过共品铸造Al-Si—Cu—Mg—Fe合金组织性能研究

通过正交试验和单因素试验,考察了Cu、Mg、Zn、Ni和Fe对Al—18Si过共晶铝硅合金室温及高温（350℃）力学性能的影响规律,利用光学金相显微镜（OM）、扫描电镜（SEM）、能谱分析仪（EDX）对合金中富Cu相、富Fe相的组织组成进行了分析．结果表明：Cu、Mg是提高AI-18Si过共晶铝硅舍金室温及高温强度的主要因素;Zn含量增加明显降低合金350℃时的高温强度,改善合金的室温和高温延伸率;Fe降低合金的室温强度,显著提高合金的高温强度;当Cr：Fe=0．35：1,Mn：Cr=2：1,含铁0．8％～1．2％时,Al-18Si-4．0Cu-0．7Mg-0．2Zn-1.0Ni-（0．8～1．2）Fe合金力学性能σb（25℃））310MPa,延伸率受（25℃）≥0．75%,σb（350℃）〉130MPa,延伸率δs（35℃）〉1．5％;合金中富铜相主要以块状Al。Cu相和白灰色花卉状A15Si。cu2Mg8相存在,富铁相主要以三叶草状、树枝状和棒状Al5Si（Cr,Mn,Fe）相存在．     

基于灰色关联度的矿料对沥青混合料力学性能的影响分析

为分析矿料含量对沥青混合料力学性能的影响,利用旋转压实方法制备了4种级配沥青混合料,并通过劈裂试验、压缩试验以及蠕变试验研究了4种级配沥青混合料的低温抗开裂能力、常温抗拉/压破坏能力以及蠕变性能。随后,利用卷积积分和Laplace变换推导了4种沥青混合料的松弛模量随加载时间的变化趋势,并结合Burgers模型和二阶广义Maxwell模型对蠕变和松弛特性进行了拟合分析。最后,根据灰色关联度算法计算了矿料含量与沥青混合料力学性能的关联度,分析了矿料含量对混合料力学性能的影响。结果表明:沥青混合料的低温抗开裂、常温抗拉/压性能主要与0.15～0.3 mm和1.18～2.36 mm两档矿料的含量具有较高的相关度;而常温抗蠕变能力主要受0.6～1.18 mm和2.36～4.75 mm两档矿料的影响;温度升高后,抗蠕变能力受矿料含量变化的影响程度增加;松弛强度受细集料含量影响较大,而松弛时间主要受较大粒径矿料含量的影响。     

热喷涂FeCrAl/Al复合涂层抗高温硫化的研究

为了提高材料的抗热腐蚀性能,采用电弧喷涂方法在钢铁基体表面施加FeCrAl/Al复合涂层,通过沉积Na2SO4的900℃热腐蚀试验以及二硫化碳生产装置中的现场挂片试验,研究了FeCrAl/Al复合涂层的高温硫化表现。实验结果表明:FeCrAl/Al复合涂层提高了钢铁材料的抗高温硫化腐蚀能力,在高温硫化初期,外表面的Al涂层首先发生氧化,形成连续的Al2O3层,显著地减缓了硫原子向复合涂层内部的扩散速度。随着复合涂层中Cr、Al等有效抗硫化合金元素的相互扩散,形成FeCr金属间化合物层,进一步阻碍硫原子扩散,对钢铁基体材料提供有效的高温硫化防护作用。     

Al2O3-TiAl基复合材料的力学性能与保温时间的关系

以压力协助放热弥散法原位合成了Al2O3-TiAl基复合材料.研究了复合材料的相组成,以及室温硬度、室温抗折强度和断裂韧性等与保温时间的变化关系.结果表明:由两种烧成制度制备的产物都是由TiAl、Ti3Al、Al2O3以及NbAl3相组成.Nb2O5的掺杂对生成基体内TiAl及Ti3Al的相对含量有一定的调控作用;保温30 min的复合材料相对密度和硬度明显高于保温60 min的复合材料;保温30 min的复合材料抗折强度高于保温60 min的复合材料,并在Nb2O5掺杂量为10%(质量分数)时达到最大,其值为509.5 MPa,而保温60 min的复合材料在Nb2O5掺杂量为6%时达到最大,其值为395.6 MPa;保温30 min的复合材料断裂韧性低于保温60 min的复合材料,保温60 min的复合材料在Nb2O5掺杂量为6%时达到最大,其值为6.9 MPa.m1/2.     

DD3单昌镍基超合金高温力学性能

采用扫描电镜研究了单昌镍基高温合金ＤＤ３的高温蠕变性能和低应变速率下的拉伸行为。结果表明，ＤＤ３合金表现出良好的蠕变强度和较高的蠕变寿命；伸过程中合金的屈服强度在室温至１０３３Ｋ之间保持不变，当温度大于１０３３Ｋ后，屈服强度显著降低。     

1860级低松弛钢绞线高温下力学性能

对4根抗拉强度标准值fptk为1860 N/mm2的φs15.2低松弛预应力钢绞线中丝进行了高温下力学性能试验.据试验结果,同时对比已有预应力钢丝高温性能研究成果,得到了高温下该种钢绞线中丝极限强度、弹性模量、比例极限、条件屈服强度的计算公式和蠕变计算公式,可用于预应力结构抗火性能研究.     

LiNbO3/Al2O3复合材料的制备及其力学性能

为了研究铁电相LiNbO3对Al2O3陶瓷材料结构及其力学性能的影响,以Al2O3 Nb2O5 和LiCO3为主要原料,分别通过高温固相法和热压烧结法,制备LiNbO3/Al2O3复合材料.对制备的复合材料进行物相分析,抗折强度的测试以及显微形貌观察.结果发现：LiNbO3的加入有利于促进Al2O3的烧结,降低了Al2O3陶瓷的烧结温度.当烧结温度超过1 200℃时,复合材料的主晶相仍然为LiNbO3和Al2O3,但由于少量Li元素挥发,生成物相LiNb3O8.在1 200℃保温3h,通过高温固相法烧结,5vol％ LiNbO3/95vol％ Al2O3复合材料的抗弯强度达到了最高,为162.34MPa.在1 300℃,150MPa（保温保压1h）热压烧结制备的15 vol％ LiNbO3/85 vol％ Al2O3复合材料致密度为92.82％,其抗弯强度和断裂韧性分别为393.94 MPa和2.38 MPa· m1/2.该复合材料中的LiNbO3晶粒出现了非180°畴结构,这种电畴结构有利于改善材料的力学性能.     

原位纳米粒子增强Al基复合材料的微观组织及高温力学性能

以纳米TiO₂为添加相,按一定比例添加B₂O₃和H₃BO₃,采用高能球磨和粉末冶金法相结合的方法制备了体积分数为4%的纳米氧化物粒子增强Al基复合材料,最后在723 K的条件下以16∶1的挤压比制备了复合材料棒材。结果表明,经过4 h的球磨后,可以实现纳米氧化物在Al基体中的弥散分布;经过893 K的真空热压后,添加相与Al基体发生原位化学反应并生成了Al₂O₃等。当Ti与B物质的量比为1.0∶1.5时,复合材料的力学性能最优;同时,当B元素的先驱体化学成分不同时,复合材料的力学性能差异显著;TiO₂+H₃BO₃/Al在室温和623 K下的拉伸强度分别为507.7 MPa和151.3 MPa,展现出最高的室温力学性能;TiO₂+B₂O₃/Al在室温和623 K下的拉伸强度分别为353.7 MPa和167....     

热挤压对AM50-1%Gd合金组织与性能的影响

针对镁合金高温力学性能差的问题,通过采用热挤压、时效处理、力学性能测试及组织形貌观察等方法,研究了热挤压处理对AM50-1%Gd合金组织与性能的影响.结果表明：AM50-1%Gd合金组织结构由α Mg、Mg₁₇Al₁₂和Mg₂Gd相组成.热挤压可明显提高AM50-1%Gd合金的抗拉强度和屈服强度,并随着挤压温度的降低,合金的强度值增大.而经时效处理后,挤压态合金在室温及高温的抗拉强度和屈服强度可再次提高.挤压态AM50-1%Gd合金中的细小晶粒来自于热挤压期间发生的动态再结晶,热挤压能提高合金抗拉强度的主要原因是形变强化和细晶强化,而细晶强化和细小第二相沿晶界弥散析出是时效态合金综合力学性能好的主要原因.     

Ag对Sn-0.7Cu焊料压入蠕变性能的影响

采用自制的蠕变装置研究了Sn-0.7Cu及Sn-0.7Cu-0.5Ag无铅焊料在温度为80～120℃、压力为25～43.2MPa下的压入蠕变性能,并利用光学显微镜和XRD对合金蠕变前后组织的演化进行了分析.结果表明:在加入0.5wt%Ag后,在相同温度和压力下,Sn-0.7Cu-0.5Ag合金的蠕变速率和总蠕变量均比Sn-0.7Cu小;形成的金属问化合物cu6sn5与Ag3Sn颗粒强化了β-Sn基体,从而提高了合金的抗蠕变性能.     

Sn对AX55铸造合金组织与蠕变性能的影响

为了提高Mg-5Al-5Ca(AX55)铸造镁合金基体组织和共晶组织的耐热性能,以Sn为变量设计了AX55-x Sn(x=0,0. 5,1. 0,1. 5)合金,研究了T61和T62对合金组织、硬度与蠕变性能的影响.结果表明,随着Sn含量的增加,合金基体中析出的Al2Ca相增多,使得α-M g基体得到强化.在共晶骨架相附近析出的CaMgSn相可使共晶组织得到强化.在175℃/70 MPa蠕变100 h条件下,AX55-x Sn合金的最小蠕变速率和蠕变总量随Sn含量的提高而降低. AX55-1. 5Sn合金性能最佳,且其最小蠕变速率为5. 21×10-8s-1,100 h总蠕变量为0. 065%.相比T61,T62能够提高AX55-x Sn合金的基体硬度和蠕变性能.     

Microstructures, mechanical properties and compressive creep behaviors of as-cast Mg-5%Sn-（0-1 .0）%Pb alloys

The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-(0–1.0)%Pb (mass fraction) alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic α-Mg and Mg₂Sn phase. The addition of Pb can refine the size of Mg₂Sn phase and grain size, reduce the amount of Mg₂Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg₂Sn phase. Pb exists in the Mg₂Sn phase or dissolves in α-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175 °C with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.     

As-cast microstructure,mechanical properties and casting fluidity of ZA84 magnesium alloy containing TiC

The as-cast microstructure, mechanical properties and casting fluidity of ZA84 alloy containing TiC were investigated. The experimental results indicate that adding 0.5wt%TiC to ZA84 alloy can refine the as-cast microstructure, and do not cause the formation of any new phase. After 0.5wt%TiC was added to the ZA84 alloy, the morphology of ternary phases on the grain boundaries changed from coarse quasi-continuous net to fine disconnected net, and the distribution of ternary phases became dispersive and homogeneous. At the same time, the tensile properties of ZA84＋0.5TiC alloy at room temperature were comparable to those of AZ91D alloy, and were higher than those of ZA84 alloy. At 150 ℃, the tensile and creep properties of ZA84＋0.5TiC alloy were also higher than those of ZA84 and AZ91D alloys. In addition, compared with the AZ91D alloy, the casting fluidity of ZA84＋0.5TiC alloy was slightly poor, but better than that of ZA84 alloy. The reason could be related to the effect of TiC on the solidification temperature range of ZA84 alloy.     

Sintering behavior, microstructure and properties of TiC-FeCr hard alloy

TiC based cermets were produced with FeCr, as a binder, by conventional P/M （powder metallurgy） to near 〉97% of the theoretical density. Sintering temperature significantly affects the mechanical properties of the composite. The sintering temperature of 〉1360℃ caused severe chemical reaction between TiC particles and the binder phase. In the TiC-FeCr cermets, the mechanical properties did not vary linearly with the carbide content. Optimum mechanical properties were found in the composite containing 57wt% TiC reinforcement, when sintered at 1360℃ for 1 h. Use of carbon as an additive enhanced the mechanical properties of the composites. Cermets containing carbon as an additive with 49wt% TiC exhibited attractive mechanical properties. The microstructure of the developed composite contained less or no debonding, representing good wettabifity of the binder with TiC particles. Homogeneous distribution of the TiC particles ensured the presence of isotropic mechanical properties and homogeneous distribution of stresses in the composite. Preliminary experiments for evaluation of the oxidation resistance of FeCr bonded TiC cermets indicate that they are more resistant than WC-Co hardmetals.     

稀土掺杂WSi2/MoSi2材料的合成及其性能

采用自蔓延高温合成（SHS）和机械合金化（MA）方法复合制备了稀土质量分数为0．2％～2．0％的WSi2／MoSi2复合材料．利用MRH-5A型环一块式摩擦磨损试验机测定了复合材料试样与CrWMn钢在油润滑条件下的滑动磨损性能，研究了稀土含量对材料的微观结构、力学性能以及摩擦学性能的影响．结果表明：稀土增强的WSi2／MoSi2复合材料具有细晶组织结构，较高的抗弯强度、硬度和断裂韧性以及较好的耐磨性能，在稀土质量分数为0．5％～0．8％时，复合材料具有最佳的力学性能和摩擦学性能．基体的致密化及强化有利于降低其摩擦磨损．此外，采用SHS＋MA工艺可在低的烧结温度获得高致密度的复合材料．     

挤压变形Mg-4%Zn-0.5%Zr-xCe合金的显微组织与拉伸性能

针对挤压态和热处理态挤压变形Mg-4%Zn-0.5%Zr-xCe合金的显微组织和拉伸性能进行了研究,以确定稀土元素Ce和T5处理对该类合金性能的影响规律.结果表明,加入稀土元素Ce可以有效地细化挤压变形Mg-4%Zn-0.5%Zr合金的组织,提高其室温抗拉强度、屈服强度和断裂伸长率.经过T5处理后,Mg-4%Zn-0.5%Zr-xCe合金的抗拉强度和屈服强度可以得到显著提高,其中Ce质量分数为1%的合金具有最优的综合拉伸性能.断口形貌观察结果表明,不同处理状态的挤压变形Mg-4%Zn-0.5%Zr-xCe合金在拉伸加载条件下主要呈现脆性和韧性混合断裂.     

Microstructure and properties of W-15Cu alloys prepared by mechanical alloying and spark plasma sintering process

W-15Cu composite powders prepared by mechanical alloying （MA） of raw powders were consolidated by spark plasma sintering （SPS） process at temperature ranged 1 230-1 300 ℃ for 10 min and under a pressure of 30 MPa. By using high energy milling, particles containing very fine tungsten grains embedded in copper, called composite particles, could be produced. The W grains were homogeneously dispersed in copper phase, which was very important to obtain W-Cu alloy with high mechanical properties, fine and homogeneous microstructure. The microstructure and properties of W-15Cu alloys prepared by SPS processes at different temperature were researched. The results show that W-15Cu alloys consolidated by SPS can reach 99.6 % relative density, and transverse rupture strength （TRS） is 1 400.9 MPa, Rockwell C hardness （HRC） is 45.2, the thermal conductivity is 196 W/m-K at room temperature, the average grain size is less than 2 μm, and W-15Cu alloy with excellent properties, homogeneous and fine microstructure is obtained.     

Al-5Fe-1.2Si-1Mg-0.6Cu-0.5Mn合金轧制变形行为及组织性能

为了细化Al-5%Fe基合金中粗大的脆性针状或针片状富铁相,采用电磁搅拌及固态挤压技术制备Al-5%Fe-1.2%Si-1%Mg-0.6%Cu-0.5%Mn合金轧制坯锭,研究Al-5%Fe基合金的轧制变形能力及合金的组织性能,并用热压缩实验模拟了铝铁合金在783~693K、变形速率为0.01~10s^-1条件下的热变形行为.结果表明：该合金高温变形时存在明显的稳态流变特征,流动应力对应变速率和温度敏感.板材力学性能较挤压态有大幅度提升,其室温下的抗拉强度和伸长率最高达到354.5MPa和7.6%,比挤压态分别提高了105.6%和184.6%.轧制对铝铁合金中富铁相的破碎作用十分明显.     

Effect of carbon addition on the microstructure and mechanical properties of CoCrFeNi high entropy alloy

The effects of C element on the microstructure and properties of CoCrFeNiCx high entropy alloys(x denoted the atomic fraction of C element at 0, 0.05, 0.1, 0.2, 0.3, and 0.5) were investigated. The equal molar CoCrFeNi alloy with FCC structure exhibits high ductility but weak strength. With the addition of C element, both the hardness and strength of the CoCrFeNiCx high entropy alloys increase as well as the wear resistance. The solution strengthening and the formation of hard carbide phase are the main factor for the improved strength, hardness and wear resistance of CoCrFeNiCx high entropy alloys.     

SiC_p/ZA22复合材料高温力学性能

采用半固态挤压铸造工艺制备了SiC_p/ZA22复合材料,并测定了其高温条件下的抗拉强度、弹性模量及冲击韧性,同时,分析了复合材料高温性能提高的影响因素,并提出了优化的碳化硅颗粒尺寸和加入量.