微量元素对Mg-Al-Zn系合金铸态组织及性能的影响

综述了Mg-Al-Zn系合金的化学成分，几种合金元素在镁合金中的作用及添加微量合金元素对Mg-Al-Zn系镁合金铸态显微组织及性能的影响。     

钛对GH150合金组织和性能的影响

采用金相显微镜、透射电镜、化学相分析和力学性能测试等方法，研究了钛含量对ＧＨ１５０合金组织和性能的影响。结果表明，在１．６３％～２．９６％Ｔｉ范围内，随钛含量的提高，γ′相析出量增加，进入γ′相中的钛［Ｔｉ（γ′）］从０．９２％增至２．１７％，可见钛在ＧＨ１５０合金中主要起时效强化作用，并显著影响力学性能。随钛含量的增加，合金的室温屈服强度、７００℃拉伸强度和持久强度均提高，同时固溶状态的室温拉伸塑性和持久塑性下降，这是γ′相和μ相综合作用的结果。     

Nb含量对TiAl合金铸态组织的影响

利用金相显微镜(OM)、X射线衍射仪(XRD)和扫描电镜(SEM)及能谱分析(EDS)等测试方法研究Nb含量对铸造TiAl-xNb(x=1,3,5,7;原子分数,%)合金组织的影响。结果表明:Nb含量为1%时,TiAl-Nb合金铸锭组织主要为单相的γ组织;随Nb含量升高,合金组织主要为α2/γ层片组织;并在层片组织间存在2种偏析,分别是网状β相和γ相,合金的层片晶团平均尺寸逐渐增加,β相的体积分数逐渐升高;当合金中Nb的含量从1%增加到7%,层片晶团平均尺寸由89μm增加至190μm,β相的体积分数从1.9%增至12.9%;随合金中Nb含量增加,β相中Nb含量增加而Cr含量减少,γ相的偏析区域宽度变窄。     

钇对Ti-43Al-9V合金组织性能的影响

采用OM，XRD，SEM和TEM等测试方法，分析了稀土元素(Y)对Ti—43Al—9V合金显微组织以及力学形能的影响。实验结果表明，Ti—43Al—9V—0．3Y合金由γ相、α2相、B2相和YAl2相组成；添加稀土可以细化Ti—43Al—9V合金的晶粒尺寸，并促进细小的α2／γ层片形成以及细化粗大的α2／γ／B2层片。对TiAl合金力学性能测试表明，适量添加稀土Y(0．3％，原子分数)可明显改善合金的室温强度和塑性，但过量添加将会造成材料性能降低；断口分析表明过量添加稀土导致沿晶断裂比例增加将损害TiAl合金的性能。     

Ca对AE41合金的显微组织和力学性能的影响

研究了Ca的低合金化对稀土镁合金AE41显微组织和力学性能的影响。研究结果表明，Ca能显著地细化合金的铸态组织，并在合金的显微组织形成热稳定性很高、分布均匀的弥散强化相颗粒Mg2Ca。少量的Ca加入AE41能有效地改善合金的力学性能，尤其是提高在150℃－225℃温度范围内的强度和蠕变抗力。在175℃，70MPa条件下，加入了0．1％Ca后，合金的蠕变速率比基体合金降低了一个数量级。从综合性能的角度考虑，在AE41中Ca的加入量以0．1％为宜。     

Sn对铸态Mg-5Gd-3Y-0.5Zr合金组织和力学性能的影响

采用X射线衍射仪、光学显微镜、扫描电镜、能谱仪和电子拉伸试验机,研究了不同Sn含量对Mg-5Gd-3Y-0.5Zr合金显微组织、力学性能以及拉伸断口形貌的影响。结果表明,铸态Mg-5Gd-3Y-0.5Zr合金主要由基体α-Mg、Mg₅Gd和Mg₂₄Y₅相组成,Sn的添加能够细化合金组织,在合金中生成新相Sn₃Y₅,促进合金中第二相的析出。Mg-5Gd-3Y-0.5Zr-0.5Sn合金中第二相呈现出分布均匀的颗粒状,Mg-5Gd-3Y-0.5Zr-1.0Sn合金中部分区域出现了长条状第二相,Mg-5Gd-3Y-0.5Zr-1.5Sn合金中部分区域出现了方块状第二相。在本文研究范围内,随着Sn含量的增加,合金的抗拉强度、伸长率以及布氏硬度都呈现出先上升后下降的趋势。Sn含量为0.5%时,铸态合金综合性能最好,此时合金的抗拉强度、伸长率以及布氏硬度分别为177 MPa、6.87%和57.47 HBW,与无Sn合金相比分别提高了5.36%、12.25%和11.96%。     

Ni含量对Cu-Ni-Cr合金组织和性能的影响

采用中频熔炼-铁模铸造-热轧-固溶-冷轧-时效处理工艺,制备了Cu-Ni-Cr合金板材.通过拉伸力学性能测试、电导率测试、金相和透射电子显微镜观察.研究了不同Ni含量对该合金组织和性能的影响.结果表明:Cu-Ni-Cr合金在Ni含量不大于2%时.其常温力学性能相差不大,在Ni含量达到5%后强度才有较大的下降;Ni可有效地调节合金的电导率,在Ni含量从0.5%变化到5%时,合金的电导率也从64%IACS变化到20.9%IACS,因此可根据具体要求选择设计合金的成分;在此处理态下,两成分的合金Cu-1.5Ni-0.5Cr和Cu-2.0Ni-0.5Cr的高温力学性能都较好,抗拉强度在350℃时在280MPa左右,延伸率也在8%左右.     

Ti含量对U-Ti合金组织和性能的影响

采用真空感应熔炼的方法制备了U-0.5％Ti、U-0.75 ％Ti和U-0.95％Ti合金试样,研究了Ti含量对合金微观组织、室温拉伸性能和耐腐蚀性能的影响.结果 表明:三种成分的U-Ti合金组织均以针状和双凸透镜状马氏体为主,物相组成主要有α'相和U2 Ti相;随着Ti含量的增加,U-Ti合金的晶粒逐渐细化,U2Ti...     

热处理对TC21合金大规格棒材组织和性能的影响

研究了不同热处理制度对TC21合金380 mm大规格棒材显微组织和力学性能的影响。结果表明,固溶温度影响初生α相含量以及形貌尺寸,固溶时间对显微组织没有显著的影响;冷却速度影响次生α相含量及尺寸,且对合金强度和塑性产生较大的影响。在890℃×2 h+FC固溶处理后进行610℃×4 h+AC时效处理,可使合金的强度和塑性得到良好的匹配。     

合金元素对高铬铸铁组织的影响

介绍了高铬铸铁的金相组织特征，以及合金元素铬、钒、镍、钨、钼对组织的影响。     

Effect of microstructure on mechanical properties of as-cast Mg-Al alloys

The mechanical properties of Mg-Al alloys are mainly determined by the microstructure, i.e., the amount and morphology of the phases, but also by the presence of defects arising from the melt handling and casting process. In order to obtain information about the isolated effect of the microstructure, it is, therefore, necessary to minimize the amounts of defects. In this study, this has been achieved by remelting and solidifying the alloys in a gradient furnace. The drawing rate was varied from 0.3 to 6 mm/s, which yielded a wide variety of microstructures. Three samples were produced for each parameter set, in order to have a statistical basis for the evaluation. The results showed that homogeneous and reproducible samples could be produced, and that the tensile properties obtained showed a very small scatter. The effects of microstructural parameters such as grain size, secondary dendrite arm spacing (SDAS), eutectic fraction, and eutectic morphology on the yield strength, ultimate tensile strength (UTS), fracture elongation, and hardness has been investigated.     

Study on microstructure and mechanical properties of as-cast Mg-Sn-Nd alloys

Microstructure, tensile properties and compressive creep behaviors of Mg-(1.65-11.52) wt.% Sn-2 wt.% Nd alloys were studied in this paper. The microstructure of the as-cast Mg-Sn-Nd alloys consisted of dendritic α-Mg, Mg2Sn and Mg-Sn-Nd ternary phase containing rare earth element. The highest ultimate tensile strength of 140 MPa and percentage elongation after fracture of 9.7%, were achieved with a composition of Mg-8.23 wt.% Sn-2 wt.% Nd. The compressive creep resistance of Mg-8.23 wt.%Sn-2 wt.% Nd alloy w...     

Effect of alloy preheating on the mechanical properties of as-cast Co-Cr-Mo-C alloys

The effect of various alloy preheatings followed by full solid solution treatments on the resultant strength and ductility of as-cast Co-Cr-Mo-C alloys was investigated. Three preheating temperatures were evaluated: 815 °C, 950 °C, and 1100 °C for 4 hours and then solid solution treated at 1225 °C for 4 hours. Tensile and compressive tests were carried out on the heat-treated alloys. It was found that the strength and ductility of the heat-treated alloys exhibited significant improvements over the as-cast condition. In particular, optimum ductility of the heat-treated alloys and alloy strength were promoted by preheating at 815 °C. A relatively fine grained structure coupled with a uniform distribution of second-phase particles promoted homogeneous plastic deformation in the bulk. Fractographic observations indicated that the exhibited ductility was associated with the development of numerous plastic bands combined with band interlockings. Alloy preheats at 950 °C and 1100 °C prior to solutionizing lead to inferior strength and ductility. Although preheating at 1100 °C led to slight improvements, in both cases, the fracture path was dominated by the presence of continuous carbide films surrounding the dendritic grains. Hence, less than optimum combinations of strength and ductility were achieved by the heat treatments at the higher temperatures.     

Effects of Be and Fe additions on the microstructure and mechanical properties of A357.0 alloys

A357 hypoeutectic alloy is a heat-treatable Al-Si-Mg system with a nominal composition of Al-7 pct Si and about 0.6 pct Mg have widespreaded applications, especially in the aerospace and automotive industries. The purpose of this study was to determine the influences of Be and Fe content on the microstructure and mechanical properties of A357.0 alloys. Distinct morphologies were discerned between Be-containing and Be-free alloys. The Be-free alloys contain larger amount of iron-bearing phases with Mg than in Be-containing alloys. The addition of Be can change the plateletlike structure of iron-bearing phases to a comparatively harmless round nodular form. Also, the amounts of iron-rich phases are significantly lower and the silicon particles are smaller and more spherical in the Be-containing alloys. Small amounts of Be in A357.0 caused significant increases in the precipitation kinetics of Mg₂Si. It was found that the addition of Be lowers the ternary and binary eutectic melting point. The amount of Mg available to form the major strengthening phase Mg₂Si is increased promoting the tensile strength of A357.0 casting. The tensile properties were improved with decreasing Fe content and the addition of Be. The effect is more apparent in the higher Fe alloys than that in the lower Fe alloys.     

稀土Nd对AZ 31镁合金铸态组织和力学性能的影响

利用气氛电阻炉制备了AZ 31-xNd合金(x=0.05%,0.1%,0.2%,0.4%,0.6%),采用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)对不同Nd含量的实验合金进行了显微组织观察和分析,结果发现,Nd在AZ 31-xNd合金中形成了Al_3Nd和Mg_(12)Nd相,这些含Nd相导致AZ 31镁合金在凝固过程中的晶粒细化,从而提高了AZ 31镁合金的铸态室温力学性能,随着Nd含量的增加,合金的铸态室温抗拉强度极限和延伸率均先升高后降低.     

添加球磨粉末对铁基高温合金锻态显微组织与力学性能的影响

采用SEM、能谱分析、XRD、密度和室温拉伸性能测定相结合的方法,研究添加球磨粉末对铁基高温合金锻态组织和力学性能的影响.结果表明:添加球磨粉末的混合粉末锻造合金的显微组织由几百纳米的细晶粒和几十微米的粗晶粒组成,具有明显晶粒尺寸双峰分布特征,其中细晶粒的形成提高了合金的界面能,有利于元素的扩散、成分均匀化和孔隙的消除...     

Effect of copper and molybdenum additions on the microstructure and mechanical properties of steel shot

The effect of copper and molybdenum additions on the microstructure of particles produced by the atomization of an iron-carbon melt by an air-water jet using a new atomizer unit has been studied. The application of air-water atomization instead of water atomization is shown to intensify the solidification of particles with a fine microstructure. The introduction of molybdenum (up to 0.6 wt %) into a melt refines the structural constituents of the granules and decreases the fraction of the retained austenite, and the introduction of copper (up to 0.8 wt %) leads to the opposite results. The addition of copper (up to 0.6 wt %) and molybdenum (up to 0.6 wt %) to a melt results in a homogeneous microstructure consisting of fine acicular martensite and fine molybdenum carbides. Low-temperature vacuum tempering at 350°C for 1 h leads to insignificant decarburization of the martensite and the precipitation hardening of the base metal due to copper alloying. The microstructure of a steel alloyed by molybdenum and copper provides an increase in the wear resistance of the steel shot by a factor of 1.5–2 and high quality of the shot (close to the best foreign analogs).     

Effects of lanthanum addition on microstructure and mechanical properties of as-cast pure copper

As-cast Cu-La alloys with La contents in the range of 0–0.32 wt.% were fabricated by vacuum melting method. The effects of La on microstructure and mechanical properties of as-cast pure copper were investigated using optical microscopy(OM), scanning electronic microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and tensile test. The results showed that La had obvious effects on the solidification microstructure and the grain refinement of as-cast pure copper. With the increase of La content, the ultimate tensile strength, the yield strength and the microhardness increased gradually, but the elongation increased first and then decreased while La content exceeded 0.089 wt.%. The improvement of mechanical properties was attributed to the effect of grain refinement strengthening, solid solution strengthening, second phase strengthening and purifying. However, excessive adding La would deteriorate the elongation owing to the excessive Cu6 La phases.     

Si和La元素对Mo丝显微组织与力学性能的影响

系统研究了La、Si单元掺杂和复合掺杂对钼丝的显微组织和力学性能的影响及其作用机制,优化出具有优异力学性能的Mo-Si-La合金丝的成分为Mo-0.15Si-(0.5～0.8)La.MoSi2与Mo原位反应生成Mo5Si3和Mo3 Si硬质相,起到良好的晶粒细化作用和弥散强化作用.La2O3颗粒通过延迟微裂纹的形成和扩...     

Effect of cobalt addition on microstructure and mechanical properties of tungsten heavy alloys

The present investigation attempts to study the microstructure and mechanical behaviour of tungsten heavy alloys with different cobalt content. Alloys with 2 and 3% cobalt were synthesized using liquid phase sintering technique. The alloys were then vacuum heat treated and finally swaged. Quantitative microstructural analyses were undertaken by determining tungsten grain size, contiguity of tungsten and volume fraction of the matrix etc. Tensile results showed that the alloy with 3% cobalt exhibited inferior properties as compared to 2% cobalt alloy. Detailed microstructural and fractographic analysis were undertaken in order to understand these trends. Work hardening analysis showed the double slope behaviour of the alloys, which could be attributed to change in deformation behaviour from single phase matrix to two phase aggregate. It was also concluded that higher cobalt alloys needed further optimization in terms of thermo-mechanical treatment in order to realize their full potential in terms of mechanical properties.