Thermal Stability Study of Ultrafine Grained 304L Stainless Steel Produced by Martensitic Process

An ultrafine grain 304L stainless steel with average grain size of about 650 nm was produced by martensitic process. 10 mm as-received sheets were 80% cold rolled in the temperature of ?15 °C and then annealed at 700 °C for 300 min to obtain ultrafine grained microstructure. The results showed that the ultrafine grained 304L steel has yield strength of 720 MPa, tensile strength of about 920 MPa, and total elongation of 47% which is about twice that of coarse grain structure. The effect of annealing temperature (750-900 °C) on the grain growth kinetics was modeled by isothermal kinetics equation which resulted in the grain growth exponent (n) and activation energy for grain growth of 4.8 and 455 KJ/mol, respectively. This activation energy was also compared with those for other austenitic steels to better understanding of the nature of grain growth and atoms mobility during annealing. It was found that activation energy for grain growth is about twice higher than self-diffusion activation energy of austenite that is related to the Zener pinning effects of the second phase particles.     

400MPa级超细晶粒钢电弧焊焊接接头组织与性能

采用普通电弧焊方法（手工电弧焊、二氧化碳气体保护焊、埋弧焊）对400MPa级超细晶粒钢进行焊接,并对不同工艺条件下的焊接接头的组织与性能进行了分析。结果表明,400MPa级超细晶粒钢电弧焊焊接接头热影响区存在着明显的晶粒长大现象;手工电弧焊和埋弧焊焊接接头性能明显下降,而二筘化碳气体保护焊焊接接头性能下降不明显。根据试验结果,实际生产中可以利用二氧化碳气体保护焊方法焊接400MPa级超细晶粒钢。     

铸轧法与挤压法生产TP2铜管组织和性能对比分析

考察和评价了铸轧法和挤压法生产铜管管坯和管材的组织和性能，并分析了水平连铸铜管坯的组织性能以及管坯和管材的拉伸断裂机制。     

不锈钢复合钢管组织及其性能

采取外层先离心浇注10号钢,再浇注内层1Cr18Ni9Ti得到离心复合空心管坯,管坯内外表面加工后进行热挤压和冷轧,试制出了47mm×4.5mm的碳钢/不锈钢复合钢管,对不锈钢离心复合管坯生产复合钢管工艺路线进行研究,并对复合管金相组织、性能及结合层质量等方面进行分析。结果表明,复合管内外层冶金结合良好,晶粒明显细化,终轧后晶粒由铸态时3.0～3.5级变为7.0～8.0级,复合管压扁、弯曲及热处理后晶界腐蚀检验合格。     

400MPa超级钢等离子弧焊焊接接头组织性能及深冷处理研究

对400MPa超级钢进行等离子弧焊焊接试验和焊后深冷处理，并对不同工艺条件下的焊接接头进行了组织性能分析。结果表明：等离子弧焊焊接热影响区没有软化；3mm厚钢板等离子弧焊焊接时加与不加焊丝都可以；深冷处理后组织形态没有明显变化;深冷处理可以改善焊接接头综合性能。     

400MPa超级钢等离子弧焊焊接接头组织性能及深冷处理研究

对400 MPa超级钢进行等离子弧焊焊接试验和焊后深冷处理,并对不同工艺条件下的焊接接头进行了组织性能分析。结果表明:等离子弧焊焊接热影响区没有软化;3mm厚钢板等离子弧焊焊接时加与不加焊丝都可以;深冷处理后组织形态没有明显变化;深冷处理可以改善焊接接头综合性能。     

喷水冷却对400MPa级超细晶粒钢焊接接头组织和性能的影响

采用手工电弧焊焊接400MPa级超细晶粒钢，并对不同冷却条件下的焊接接头显微组织及力学性能进行分析。结果表明，400MPa级超细晶粒钢手工焊焊接接头热影响区存在着严重的晶粒长大和强度下降现象；焊接过程中采用喷水冷却可明显提高焊接接头强度，实际生产中可以应用手工电弧焊水冷处理方法焊接400MPa级超细晶粒钢。     

径向挤压对Zn-15Al合金线材组织和性能的影响

为了改善锌铝合金线材加工使用性能,依据90°转角挤压原理,采用径向挤压出线工艺制取线材,研究了线材拉拔后的微观组织和力学性能,并与轴向挤压出线工艺进行对比.结果表明,径向挤压出线工艺可明显细化合金组织,且有纤维化倾向.线材抗拉强度降低15%,而伸长率提高30%.该工艺有利于线坯的拉拔加工,减少喷枪送丝途中的阻力.     

热挤压对7055铝合金力学性能及组织的影响

采用挤压铸造成形工艺制备7055高强铝合金,研究了热挤压参数对合金力学性能及微观组织的影响,并与铸态下的力学性能及微观组织进行了对比.结果表明,热挤压态下的7055铝合金的微观组织和力学性能均优于铸态,并且晶粒随着比压的增加趋于细化,抗拉强度随着比压的增加趋于提高.当比压为75 MPa时,在730 ℃温度下进行挤压浇注,经过双级固溶处理和时效后,合金的晶粒明显细化,抗拉强度达到681.4 MPa,伸长率达到7.14%.     

400MPa级超级钢不同焊接方法焊接接头组织性能分析

采用手工电弧焊，二氧化碳气体保护焊，等离子弧焊焊接400MPa级超级钢，并对焊接接头显微组织及力学性能作了分析研究，结果表明，实际生产中可以应用二氧化碳气体保护焊焊接400MPa级超细晶粒钢。     

Microstructure and Mechanical Properties of Ultrafine Lath-Shaped Low Carbon Steel

The mechanical properties of ultrafine lath-shaped low-carbon steel plates were studied. Results indicated that the hardness and tensile strength of the conventional low-carbon steel are HRC 19 and 410?MPa, respectively. With the decreased grain size of the ultrafine lath-shaped steel plates, the hardness and tensile strength of the test samples rapidly increase. Mechanical properties are at their optimum when grain size reaches 90?nm. Furthermore, both the hardness and the tensile strength values reach their maximum, which are HRC 53.5 and 1217?MPa, respectively.     

超细晶粒高强度钢的延迟断裂行为

对于微合金化处理的42CrMoVNb钢，通过快速循环热处理的方法获得最小2μm的超细奥氏体晶粒，采用缺口拉伸延迟断裂实验研究了超细晶粒试样的延迟断裂行为。结果表明，随着晶粒细化，42CrMoVNb钢的强度和缺口拉伸延迟断裂抗力逐渐提高；但当晶粒细化到2μm时，强度和延迟断裂抗力均不再提高，在高温回火态，当晶粒尺寸在20—4μm范围时，断裂机制主要为穿晶断裂；但当晶粒进一步细化到2μm时，断裂机制转变为沿晶断裂，在低温回火态，不同晶粒尺寸的试样均主要为沿晶断裂，从降低应力集中和夹杂元素晶界偏聚等角度对超细晶粒高强度钢的延迟断裂行为进行了探讨。     

Microstructure and Tensile Properties of Nanostructured and Ultrafine Grained FeMoB Alloys Produced by Spark Plasma Sintering of Mechanically Alloyed Powders

Boron alloyed Fe-1.5%Mo alloys (B from 0.42 to 1.66%) were produced starting from a prealloyed ferrous powder and an elemental boron powder, by mechanical alloying and spark plasma sintering. Near full density samples were obtained (density >99%) with a nano- and ultrafine grained structure, consisting in a ferritic matrix with a fine dispersion of Fe and Mo borides. High boron content and a low sintering temperature are favorable to minimize grain growth on sintering. On increasing the boron content from 0.42% up to 1.66%, yield strength increases and ductility decreases; this effect is enhanced by the sintering temperature because of the structural coarsening. Both ultrafine grained and nanostructured materials have a dimpled ductile fracture. On increasing the crystallite size, a mixed dimpled-cleavage fracture is observed.     

Microstructure,Mechanical Properties and Texture Evolution of Mg-Al-Zn-La-Gd-Y Magnesium Alloy by Hot Extrusion and Multi-Pass Rolling

A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86Y (wt%) alloy was developed by hot extrusion and multi-rolling processes. Relationships between microstructure, mechanical properties and texture evolution of the extruded and rolled alloy were investigated. The rolling process had significant effect on grain refinement of the extruded plate. The grain size reduced from 12.3 to 4.9 μm with the increasing rolling pass. With the increase in rolling pass, the proportion of dynamic recrystallized (DRXed) grains increases due to particle-stimulated nucleation, grain boundary nucleation and twin induced nucleation. In the process of multiple rolling, the basal pole gradually tilted from normal direction to transverse direction due to the asymmetric deformation and irregular grain deformation, resulting in the weakening of the base texture. The results showed that grain refinement and texture weakening were the main reasons for the good ductility of the alloy.     

对微量钒处理45钢的组织和力学性能的研究

对五种经正火处理的45钢的金相组织和力学性能进行了分析。结果表明45钢的强度和塑性主要受碳含量的控制,随着碳含量的升高,强度增强,塑性下降,合金元素钒的加入可以有效地改善其显微组织和力学性能。     

马氏体-贝氏体钢复合组织的力学性能

Cr12钢经980℃奥氏体化后,于280℃硝盐中等温不同时间获得不同比例的马氏体-贝氏体复合组织与力学性能的关系,并与常规淬火、回火后的力学性能进行比较.结果表明:具有马氏体-贝氏体复合组织Cr12钢与常规淬火、回火的回火的马氏体组织相比,除硬度有所降低外,抗弯强度、挠度、冲击韧性及耐磨性均有较大幅度的提高.经980℃加热、280℃等温5 h、180℃回火后,Cr12钢具有最佳的综合力学性能.     

等通道转角挤压制备超细晶GCr15钢研究

研究了GCr15钢等通道转角挤压(ECAE)的原理与技术实施手段。通过设计ECAE模具的几何结构,研究了剪切应变累积效应的计算方法。通过对GCr15钢单道次ECAE加工后光学微观组织的观察,讨论了模具几何结构条件(转角与背转角大小)对GCr15钢微观组织变化的影响。结果表明:GCr15钢的ECAE变形组织形态较好地符合理论预测结果;多道次ECAE加工显著改善了GCr15钢的微观组织;通过ECAE工艺,也能够制备出大尺寸致密的细晶材料。     

400MPa级超级钢CO2气体保护焊不同焊接工艺焊接接头组织性能

采用二氧化碳气体保护焊焊接400MPa级超级钢，并对不同冷却条件下的焊接接头显微组织及力学性能进行分析。结果表明，实际生产中可以直接应用二氧化碳气体保护焊焊接400MPa级超细晶粒钢。     

选区激光熔化成形316L不锈钢多孔结构及力学性能

基于选区激光熔化技术(SLM),制备了BCC、FCC、FCCZ 3种不同拓扑单元的316L不锈钢多孔结构,验证了该技术成形复杂多孔结构件的可行性。对试样进行了准静态压缩试验,得到了多孔结构在压缩过程中的变形模式和力学响应曲线,对比分析了3种结构试样的力学性能。结果表明,FCCZ型多孔结构的抗压性能和能量吸收特性均优于BCC型和FCC型结构;利用ABAQUS/Explicit软件进行准静态压缩仿真,仿真结果和试验结果基本符合。     

自行车变速轴零件的冷挤压

自行车变速轴零件的冷挤压是我国早期应用无屑加工技术制造高难度复杂零件的典型范例之一，本文以作者亲身的经历回顾了四种内具，内棘齿零件冷挤压成形的研制过程，着重介绍了其中一种零件的挤压工艺分析，实际生产工序和所用模具的特点，对长期处于保密状态的技术予以适当解密。