AZ31B镁合金电子束焊接接头显微组织及疲劳性能

为了改善镁合金焊接接头的微观组织及其力学性能,采用真空电子束焊接工艺对厚10 mm的AZ31B镁合金板材进行焊接,分析电子束对接接头的显微组织、元素分布和物相组成,检测了电子束对接接头静载拉伸性能和疲劳性能.试验结果表明AZ31B镁合金电子束焊接接头的微观组织和力学性能均得到了改善:焊缝区晶粒明显细化,焊缝区Mg、Zn元素的质量分数分别降低了0.12%和0.28%,Al、Mn元素的质量分数分别增加了0.24%、0.14%,焊缝区为单相α-Mg,无明显的低熔点β-Mg17Al12脆性;焊接接头的抗拉强度为242 MPa,能够达到母材的抗拉强度;在脉动载荷（R=0.1）、2×106循环次数下,其接头的疲劳强度为91 MPa,能达到母材的78.4%.      

X射线衍射法测试高速列车车体铝合金残余应力

为了准确、无损、快速地检测高速列车铝合金的表面残余应力,采用等强杆拉伸试验方法,用X射线衍射法对测试结果进行标定,并用X射线衍射法、盲孔法以及有限元法对测得的车体铝合金焊接接头残余应力进行了对比.结果表明:等强杆拉伸试验标定过程中,在10～70 MPa范围内,随着拉伸载荷的增加,X射线法测得的应力与载荷应力具有一致性,可采用X射线衍射法对车体关键部位应力状态进行测试分析,X射线衍射法残余应力的数值略大于理论计算值和电测法计算值;车顶铝合金焊接接头最大残余应力可达146.3 MPa;X射线衍射法与等强杆标定方法、盲孔法、有限元计算模拟方法的残余应力结果保持了较好的一致性.     

中间处理对粉末高温合金FGH4095组织性能的影响

为了研究热处理制度对粉末高温合金FGH4095组织强化相γ'形态分布特征的影响,采用氩气雾化制备FGH4095高温合金粉末,经筛分、除夹杂处理后,热等静压烧结成形,对比研究不同的热处理条件下, FGH4095合金组织γ'相的大小、形貌及分布,测试了室温20 ℃和高温650 ℃下合金的拉伸性能,并对650 ℃高温下拉伸断口进行了比较分析.结果表明:中间热处理能够改善γ'相的形状及分布;经中间处理,材料高温拉伸性能明显提高,屈服强度从1 150 MPa提高到1 210 MPa,拉伸强度从1 230 MPa提高到1 460 MPa;中等尺寸γ'相数量增加,晶界得到优化,合金高温塑性得到提高.      

Influence of Ca Element on Microstructure and Mechanical Properties of AZ61-1.2Y

The effects of Ca element on the microstructure and mechanical properties of AZ61-1.2Y alloy were investigated by microstructure observation, tensile tests and fracture analysis. The results show that, with the addition of Ca element, the microstructure of AZ61-1.2Y was obviously refined, high melting point Al2Ca intermetallic compound formed, and β-Mg17Al12 phase disappeared. With 1.0% Ca addition, the values of tensile strength at 25, 150 and 175 ℃ reached their maxima simultaneously, 225, 182, and 175 MP...     

Ca含量对AMCa镁合金超高周疲劳断裂行为的影响

为了阐明Ca含量对镁合金疲劳性能的影响,采用旋转弯曲疲劳试验机对两种AMCa镁合金进行超高周疲劳实验,并利用扫描电子显微镜SEM （scanning electron microscope）和X射线能谱仪EDS （X-ray energy dispersive spectroscopy）观察疲劳试样的断口形貌,分析了两种镁合金疲劳S-N（疲劳应力-疲劳寿命）曲线特性和疲劳断裂行为,讨论了Ca元素含量增加对镁合金疲劳寿命和疲劳裂纹萌生机制的影响. 结果表明,AM1.77 Ca镁合金S-N曲线没有传统的疲劳极限,呈现曲线连续下降趋势;AM1.85 Ca镁合金具有双S-N曲线特性,在130 MPa左右出现转折点;Ca元素含量增加导致镁合金产生微观结构缺陷,使材料的疲劳裂纹萌生模式从AM1.77 Ca镁合金的表面萌生模式转变为AM1.85 Ca镁合金的两种疲劳裂纹萌生模式,即表面萌生和次表面萌生模式,这种转变对材料抗疲劳性能的提升不利.      

WELDOX960E高强钢手工电弧焊焊接接头组织与力学性能

通过拉伸、弯曲、冲击、硬度和金相组织分析等试验,对手工电弧焊焊接WELDOX960E高强钢焊接接头组织和力学性能进行研究.研究结果表明：采用Phoenix SH Ni2 K130焊条、手工电弧焊焊接WELDOX960E高强钢时,可以获得拉伸、弯曲、冲击性能良好的接头;其焊缝组织为针状铁素体与粒状贝氏体的混合分布;熔合区及粗晶区组织为板条马氏体和少量白色M-A块区;正火区组织为块状铁素体、粒状贝氏体和珠光体;母材显微组织为回火索氏体;WELDOX960E高强钢焊缝硬度为270 ～ 300 HV,且距离熔合线30 mm处出现软化区.     

表面处理对HDPE/EVA/EG复合材料性能的影响

为了获得热稳定、阻燃和力学性能均较好的复合材料,以高密度聚乙烯/乙烯-醋酸乙烯酯(HDPE/EVA)共混物为基体,可膨胀石墨(EG)作为无卤阻燃剂,通过熔融共混方法制备了HDPE/EVA/EG阻燃复合材料.采用热重分析(TGA)、锥形量热仪、电子扫描电镜(SEM)等方法研究了钛酸酯偶联剂改性前后EG对复合材料的热稳定性能、阻燃性能以及力学性能的影响.研究结果表明, EG能提高聚合物基体材料的热稳定性能和阻燃性能,但力学性能降低;用钛酸酯偶联剂对EG改性后, HDPE/EVA/EG复合材料的断裂伸长率从232.3%提高到315.3%,拉伸强度由9.0 MPa增到了10.0 MPa,冲击强度由88 kJ/m2提高到129 kJ/m2.偶联剂的存在提高了EG与基体间的界面粘结力,使阻燃复合材料的综合力学性能得到改善.      

GFRP变形筋粘结性能试验研究

基于CSA标准,利用30个拉拔试件研究了8种不同表面形式的GFRP变形筋与混凝土之间的粘结性能,比较了不同表面形式GFRP变形筋的粘结强度,并确定了GFRP变形筋的最优表面形式.试验结果表明:(1)试件的破坏形式为肋的剪切破坏和肋的脱落,混凝土并没有发生破坏;(2)GFRP变形筋的粘结强度较高,粘结强度为7.01~12.25M Pa;(3)最佳肋间距不应超过直径的2.5倍,肋高度应不小于直径的3%.     

Effects of RE on the Microstructure of Mg-8Zn-4Al Magnesium Alloys

IntroductionMagnesium alloys are called green-engineeringmaterial with great development potential becauseof its low density, high specific strength and stiff-ness, superior damping capacity, good electromag-netic shielding characteristics and good machinabil-ity[1]. However, the number of commercially avail-able magnesium alloys is still limited especially forapplication at elevated temperatures. The applica-tions of most common magnesium alloys such asAZ91 and AM60 with outstanding mechani…     

Microstructures and mechanical properties of various Mg-Li wrought alloys

Three kinds of ultra-light Mg-Li wrought alloys,Mg-5.5Li-3Al-1Zn-1Ce,Mg-7.0Li-3Al-1Zn-1Ce and Mg-10.5Li-3Al-1Zn-1Ce,were prepared by vacuum induction melting furnace;then the alloys were extruded and rolled.The microstructures and properties of these alloys were studied.The results indicate that the Mg-5.5Li3Al-1Zn-1Ce alloy has the highest strength,the Mg-10.5Li-3Al-1Zn-1Ce alloy has maximum elongation,and the Mg-7.0Li-3Al-1Zn-1Ce alloy has good comprehensive performance.Rolling deformation can increase strength further after extrusion deformation.     

LY12铝合金搅拌摩擦焊工艺研究

对LY12铝合金进行了搅拌摩擦焊接工艺试验,并对焊接接头进行了金相观察和力学性能检测.试验结果表明,合理的焊接参数匹配是取得性能优良焊接接头的前提.当旋转速度为905 r/min、焊接速度为33.6 mm/min、肩部压力为48 MPa时施焊,可获得成型良好无缺陷焊接接头,且焊缝区晶粒细小.搅拌摩擦焊焊接轧态LY12铝合金时,焊接时的热输入可部分消除接头处金属的冷作硬化.随着焊接速度的提高,焊接热输入量降低,消除冷作硬化的能力减弱,焊接接头抗拉强度提高.     

LY12铝合金搅拌摩擦焊工艺研究

对LY12铝合金进行了搅拌摩擦焊接工艺试验,并对焊接接头进行了金相观察和力学性能检测.试验结果表明,合理的焊接参数匹配是取得性能优良焊接接头的前提.当旋转速度为905 r/m in、焊接速度为33.6 mm/m in、肩部压力为48MPa时施焊,可获得成型良好无缺陷焊接接头,且焊缝区晶粒细小.搅拌摩擦焊焊接轧态LY12铝合金时,焊接时的热输入可部分消除接头处金属的冷作硬化.随着焊接速度的提高,焊接热输入量降低,消除冷作硬化的能力减弱,焊接接头抗拉强度提高.     

Application of waste bamboo materials on produced eco-brick

With regard to the optimization test of mixing ratio between waste bamboo and cement, the single axial compression strength of the second set (5: 95) is the highest. By increasing the mixing ratio to 10: 90 and complying with Chinese national standard (CNS) required strength for water permeable bricks. In the test for optimizing the mixing ratio of waste bamboo-charcoal and cement, the second set of single-axial compression strengths is the highest. Further increasing the ratio to 40: 60, the single-axial compression strength also can be up to 9.212MPa, and complying with CNS requir 7.840MPa for the strength of decoration bricks. In the investigation of the optimization ratio for the mixture ratio of 2 (hammered fine coal debris):1 (fly-ash): 1 (cement) after a 28-day aging, and the resultant strength of 39.788 MPa are observed for each set, and complying with the strength required by CNS for high-pressure brick C-grade. By means of natural strengthen agents can increase the strength, it is concluded that the strengthen agents can significantly increase the strength after aging for 6 to 28 days. For competitive strategy for a future market, it should be focused on the creation of differentiation for product and technology, the increase of service and features, as well as the branding effect to become a price-leader.     

Thermodynamic analyse on equilibrium precipitation phases and composition design of Al-Zn-Mg-Cu alloys

The solidification paths of Al-Zn-Mg-Cu alloys and its precipitation behavior are analyzed using software package JMatPro 6.0 for material property simulation of Al-base alloys. The microstructures of the experimental alloys are analyzed; the experimental results of microstructural analysis are in agreement with the thermodynamic prediction. Through orthogonal experimental method, this paper designs the composition of Al-Zn-Mg-Cu alloys by studying the variation of ?? (MgZn₂) phase, S (Al₂CuMg) phase, T (AlZnMgCu) phase amount and precipitation temperatures with different Zn, Mg and Cu contents. It is found that with the optimum mass fraction of Zn of 6.7%, Mg of 2.2%?C2.5% and Cu of 1.6%?C2.0%, the mass fraction of ?? phase can be up to 8.7%?C9.22% and that of S phase and T phase can be lower than 0.5%.     

Recycling of aluminum from fibre metal laminates

Recycling of aluminum alloy scrap obtained from delaminated fibre metal laminates (FMLs) was studied through high temperature refining in the presence of a salt flux. The aluminum alloy scrap contains approximately mass fraction w(Cu) = 4.4%, w(Mg) = 1.1% and w(Mn) = 0.6% (2024 aluminum alloy). The main objective of this research is to obtain a high metal yield, while maintaining its original alloy compositions. The work focuses on the metal yield and quality of recycled Al alloy under different refining conditions. The NaCl-KCl salt system was selected as the major components of flux in the Al alloy recycling. Two different flux compositions were employed at NaCl to KCl mass ratios of 44:56 and 70:30 respectively, based on either the eutectic composition, or the European preference. Different additives were introduced into the NaCl-KCl system to study the effect of flux component on recycling result. Although burning and oxidation loss of the alloying elements during re-melting and refining take place as the drawbacks of conventional refining process, the problems can be solved to a large extent by using an appropriate salt flux. Experimental results indicate that Mg in the alloy gets lost when adding cryolite in the NaCl-KCl salt system, though the metal yield can reach as high as 98%. However, by adding w(MgF₂) = 5% into the NaCl-KCl salt system (instead of using cryolite) all alloying elements were well controlled to its original composition with a metal yield of almost 98%.     

装配式空心板桥改进型铰缝结合面受力性能

为了改进装配式空心板桥横向受力性能，设计了在铰缝结合面上利用连续钢板代替间断钢筋和改进铰缝结构与填充材料的2种铰缝改进措施，采用局部模型试验计算了铰缝结合面的法向和切向强度，提出了采用间断钢筋和连续钢板的铰缝结合面抗弯、抗剪承载能力计算公式。研究结果表明:局部模型试验值与公式计算值的误差不超过10%，表明所提出的抗弯、抗剪承载能力计算公式可以准确地计算采用连续钢板的铰缝结合面承载能力；未采用结合面钢筋的深铰缝，结合面法向强度为1.29 MPa，为弱侧混凝土轴心抗拉强度的39%，结合面切向强度为0.45 MPa，为弱侧混凝土轴心抗压强度的1.5%；采用间断钢筋和连续钢板的铰缝结合面法向强度较未采用结合面钢筋的铰缝分别提高了98%和73%，结合面切向强度分别提高了71%和78%；普通混凝土浅铰缝结合面法向强度为1.30 MPa，为弱侧混凝土轴心抗拉强度的40%，结合面切向强度为0.33 MPa，为弱侧混凝土轴心抗压强度的1.1%；采用UHPC填充深、浅铰缝的结合面法向强度较普通混凝土填充深、浅铰缝分别提高了13%和21%，结合面切向强度分别提高了64%和94%。      

形变Cu-13．2vol．％Fe原位复合材料导线研究

研究了采用感应加热熔炼和室温变形制备Cu-13．2vol．％Fe原位复合材料导线的工艺过程，并探讨了降低电阻率的中间热处理作用，用光学显微镜、SEM和TEM观察分析了变形过程中组织结构的变化，结果指出，Fe树枝晶的变形是不均匀的，中间热处理有利于均匀变形，在较大变形量下，Fe树枝晶形成纤维，空间形态为薄片状，相结构为α-Fe，测定了力学性能和电阻率，结果是变形量越大，强度越高，电阻率越大。经中间热处理，可在不降低强度的同时，大大降低电阻率，几个较好的电导率／极限拉伸强度组合为：70．6％IACS/659MPa、64．6％/752MPa和51.9％IACS/880MPa。     

SiCp/AlSi7Mg1复合材料的摩擦和磨损特性

研究了在№２０机油摩擦条件下，采用环状试验块、ＡｌＳｉ７Ｍｇ１、１０ＳｉＣｐ／ＡｌＳｉ７Ｍｇ１和 ２５％ＳｉＣｐ／ＡｌＳｉ７Ｍｇ１的复合材料滑动摩擦行为．试验结果表明，复合材料无论在低载荷或在高载荷时都比没增强基体具有优异的耐磨性能，两种体积率复合材料的磨损速度是其基体的 １／８．应用 ＳＥＭ、 ＥＤＸＡ观察摩擦表面以研究其机理．     

Mechanical properties and residue stress of four kinds of ZrC coatings prepared by chemical vapor deposition

Four kinds of ZrC coatings with nearly the same thickness have been successfully prepared on graphite substrate by chemical vapor deposition (CVD) through controlling the ratio of inlet reacting gases. From backscattered electron images, it can be inferred that ZrCIII coating has the best tightness of all coatings. Meanwhile, line energy spectrum curve shows that zirconium and carbon elements distribute uniformly along the normal direction of the ZrCIII coating. As for varied microstructures, the coatings show different mechanical properties and residue stress. The strength and elastic modulus of ZrCIII coating were up to 89.57 and 1 192.5GPa, respectively. Those make it near the level of diamond. Value of residue tensile stress of ZrC+C composite coating was only 7.729MPa and that of ZrCIII coatings was 349.632 MPa. The strong combination of small-size grains in ZrCIII coating plays a decisive role to the best mechanical properties. However, strong misfit of lattice between ZrCIII coating and substrate can induce high residue stress.     

X65管线厚板控制冷却时的相变效应

为明确相变效应对X65管线厚板控制冷却的影响,通过开发线性混合热膨胀模型、拓展Avrami相变动力学模型和应用Leblond模型建立了热力耦合有限元模型.用该模型研究了X65管线厚板在上下层流冷却系数分别为3和1 kW/(m2.K)的非对称控制冷却时,相变效应对温度、残余应力和应变的影响.结果表明:相变期间,潜热减缓心部和下表面的冷却速度达50%、25%;潜热和TRIP效应分别产生峰值为89、-89 MPa,并且130、-170 MPa的应力可减小整体残余应力;相变膨胀产生峰值为723、-479 MPa的组织应力决定了整体残余应力大小及分布.