高硅 FeSi 合金层对普通取向硅钢磁性能的影响

目的提高硅钢的磁性能。方法采用多弧离子镀技术,在普通取向硅钢薄板两面沉积高硅FeSi合金层制得高硅梯度硅钢,并进行热处理,观察其显微组织,测量磁性能。结果退火态高硅梯度硅钢表面的高硅FeSi合金层与基底结合紧密,均匀致密。高硅梯度硅钢中硅含量呈梯度分布,最表层硅质量分数为11.0%,随着深度增加,硅含量逐渐降低,在距表面20μm处硅质量分数仍能达到6.5%。沉积态高硅梯度硅钢的电阻率ρ、低频铁损P10/50、高频铁损P10/1k及磁感应强度B8分别为68.6μΩ·cm,0.82W/kg,83.3 W/kg和1.73 T,退火后分别为63.1μΩ·cm,0.44 W/kg,54.38 W/kg和1.89 T。结论由于表层高硅FeSi合金层的存在,梯度高硅钢的低频磁学性能良好,但高频损耗需进一步改善。     

Effect of Gd content on microstructure and mechanical properties of Mg-Y-RE-Zr alloys

Four kinds of Mg-Y-RE-Zr alloys with different Gd contents were prepared,and the effect of Gd content on microstructure and mechanical properties of the alloys was researched.Based on the experimental investigation,the compounds at the grain boundaries are mainly Mg_(24)Y_5,Mg_(41)Nd_5,and Mg_5Gd phases.The average grain size of as-cast alloys is 50-60μm.After T4(535℃, 24 h)treatment,Mg_5Gd phases mostly decompose and dissolve into the matrix,and the disperse spotted phases are mainly Mg_(24)Y_5 and Mg_(...     

Preparation and mechanical properties of Ni-Cr-Al alloy by EB-PVD

Ni-Cr-A1 alloy was deposited by electron beam-physical vapor deposition(EB-PVD) method. The microstructure was investigated on as-deposited and long-term aged alloy. The results indicate that grain on surface of asdeposited alloy is about 185 nm in size, and a laminated structure in cross-section is observed. However, after aging for 16 and 120 h at 760℃, the laminated structure is dissolved, and the individual grain can be seen clearly. Columnar crystals form on the evaporation side, and exquiaxed grains form on the substrate side. The major precipitate is γ‘ phase after prolonged aging at 760℃. Mechanical properties of the Ni-Cr-A1 alloy were also studied. The results show that the fracture of as-deposited alloy has mixed type at room temperature, and intergranular fracture among columnar crystals is observed. Compared to that of as-deposited alloy, fracture of alloy after aging for 16 and 120 h at 760℃ appears to involve ductile fracture with dimples.     

含Sm、Mn的P型FeSi2基热电材料的电学性能

用悬浮熔炼法制备了含Sm、Mn的P型FeSi2基热电材料。实验结果表明，其电学性能是由掺杂的两种元素共同决定的，Sm对降低样品电阻率的作用较大，而Mn有助于提高样品的热电动势率。要保证有较高功率因子，Mn、Sm掺杂总摩尔分数应小于5％，而Mn的最住掺杂摩尔分数在1．7％左右。     

C含量对铸造TiAl合金组织和力学性能的影响

在Ti-47.5Al-3.7(Cr,V,Zr)合金中添加0.05%~0.2%C(原子分数,下同),采用冷坩埚悬浮熔炼方法制备出了层片组织TiAl合金铸棒,通过组织观察、室温拉伸和蠕变性能测试研究了C含量对TiAl合金组织和力学性能的影响。结果表明,添加0.05%~0.2%C后,合金仍可获得择优取向层片组织。随C含量增加α2层片体积分数略有增加,层片间距呈细化趋势。当C含量超过0.1%时,在α2和γ层片内和层片界面上有细小的Ti2AlC型碳化物析出,碳化物析出相的尺寸和数量随C含量增加有所增加。添加0.05%~0.2%C后提高了合金室温的抗拉强度和屈服强度,且随C含量增加提升幅度逐渐增大,当C含量为0.2%时,分别将抗拉强度和屈服强度提升了101和123 MPa。添加C元素后显著改善了合金的蠕变性能,当C含量为0.1%时蠕变性能最佳,与不含C的合金相比,其塑性蠕变应变降低了一半、相同应变时的蠕变速率降低了1个数量级以上。添加0.1%C提升合金蠕变抗力的机制主要是通过抑制合金在蠕变初期的位错萌生和增殖过程;在γ层片中形成割阶和位错碎片阻碍位错继续运动,使得合金在蠕变第一阶段的应变硬化程度迅速增加;此外,析出的Ti2AlC型碳化物进一步强化层片界面和基体,与层片间距细化共同提高了穿层片滑移位错的运动阻力。     

铸态Mg-Li-Al-xSi合金微观组织和力学性能

本文通过真空熔炼炉在氩气保护下制备了Mg-9Li-3Al-xSi(x=0,0.1,0.5,1.0 wt%)合金。实验使用光学显微镜(OM),扫描电子显微镜(SEM),力学性能测试和X射线衍射(XRD)研究合金的微观组织和力学性能。实验结果表明：铸态Mg-9Li-3Al合金组织中主要由α-Mg、β-Li、Mg₁₇Al₁₂相组成。加入Si后,合金中出现了新相Mg₂Si,晶粒得到了明显细化;当合金中的Si含量过高时,α-Mg相粗化,且会在相界处出现块状和汉字状的Mg₂Si相。合金的强度随着Si含量的增加呈现先增加后降低的趋势,合金的延伸率随着Si含量的增加呈现逐渐降低的趋势。当合金中Si含量为0.1%时,抗拉强度达到最大值182.5MPa,延伸率为12.1%,相比未添加Si的Mg-9Li-3Al合金,抗拉强度提高了59.6%。     

Effect of Si, Cu and Fe on mechanical properties of cast semi-solid 206 alloys

The development of a modified 206 alloy whose composition was optimized to minimize hot tearing during semi-solid forming was reported. The effect of varying silicon, copper and iron contents was investigated using a design of experiment (DOE) approach. Semi-solid slurries were prepared using the SEED process and injected into a high pressure die casting press. The hot tearing sensitivity results were reported for different alloy variants. The microstructure evolution during the semi-solid preparation was presented along with actual die cast components. The effects of silicon, copper and iron on mechanical properties in the T7 condition were also analyzed. Beyond the benefit of reducing hot tearing, it is shown that the tensile and fatigue properties remain compatible with the automotive industry requirements.     

Microstructures and properties of rapidly solidified Mg-Zn-Ca alloys

Ternary alloys based on the Mg-Zn-Ca system were produced by twin-roll rapid solidification.The alloys were characterized by OM,SEM,HRTEM,XRD,EDS and Micro-hardness.The results show that the rapidly solidified flakes are of fine dendritic cell structures with the cell size ranging from 1 to 5μm.The Mg-6Zn-5Ca alloy in RS and annealing(200℃for 1 h) states are mainly composed ofα-Mg,Mg_2Ca,Ca_2Mg_6Zn_3 and a small quantity of Mg_(51)Zn_(20),MgZn_2 and Mg_2Zn_3.Micro-hardness increases with the increment of...     

工作压强对PECVD法制备DLC薄膜微观结构与力学性能的影响

采用脉冲等离子体增强化学气相沉积方法(Pulse-PECVD)于316L不锈钢基体上制备类金刚石(DLC)薄膜,研究不同工作气压对DLC薄膜的沉积速率、表面形貌、微观结构、纳米硬度、弹性模量以及结合强度的影响规律。结果表明:随沉积气压增大,薄膜的沉积速率随之增大,压强在3 Pa时沉积速率可高达1. 4μm/h;不同气压下沉积的DLC薄膜均体现出平整光滑的表面形貌和高于不锈钢基体3倍以上的纳米硬度;沉积气压为2 Pa时,DLC薄膜在拉曼光谱中具有最小的ID/IG值,对应最高的纳米硬度16. 1 GPa和弹性模量152. 7 GPa,以及最低的粗糙度和摩擦因数0. 206。      

Preparation and mechanical properties of carbon/carbon composites with high textured pyrolytic carbon matrix

Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon (C/C) composites was 1.89 g/cm³ after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.     

Corrosion and mechanical properties of hot-extruded AZ31 magnesium alloys

AZ31 magnesium alloys were hot-extruded at 573 K and 623 K with extrusion ratio(λ) of 20,35 and 50.The corrosion and mechanical behavior of hot-extruded AZ31 were studied by galvanic tests and tensile tests.The microstructures of the studied AZ31 alloys were also investigated with optical microscope.The results show that,compared with the as-cast AZ31 alloy,the corrosion potentials of all hot-extruded AZ31 alloys are increased by 60 mV.Moreover,at the extrusion temperature of 623 K,the galvanic current o...     

富铁Fe-Nd-Al系大块非晶合金的制备及其性能

利用普通的铜模铸造制备了一系列富Fe的Fe-Nd-Al块状非晶合金,采用X射线衍射仪、差示量热扫描仪、振动样品磁场仪和Instron万能材料试验机研究了Fe-Nd-Al块状非晶合金的热稳定性、室温磁性和力学性能。结果表明：Fe50Nd35Al15、Fe45Nd40Al15和Fe42.5Nd42.5Al15块状非晶合金的△Tm（△Tm=Tm-Tx）和晶化开始温度（Tx）与熔点（Tm）的比值分别为106、90和64K及0.88、0.90和0.93;其临界尺寸分别为1.5、3和4mm。此外,随Fe含量的减少,大块非晶的非晶形成能力和硬磁性能提高,但其力学性能有所下降。     

Microstructure and mechanical properties of Mg-xLi-3Al-1 Ce alloys

Several Mg-xLi-3Al-lCe alloys were prepared by vacuum induction heating. These alloys are Mg-5Li-3Al-lCe, Mg-8Li-3Al-lCe and Mg-14Li-3Al-1C e, respectively. The microstructure and phase composition of these alloys were analyzed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometry. The mechanical properties of these alloys were measured with tensile tester. The results show that, Mg-5Li-3Al-1Ce has a single phase （α） structure, Mg-8Li-3Al-lCe has a double phases （α＋β） structure, Mg-14Li-3Al-1Ce has a single phase （β） structure. And some compounds distribute in the matrix. After being rolled, the grain size of all the alloys is refined. Under the condition of the same content of other alloying elements, the mechanical properties of Mg-5Li-3Al-1Ce are relatively high. With increasing Li content, the strength of both as-cast and as-rolled alloy decrease. For the as-cast alloys, with increasing Li content, the elongation increases. While for the as-rolled alloys, with increasing Li content, the elongation decreases. Ce has refining effect on these alloys.     

Regulative effect of Mg/Si ratio on microstructure evolution and mechanical properties of cast Al-Li-Mg-Si alloys

The effect of the Mg/Si ratio of Al-2.5Li-1Cu-0.8Mg-0.8Si,Al-2.5Li-1Cu-1.6Mg-0.8Si,and Al-2.5Li-1Cu-2.4Mg-0.8Si alloys on the microstructure evolution and mechanical properties was investigated.The results show that the primary phases and their morphologies in the as-cast alloys are found to vary with the Mg/Si ratio.The improvement of Mg/Si ratio of as-cast alloys promotes the formation of Mg₂Si primary phase at the expense of the AlLiSi primary phase.Moreover,a tiny amount of T_B-Al_7.5Cu₄Li phase transforms into S-Al₂CuMg phase with the increase of Mg content.In addition,the increase of Mg/Si ratio also causes the Cu-rich intergranular phase distributed along crystal boundary to Si-rich intergranular phase.After ageing treatment,the precipitation sequence as a function of Mg/Si ratio is as follows:δ/δ'+AlLiSi(Mg/Si is~1)→δ/δ'+β'-Mg₂Si+AlLiSi(Mg/Si is~2)→δ/δ'+β'-Mg₂Si(Mg/Si is~3).A good combination of strength and ductility can be obtained in Al-2.5Li-1Cu-2.4Mg-0.8Si alloy after solution and ageing.The rod-likeβ'-Mg₂Si precipitate has a positive influence on the comprehensive mechanical properties of the alloy.     

铸态钛锡合金的马氏体形貌及力学性能

研究了锡元素对钛合金组织与力学性能的影响,综述了Ti-(0～20)Sn合金(质量分数,%)的强化机理。在纯钛中添加不同含量的纯锡进行熔炼,结果发现铸态钛锡二元合金的强化机制不仅与合金中的锡含量有关而且还受到马氏体形貌的影响。硬度和冲击韧性变化曲线在锡含量为10%时出现一个拐点,伸长率变化曲线在含锡量为15%时出现一个转折点。这是因为,当锡含量低于10%时合金组织为条状马氏体,锡含量达到和高于15%时组织为针状马氏体。XRD结果显示所有Ti-(0～20)Sn合金组织为α-Ti。锡含量增加导致针状马氏体的出现是因为锡元素降低了Ms点。     

Effect of applied dc bias voltage on composition, chemical bonding and mechanical properties of carbon nitride films prepared by PECVD

Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.     

AlCoCrFeNiBx 高熵合金微结构与性能

本文系统研究了 B 元素对高熵AlCoCrFeNiBx (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0)合金的微结构和性能的影响。其中添加的B元素含量为0.1时AlCoCrFeNi 高熵合金的形貌从等轴晶转变为枝晶形貌。 其中在等轴晶的内部可以观测到调幅分解结构。当 x>0.1时, 枝晶和调幅分解结构都逐渐消失了,但是越来越多的硼化物开始出现了。这个转变归因于 Cr-B 和Co-B之间高的负混合焓.随着B元素的增加, AlCoCrFeNiBx高熵合金的结构从B2 BCC 结构向B2 BCC FCC 结构的转变, 最后形成了 B2 BCC FCC 以及硼化物的混合结构。 随着B元素的添加硬度值从 HV486.0 下降到了 HV460.7, 然后增加到 HV615.7,其中x=0.1时合金的硬度最低。合金的压缩强度随B元素的增加明显下降,当x=0.25时,合金具有最大的压缩强度,但是当x =0.75时, 由于硼化物的大量生成合金在弹性变形阶段就发生了断裂。随着B含量增多合金的矫顽力和饱和磁化强度开始下降. 下降的矫顽力显示合金具有很好的软磁性能。