Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electron microscopy,X-ray diffraction,tensile test,and hardness test were used.The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo,Ti)Laves phase particles,which are stable at high temperatures.These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fiacture in the subsequent aging treatment.     

Mo、B对低合金高强钢组织和性能的影响

对两种不同成分的C—Mn—Mo系低合金高强钢（HSLA）进行拉伸和;中击试验,采用光学显微镜和扫描电子显微镜观察试验钢种的微观组织,分析Mo和B对HSLA钢组织和性能的影响。结果表明,通过控制钢种的成分和工艺,可得到具有高强度、高韧性匹配的C—MnMo系HSLA钢,钢种具有贝氏体组织;在C—Mn—Mo系HSLA钢中,适当增加Mo和B的含量,可以明显提高钢种的强度,且不损害其塑韧性。     

Modeling of microstructure evolution and mechanical properties during hot-strip rolling of Nb steels

An integrated metallurgical model was developed for Nb steels to predict the microstructure evolution and mechanical properties during the hot-strip rolling and cooling process. On the basis of the industrial data, the transformation kinetics, strength, and elongation rate were evaluated for different chemical compositions and processing parameters. The yield strength and tensile strength increase with increasing Nb content or decreasing finishing temperature. The bainite distributed in finer ferrite matrix, which is produced at relatively low coiling temperatures, can greatly increase the strength of steel, especially tensile strength, thereby decreasing the yield ratio. A reasonable agreement was found between the predicted and measured results. It indicates that the present models can be used to simulate the actual production process.     

稀土镁复合处理对X70管线钢组织和性能的影响

采用金相观察、硬度测试、力学性能测试等方法,研究了稀土镁处理对X70管线钢组织与性能的影响.结果表明,微量稀土镁可显著减小晶粒尺寸,提高X70管线钢室温和高温的力学性能;但随温度升高稀土镁对材料的高温力学性能影响会逐步减小.     

高温应力时效后T91钢组织与性能的演变

为研究电站高温金属部件在高温应力作用下显微组织老化损伤程度的演化规律,设计了高温应力时效老化试验,对供货态T91钢在不同温度不同应力条件下进行高温时效老化.用金相显微镜、扫描电镜、透射电镜、定量金相和显微硬度等试验方法研究组织性能变化.结果表明,T91经不同温度老化后的微观组织随着温度和应力的升高,回火马氏体位向特征分散,晶界和晶内沉淀相粒子尺寸粗化,沉淀相颗粒Feret直径从原始供货态0.200μm增加到0.435μm.在相同温度下应力对组织老化的影响明显,马氏体板条内位错密度降低,板条亚结构退化,马氏体板条特征逐渐消失.随着温度的提高硬度呈现加速下降变化趋势,硬度的下降与析出相颗粒尺寸的增加同步变化,且变化趋势相似.     

热处理工艺对27SiMn钢组织及力学性能的影响

为得到热处理工艺对27SiMn钢显微组织及力学性能的影响,制定了9种热处理工艺,并对其进行显微组织观察和力学性能测试.实验结果表明,27SiMn钢淬火＋回火后的显微组织与回火温度和时间有关,当回火温度低、时间短时,显微组织为回火屈氏体＋马氏体;当回火温度高、时间长时,显微组织为回火屈氏体＋回火索氏体.同时,回火温度和时间对27SiMn钢的力学性能有很大影响,当回火温度为450℃,时间为45 min时力学性能最高,抗拉强度为1 175 MPa。当热处理温度为490℃,时间为75 min时力学性能最差,抗拉强度为975 MPa.综合分析27SiMn钢热处理最优工艺为900℃淬火＋475℃回火75 min。     

Effect of cooling parameters on the microstructure and properties of Mobearing and Cr-bearing steels

To develop low-cost low carbon bainitic steel,Mo-bearing and Cr-bearing steels were melted in a vacuum induction furnace and were researched by thermal simulation and hot rolling at the laboratory.As the cooling rate increases from 0.2 to 50℃/s,the transformation temperatures of two steels lie between 650 and 400℃,and the final microstructures of them change from quasi-polygonal ferrite and granular bainite to lath bainite.Compared with cooling in air or by interrupted cooling,Mo-bearing and Cr-bearing steel plates cooled by sprayed water boast higher strength and superior toughness,for large-size islands are responsible for the poor mechanical properties.Compared to Mo,Cr is effective to isolate the bainitic reaction in low carbon steel,and the bainitic microstructure can also be obtained in Cr-bearing steel cooled at a wide range of cooling rate.     

Machine learning of mechanical properties of steels

Knowledge of the mechanical properties of structural materials is essential for their practical applications. In the present work,three-hundred and sixty data samples on four mechanical properties of steels—fatigue strength, tensile strength, fracture strength and hardness—were selected from the Japan National Institute of Material Science database, comprising data on carbon steels and low-alloy steels. Five machine learning algorithms were used to predict the mechanical properties of the materials represented by the three-hundred and sixty data samples, and random forest regression showed the best predictive performance.Feature selection conducted by random forest and symbolic regressions revealed the four most important features that most influence the mechanical properties of steels: the tempering temperature of steel, and the alloying elements of carbon, chromium and molybdenum. Mathematical expressions were generated via symbolic regression, and the expressions explicitly predicted how each of the four mechanical properties varied quantitatively with the four most important features. This study demonstrates the great potential of symbolic regression in the discovery of novel advanced materials.     

ZrO2含量对WC基复合材料的力学性能和微观结构的影响

摘要：以提高WC基复合陶瓷的断裂韧性和硬度为目标,利用ZrO2作为材料粘结剂和增强相,同时引入Al2O3添加相,采用热压烧结工艺成功制备了WC-ZrO2-Al2O3(WZA)复合刀具材料.在此基础上,添加一定量的VC作为晶粒生长抑制剂和助烧剂,以实现材料最大程度的致密化.并对热压后复合材料的硬度、抗弯强度和断裂韧性进行了测试和分析.探讨了ZrO2含量对材料微观结构和力学性能的影响,研究了复合材料断面断裂方式和材料相的组成.     

营养盐浓度对胶结重塑泥岩试样力学特性及微观结构的影响试验研究

采用一次浸泡菌液的方式，制备不同浓度（0、0.3、0.5、0.7 mol/L）营养盐处理的微生物诱导碳酸钙沉淀（MICP）胶结重塑泥岩样。基于直接剪切、碳酸钙酸洗法、扫描电镜（SEM）等试验测试胶结试样，分析了营养盐浓度对胶结试样力学性能、碳酸钙含量及微观结构的影响。结果表明：同等反应条件下（相同时间、体积），随着营养盐浓度的增加抗剪强度先增大后减小，当营养盐浓度达到0.5 mol/L时抗剪强度最大，此时，试样黏聚力、内摩擦角分别为15.5 kPa、18.83°；碳酸钙含量随着营养盐浓度的增加而增加，当营养盐浓度达到0.7 mol/L时，试样平均碳酸钙含量提高较少；碳酸钙晶体分布均匀性随着营养盐浓度由低到高变化呈凸字形态；胶结试样的强度依赖于生成的CaCO₃晶体量及其分布形态；生成的方解石型碳酸钙晶体主要沉积在颗粒接触处形成积聚晶体或填充在孔隙中形成“胶结桥”，产生胶结效果而增强试样的力学性能。     

热处理对Mg-Y-Gd-Nd-Zr显微组织及力学性能的影响

以快速凝固Mg-Y-Gd-Nd-Zr镁合金为研究对象,采用金相显微镜、扫描电镜和能谱仪等研究了热处理工艺对镁合金组织和性能的影响.结果表明,铸态镁合金内部存在严重的成分偏析,Mg12Nd和Mg24(Y,Gd)5共晶相在晶界处聚集.在525℃固溶处理温度下,随着固溶处理时间(6,8,10 h)延长,合金中非平衡共晶相发生溶解,晶粒不断长大.在525℃/8 h工艺时,Mg5Y第二相分布均匀且合金晶平均尺寸最为理想,成分偏析基本消除.525℃/8h+250℃/16 h热处理后合金晶粒内部析出细小弥散的β析出相,能够阻碍晶粒长大改善镁合金组织及力学性能,因此该工艺是Mg-Y-Gd-Nd-Zr铸态合金最优热处理方案.     

芳纶纤维表面改性及其对芳纶纸力学性能的影响

利用氯磺酸、醋酸酐对芳纶短切纤维进行了改性处理,再用处理后的纤维配抄芳纶纸,探讨了处理工艺对芳纶纸力学性能的影响.结果表明,当氯磺酸浓度为2%,处理时间为10min,处理温度为50℃时,芳纶纸的力学性能较好.用100%的醋酸酐对芳纶纤维进行处理然后配抄成纸,所得纸张的抗张指数和撕裂指数分别提高了63.8%和21.4%.另外,芳纶纤维经过醋酸酐浸泡1min后再用甲醇处理3min,芳纶纸的抗张指数和撕裂指数分别提高了84.7%和38.4%.     

Acoustic emission study of the plastic deformation of quenched and partitioned 35CrMnSiA steel

Acoustic emission （AE） monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning （Q-P） heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering （Q-T） and austempering （AT）. AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite （RA） in the microstructure （obtained via Q-P and AT heat treatments） due to an austenite-to-martensite phase transformation. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA degenerated by tempering for the Q-P treated steel.     

Mechanical properties and microstructure of TRIP steels produced using TSCR process

C-Si-Mn TRIP steels were produced using the thin slab casting and rolling （TSCR） process under simulation in laboratory. The results of tensile tests show that the yield strength, tensile strength, and the total elongation of the experimental TRIP steels are 430 MPa, 610 MPa, and 28.4%, respectively. Optical microscopy, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM） were employed to identify the microstructures of the TRIP steels. The final microstructures consist of ferrite, bainite, and retained austenite. The results of quantitative color metallography show that the fraction of the retained austenite is about 5.8%.     

石墨烯对水泥净浆力学性能及微观结构的影响

为改善石墨烯纳米材料疏水性,采用硝酸氧化和超声波法制备石墨烯分散悬浮液,考察石墨烯质量分数对水泥净浆力学性能及其微观结构的影响,探讨石墨烯的增强增韧作用机制,结果表明,水泥基复合材料的抗压、抗折强度随着石墨烯质量分数的增加呈先增大后减小的趋势,且最佳质量分数为水泥质量的0.02%.通过SEM和FT-IR对硬化水泥石的结构进行表征,发现石墨烯能够促进水泥水化产物的生长,改变水化晶体的形状、尺寸,使其有形成完整、簇状的趋势,但并未与水泥发生化学反应,改变其生成物类型.     

Microstructure characteristics and mechanical properties of X80 pipeline steels

The relation between microstructure characteristics and mechanical properties of X80 pipeline steels was investigated using optical microscopy,scanning electron microscopy,etc.It is shown that the structure consists of polygonal ferrite(PF),quasi-polygonal ferrite(QPF),acicular ferrite(AF),and granular bainitic ferrite(GF).With increasing volume fraction of M-A islands(below 3%),the yield strength increases.With increasing content of higher angle grain boundaries(HAGBs),the yield strength,elongation,and DWTT properties at-15 ℃ increase,and the volume fraction of M-A islands reaches its highest point in the steel containing the most volume fraction of GF.     

热处理对TRIP590钢微观组织及力学性能的影响

采用Gleeble3800热模拟机对TRIP钢拉伸试样进行不同工艺条件的快速热处理模拟实验,并采用金相分析、显微硬度测试等方法对试样进行组织观察和性能测试,目的是通过适宜的热处理工艺促使材料微观组织中出现适量的残余奥氏体组织,增强该材料在变形过程的相变诱导塑性（TRIP）效应,强化材料.结果表明：在两相区内,TRIP钢中的残余奥氏体含量随着退火温度和退火时间的增加而增大,以25℃/s缓慢加热到700℃,再以150℃/s的速率快速加热到820℃保温120 s后淬火处理,处理后的试样,残余奥氏体体积分数达到13%,显微硬度最高,达到262 HV.     

Influence of silicon on the microstructures,mechanical properties and stretch-flangeability of dual phase steels

Uniaxial tension tests and hole-expansion tests were carried out to determine the influence of silicon on the microstructures, mechanical properties, and stretch-flangeability of conventional dual-phase steels. Compared to 0.03wt% silicon, the addition of 1.08wt% silicon induced the formation of finer ferrite grains （6.8μm ） and a higher carbon content of martensite （Cm≈ 0.32wt%）. AS the silicon level increased, the initial strain-hardening rate （n value） and the uniform elongation increased, whereas the yield strength, yield ratio, and stretch-flangeability decreased. The microstructures were observed after hole-expansion tests. The results showed that low carbon content martensite （Cm ≈ 0.19wt%） can easily deform in coordination with ferrite. The relationship between the mechanical properties and stretch-flangeability indicated that the steel with large post-uniform elongation has good stretch-flangeability due to a closer plastic incom- patibility of the ferrite and martensite phases, which can effectively delay the production and decohesion of microvoids.     

Effect of lanthanum-praseodymium-cerium mischmetal on mechanical properties and microstructure of Mg-Al alloys

The effects of lanthanum-praseodymium-cerium mischmetal (LPC) on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was deposited in the alloy. LPC greatly improves the tensile strength of cast Mg-Al alloys but negatively affects the elongation of cast alloys above 473 K. Cast alloys are strengthened by both precipitation strengthening and dispersion strengthening at ambient temperature. When the temperature exceeds 473 K, only the dispersion operates as a strengthening mechanism.