显微组织对Cu—Cr—Ni合金高温氧化行为的影响

研究了两种单／双相Cu-Cr-Ni合金的高温氧化行为。结果表明,合金氧化动力学偏离抛物线规律,其瞬时抛物线速率常数随时间延长而降低。两种合金表面氧化膜的结构差别较大,单相合金表面形成－连续的Cr2O3层,双相合金表面氧化膜外层是一边疆的CuO层,Ni和Cr的氧化发生在合金内部,这种合金与氧化物共存的混合内氧化与经典的内氧化明显不同,氧化层最里面形成了一连续的CrO3膜,抑制了合金的进一步氧化。     

Y对Al-Zr合金微观组织与性能的影响

采用电导率、显微硬度、扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究Al-0．30Zr与Al-0．30Zr-0．08Y合金的微观组织与性能。铸态Al-Zr-Y合金中微米尺度初生Al3Y相通过共晶反应在晶内和晶界上同时生成。在Al-Zr-Y合金中,Y明显加速了Al3Zr（Ll2）的析出动力学。由于较大体积Al3（Zr,Y）析出相的生成,Al-Zr-Y合金的电导率明显高于Al-Zr合金的。在Al-Zr-Y合金中观察到了高密度的弥散球状Ll2结构Al3（Zr-Y）析出相。Al-0．30Zr-0．08Y合金具有比Al-0．30Zr合金更强的抗再结晶能力。     

稀土Y含量对Mg-Al合金组织细化的影响

通过合金制备、金相显微镜和扫描电镜等方法研究了稀土元素Y对Mg-Al合金组织细化的影响。结果表明,适量Y的加入能明显细化基体晶粒,使β相分布更为弥散,Y的加入还使基体中出现点状新相Al2Y。冷速为200℃/min时,Mg-5Al和Mg-7Al合金中加入0.5%Y时的组织和成分更均匀,细化效果最好,晶粒直径分别由92.64μm、82.40μm变为52.83μm、39.47μm,β相含量由11.91%、12.17%变为8.29%、8.81%,合金硬度从50.1 HV5和52.8 HV5升高到56.4HV5和62.2 HV5;随着Y含量的进一步增多,合金又开始呈粗化趋势。在同样的冷速和变质条件下,Mg-7Al合金比Mg-5Al合金晶粒更细,变质效果也更好。     

Effect of La on arc erosion behaviors and oxidation resistance of Cu alloys

Cu with and without La addition was prepared and the effect of a trace amount of La on the arc erosion behaviors and oxidation resistance of Cu alloys was investigated. The results indicate that CuLa alloy exhibits superior oxidation resistance and arc erosion resistance. The contact resistance and temperature rise were obviously improved. The oxidation resistance of CuLa alloy mainly is due to the interface wrapping of La₂O₃ particles and CuLa alloy phase on Cu atoms. Thermodynamic calculation indicated that La₂O₃ could form preferentially in the CuLa alloy, which was beneficial for the protection of the Cu substrate. According to kinetics analysis, the activation energy of CuLa alloy was higher than that of pure Cu, indicating the better oxidation resistance of CuLa alloys.     

硅对自保护明弧堆焊合金Fe-Cr-C-B显微组织及性能的影响

采用药芯焊丝自保护明弧焊方法在Q235A基体上制备了Fe-Cr-C-B-Si耐磨合金.借助光学显微镜、扫描电镜、X-射线衍射仪和硬度测试等手段研究了以Fe-Si形式加入的硅含量对其组织和性能的影响.结果表明,硅含量显著影响其碳化物形貌、分布及尺寸,具体表现为硅含量提高,随之出现了硬度高达9.75～13.54 GPa的白色团状相,尺寸增大并呈聚集分布;背散射电子扫描图、电子能谱分析和显微硬度测试显示该团状相为双相复合碳化物,其内部为M23C6相,外表则是较低Cr,C元素含量的碳化物.此外湿砂磨粒磨损试验结果表明,适量硅显著改善了明弧堆焊合金的耐磨性,所含M23C6相尺寸和显微硬度明显影响其磨损失重.     

电流对明弧高硼堆焊合金显微组织及耐磨性的影响

采用药芯焊丝明弧自保护焊方法制备了Cr12B4SiMn高碳型高硼合金,借助光学显微镜、X射线衍射仪、显微硬度计、扫描电镜以及电子能谱仪,考察了电流对其显微组织及耐磨性的影响。结果表明,随电流增大,在团状先析出相中,内置式块状M₂B相的形成数量增加,其显微硬度提高,M₂₃(C,B)₆和马氏体等相减少,γ-Fe消失;合金宏观硬度随之先升高一定值然后降低,耐磨性先显著增加,接着小幅波动。块状M₂B数量及其显微硬度增加是导致该合金耐磨性改善的主要原因,合金磨损机制主要为显微剥落。     

Microstructure and properties of cold consolidated amorphous ribbons from (NiCu)ZrTiAlSi alloys

Amorphous ribbons of compositions (Ni₅₆Cu₂)Zr₁₈Ti₁₃Al₆Si₅ and (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ were consolidated by high pressure torsion (HPT) at room temperature. In the HPT experiments a 6 GPa pressure and two turns were applied. Samples in the form of discs, 6–7 times thicker than the ribbons and about 10 mm in diameter were achieved. The minimal deformation for the homogenous consolidation was estimated to be in the range of 400%. XRD showed that the microstructure was dependent on the composition. The sample with high Cu content remained amorphous while the sample with low Cu content revealed some crystallization. DSC experiments allowed a comparison of the glass transition temperature T_g and crystallization process of the amorphous ribbon and HPT sample which were different. The glass transition temperature T_g of the amorphous HPT sample of (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ composition decreased. For both alloys the nanohardness and the elastic modules showed decrease for cold consolidated samples in comparison to the ribbons.     

Effect of Y2O3 on microstructure and oxidation of chromizing coating

A Y2O3-modified chromizing coating was produced by chromizing an as-electrodeposited Ni-Y2O3 composite film using pack cementation method at 1 100 ℃ for 3 h. For comparison, chromizing was also performed under the same condition on an asdeposited Ni film without Y2O3 particles. Oxidation at 900 ℃ for 120 h indicates that although on both two chromizing coatings chromia scales grow during oxidation, the Y2O3-modified chromizing coating exhibits an increased oxidation resistance due to the formation of thinner, denser and finer-grain scale. The effect of Y2O3 on the coating formation and the coating oxidation behavior was discussed in detail.     

稀土Y对Nb-Ti-Si基超高温合金组织及抗氧化性能的影响

采用真空非自耗电弧熔炼法制备了5种成分为Nb-22Ti-15Si-5Cr-3Al-3Hf-x Y(x=0,0.03,0.06,0.12,0.30 at%)的合金,并在1250℃下分别进行了1、10、20和50 h的高温氧化实验,研究Y含量对合金电弧熔炼态组织及其高温抗氧化性能的影响。结果表明:添加Y不改变电弧熔炼态合金相组成,组织仍由Nbss及γ-(Nb,X)5Si3相组成,但细化了共晶组织。高温氧化实验结果表明,不同Y含量合金在氧化不同时间后,氧化膜均由Nb2O5,Ti O2,Ti2Nb10O29和Ti Nb2O7组成;随着Y含量的增加,氧化膜中的孔洞和裂纹减少,合金单位面积氧化增重也逐渐减小,表明Y的添加能够显著提高合金的高温抗氧化性能。     

电弧增材制造(WAAM)ZL114A铝合金组织与性能的研究

采用金相显微镜、扫描电镜、电子万能试验机等分析测试手段,研究了电弧增材制造工艺方法对ZL114A铝合金组织与性能的影响。与传统铸造成形方法相比,铸态组织具有更小的枝晶间距、Si相细小分布均匀;化学成分可有效控制;T6热处理后,Si相球化充分,第二相弥散分布在α-Al基体上,力学性能显著提升,抗拉强度、屈服强度及延伸率分为360MPa、315MPa、7.5%,延伸率是砂型铸造试样的2.1倍,拉伸断口呈现韧性断裂特征。WAAM成形试样缺陷主要为小于30μm的气孔,经过热处理后气孔数量减少,尺寸有变大趋势。     

Role of defects on microstructure development of beta titanium alloys

Microstructures of α precipitation from a deformed β matrix by thermomechanical processing were studied in a representative β titanium alloy, i.e. Ti-15V-3Cr-3Sn-3Al alloy. In the aged specimens, after solution treatment, the grain boundary is the most preferential nucleation site in the a precipitation. Localized slip occurs in the β matrix by cold rolling after solution treatment whereas (332)<113> deformation twins are formed by subzero rolling at 77 K. After subsequent aging of the rolled specimens, the α phase preferentially forms on those defects in the β matrix with a low energy orientation relationship (Burgers relationship). There is strong variant restriction in heterogeneous nucleation on such defects. Controlled short time annealing above the β transus (β recovery treatment) after cold rolling produces the fine β subgrain. By subsequent aging, α precipitates form preferentially on β subgrain boundaries and also within β subgrains. A great number of α variants are observed locally in the recovered and aged specimens than those in the cold rolled and aged specimens. β recovery treatment prior to aging improves the strength-ductility balance mostly because of the increase of local elongation.     

机械搅拌对Fe-Cr-C系明弧堆焊合金显微组织及其耐磨性的影响

采用高碳高铬铸铁药芯焊丝,通过自改装的自动搅拌式明弧堆焊机在Q235钢表面堆焊了Fe-Cr-C系耐磨高铬铸铁焊层。借助XRD、SEM、EDS和光学显微镜(OM)分析了堆焊层的物相组成,观察了堆焊层的宏观和微观组织形貌。运用洛氏硬度计和动载冲击磨料磨损试验机测试了堆焊层的表面硬度和磨损性能。结果表明,机械搅拌作用下的明弧堆焊层中裂纹明显减少,焊层内部奥氏体和碳化物更加混乱、细小,局部区域出现了波纹状组织。搅拌作用下的明弧堆焊层最高硬度达57 HRC,相对耐磨性是一般明弧堆焊层的2倍。磨损机制表现为金属的塑性变形和磨料对堆焊层的短距离切削。     

Al-Ag-(Sc)合金的时效析出行为

通过时效硬化曲线的测量及时效组织的透射电镜分析,研究了微量钪对Al-Ag合金时效析出行为的影响.研究结果表明:在Al-Ag合金中添加0.2%Sc(质量分数),可增强合金350℃的时效硬化效果,延长达到峰时效的时间.微观组织分析发现,微量钪的添加促使合金中γ'相弥散细小地析出,同时钪的存在减少了γ'相宽面上的位错台阶数.含钪Al-15Ag合金中γ'相长大过程比较缓慢的微观机理是微量钪的添加影响了合金中γ'相宽面上的台阶分布.     

Mo对高硬度明弧堆焊合金显微组织及耐磨性的影响

采用药芯焊丝自保护明弧焊方法制备了含有11%~13%Cr、3.5%~3.8%C、2.1%~2.3%Nb、0.6%~0.7%B、0%~4.0%Mo (质量分数)且宏观硬度高达65 HRC的耐磨合金。采用光学显微镜、X-射线衍射仪和扫描电镜,研究了钼含量对其显微组织及耐磨性的影响。结果表明,随着钼含量增加,合金组织整体细化,形成了强韧性配合良好的奥氏体+针状马氏体复合基体以及韧性更好的M23(C,B)6+原位析出NbC耐磨相,脆性变态莱氏体Ld′的形成得到明显抑制。此外,湿砂磨粒磨损试验结果表明,适量Mo减小碳化物间隔尺寸及NbC颗粒脱落几率,显著改善耐磨性,但如加入过多,合金磨损机制会变为磨粒显微切削。     

电参数对镁合金微弧氧化膜厚度的影响

在自行研制的电解液中,采用四因素三水平正交实验,系统研究频率、占空比、电流密度和终电压对AZ91HP镁合金氧化膜厚度的影响。结果表明,各因素的主次顺序为终电压〉电流密度〉占空比〉频率。终电压对氧化膜厚度影响显著,电流密度对氧化膜厚度有影响但不显著,占空比和频率对氧化膜厚度无显著影响。氧化膜层的耐蚀性并不是仅仅由厚度决定,而是由多种因素综合作用的结果。     

Processing and microstructure of high-pressure consolidated ceramic nanocomposites

Al₂O₃/TiO₂ nanocomposites were prepared by high-pressure sintering (HPS). The addition of nano-MgO powder improved the densification and retarded grain growth. The pressure decreased the energy barriers for nucleation, and caused the decomposition of Al₂TiO₅ and the phase transformation of Al₂O₃ to take place at lower temperatures.     

Transient oxidation in Fe-Cr-Ni alloys: A Raman-scattering study

Using Raman scattering we have investigated the oxidation, in air, of the Fe-Cr-Ni stainless steels Fe-25Cr-20Ni, Fe-25Cr-20Ni-3Zr, and Fe-24Cr-3Zr (wt.%) as a function of temperature in the range 300 to 1000°C. The Raman technique is very sensitive to, and provides a clear identification of, the oxides Fe₂O₃ and Cr₂O₃. However, the technique is insensitive to NiO, FeO, and does not give a clear identification of spinels. The Fe–Cr–Ni alloys form chromia scales at temperatures greater than 800°C. At lower oxidation temperatures, transient phases are observed. With a 1-h heat treatment at 300°C, we observe the formation of an unidentified scale; we speculate that it is either amorphous or consists of disordered spinel(s). Near 400°C we begin to observe hematite (Fe₂O₃). The intensity of the Fe₂O₃ signal increases with temperature to 600°C and then decreases, being largely replaced by the signal from Cr₂O₃. The thickness of the Cr₂O₃ scale increases with temperature up to 1000°C above which spallation becomes apparent. Spinel phases also apparently persist in the scale to 1000°C.     

Fe-RE(Y、La和Ce)合金中相稳定性和固溶度的第一性原理研究

合金元素的固溶度对于新型合金的设计和合金动力学过程的研究具有重要的作用。本文利用密度泛函理论,计算了Fe-RE二元化合物的基态,确定了Fe-Y和Fe-Ce体系的稳态和亚稳态结构。计算结果表明,Fe-Y的稳定结构为Fe₁₂Y.tI26、Fe₁₇Y₂.hP38和Fe₂Y.cF24,Fe-Ce的稳定结构为Fe₁₇Ce₂.hP38、Fe₁₉Ce₅.hR24和Fe₂Ce.cF24。基于稀格子气统计热力学理论,利用第一性原理计算得到了稀土元素在α-Fe中随温度变化的固溶度曲线。结果显示,稀土Y、La和Ce元素在α-Fe中的固溶度为S_La>S_Ce>S_Y,这一趋势对应于三者在α-Fe中的溶解形成焓关系H_sol(La)< H_sol(Ce)< H_sol(Y).     

Y参杂对真空热压烧结TiAl基合金显微组织和力学性能的影响

Ti-45Al (at %)和Ti-45Al-0.3Y (at %)样品通过真空热压烧结的方法制备。样品通过x射线衍射(XRD)、光学显微镜(OM)、背散射电子(BSE)以及压缩和硬度测试来研究Y参杂和热压工艺参数对TIAl基合金的显微组织和力学性能的影响。最优烧结参数为压力42MPa,在1400℃下保温保压90分钟。在此参数下,得到了组织均匀、晶粒细小的由γ相和γ+α2片层结构组成的双态组织。在热压温度1400℃,保温时间240分钟下,反应能完全达到,但会出现晶粒粗大现象。Y的加入对细化晶粒和片层间距有明显的作用,这有助于提高合金的机械强度。     

Early oxidation behaviors of Mg–Y alloys at high temperatures

The early oxidation behaviors of Mg–Y alloys (Y = 0.82, 1.09, 4.31 and 25.00 wt.%) oxidized in pure O₂ have been investigated at high temperatures. The results showed that the oxidation behaviors of the Mg–Y alloys (Y = 4.31 and 25.00 wt.%) obeyed a parabolic law, while that of the Mg–Y (Y = 0.82 and 1.09 wt.%) exhibited both parabolic and linear kinetics depending on the oxidation temperature. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses indicated that an oxide film with a single structure composed of MgO and Y₂O₃ had formed. Moreover, the higher the oxidation temperature was, the thicker the oxide film was. Finally, the corresponding oxidation mechanism has been discussed, and the improved oxidation resistance of the Mg–Y alloys can be due to the formation of a continuous Mg-dissolving Y₂O₃ protective film.