through microstructural observation, it is also found that no TCP phase is formed in alloy F after long-time exposure at high temperature. So alloy F has well balance of phase stability and mechanical properties in view of application for gas turbines. It is proved that d-electron approach can be applied for design and development of nickel-base superalloys for gas turbine application.     

高Cr铸造镍基高温合金K4648的母合金净度研究

对两炉冲击韧性存在明显差异的高Cr铸造镍基高温合金K4648进行了对比研究,通过分析两炉母合金的主量元素和气体含量,采用电子束纽扣锭(EB锭)实验观察合金内夹杂物和对母合金用原材料金属Cr的显微组织分析等方法研究了K4648母合金净度。结果表明:1#与2#炉批母合金主量元素无明显差别。1#母合金由于气体元素O含量高达(20.5±7.5)×10-6,远高于2#合金的6×10-6,造成其室温冲击韧性(aku)不及2#合金的一半,低于技术条件要求的19.6J/cm2。电子束纽扣锭(EB锭)实验可有效地将K4648中的夹杂物汇聚,经分析主要是富Y,Ce的氧化物和富Al氧化物。证明高Cr铸造镍基高温合金K4648中添加稀土元素Y,Ce可有效攫取合金中自由态的O和S,生成稳定的稀土氧化物或硫化物,起到净化合金的作用。K4648母合金原材料中金属Cr基体中固溶有15%(质量分数)的元素O,还分布有富Cr氧化物和Cr,Al,Si的复合氧化物。此外,还存在含N、贫O区域,该区域的维氏显微硬度可达8.2GPa,是Cr基体1.3GPa的6倍,证明N使金属Cr的硬度明显升高。     

Y微合金化高铌TiAl基合金微观组织研究

采用真空非自耗电弧炉制备了名义成分为Ti-45Al-8Nb-xY(x=0,0.1,0.3,原子分数/%,下同)的合金,利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及能谱分析仪(EDS)观察了Y的添加与均匀化热处理制度对合金组织的影响。结果表明:稀土Y可以细化(α2+γ)层片团,较多的Y加入量(0.3%)细化效果显著;Y在合金中可形成分布在层片团晶内和晶界的粒状及棒状Y2O3和YAl2相;Y提高了Ti-45Al-8Nb合金的Tα转变温度,使同一均匀化热处理工艺下三种高铌TiAl基合金的组织差别较大。     

对高Al镁合金挤压变形影响因素的研究

以AZ91-D镁合金成分范围为基础设计四种不同Al,Zn,Mn元素含量的高强度镁合金,在650t挤压机上进行不同挤压模具、预处理条件下的热挤压成形.结果表明:合金元素Al,Zn对挤压成形性有较大影响,但未见Mn有明显作用.均质化预处理可以在一定程度上提高材料的塑性.流线型模具较平模、锥模可显著地改善材料的流动性.挤压后合金的强度和塑性同时得到大幅度提高,挤压后晶粒被细化至平均20μm,棒材抗拉强度可达到340MPa,延伸率超过12%.     

Solidification Behavior and Segregation of Re-containing Cast Ni-base Superalloy with Different Cr Content

The effect of chromium(Cr) on solidification and segregation behavior of Re-containing cast Ni-base superalloys was investigated by optical microscopy(OM),scanning electron microscopy(SEM) and electronic probe micro analysis(EPMA).The results show that Cr has significant effect on solidification and segregation behavior of Re-containing cast Ni-base superalloys.The liquidus and solidus of alloy decrease with increasing Cr in alloys.The segregation coefficient(K) of Mo increases and that of W and Re decreases gradually with increasing Cr element.     

Influence of Sputtered NanocrystaUine Coating on Oxidation and Hot Corrosion of a Nickel-based Superalloy M951

The isothermal and cyclic oxidation behaviors in air and hot corrosion behaviors in Na2SO4 ＋ 25 wt% K2SO4 salt of M951 cast superalloy and a sputtered nanocrystalline coating of the same material were studied. Scanning electron microscopy, energy dispersive X-ray spectroscope, X-ray diffraction, and transmission electron microscopy were employed to examine the morphologies and phase composition of the M951 alloy and nanocrystalline coating before and after oxidation and hot corrosion. The as-sputtered nanocrystalline layer has a homogeneous y phase structure of very fine grain size （30-200 nm） with the preferential growth texture of （111） parallel to the interface. Adherent AI203 rich oxide scale formed on the cast M951 alloy and its sputtered coating after isothermal oxidation at 900 and 1000 ℃. However, when being isothermal oxidized at 1100℃ and cyclic oxidized at 1000 ℃, the oxide scale formed on the cast alloy was a mixture of NiO, NiAl2O4, Al2O3 and Nb205 and spalled seriously, while that formed on the sputtered coating mainly consisted of Al2O3 and was very adherent. Nanocrystallization promoted rapid formation of Al2O3 scale during the early stage of oxidation and enhanced the adhesion of the oxide scale, thus improved the oxidation resistance of the substrate alloy. Serious corrosion occurred for the cast alloy. The sputtered nanocrystalline coating apparently improved the hot corrosion resistance of the cast alloy in the mixed sulfate by the formation of a continuous Al2O3 and Cr2O3 mixed oxide layer on the surface of the coating, and the pre- oxidation treatment of the coating led to an even better effect.     

高强Al-Mg-Si-Cu铝合金的时效工艺研究

目的 研究时效工艺参数对高强Al-Mg-Si-Cu铝合金微观组织和力学性能的影响规律,以得到Al-Mg-Si-Cu铝合金时效后最优的性能和微观组织。方法 在不同时效处理工艺参数条件下,通过对Al-Mg-Si-Cu铝合金时效处理后的硬度、电导率、室温力学性能进行测试与对比分析,并结合微观组织观察实验,分析了不同时效温度及时效时间对Al-Mg-Si-Cu铝合金时效强化相及力学性能的影响规律。结果 在不同时效温度条件下,经不同时效时间的时效处理后,Al-Mg-Si-Cu铝合金的电导率随时效温度的升高和时间的延长而增大,当时效温度为170、180、190 ℃时,硬度和力学性能在时效时间为16、12、8 h时达到峰值。同时,当时效时间为8、12、16 h时,Al-Mg-Si-Cu铝合金的时效强化相分别是β''相、β''相和Q''相;在峰值时效和过时效工况下,Al-Mg-Si-Cu铝合金的析出相均存在Q''相,该相对合金的强度具有明显的贡献。在过时效阶段,Al-Mg-Si-Cu铝合金强化相明显初化,力学性能和硬度均有明显降低。结论 经淬火处理+180 ℃/12 h时效处理后,高强Al-Mg-Si-Cu铝合金的力学性能最优,抗拉强度和屈服强度分别为404 MPa和388 MPa,硬度为136HV。