FGH95镍基合金的蠕变行为及影响因素

通过蠕变曲线测定和组织形貌观察,研究FGH95合金的蠕变行为及影响因素。结果表明:经1150℃固溶和时效处理后,在晶界处有粗大γ′相不连续分布,其周围存在γ′相贫化区;经1165℃固溶和时效后,合金的晶粒尺寸明显长大,并在晶界形成连续的碳化物膜;经1160℃固溶后,合金中无粗大γ′相,在晶内弥散析出细小γ′相,其中,有粒状(Nb,Ti)C相在晶内及沿晶界不连续析出,可提高合金的晶界强度,抑制晶界滑移,是使合金具有较好蠕变抗力的主要原因。蠕变期间,合金的变形机制是位错剪切或绕过γ′相,蠕变后期,在晶内发生单取向和双取向滑移,并引起应力集中,致使裂纹在晶界处萌生及扩展是合金的蠕变断裂机制。     

Effects of heat treatment on microstructure evolution and mechanical properties of Mg-6Zn-1.4Y-0.6Zr alloy

To investigate the effects of solution temperature and the decomposition of I-phase on the microstructure, phase composition and mechanical properties of as-cast Mg-6Zn-1.4Y-0.6Zr alloy, solution treatment at 440 oC, 460 oC and 480 oC and further aging treatment were conducted on the alloy. The results indicate that the net-like intermetallic compounds(mainly I-phase) dissolve into the α-Mg matrix gradually with the increase of solution temperature from 440 oC to 480 oC. Besides, the I-phase decomposes completely at 480 oC, with the formation of fine W-phase(thermal stable phase) and Mg_7Zn_3 phase. In addition, a great number of fine and dispersive Mg-Zn binary phases precipitate in the α-Mg matrix during the aging treatment. Due to the increase of solute atoms and the precipitation of strengthening phases, such as W-phase and Mg-Zn phases, the optimal strength is obtained after solution treatment at 460 oC for 8 h and aged at 200 oC for 16 h. The yield strength(YS), ultimate tensile strength(UTS) and elongation are 208 MPa, 257 MPa and 3.8%, respectively. Compared with the as-cast alloy, the increments of YS and UTS are 117% and 58%, respectively, while the decrement of elongation is 46%.     

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。     

Cu-Cr-Zr-Sn合金的时效析出行为与性能

采用TEM对Cu-0.22Cr-0.05Zr-0.05Sn合金不同形变热处理状态微观组织的演变以及时效过程中析出相的状态进行研究,并以此解释形变热处理过程中合金力学性能和导电性能的变化.结果表明,合金中存在2种析出相,分别是Cr相和Cu4Zr相.其中Cr相在时效过程中分别经历了固溶体、GP区、脱溶并与基体共格以及长大;而Cu4Zr相则以早期Cr析出相为核伴随析出,与基体半共格.由于析出相尺寸很小,且分布较为均匀,使合金具有很强的时效强化效果,经940℃固溶1h后冷加工至变形率为96％并在400℃时效4h,合金的抗拉强度和电导率可分别达到400 MPa和84％IACS.对于该合金,时效温度是决定合金综合性能的关键,而时效时间对综合性能的影响并不显著.     

一种汽车发动机气阀用节镍型高温合金的固溶时效工艺

研究了不同热处理工艺下汽车发动机气阀用节镍型高温合金的微观组织、硬度及力学性能。试验结果表明,在900~1100 ℃固溶温度范围内,该材料的晶粒尺寸随温度的升高逐渐增大,硬度逐渐降低,1050 ℃后晶粒长大明显、急剧粗化,固溶温度宜选择为1000~1050 ℃,以保证主要强化相必要的析出条件且具有适宜的晶粒度;在700~760 ℃时效温度范围内,该材料的强度随时效温度的升高而逐渐增强,但韧塑性逐渐降低。当固溶时效工艺为1020 ℃×30 min固溶(水冷)+ 720 ℃×4 h时效(空冷)时,该节镍型高温合金可获得良好的强韧性匹配,满足技术要求。     

恢复热处理对K403镍基高温合金组织与性能的影响

对涡轮叶片用典型材料镍基高温合金K403进行应力时效模拟使用后的叶片,再对其进行恢复热处理。采用扫描电镜和力学测试设备对铸态试样、预先应力时效试样和恢复热处理试样的微观组织与力学性能进行了测试分析。结果表明,不同时间预先应力时效K403合金试棒经恢复热处理以后,微观组织中的γ′强化相明显细化,形貌接近立方,恢复热处理试样的高温抗拉强度和高温持久寿命都优于未经处理的合金试棒。预先应力时效时间越长,恢复热处理后合金试棒的高温持久寿命提高率越高。     

半固态挤压铸造A356合金在热处理过程中的组织和性能演化

半固态挤压铸造的A356合金首先在540℃下进行固溶处理,随着固溶温度升高,Mg和Si原子逐渐溶解于基体中,并产生了固溶强化作用。抗拉强度、延伸率和硬度在固溶6 h达到峰值,之后合金力学性能随固溶时间延长而下降。在固溶处理之后合金在180℃下进行了不同时间的时效处理。随着时效时间延长,Mg₂Si相逐渐在基体中析出,析出相显著球化细化,尺寸约为2μm。经过对合金组织和力学性能的分析,半固态挤压铸造A356合金的最佳热处理制度为:540℃固溶6h,180℃时效4h。经过固溶和时效处理后的合金抗拉强度达到336 MPa,延伸率达到6.9%,硬度达到1240 MPa,相较于热处理前的性能提升了106.7%。     

Effects of Different Heat Treatments on the Microstructures and Creep Properties of GH4169 Superalloy

Experiments were conducted to evaluate the effects of different heat treatments on the microstructures and creep properties of GH4169 alloy. In order to study the strengthening effect of the δ phase, three different heat treatments were performed in this research. (1) High standard treatment (namely, HST), i.e., 960 °C × 2 h/air cooling (AC) + 720 °C × 8 h/furnace cooling (FC) at 55 °C/h to 620 °C + 620 °C × 8 h/AC. (2) Standard treatment (namely, ST), i.e., 960 °C × 1 h/AC + 720 °C × 8 h/FC at 55 °C/h to 620 °C + 620 °C × 8 h/AC. (3) Direct aging treatment (namely, DA), i.e., 720 °C × 8 h/FC at 55 °C/h to 620 °C + 620 °C × 8 h/AC. In HST specimen, it is observed that the δ phases exist not only at the boundaries but also locate inside the grains. However, few δ phases can be observed in DA specimen. All the samples were creep tested to failure under the condition of 650 °C/725 MPa. The DA alloy exhibited the best creep property and the creep rupture life was as long as 169 h. The creep rupture life of the ST alloy was the shortest, which is only about 88 h. The reasons can be summarized as the amount of the strengthening phases, the compactness of the boundaries, the fixing effect of the δ phase and the favorable strength coordination. All the points are closely related with the δ phase. It is reasonable to conclude that the quantity and distribution of δ phase have great influence on the creep properties of GH4169 alloy. Moreover, the fracture modes of the three samples are also discussed in this paper.     

选区激光熔化Mar-M509合金成形性能及热处理工艺研究

针对选区激光熔化（SLM）成形Mar-M509合金进行了打印工艺参数优化,得到孔隙和微裂纹较少的优化工艺参数。并设计固溶、固溶+时效两种热处理制度,研究热处理对显微组织及力学性能的影响。与直接打印态样品相比,热处理主要导致两种析出相的产生,亮白色近圆形富Cr-Co碳化物颗粒和暗灰色不规则长条形富Ta-W碳化物。室温拉伸试验结果表明,沉积态样品表现出高的抗拉强度和屈服强度,固溶热处理后的抗拉强度降低500MPa,固溶+时效热处理后抗拉强度下降约350MPa。造成强度降低的主要原因是热处理过程中发生了晶粒粗化和残余应力消除。固溶处理后样品中析出物以富Cr- Co碳化物为主,少量大尺寸Ta-W碳化物沿晶界析出。固溶+时效处理后Ta-W碳化物含量增加,以沿晶界和晶内两种方式存在。热处理后材料塑性未得到改善,两种热处理制度均导致产生大量沿晶界析出的碳化物,推测会对材料塑性产生不利影响。为了改善SLM Mar-M509的强度和塑性,需通过热处理工艺对析出碳化物的尺寸和分布进一步调控。     

时效温度对GH2132合金组织与力学性能的影响

采用光学显微镜、扫描电镜、微机控制电子万能试验机等仪器研究了620、650、680、720、750、780 ℃单级时效和720 ℃+650 ℃双级时效对GH2132合金显微组织及力学性能的影响。结果表明:双级时效的抗拉强度和剪切强度高于单级时效的抗拉强度和剪切强度,抗拉强度达到1130 MPa,剪切强度达到720 MPa。且在620~780 ℃的温度范围内进行单级时效时,随着时效温度的提高,合金的抗拉强度和剪切强度呈现先升高后降低的趋势,在720 ℃时抗拉强度达到最大值1065 MPa,剪切强度达到最大值685 MPa。     

胎盘组织核因子-κB与妊娠并发症关系研究进展

核因子-κB（NF-κB）是一种细胞内重要的转录因子,调控包括炎症、凋亡在内多种基因的表达,在胎盘中分布广泛。本文对胎盘组织中NF-κB与先兆子痫、HELLP综合征和胎膜早破等妊娠并发症的关系研究进行综述,概括了胎盘NF-κB在这些妊娠并发症发生过程中的作用以及依赖NF-κB途径治疗相关疾病的研究进展,为胎盘相关疾病的深入研究奠定基础,为妊娠并发症疾病的诊治提供新思路。     

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。     

高温时效时间对定向凝固DZ951镍基高温合金组织和持久性能的影响

采用光学显微镜和扫描电子显微镜研究了高温时效时间对DZ951合金组织及其持久性能的影响。结果表明,合金在1130℃高温时效时,碳化物由铸态时的骨架状变成块状,呈不连续状分布在晶界。随着保温时间的延长,γ′立方度降低,尺寸增加。保温6h时,γ′粗化形筏。合金在1130℃高温时效时,由于γ′部分固溶,并在随后的冷却过程中析出细小球形γ′相,随着保温时间的增加,细小γ′相的体积分数增多。DZ951合金在1100℃,60MPa的持久寿命随保温时间增加而降低,延伸率增加。γ′粗化形筏对合金持久寿命是不利的。     

Effect of Heat Treatment on Microstructure and Stress Rupture Properties of a Ni-Mo-Cr-Fe Base Corrosion-Resistant Superalloy

The influences of heat treatment and test condition on the microstructure and stress rupture properties of a Ni-Mo-Cr-Fe base corrosion-resistant superalloy have been investigated in this paper. Optical microscope and scanning electron microscope were employed for the microstructure observation, and X-ray diffraction, electron probe micro-analyzer, and transmission electron microscope were used for phase determination. It was found that the grain size increased and the volume fractions of initial M₆C carbides decreased along with the increase in solution treatment temperature. When tested at 650 °C/320 MPa, the stress rupture lives decreased with the increase in solution treatment temperature, but the stress rupture lives increased slightly at first and then decreased for the samples solution heat treated at 1220 °C when tested at 700 °C/240 MPa. The elongations showed the descendent trends under these two conditions. The stress rupture life and elongation for the aged samples all showed a noticeable improvement at 650 °C/320 MPa, but there was no noticeable improvement at 700 °C/240 MPa. The reasons can be attributed to the grain size, test conditions, and the initial and secondary carbides.     

时效温度对0Cr15Ni70Ti3AlNb合金组织和性能的影响

采用相分析、SEM、万能拉伸试验机等手段,研究了不同时效温度对0Cr15Ni70Ti3AlNb合金组织和性能的影响。结果表明:0Cr15Ni70Ti3AlNb合金在不同的时效温度下析出相有MC相、M23C6相和γ′相。MC和M23C6碳化物在650、670、690℃时的含量基本保持不变。随着时效温度的升高,γ′相的含量和尺寸不断增加。时效温度从650℃升高到720℃,γ′相质量分数由4.971%增加至10.744%,γ′相晶粒尺寸由11.0 nm增大到38.8 nm。在650℃保温14 h后,基体内部析出细小的球状γ′相,当时效温度为750℃时,合金内部出现链状的γ′相,当时效温度为810和840℃时,合金中存在方形的γ′相。随着时效温度的升高,合金室温抗拉强度和屈服强度呈现先增高后减小的趋势,当时效温度高于750℃后,室温抗拉强度和屈服强度均迅速下降,时效温度为720℃时,合金的冲击韧性值最小。     

Precipitation Behavior of α Phase and Mechanical Properties in Severely Plastic Deformed Ti-15-3 Alloy

研究了大变形量冷轧Ti-15-3合金的时效析出行为和时效过程中力学性能的变化。冷变形使Ti-15-3合金中形成部分纳米晶。冷变形合金在450～650℃时效时,从β相纳米晶区析出极为细小的针状α相,而从β相非纳米晶区析出的α相随着时效温度的升高由针状逐渐长大为条状,进而演变为凸透镜状。冷变形合金在450℃时效4h后,硬度达到了峰值,HV为5328MPa。450℃时效时在硬度峰值处同样达到了强度峰值,屈服强度和抗拉强度分别可高达1483和1562MPa。时效温度升高,达到峰值硬度的时间缩短,硬度值大幅度下降。650℃时效后的强度和硬度均低于时效前,粗大的透镜状析出相、纳米晶的长大以及位错密度的急剧下降是650℃时效时硬化效果消失的主要原因。不同时效工艺下的强度和硬度的变化规律相似,性能的变化与时效过程中析出相的状态有关。     

时效对超高强含Sc铝合金组织和性能的影响

采用维氏硬度测量、室温拉伸性能测试和显微组织结构分析,研究了不同时效制度下Al-Zn-Cu-Mg-Sc-Zr合金的力学性能、腐蚀性能和显微组织.结果表明,该合金具有显著的时效硬化效应,随时效温度的升高,合金达到时效硬度峰值的时间缩短.合金适宜的时效制度为120℃24h.此时,合金的抗拉强度、屈服强度、伸长率和维氏硬度分别为696N/mm2、654N/mm2、11.1％和211.2HV.合金中主要强化相为GP区和η'相,主要强化作用为沉淀强化及弥散强化.时效过程中Al3Sc和Al3(Sc,Zr)质点表现出较强的热稳定性;合金抗晶间腐蚀能力随时效时间的延长而增强.     

Influence of heat treatment on the microstructure and mechanical properties of DZ951 alloy

DZ951 directionally solidified nickel-base superalloy is mainly strengthened by y phase.Regularly aligned cuboidal and bimodal γ precipitates were attained by two heat treatments.The effect of microstructure on the mechanical properties of DZ951 alloy has been investigated.The results indicate that MC carbide changes to little blocks during aging treatment at 1050℃ (HT1).MC carbide partly degrades into M23c6 and there is a layer of γ around the carbide during aging treatment at 115℃ (HT2),which is beneficial to the elongation of DZ951 alloy.Small γ volume fraction and the uneven deformation structure are contributed to low mechanical propexties of the as-cast alloy.HT1 alloy has a better stress rupture life at 1100℃50 MPa and yield stress at 20℃,800℃ and 1100℃,which is attributed to regularly aligned cuboidal γ phase and even deformation structure.HT2 alloy has a good combination of strength and ductility.This arises fi'om the bimodal γ precitates and the degeneration of MC carbide.     

Rejuvenation Heat Treatment of the Second-Generation Single-Crystal Superalloy DD6

The second-generation single-crystal superalloy DD6 with [001] orientation was prepared by screw selecting method in the directionally solidified furnace. The long-term aging of the alloy after full heat treatment was performed at1100 °C for 400 h. Then the rejuvenation heat treatment 1300 °C/4 h/AC ? 1120 °C/4 h/AC ? 870 °C/24 h/AC was carried out. The stress rupture properties were investigated at 760 °C/800 MPa, 850 °C/550 MPa, 980 °C/250 MPa and1100 °C/140 MPa after different heat treatments. The microstructures of the alloy at different conditions were studied by SEM. The results show that c0 phase of the alloy became very irregular and larger after long-term aging at 1100 °C for 400 h. A very small amount of needle-shaped TCP phase precipitated in the dendrite core. The coarsened c0 phase and TCP phase dissolved entirely after rejuvenation heat treatment. The microstructure was restored and almost same with the original microstructure. The stress rupture life of the alloy decreased in different degrees at various test conditions after long-term aging. The stress rupture life of the alloy after rejuvenation heat treatment all restores to the original specimen more than 80%at different conditions. The microstructure degradation of the alloy during long-term aging includes coarsening of the c0 phase,P-type raft and precipitation of TCP phase, which results in the degeneration of stress rupture property. The rejuvenation heat treatment succeeds in restoring the original microstructure and stress rupture properties of the alloy.     

Effects of different metallurgical processing on microstructures and mechanical properties of inconel alloy 783

Different metallurgical processing, including the standard heat treatment, heat treatment without β aging, addition of high amount of Cr, and long-term isothermal exposure, was conducted on superalloy Inconel 783. For these processed materials, the tensile property and hardness at room temperature and stress relaxation behavior at 650 °C were examined. The testing results showed that isothermal exposure and heat treatment without β aging slightly enhanced the yield strength of alloy 783 at room temperature as well as all metallurgical processing in this study produced an identical stress relaxation behavior at 650 °C. The microstructure variation with different processing was analyzed using optical microscope, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).