成形和淬火工艺对高强度热成形零件硬度-强度的影响

通过热成形高温平板分区冷却系列试验,以淬火前后热成形材料力学性能为评价指标,结合正交试验分析方法研究了热成形工艺条件下保压时间、压强和板料厚度对热成形零件硬度强度的影响规律。采用统计学"3σ法则"对优化工艺下热成形零件力学性能进行分析,建立了基于柔性指数模型的热成形钢板强度硬度非线性回归方程和热成形钢板强度-硬度等级评估区间图。并基于优化条件下的U型热冲压实验验证了该模型的正确性。结果表明:建立的性能评价标准可为热成形零件的力学性能预测和在线质量检测控制提供重要指导依据。

高强度热成形钢板冷却速率-强度-硬度预测

基于高强度钢板热成形平板模具分区冷却试验获得了淬火过程阶段冷却速度对机械强度-硬度的影响规律。采用量纲分析法建立了热成形材料冷却速率-机械强度-硬度指数模型,并验证了该模型的有效性。通过编制用户子程序将该模型引入自主开发的KMAS_HF软件平台中,实现了对典型U形热成形产品淬火后强度硬度的数值仿真预测。结果表明:该模型对热成形高强度钢淬火后机械性能仿真预测具有较好的适用性,为实现梯度硬度复合热成形工艺优化及产品性能分析提供了一种新的仿真分析流程。

里氏硬度法现场检测建筑钢材强度试验研究

通过试验研究及对试验数据的回归分析,分别得到了里氏硬度计在C冲击装置和D冲击装置条件下既有钢结构建筑钢材里氏硬度——抗拉强度关系曲线,该方法为一种测试钢材抗拉强度的无损检测方法。

压延擦胶法生产高强度高硬度擦胶帆布

介绍用压延擦胶法生产高强度高硬度擦胶帆布的配方和工艺。擦布胶的配方确定为 :NBR 80 ;聚丙烯酸酯橡胶 2 0 ;氧化锌 8;氧化镁 4;硬脂酸 1;防老剂DFC 3 4 1 5 ;炭黑N660 5 0 ;轻质碳酸钙 8;古马隆树脂 10 ;甲基丙烯酸树脂 15 ;邻苯二甲酸二辛酯 2 0 ;促进剂 2 ;乌洛托品 1;硫黄 1 5 ,合计 2 2 2 ,含胶率 45 0 4%。生胶在开炼机上进行三段塑炼 ,塑炼胶的塑性值必须大于 0 45。压延擦胶的主要工艺条件为 :上下辊辊温 90～ 110℃ ,中辊辊温 80～ 90℃ ,上中下辊速比 1∶1 5∶1,挂胶速度 15m·min- 1 ,挂胶量 约 2 75 g·m- 2 。擦胶帆布在平板硫化机上硫化 ,硫化条件为 (14 5± 3 )℃× 3 0min。擦胶帆布断裂强度为 45MPa。用压延擦胶法生产高强度高硬度擦胶帆布具有生产效率高、产品质量好和生产成本低等特点。

选区激光熔化成形Ti6Al4V的力学性能预测

选区激光熔化是激光增材制造技术的一种,Ti6Al4V 是航空航天和医疗领域中常见的材料。本文采用 BP 人工神经 网络、遗传算法和思维进化算法对 SLM 成形 Ti6Al4V 的剪切强度和硬度进行预测。通过对比预测结果指标(相关系数、均方根 误差、平均绝对百分比误差和最大相对误差),发现思维进化算法和遗传算法对 BP 人工神经网络都具有较好的优化能力,思维 进化算法的优化能力优于遗传算法。

硬度测试在检验T91材料性能中的作用

T91为美国研发的合金结构钢钢管牌号,主要用于制造大型发电机机组的过热器、再热器,相当于我国GB5310标准中的10Cr9Mo1VNb,本文介绍了在缺乏材料金相显微组织评级标准的情况下,硬度测试可作为该材料性能的辅助评定手段。

复杂结构灰铸铁零件硬度控制的热处理工艺研究

以HT200材料的多油道复杂零件支撑板为对象,通过热处理试验对其工艺进行优化和改进,使零件能够满足图纸特殊硬度和强度要求。此工艺可以推广应用到其他类似零件的热处理过程中。

硼酸盐交联的层层自组装氧化石墨烯膜的研究

以无机交联剂硼酸盐为交联剂,采用层层自主装法制备层状氧化石墨烯膜.采用FTIR和Raman分析氧化石墨烯(GO)和硼酸盐的交联反应机理,采用DMA测定硼酸盐的加入对膜强度的影响,并测试了GO膜的通量和对染料的截留效果.实验结果表明:硼酸盐与氧化石墨烯的羟基基团发生反应,缠结在GO表面.膜强度有所提升,为GO膜的1.36倍.该复合膜的纯水通量为21.60 L/(m2·h·bar).对于甲基橙、罗丹明B和亚甲基蓝的截留分别为72.13%、67.08%和71.86%.

Effect of minor B addition on microstructure and properties of AlCoCrFeNi multi-compenent alloy

The influences of slight amount of B element on the microstructure and properties of AlCoCrFeNiBx high entropy alloys（x = 0,0.01,…,0.09 and 0.1,mole fraction） were investigated.The AlCoCrFeNi high entropy alloy exhibits equiaxed grain structures with obvious composition segregation.However,with the addition of B element,the alloys exhibit dendrite structures.Inside the dendrites,spinodal decomposition structure can be clearly observed.With the addition of B element,the crystal structures change from（B2 ＋ BCC） to（B2 ＋ BCC ＋ FCC） structures,and the hardness firstly increases from HV 486.7 to HV 502.4,then declines to HV 460.7（x ≥ 0.02）.The compressive fracture strength firstly shows a trend of increasing,and then declining（x ≥ 0.08）.The coercive forces and the specific saturation magnetizations of the alloys decrease as B addition contents increase,the decreasing coercive forces show a better soft magnetic behavior.

退化程度对三江源泽库高寒草甸土壤理化性质及持水能力的影响

通过野外原位测定和室内分析相结合的方法,分析了不同退化程度对高寒草甸土壤理化特征及持水能力的影响。结果表明:(1)高寒草甸草毡层的退化消失显著降低了土壤抗蚀能力。从原生植被至中度退化阶段,高寒草甸土壤硬度和抗剪强度逐渐增加,至重度退化阶段二者急剧下降(P<0.05)。(2)随着退化程度的加剧,高寒草甸土壤呈现贫瘠化。同时,随着土壤深度的增加,退化程度对土壤有机碳和全氮的影响作用逐步减弱。(3)退化程度对高寒草甸土壤持水能力的影响作用随深度的增加而降低,其对表层土壤持水能力的影响最为显著。从原生植被至中度退化阶段,0~10cm土壤饱和持水量、毛管持水量及田间持水量呈增加趋势,至重度退化阶段,三者均显著降低。地表草毡层是保持高寒草甸土壤肥力、抗侵蚀能力和水源涵养功能的关键。

Precipitation behavior and properties of a new high strength Al-Zn-Mg-Cu alloy

The microstructure and the associated hardness, strength and electrical conductivity of a new Al-Zn-Mg-Cu alloy during one-step ageing treatment were systematically studied. The results show that the electrical conductivity of the alloy increased continuously with increasing ageing temperature and ageing time. At the early stage of ageing, the hardness and strength of the alloy increased rapidly and then reached the peak value. When aged at 120 °C, the hardness and strength maintained at high level for a long time after the peak value. The main precipitations are GPI zones, GPII zones and metastable η′ phase. GPI and GPII zones are found in the alloy after ageing for 24 h at 120 °C, which indicates that some stable GP zones can exist through the ageing process. When aged at 160 °C, the hardness and strength decreased rapidly after the peak value. The precipitation process is significantly promoted compared with that aged at 120 °C. Both GPI zones and GPII zones disappeared after ageing for 1 h at 160 °C. The main precipitates are η′ phase when aged at 160 °C for 1 h. The main precipitates are η phase when the ageing time prolongs to 24 h.

高能球磨制备NiCr-Cr_2O_3-BaF_2/CaF_2复合粉末及其爆炸喷涂层的性能

为了制备高性能复合涂层,以70%NiCr、20%Cr2O3及10%BaF2/CaF2为原料,采用高能球磨方法制备了复合粉体,并通过特定的爆炸喷涂工艺制得复合涂层。利用扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)等对球磨后粉体和喷涂层的微观形貌、组织结构、成分及物相组成进行了分析。根据HB5143-96测定了爆炸喷涂复合涂层与基体间的结合强度。结果表明:随球磨时间的延长,粉体球形化程度逐步加大,颗粒尺寸逐步减小,粒度分布趋于集中,颗粒成分及结构均匀性逐步提高;当球磨11h后,粉体中的BaF2和CaF2固溶于NiCr合金,Cr2O3颗粒在NiCr基体内部镶嵌;通过爆炸喷涂将球磨粉喷涂在不锈钢基体上,其涂层微观组织均匀致密,显微硬度Hv为578,涂层与基体结合强度为67MPa,综合性能优于混合粉喷涂层。

椎体成形术中骨水泥量对椎体机械性能的影响

目的 探讨聚甲基丙烯酸甲酯 (PMMA)和自固化磷酸钙骨水泥 (CPC)的不同用量对骨质疏松性椎体强度和硬度的影响 ,明确恢复椎体强度及硬度所需的最小骨水泥用量。方法 取 5具老年女性 (6 5～ 73岁 )脊椎标本 (T6～L3 ) ,分解后压缩并测量其强度和硬度 ,将 3ml,5ml,7mlPMMA和CPC注入压缩后的椎体 ,再测其强度和硬度 ,并与原来的强度和硬度进行比较。结果 所有椎体注入骨水泥后强度都得到恢复 ,注入 5ml,7ml骨水泥后强度明显增加 ;注入PMMA后硬度都得到恢复 ,而注入CPC 5ml,7ml才能恢复椎体硬度。结论 骨质疏松性椎体骨折后 ,注入骨水泥可有效恢复椎体的强度和硬度 ,此结果可有利于指导椎体成形术的临床应用。

Preparation and mechanical properties of in situ Al_2O_3/Al composites by adding NH_4AlO(OH)HCO_3

Aluminium matrix composite reinforced by Al2O3 particles was produced by adding NH4AlO（OH）HCO3 into molten aluminum.The mechanical properties and wear behavior of the as-fabricated composites were studied.The results show that during stirring γ-Al2O3 particles were formed via decomposition reaction of NH4AlO（OH）HCO3,and the distribution of Al2O3 particles is more uniform in the matrix aluminum than directly added Al2O3 into molten aluminum.The density and the hardness values of the as-fabricated composites increase with increasing the particle volume fraction,while the tensile strength of the composites decreases with increasing the volume fraction of the Al2O3 particles.The wear rate of the composites decreases with increasing the volume fraction of the particle and loading.The in situ formed Al2O3/Al composite by adding NH4AlO（OH）HCO3 shows more superior mechanical and wear behaviors than that prepared by directly adding Al2O3 particles.

Effects of heat treatment on phase contents and mechanical properties of infiltrated B_4C/2024Al composites

The B4C/2024Al composites were successfully produced by pressureless infiltration method, and the effects of heat treatment on phase content and mechanical properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and mechanical properties testing. The results show that phases of BnC/2024Al composites include B4C, Al, Al3BC, AlB2 and Al2Cu. The phase species remain unchanged; however, the phase content of the composites changes significantly after heat treatment at the temperature of 660, 700, 800 or 900 ℃ for 12, 24 or 36 h. It is found that the heat treatment results in not only considerable enhancement in hardness, but also reduction in bending strength of the composites. Heat treatment at 800 ℃ for 36 h does best to hardness of the composites, while at 700 ℃ for 36 h it is the most beneficial to their comprehensive mechanical properties.

Microstructure and mechanical properties of AlCuFe eutectic alloy

In the production of AlCuFe alloy for a special application,the growth rate was changed and the results were evaluated.Changes in the eutectic spacing(microstructure)of a material due to the growth rate are known to affect its mechanical,electrical and thermal properties.To evaluate its microstructure,the eutectic composition of Al−32.5wt.%Cu−0.5wt.%Fe was prepared and directional solidification experiments were conducted using a Bridgman-type furnace at a constant temperature gradient(G=8.50 K/mm)and five growth rates(V=8.25,16.60,41.65,90.05,164.80μm/s).The effect of the growth rate on the eutectic spacing was then determined,and the resulting microhardness and ultimate tensile strength were obtained based on the change in the microstructure by regression analysis and Hall−Petch correlations.Despite the fact that the growth rate increased by approximately twenty times,the eutectic spacing decreased by a factor of approximately 5,and these changes in the growth rate and microstructure caused the mechanical properties to change by a factor of approximately 1.5.

Strength prediction of multi-layered copper-based composites fabricated by accumulative roll bonding

This work aims to evaluate the feasibility of the fabrication of nanostructured Cu/Al/Ag multi-layered composites by accumulative roll bonding(ARB),and to analyze the tensile properties and electrical conductivity of the produced composites.A theoretical model using strengthening mechanisms and some structural parameters extracted from X-ray diffraction is also developed to predict the tensile strength of the composites.It was found that by progression of ARB,the experimental and calculated tensile strengths are enhanced,reach a maximum of about 450 and 510 MPa at the fifth cycle of ARB,respectively and then are reduced.The electrical conductivity decreased slightly by increasing the number of ARB cycles at initial ARB cycles,but the decrease was intensified at the final ARB cycles.In conclusion,the merit of ARB to fabricate this type of multi-layered nanocomposites and the accuracy of the developed model to predict tensile strength were realized.

Application of response surface methodology to maximize tensile strength and minimize interface hardness of friction welded dissimilar joints of austenitic stainless steel and copper alloy

An attempt was made to optimize friction welding parameters to attain a minimum hardness at the interface and a maximum tensile strength of the dissimilar joints of AISI 304 austenitic stainless steel （ASS） and copper （Cu） alloy using response surface methodology （RSM）. Three-factor, five-level central composite design matrix was used to specify experimental conditions. Twenty joints were fabricated using ASS and Cu alloy. Tensile strength and interface hardness were measured experimentally. Analysis of variance （ANOVA） method was used to find out significant main and interaction parameters and empirical relationships were developed using regression analysis. The friction welding parameters were optimized by constructing response graphs and contour plots using design expert software. The developed empirical relationships can be effectively used to predict tensile strength and interface hardness of friction welded ASS-Cu joints at 95% confidence level. The developed contour plots can be used to attain required level of optimum conditions to join ASS-Cu alloy by friction welding process.

Influence of heat treatment on microstructure and mechanical properties of FeCrNi coating produced by laser cladding

The FeCrNi alloy powders were used on the dovetail groove of FV520B steel to fabricate the multilayer laser cladding layers. The effects of heat treatment on the microstructure and mechanical properties of FeCrNi layers were investigated. The results showed that the heat treatment at the temperature ranged from 1073 to 1273 K refined the grains of the substrate materials and removed the soft zone of hardness between the fused zone (FZ) and base material (BM) effectively mainly due to a secondary quench of heat treatment. When the temperature of heat treatment was 1073 K, the maximum ultimate tensile strength (UTS) values of the laser cladding component were obtained. However, the heat treatment at high temperature had a bad effect on wear resistance of coatings at some extent.

Production and mechanical properties of nano SiC particle reinforced Ti-6Al-4V matrix composite

Different mass fractions （0, 5%, 10%, and 15%） of the synthesized nano SiC particles reinforced Ti-6Al-4V （Ti64） alloy metal matrix composites （MMCs） were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density （93.33%） was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic （SEM） observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.