固溶处理对Stellite 6B钴基高温合金中碳化物的影响

研究了锻造后钴基高温合金Stellite 6B中碳化物的类型和组织形貌,以及高温固溶处理对合金中碳化物的影响。研究表明,Stellite 6B合金的显微组织由面心立方钴基固溶体与一次碳化物M_7C_3和二次碳化物M_(23)C_6组成。高温固溶处理下,碳化物M_(23)C_6先转变为M_7C_3,然后溶解到基体,当固溶时间短时,易形成分布在晶界处的连续的网状碳化物。固溶温度为1280℃,保温10 h时,网状碳化物溶解的更加充分,能够得到完全固溶的奥氏体基体。     

Ni-Fe-Cr合金固溶处理后的组织变化及其对性能的影响

采用OM和SEM研究了不同C含量Ni-Fe-Cr合金在950~1050℃固溶后的组织变化及其对拉伸性能和晶间腐蚀性能的影响。结果表明,C含量的变化影响固溶处理过程中碳化物的回溶行为和晶粒尺寸,从而造成不同C含量合金力学性能和晶间腐蚀性能的差异。C含量为0.010%(质量分数)时,950℃固溶处理可使热加工过程中产生的M_(23)C_6碳化物完全回溶,并获得平均晶粒尺寸约38 mm的等轴晶组织;C含量增加到0.026%时,固溶温度提高至1000℃可使M_(23)C_6碳化物完全回溶,获得平均晶粒尺寸约42 mm的等轴晶组织;C含量在0.010%~0.026%范围内,合金具有较低的晶间腐蚀敏感性,随C含量增加合金的强度升高,延伸率基本没有变化;C含量为0.056%时,1050℃固溶处理后,局部区域仍存在未回溶的碳化物,碳化物阻碍晶界迁移使晶粒长大缓慢,造成晶粒尺寸不均匀。同时,未回溶碳化物的存在使合金的强度略有提高,但延伸率降低;未回溶碳化物造成碳化物/基体界面处贫Cr区的出现,显著增加了合金的晶间腐蚀敏感性。     

固溶温度和冷却方式对转子用改型IN617合金晶粒尺寸及碳化物的影响

研究了不同固溶处理温度和冷却方式对转子用改型IN617合金晶粒尺寸及碳化物的影响。结果表明,随着固溶处理温度的升高,M_(23)C_6和M_6C先后回溶到基体中,且固溶温度高于1180℃时,细小的MC也可回溶。当晶界M_6C完全回溶到基体中后,失去钉扎作用的晶粒在高于1140℃的温度保温时会快速长大。固溶处理后较慢的冷速会使得晶界析出连续的碳化物,从而影响材料的力学性能。     

热处理对GH4199合金组织的影响

采用金相显微镜、扫描电镜(SEM)、X射线能谱(EDS)、X射线衍射(XRD)、透射电镜(TEM)及布氏硬度实验研究了热处理制度对GH4199合金组织和硬度的影响。结果表明:在1080~1180℃进行固溶处理,合金硬度随着加热时间的延长逐渐下降,固溶温度越低,达到稳定硬度值所需的时间越长,且稳定硬度值也就越高;随着固溶温度的增加奥氏体晶粒逐渐长大,超过1120℃后晶粒明显粗化;在1120℃以下,固溶处理时间对晶粒大小几乎没有影响;合金组织中含有大量的碳化物,主要以M6C形式存在,也有少量的M23C6和MC。随着固溶温度的增加和时间的延长,在晶界呈链状不均匀分布的碳化物逐渐溶解、粗化。     

固溶处理对Haynes282耐热合金组织与硬度的影响

研究了不同固溶处理工艺对Haynes282耐热合金组织与硬度的影响。结果表明,在1060~1150 ℃范围内保温2 h固溶处理时,Haynes试验合金的晶粒长大缓慢,固溶温度高于1150 ℃时,晶粒尺寸长大明显,M₂₃C₆和MC型碳化物基本溶解。1120 ℃固溶处理时,随着保温时间的延长,晶粒长大,未溶碳化物不断溶解。计算表明,Haynes试验合金固溶处理晶粒长大激活能Q约为382 kJ/mol。提高固溶处理温度和延长保温时间时,合金硬度降低,晶粒粗化和未溶碳化物的溶解是造成硬度降低的主要原因。     

热处理对N06600冷轧管材组织与性能的影响

对N06600冷轧管材进行了热处理,研究了热处理对力学性能、显微组织和固溶情况的影响。结果表明:当热处理时间为5 min、温度为950~1150℃时,随温度升高N06600管材强度逐渐降低,伸长率升高,纤维状显微组织逐渐发生再结晶并晶粒长大;当热处理时间为2 min、温度为1050~1100℃时,力学性能稳定,显微组织发生完全再结晶,随温度升高晶粒没有明显长大;950℃热处理时,晶内及晶界有未完全固溶的C与Cr形成的碳化物。随着温度的升高,碳化物逐渐溶解;1150℃时,碳化物已完全溶解。     

超低铁Inconel 625合金的热处理

基于10%草酸电解腐蚀特性及硬度测试结果,研究确定了超低铁Inconel 625合金的热处理工艺,利用金相显微镜和扫描电镜观察组织及腐蚀形貌。结果表明:随着固溶温度的提高及保温时间的延长,合金第二相逐渐溶入Ni基体,1140℃保温4 h第二相溶解充分,晶粒分布均匀,未发生快速长大,合金硬度为172 HV10,腐蚀倾向小,质量损失速率为4.97 kg·(m~2·h)~(-1)。固溶处理合金经1000℃稳定化6 h,基体上分布着MC和M_6C两种形式的碳化物,颗粒尺寸细小,合金硬度提高至186 HV10,750℃保温处理10 h后,质量损失速率为4.89 kg·(m~2·h)~(-1)。确定超低铁Inconel 625合金的最佳热处理工艺为:1140℃×4 h固溶+1000℃×6 h稳定化,合金可获得良好耐蚀性,适宜的硬度及晶粒尺寸。     

固溶处理对热等静压Inconel 625合金组织与拉伸性能的影响

研究了固溶处理温度和保温时间对热等静压Inconel 625合金组织与拉伸性能的影响.结果表明,随固溶温度升高,碳化物逐渐溶解,原始颗粒边界消退,从而提高合金的塑性,温度过高(1200℃)时,由于部分碳化物长大且存在过烧组织,导致硬度、强度和塑性剧烈下降.随固溶保温时间的延长,碳化物逐渐溶解,原始颗粒边界消退从而提高合金的塑性,保温时间过长(40～50 min)时,由于部分碳化物发生聚集和转变,强度明显下降.最佳固溶处理工艺为1100℃×30 min水冷,室温拉伸断裂方式为韧性断裂,综合力学性能良好.     

固溶工艺对GH690合金组织和硬度的影响

研究了不同固溶温度和保温时间对GH690合金微观组织和性能的影响规律。结果表明:GH690合金的晶粒尺寸随固溶温度的升高或保温时间的延长而增大,当温度超过1100℃时,晶粒长大速度加快;合金中的碳化物随固溶温度升高或者保温时间延长溶解增多,当温度超过1150℃后,合金中的碳化物被全部溶解;合金的硬度随固溶温度升高或保温时间延长逐渐降低,保温时间对合金硬度的影响弱于固溶温度对合金硬度的影响。     

固溶工艺对GH690合金组织和硬度的影响

研究了不同固溶温度和保温时间对GH690合金微观组织和性能的影响规律。结果表明:GH690合金的晶粒尺寸随固溶温度的升高或保温时间的延长而增大,当温度超过1100℃时,晶粒长大速度加快;合金中的碳化物随固溶温度升高或者保温时间延长溶解增多,当温度超过1150℃后,合金中的碳化物被全部溶解;合金的硬度随固溶温度升高或保温时间延长逐渐降低,保温时间对合金硬度的影响弱于固溶温度对合金硬度的影响。     

Thermal stability evaluation of nanostructured Al6061 alloy produced by cryorolling

Grain growth of nanostructured Al6061 produced by cryorolling and aging process was investigated during isothermal heat treatment in 100–500 °C temperature range. Transmission electron microscopy (TEM) observations demonstrate that after cryorolling and aging at 130 °C for 30 h, the microstructure contains 61 nm grains with dispersed 50–150 nm precipitates and 0.248% lattice strain. In addition, an increase in tensile strength up to 362 MPa because of formation of fine strengthening precipitation and nano-sized grains was observed. Thermal stability investigation within 100–500 °C temperature range showed release of lattice strain, dissolution of precipitates and grain growth. According to the X-ray diffraction (XRD) analysis, Mg₂Si precipitates disappeared after annealing at temperatures higher than 300 °C. According to the results, due to the limited grain growth up to 200 °C, there would be little decrease in mechanical properties, but within 300–500 °C range, the grain growth, dissolution of strengthening precipitates and decrease in mechanical properties are remarkable. The activation energies for grain growth were calculated to be 203.3 kJ/mol for annealing at 100–200 °C and 166.34 kJ/mol for annealing at 300–500 °C. The effect of precipitation dissolution on Al lattice parameter, displacement of Al6061 (111) XRD peak and Portevin–LeChatelier (PLC) effect on stress–strain curves is also discussed.     

热连轧GH4169合金的晶粒长大行为

对热连轧(HCR)GH4169合金在固溶处理过程中晶粒长大行为进行系统研究。结果表明,该合金?相溶解温度在990～1000℃之间,δ相对晶粒长大有显著阻碍作用,在低于δ相溶解温度进行固溶处理时,析出的δ相使得晶粒长大缓慢;在高于δ相溶解温度以上时,晶粒随温度的升高快速长大。晶粒长大动力学表明:在高于δ相固溶线温度以上进行固溶处理时,晶粒生长指数随着固溶温度的升高而增加;固溶处理温度为1000和1050℃时的晶粒长大激活能为223.849kJ/mol,晶粒长大机制为自扩散过程控制机制,并建立了相应的晶粒长大动力学方程。     

GH690合金管材热处理工艺优化

以国外Inconel 690成品管的显微组织为参照对象,对国产GH690合金管材在不同工艺条件下的固溶处理与TT处理工艺进行了研究;采用OM、SEM和TEM等表征手段分析了工艺参数对其晶粒度、晶界碳化物形貌和贫Cr区的影响。结果表明:国产GH690合金管在固溶处理过程中,随着固溶温度的提高,尺寸较大晶粒所占比例逐渐升高,长大激活能为265 kJ/mol。当固溶温度超过1100℃时,保温时间对晶粒尺寸影响显著。国产GH690合金管析出细小半连续晶界碳化物的TT处理工艺参数为680℃/10~20 h,715℃/10~20 h,750℃/5~15 h。经1090~1110℃/5 min固溶处理以及715℃/10 h或15 h的TT处理后,国产GH690合金管晶粒尺寸分布、晶界碳化物形貌特征和贫Cr区演化特征与国外Inconel 690成品管非常相似;而其TiN颗粒数量和尺寸明显少于和小于后者,贫Cr区的最低Cr浓度高于后者。通过对显微组织特征的综合评价,表明国产GH690合金管的显微组织总体优于国外Inconel 690成品管。同时,兼顾实际生产中的成本问题,提出国产GH690合金管热处理工艺优化的建议。     

多次真空固溶处理对GH1131高温合金组织和力学性能的影响

利用真空高压气淬工艺研究了GH1131高温合金经1100~1170 ℃范围内多次真空固溶处理后的组织和力学性能。结果表明,固溶态组织包含奥氏体晶粒和颗粒状碳化物,且随着固溶温度的升高,晶粒度稍有增大趋势。GH1131高温合金经多次真空固溶处理后组织均匀,常温与高温力学性能稳定,经1100 ℃+1130 ℃+1170 ℃三次真空固溶处理后,晶粒度维持了6~8级,900 ℃高温抗拉强度达到200 MPa。     

The Microstructural Evolution of Inconel Alloy 740 During Solution Treatment, Aging, and Exposure at 760?°C

In this study, the microstructural evolution of Inconel alloy 740 during solution treatment and aging was characterized using optical and scanning electron microscopy. During double solution heat treatment, carbon is liberated from the dissolution of MC carbides during the first solution treatment at 1150 °C, and fine MC carbides are precipitated on gamma grain boundaries during the second solution treatment at 1120 °C. Due to the concurrent decrease in carbon solubility and the increase in the contribution of grain boundary diffusion at lower temperatures, the MC carbides on the gamma grain boundaries provide a localized carbon reservoir that aids in M₂₃C₆ carbide precipitation on gamma grain boundaries during exposure at 760 °C. The γ′ phase, which is the key strengthening phase in alloy 740, is incorporated into the alloy microstructure during aging at 850 °C. The main source of microstructural instability observed during exposure at 760 °C was the coarsening of the γ′ phase.     

Effect of Heat Treatment Parameters on the Microstructure and Properties of Inconel-625 Superalloy

Inconel-625 is a solid solution-strengthened alloy used for long-duration applications at high temperatures and moderate stresses. Different heat treatment cycles (temperatures of 625-1025 °C and time of 2-6 h) have been studied to obtain optimum mechanical properties suitable for a specific application. It has been observed that room temperature strength and, hardness decreased and ductility increased with increase in heat treatment temperature. The rate of change of these properties is found to be moderate for the samples heat-treated up to 850 °C, and thereafter, it increases rapidly. It is attributed to the microstructural changes like dissolution of carbides, recrystallization and grain growth. Microstructures are found to be predominantly single-phase austenitic with the presence of fine alloy carbides. The presence of twins is observed in samples heat-treated at lower temperature, which act as nucleation sites for recrystallization at 775 °C. Beyond 850 °C, the role of carbides present in the matrix is subsided by the coarsening of recrystallized grains and finally at 1025 °C, significant dissolution of carbide results in substantial reduction in strength and increase in ductility. Elongation to an extent of >71% has been obtained in sample heat-treated at 1025 °C indicating excellent tendency for cold workability. Failure of heat-treated specimens is found to be mainly due to carbide particle-matrix decohesion which acts as locations for crack initiation.     

固溶处理和人工时效对Al-Cu合金显微组织和力学性能的影响(英文)

对Al-Cu合金进行析出强化和人工时效处理以获得优异的力学性能,如高的强度、好的韧性。其热处理工艺条件为:510～530℃固溶处理2h;60℃水淬;160～190℃人工时效2～8h。采用光学显微镜、扫描电镜、能谱分析、透射电镜和拉伸实验对经固溶和人工时效处理的Al-Cu合金的组织和力学性能进行表征。固溶处理实验结果表明,Al-Cu合金的力学性能随着固溶处理温度的升高先增加,然后降低。这是由于Al-Cu合金的残余相逐渐溶解进入基体中,从而导致析出相的数量和再结晶晶粒尺寸不断增加。相较于固溶处理温度,固溶处理时间对Al-Cu合金的影响较小。人工时效处理实验结果表明,合金经180℃时效8h,可以获得最大的拉伸强度。合金的最大拉伸强度和屈服强度随着时效时间的延长和温度的升高而升高。     

The Effect of Grain Size and Dislocation Density on the Tensile Properties of Ni-SiC<Subscript>NP</Subscript> Composites During Annealing

The grain size refinement, enhancement of mechanical properties, and static recrystallization behavior of metallic nickel-silicon carbide nano-particle (Ni-3wt.%SiC_NP) composites, milled for times ranging from 8 to 48 h have been examined. One set of Ni-SiC_NP composite samples were annealed at 300 °C for 250 h, while the other set of samples were maintained at room temperature for control purposes (reference). The electron backscatter diffraction results indicate that the grain size of the annealed Ni-SiC_NP composite was refined due to grain restructuring during static recrystallization. The x-ray diffraction results indicate that low-temperature annealing effectively reduced the density of dislocations; this can be explained by the dislocation pile-up model. Additionally, the tensile tests indicated that the annealed Ni-SiC_NP composite had a significant increase in strength due to an increase of the Hall–Petch strengthening effect with a slight increase in the total elongation. The decrease of dislocation pile-up in the grain interiors and the increase in grain boundary sliding are assumed to be the main mechanisms at play. The relationship between the microstructural evolution and the variation of tensile properties is examined in this study.     

Effects of solution heat treatment on the microstructure, oxidation, and mechanical properties of a cast Ni3Al-based intermetallic alloy

Solution heat treatment is employed in an attempt to improve oxidation and mechanical properties of an as-cast Ni₃Al alloy (IC221M) at operation temperature, 900 °C. Solution heat treatment was hypothesized to have beneficial effects through dissolving γ Ni₅Zr eutectic into the matrix. The microstructures, oxidation behavior in air at 900 °C, and mechanical properties with aging times at 900 °C were examined after solution heat treatment of as-cast Ni₃Al alloy in Ar for up to 100 h at 1100 °C. The oxide penetration depth into the matrix was dramatically decreased and more homogeneous surface oxides were obtained relative to the no solution, treatment case. Hardness was improved by solution heat treatment due to a solid solution strengthening effect by Zr, but the tensile properties after solution heat treatment were not significantly different from those prior to treatment.     

High temperature mechanical properties and microstructure of die forged Al−5.87Zn−2.07Mg−2.42Cu alloy

The high temperature mechanical properties (250 °C) and microstructure of a die-forged Al−5.87Zn− 2.07Mg−2.42Cu alloy after T6 heat treatment were investigated. High temperature tensile tests show that as the temperature increases from room temperature to 250 °C, the ultimate tensile strength of the alloy decreases from 638 to 304 MPa, and the elongation rises from 13.6% to 20.4%. Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) were applied for microstructure characterization, which indicates that the increase of tensile temperature can lead to the coarsening of precipitates, drop of dislocation density, and increase of dynamic recovery. After tensile testing at 250 °C, a sub-grain structure composed of a high fraction of small-angle grain boundary is formed.