锰含量对超细晶粒C-Mn钢显微组织和机械性能的影响

研究了锰含量对两种超细晶粒C-Mn钢(碳含量为0.2%)显微组织和机械性能的影响.大压下量温变形和连续退火可形成超细晶粒显微组织,最终钢的显微组织由含有细小渗碳体颗粒的超细粒状铁素体组成.渗碳体颗粒内锰富集,因此,铁素体晶粒的平均尺寸随锰含量的增加而减小(锰含量从0.74%增加到1.52%时,晶粒尺寸由1.3μm减小到0.8μm).锰含量越高,晶粒越细.延展性和韧性相同的情况下,增加锰含量将提高钢的强度.     

钇对2519铝合金的组织与性能的影响

用X射线、光学显微镜及扫描电镜等研究了钇对2519铝合金的组织及力学性能的影响,实验结果表明:加入适量钇(0.1%质量分数)后,合金的强度、硬度、伸长率提高,合金的再结晶组织细化,当钇含量超过0.1%时,合金的强度、硬度、伸长率随钇含量的增加而逐渐降低,适宜的含钇量为0.1%,钇主要以Al6Cu6Y化合物的形式存在并沿晶界分布。     

Effect of Finishing Rolling Temperature on Microstructure and Mechanical Properties of Microalloyed TRIP Steels

Different samples of TRIP (transformation induced plasticity) steel obtained by two different hot-rolling schedules are investigated by using a SEM (scanning electron microscope). The microstructure is characterized by using an OM (optical microscope) for phase distribution and by EBSD (electron backscatter diffraction) for texture and phase mapping. ODF (orientation distribution function) graphs are used to investigate the effect of recrystallization behavior of the hot-deformed austenite on phase transformation during the controlled cooling process. The mechanical behavior is interpreted in terms of the strength of both hard and soft phases, in combination with the quantity, location and transformation kinetics of the mechanically induced martensite (TRIP effect). The results show that more austenite grains exist in the steels obtained at finishing rolling temperature (FRT) of 750 °C, which inherited the deformation structure after the hot-rolling process. The instantaneous n value (n_i) of those steels is kept high during a large range of strain before failure, while the tensile strength and total elongation of the steels with respect to the different finishing rolling temperatures do not show any significant differences.     

超快速冷却对中碳钢组织和性能的影响

利用超快速冷却装置,通过控制轧后冷却路径,对某中碳钢的显微组织和力学性能进行了系统的研究.结果表明:超快速冷却可以抑制先共析铁索体的生成,破坏原有先共析铁素体的网状分布;超快速冷却显著缩小了珠光体的片层间距;随着超快速冷却后温度的降低,实验钢的强度和室温冲击韧性同时得到了提高.高温终轧+超快速冷却工艺可以使中碳钢获得良好的力学性能,避免了低温轧制带来的轧机负荷大的弊端,提高了轧制节奏.     

分级均匀化处理对7068新型高强铝合金组织及性能的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)及差热分析(DSC)研究了7068高强高韧铝合金均匀化热处理制度及其微观组织演变;通过单向拉伸试验及四探针电阻率法测定了不同均匀化后T6态合金的拉伸性能及电导率。结果表明:7068铝合金铸态组织存在枝晶偏析,非平衡共晶相沿晶界呈连续网状分布,低熔点共晶相初始溶解温度为467.3°C;合金经455°C×16h+465°C×4h+475°C×4h三级均匀化处理后,成分均匀,残留共晶很少且T6态的抗拉强度、延伸率以及电导率均达到所做均匀化处理中最佳,分别为715MPa、13.3%和34.5%IACS。     

Effect of Zn Content on Microstructure and Mechanical Properties of MgZnYLaMM Alloys

The effect of Zn content on microstructure, existing phases, and mechanical properties of rapidly solidified MgZn _x Y₁LaMM₁Mn_0.5 alloys (X?=?2, 3, 4 at.?pct) has been investigated. To assess the microstructural characterization of nanocrystalline alloys, the study also includes microstructural characterization of the master alloys. The microstructure of the alloys in as-rapidly solidified condition consisted of supersaturated magnesium dendrites and fine (Mg,Zn)₁₇La₂ and W phase (Mg₃Y₂Zn₃) segregated at grain and cell boundaries. During continuous heating, the metastable solid solution in Mg dendrites breaks down, increasing the volume fraction of second-phase particles. After annealing for 1?hour at 673?K (400?°C), very small spherical Mn-rich precipitates appeared in the three alloys and a long-period stacking ordered (LPS) phase of rectangular morphology precipitated inside the Mg grains in the alloy with the lowest Zn content. The nanocrystalline nature of the ribbons accounts for the high hardness and yield stress values in as-rapidly solidified state, although both decrease with increasing zinc content. This fact has been related to a coarser microstructure and higher volume fraction of the W phase as the Zn content increases. The highest yield stress value of 350?MPa is attained by the MgZn₂Y₁LaMM₁ ribbon in as-rapidly solidified condition. A decrease in yield stress values (about 50?MPa) is observed for all ribbons when they are heated at 673?K (400?°C) for 1?hour.     

Effect of Nitrogen Content on the Microstructure and Mechanical Properties of Ti-Mo-N Coating Films

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate ( f_textN2 ) left( {f_{{{text{N}}_{2} }} } right) and showed a maximum hardness of about 30 GPa at a f_textN2 = 0.3 textccm f_{{{text{N}}_{2} }} = 0.3,{text{ccm}} . On the one hand, the films deposited at f_textN2 3 1.0  textccm f_{{{text{N}}_{2} }} ge 1.0;{text{ccm}} showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at f_textN2 = 2.0  textccm. f_{{{text{N}}_{2} }} = 2.0;{text{ccm}}.     

热处理温度对高强变形铝青铜的组织和力学性能的影响

针对一种新型高强变形铝青铜合金,考察了淬火温度和回火温度对该合金的微观组织和力学性能的影响。研究结果表明,淬火温度越高,合金内部的β'马氏体相越多,材料的硬度越高,但淬火温度过高时,由于针片状α相的出现,使材料的强度和塑性有较大下降。试验合金适宜的淬火温度为900℃。淬火态材料经低温回火,强度可进一步提高,400℃回火时材料的强度和硬度达到峰值,此后随着回火温度的升高,材料的强度和硬度逐渐下降,延伸率逐渐提高。600℃回火态材料的抗拉强度和延伸率分别达到900 MPa和17%以上,具有优良的强韧配合。     

Effect of Carbon Content on Mechanical Properties and Weather Resistance of High Performance Bridge Steels

The influence of carbon content on the mechanical properties of high yield strength bridge steel has been in-vestigated. The results show that the excellent mechanical properties and corrosion resistance are obtained for the steel with carbon content of 0.03%-0.05% (mass percent). According to the results, a new weathering bridge steel plate with carbon content of 0.045% (mass percent)has been developed. The appropriate controlled cooling process should be taken due to the results of CCT (continuous cooling transformation)and TTT (time-temperature-transformation)to ensure both microstructure and mechanical properties. CCT curve of the newly developed steel shows that when accelerated cooling speed is higher than 5℃/s, the intermediate transformation products can be formed. The TTT curve displays that the intermediate transformation temperature ranges from 600 to 530℃. Yield strength of the newly developed steels reaches 500 MPa, and their elongation and toughness are excellent.     

2011易切削铝合金的微观组织结构与性能

采用力学性能测试、DTA热分析、X射线衍射物相分析和透射电镜分析技术研究了时效工艺对固溶-冷拉处理的2011合金显微组织结构特征和力学性能的影响。结果表明：合金的最佳时效工艺为170℃／8h。在此条件下,合金棒材的抗拉强度为472MPa,屈服强度为378MPa,延伸率为10．1％;合金的物相组成为铝基同溶体、低熔点相Pb2Bi3和Bi以及主要强化相CuAl2。球形低熔点共晶组成物（Pb7Bi3＋Bi）的熔化温度为156．02％,CuAl2相的析出强化以及低熔点共晶组成物（Pb7Bi3和Bi）的存在使合金同时具有较高的强度和良好的易切削加工性能。     

铌对低温钢组织及性能的影响

通过金相组织观察、低温冲击试验和拉伸试验及拉伸断口形貌观察,研究了铌对正火+调质处理低温钢组织及性能的影响。结果表明:铸态下随着试样中铌含量的增加,组织中珠光体片间距逐渐减小,经过930℃正火+900℃淬火+630℃回火热处理后,铌质量分数为0.039%的试样组织及综合性能最佳,组织为回火索氏体,-20、-40℃夏比冲击功分别达到44.4和28.4J,抗拉强度和屈服强度分别为995和885MPa,断后伸长率达到17.0%。     

Effects of Tungsten Addition on the Microstructure and Mechanical Properties of Microalloyed Forging Steels

In the current study, the effects of tungsten (W) addition on the microstructure, hardness, and room/low [223 K and 173 K (?50 °C and ?100 °C)] temperature tensile properties of microalloyed forging steels were systematically investigated. Four kinds of steel specimens were produced by varying the W additions (0, 0.1, 0.5, and 1 wt pct). The microstructure showed that the addition of W does not have any noticeable effect on the amount of precipitates. The precipitates in W-containing steels were all rich in W, and the W concentration in the precipitates increased with the increasing W content. The mean sizes of both austenite grains and precipitates decreased with the increasing W content. When the W content was equal to or less than 0.5 pct, the addition of W favored the formation of allotriomorphic ferrite, which subsequently promoted the development of acicular ferrite in the microalloyed forging steels. The results of mechanical tests indicated that W plays an important role in increasing the hardness and tensile strength. When the testing temperature was decreased, the tensile strength showed an increasing trend. Both the yield strength and the ultimate tensile strength obeyed an Arrhenius type of relation with respect to temperature. When the temperature was decreased from 223 K to 173 K (from ?50 °C to ?100 °C), a ductile-to-brittle transition (DBT) of the specimen with 1 pct W occurred. The addition of W favored a higher DBT temperature. From the microstructural and mechanical test results, it is demonstrated that the addition of 0.5 pct W results in the best combination of excellent room/low-temperature tensile strength and ductility.     

Microstructure and Mechanical Properties of Gear Steels After High Temperature Carburization

High temperature carburization is becoming more and more attractive because it can remarkably reduce processing time and increase productivity. However, the commonly used gear steels which are microalloyed by Al are not suitable for high temperature carburization due to abnormal grain coarsening. The gear steel 20CrMnTiNb, which is microalloyed with 0. 048% Nb and 0. 038% Ti, has been compared with the gear steel 20CrMn in terms of microstructure in the case of hardened layer and in the core after carburizing at 1000 °C for 4 h and mechanical properties after carburizing and pseudo-carburizing. The results indicate that the fine austenite grains exist in the carburized case of 20CrMnTiNb steel, while there is abnormal coarsening and duplex grain structure in the case and core of steel 20CrMn. The average prior austenite grain sizes are 19.5 and 34.2 μm for the steels 20CrMnTiNb and 20CrMn, respectively. In addition, the mechanical properties of 20CrMnTiNb steel are superior to those of 20CrMn steel. In particular, the HV hardness of the former is higher than that of the latter by about 40–70 in the range of less than 0.7 mm in depth. Therefore, the steel 20CrMnTiNb is suitable for high temperature carburization.     

Effect of Equal Channel Angular Pressing on Microstructure and Mechanical Properties of Commercial Purity Aluminum

Commercial purity aluminum was deformed by equal channel angular pressing (ECAP) using steel dies producing two different shear strains of either 1.15 or 0.60 in each pass. Two sets of samples were selected for study, of which the first set consists of aluminum billets repeatedly deformed without changing orientation (process A) up to three passes using first die. The second set of samples was equal channel angular pressed (ECAPed) using the second die up to 10 passes adopting process B_c, where samples were rotated by 90 deg between successive passes. The flow patterns were revealed by optical metallography. Tensile strength and hardness were measured. The ECAPed samples were isochronally-annealed and recrystallization behavior was studied by microscopy and Vickers hardness measurements. Refinement of grain size, substructure, and texture was studied by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The results show that flow patterns are complex and distinct from simple shear. Strain is higher at the outer surfaces, highest at the bottom surface, and intermediate in the middle of the billet. The work piece strain hardens significantly in first pass with an attendant drop in ductility. The degree of strengthening reduces in subsequent passes. The high defect density introduced during the initial passes leads to grain refinement to an ultrafine level and advantageously the material regains ductility. The refinement in microstructure obtained after two to three passes is stable up to 250 °C. The flow patterns are very similar to those obtained by physical modeling in our earlier studies using plasticine. Equiaxed ultrafine-grained structure (average grain size = 0.53 μm) was obtained after ECAP at an equivalent shear strain of 6.0. This article is based on a presentation given in the symposium entitled “Materials Behavior: Far from Equilibrium” as part of the Golden Jubilee Celebration of Bhabha Atomic Research Centre, which occurred on December 15–16, 2006 in Mumbai, India.

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固溶处理对2E12铝合金显微组织和力学性能的影响

通过光学显微镜、扫描电镜、DSC差热分析、室温拉伸、硬度与电导率测试措施,研究了固溶处理对2E12铝合金轧制态板材显微组织和力学性能的影响。结果表明,随着固溶处理温度升高,固溶时间延长,合金基体内未溶残留相逐渐减少,材料屈服强度、抗拉强度逐渐升高,硬度在500℃/30m in和500℃/1h时出现峰值,伸长率呈上升趋势,电导率呈下降趋势;2E12铝合金较为适宜的固溶处理制度为495~500℃/1h。