共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
采用光学显微镜、扫描电镜、X射线衍射仪、洛氏硬度计和磨损试验机对比研究了电渣重熔、喷射成形以及粉末冶金工艺生产的锻造高速钢轧辊的组织性能。结果表明,采用电渣重熔工艺所得锻造高速钢轧辊组织中存在明显沿锻造方向分布的网状共晶碳化物,碳化物尺寸粗大,分布不均,导致其耐磨性最差;喷射成形工艺所得锻造高速钢轧辊网状碳化物组织得到明显改善,但局部区域碳化物偏聚较严重,碳化物尺寸较大且主要以M6C型为主,其耐磨性比电渣重熔工艺有明显提升;粉末冶金工艺所得锻造高速钢轧辊组织晶粒细小,碳化物细小且弥散均匀分布,碳化物类型中MC型占比很高,表现出最优的耐磨性能。根据3种制备工艺下的组织和性能分析,并结合目前3种制备工艺的成熟度、经济性和制造能力,未来可对喷射成形工艺做进一步研究,并逐步在较大规格锻造高速钢轧辊中推广应用。 相似文献
3.
4.
采用传统冶炼技术生产的高速钢存在碳化物粗大及其偏析严重等质量问题。高性能高速钢的生产技术有电渣重熔法、粉末冶金法和喷射成形法等。控制高速钢中碳化物的技术有稀土元素合金化、孕育剂变质处理等化学方法,以及电磁搅拌、脉冲电流技术、脉冲磁场技术、脉冲磁致振荡技术等物理方法。脉冲磁致振荡技术(pulse magneto-oscillation, PMO)是新一代电磁冶金技术,其改善高速钢凝固组织的效果更明显。今后,应进一步研究PMO细化高速钢碳化物的机制,优化适用于高速钢工业生产的PMO参数,探索PMO与稀土元素的共同作用对高速钢凝固组织的影响。 相似文献
5.
采用普通电渣重熔工艺和新型抽锭式电渣重熔工艺制备M2高速钢,研究了熔池深度与局部凝固时间等参数对高速钢铸锭共晶碳化物形貌和类型的影响.结果表明,电渣重熔工艺不改变碳化物类型,两种工艺制备的M2铸锭都存在M6C、MC、M2C三种类型的碳化物.抽锭式电渣重熔工艺通过有效控制电渣锭直径(D=120 mm)、熔速(11 mm/min)及熔池深度(h=50 mm),减少局部凝固时间,促进平直层片状共晶碳化物转变为离异棒状、粒状碳化物,碳化物平均晶粒尺寸小于50 μm.加快冷却速度会降低组织中共晶碳化物的质量分数,同时也会降低共晶碳化物中强碳化物形成元素如W、Mo、V的含量,使更多碳化物及合金溶于基体中. 相似文献
6.
7.
李福林 《稀有金属材料与工程》2016,45(6):1437-1442
利用电渣重熔连续定向凝固技术(ESR-CDS)成功制备了Rene88DT高温合金铸锭。借助于金相显微镜,带有能谱的扫描电镜以及透射电镜,对电渣重熔连续定向合金Rene88DT铸锭进行分析,并与传统电渣铸锭进行了对比。研究结果显示,电渣重熔连续定向凝固合金Rene88DT铸锭消除了最为严重的中心偏析,中心偏析在传统电渣铸锭中是普遍存在的,这种偏析存在于柱状晶与等轴晶交界处或者柱状晶之间相互交界面处。此外,电渣重熔连续定向凝固合金二次枝晶间距较传统电渣铸锭小,析出相尺寸也较小。由于微观偏析程度的降低,使得合金在经过1200℃/24h后的热处理即可达到均匀化效果。夹杂物统计结果显示,电渣重熔连续定向凝固合金夹杂物最大尺寸为5.89微米,与传统电渣合金和粉末合金相比夹杂物数量降低60%。电渣重熔连续定向凝固合金宏观偏析和夹杂物水平的降低可提高热加工塑性,为铸&锻工艺实施提供基础。 相似文献
8.
《稀有金属材料与工程》2016,(6)
利用电渣重熔连续定向凝固技术(ESR-CDS)成功制备了Rene88DT高温合金铸锭。借助于金相显微镜,带有能谱的扫描电镜以及透射电镜,对电渣重熔连续定向合金Rene88DT铸锭进行分析,并与传统电渣铸锭进行了对比。研究结果显示,电渣重熔连续定向凝固合金Rene88DT铸锭消除了最为严重的中心偏析,中心偏析在传统电渣铸锭中是普遍存在的,这种偏析存在于柱状晶与等轴晶交界处或者柱状晶之间相互交界面处。此外,电渣重熔连续定向凝固合金二次枝晶间距较传统电渣铸锭小,析出相尺寸也较小。由于微观偏析程度的降低,使得合金在经过1200℃,24 h后的热处理即可达到均匀化效果。夹杂物统计结果显示,电渣重熔连续定向凝固合金夹杂物最大尺寸为5.89μm,与传统电渣合金和粉末合金相比夹杂物数量降低60%。电渣重熔连续定向凝固合金宏观偏析和夹杂物水平的降低可提高热加工塑性,为铸和锻工艺实施提供基础。 相似文献
9.
10.
采用OM、SEM等微观组织分析手段研究了H13钢铸态组织和扩散退火过程中显微组织和成分偏析的演变规律。结果表明,H13钢电渣锭的铸态组织为粗大马氏体+贝氏体+液析碳化物,枝晶间和晶界处分布着高熔点液析碳化物和大尺寸二次碳化物,存在严重的枝晶偏析和成分偏析。随着扩散退火温度的升高,组织中的碳化物逐渐回溶到基体中,枝晶内的碳化物溶解速度和元素扩散速度明显快于枝晶间和晶界处,会优先达到成分均匀性要求。在1240℃进行扩散退火时,枝晶间的大尺寸二次碳化物几乎全部回溶到基体中,晶界处的高熔点液析碳化物数量明显减少,仅残存少量未完全溶解的小颗粒液析碳化物。从节能和提高成材率方面考虑,建议H13钢较佳的扩散退火工艺为1240℃×10 h。 相似文献
11.
Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang 《金属学报(英文版)》2019,32(6):684-694
In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone. 相似文献
12.
After nearly two years'tense construction the first phase of industrialized base of Shenyang Research Institute of Foundry 《中国铸造》2008,5(1):63-64
After nearly two years' tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry (SRIF), located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation. 相似文献
13.
Z. Sun S.L. Zheng Y. Zhang 《金属学报(英文版)》2007,20(3):187-192
Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process. 相似文献
14.
R. González-Martínez 《金属学报(英文版)》2007,20(4):235-240
The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke. 相似文献
15.
The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C). 相似文献
16.
The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel. 相似文献
17.
This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
18.
Chao Yang He-Fei Huang Massey de los Reyes Long Yan Xing-Tai Zhou Tian Xia De-Liang Zhang 《金属学报(英文版)》2015,28(7):809
Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties. 相似文献
19.
Lei Li Bo Xu Wei-Ping Tong Hui Zhang Chun-Yan Ban Li-Zi He Zhi-Hao Zhao Yu-Bo Zuo Qing-Feng Zhu Jian-Zhong Cui 《金属学报(英文版)》2015,28(6):725
A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed. 相似文献
20.
综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。 相似文献