706/705铝合金多层复合材料低速冲击性能及其有限元模拟研究

为了研究7×××铝合金多层复合材料在低速冲击载荷下的性能,进行了摆锤冲击实验,并利用ABAQUS有限元分析软件对复合材料的冲击断裂行为进行了数值模拟。对单一706铝合金和不同706/705铝合金复合比(2. 98、3. 11、4. 69、4. 95、5. 84)的多层复合材料进行摆锤冲击实验。结果表明:706/705铝合金多层复合材料的冲击功较单一706铝合金的提高了89. 03%~140. 13%;单一706铝合金为准解理断裂,多层复合材料为准解理-韧窝混合断裂,多层复合材料完全断裂所需要的时间均长于706铝合金的。有限元模拟和实验条件下冲击功随时间的变化趋势基本一致,所建立的摆锤冲击模型可以用来预测多层铝合金复合材料的冲击行为。

新能源车用多层铝合金复合材料开发及其性能研究

新能源汽车换热部件的发展趋势是追求轻量化和更好的耐久性,为了满足工业发展的需求,开发新型的钎焊铝合金复合材料是势在必行。通过添加优化的中间层合金改变传统的3层铝合金复合材料为多层的结构设计,借助显微组织分析、钎焊溶蚀观察、常温抗拉强度对比、模拟海水的腐蚀试验研究等工作,得出新型的多层复合材料相比于目前常规长寿命3层复合材料,轩焊过程中对母材的溶蚀明显减轻,耐腐蚀能力提高一倍以上,新型复合材料的强度提高30%左右。10%4343/10%3003MOD/C芯材/10%3003MOD/10%4343复合材料无论在强度和耐腐蚀能力上均为最佳。该新型复合材料在新能源冷却部件制造中有好的应用前景,可以延长部件的使用寿命、具有高的耐久性以及满足新能源冷却部件更好的内腔洁净度要求。

钻头几何角度对CFRP和钛合金叠层制孔的影响

针对碳纤维复合材料(CFRP)与钛合金叠层结构钻孔刀具寿命低、出入口质量不易保证、影响加工质量和制孔效率等问题。以钻头螺旋角、外缘后角和顶角为主要研究对象,进行试验方案设计,揭示钻头几何角度对叠层结构制孔切削力及出入口质量的影响规律,表明:碳纤维复合材料与钛合金叠层结构制孔的钻头最佳几何角度:螺旋角25°左右,顶角140°左右,外缘后角12°左右。

CFRP与钛合金叠层制孔钻头横刃结构优化

针对碳纤维复合材料(CFRP)与钛合金夹层结构制孔过程中加工质量、制孔效率与钻头寿命低等问题,以钻头的横刃结构为主要研究对象设计试验方案,对钻头横刃结构进行优化,以提高加工质量、制孔效率与钻头寿命。结果表明:优化后的横刃结构加工性能优于普通"X"形钻头横刃结构,不论是碳纤维复合材料部位还是钛合金部位轴向切削力明显减小。

铝/铝-镁合金层合板疲劳性能研究

为同时满足承载和防腐蚀两个要求,铁路浓硝酸罐车罐体选用铝/铝镁合金层合板复合材料,纯铝为其内胆材料,铝镁合金为承载材料。现对上述层合板材料试样进行疲劳性能试验以及弹塑性分析,发现随着外载的增加,由于层合板两种材料变形不协调,界面产生应力集中从而造成界面开裂,裂纹向纯铝层扩展,纯铝层断裂,最终导致层合板断裂。据此,建立了层合板材料的名义应力—寿命曲线和局部应变—寿命曲线,为浓硝酸罐车罐体的疲劳设计提供重要依据。

CFRP复合材料/钛合金叠层螺旋铣孔工艺

利用螺旋铣变偏心距加工的特点,提出了在刀具回程过程中进行二次精加工的工艺策略。通过正交试验研究了回程各工艺参数对CFRP/Ti-6Al-4V叠层孔加工质量和加工精度的影响规律,并依此优化工艺参数。试验结果显示:采用优化参数的回程精加工工艺提高了叠层孔的制孔精度,避免了复合材料孔壁加工损伤,复合材料孔粗糙度均值从Ra3.52降低到Ra1.31,入口撕裂明显改善,钛合金孔出口无毛刺。

碳纤维复合材料/钛合金叠层结构高低频复合振动钻削试验

碳纤维复合材料(Carbon fiber reinforced plastic,CFRP)/钛合金叠层结构基于其特殊的性能,被广泛用于航空航天等领域。由于CFRP与钛合金不仅材料性能差异巨大,且二者均属于难加工材料,导致了CFRP/钛合金叠层结构一体化制孔普遍存在刀具磨损严重、加工质量差等问题,严重制约了CFRP/钛合金叠层结构的应用。搭建了高低频复合振动钻孔实验平台,在钻削轴向力、钛合金断屑、钻削温度、CFRP孔出入口质量和CFRP孔壁形貌等方面,对普通钻削,超声振动钻削,低频振动钻削和高低频复合振动钻削四种钻孔方式进行对比分析。研究表明:超声振动有效降低了钻削轴向力,低频振动可达到良好的钛合金断屑效果,并最大程度的降低了钛合金的钻削温度,高低频复合振动钻削CFRP/钛合金叠层结构得到的孔CFRP入口撕裂最小,出口损伤最低,孔壁质量最好。

Tribological properties of nanostructured Al_2O_3-40%TiO_2 multiphase ceramic particles reinforced Ni-based alloy composite coatings

The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.

Synthesis of Y_2O_3 particle enhanced Ni/TiC composite on TC4 Ti alloy by laser cladding

A Y2O3 particle enhanced Ni/TiC composite coating was fabricated in-situ on a TC4 Ti alloy by laser surface cladding. The phase component, microstructure, composition distribution and properties of the composite layer were investigated. The composite layer has graded microstructures and compositions, due to the fast melting followed by rapid solidification and cooling during laser cladding. The TiC powders are completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The size of TiC dendrites decreases with increasing depth. Y2O3 fine particles distribute in the whole clad layer. The Y2O3 particle enhanced Ni/TiC composite layer has a quite uniform hardness along depth with a maximum value of HV1380, which is 4 times higher than the initial hardness. The wear resistance of the Ti alloy is significantly improved after laser cladding due to the high hardness of the composite coating.

Tribological behavior and mechanisms of graphite/CaF_2/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and improve the wear resistance of mechanical parts, which work in the severe friction and wear conditions at heavy loads, the graphite/CaFg/TiC/Ni-base alloy composite coatings were prepared by plasma spray and their tribological behavior and mechanisms were investigated. The results show that the friction coefficients of the composite coatings are in the range of 0.22-0.288, which are reduced by 25.9% to 53% compared with those of the pure Ni-base alloy coatings, and the wear rates of the former are 18.6%-70.1% less than those of the latter. When wear against GCr15 steel balls, a transferred layer mainly composed of ferric oxides, graphite and CaF2 may gradually develop on the worn surface of the composite coatings, which made the friction and wear between GCr15 steel ball and the composite coatings change into that between the former and the transferred layer. So the friction coefficients and the wear lubrication effect of the transferred layer. The main wear layer in friction process. rates of the composite coatings are greatly reduced because of the solid mechanism of the composite coatings is delamination of the transferred

Tribological properties and wear prediction model of TiC particles reinforced Ni-base alloy composite coatings

TiC particles reinforced Ni-based alloy composite coatings were prepared on 7005 aluminum alloy by plasma spray. The effects of load, speed and temperature on the tribological behavior and mechanisms of the composite coatings under dry friction were researched. The wear prediction model of the composite coatings was established based on the least square support vector machine (LS-SVM). The results show that the composite coatings exhibit smaller friction coefficients and wear losses than the Ni-based alloy coatings under different friction conditions. The predicting time of the LS-SVM model is only 12.93%of that of the BP-ANN model, and the predicting accuracies on friction coefficients and wear losses of the former are increased by 58.74%and 41.87%compared with the latter. The LS-SVM model can effectively predict the tribological behavior of the TiCP/Ni-base alloy composite coatings under dry friction.

Formability of AA5052/polyethylene/AA5052 sandwich sheets

The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the hot pressing adhesive method. Then, the uniaxial tensile tests were conducted to investigate the mechanical properties of AA5052/polyethylene/ AA5052 sandwich sheets, and the stretching tests were carried out to investigate the influences of polymer core thickness on the limit dome height of the sandwich sheet. The forming limit curves for three kinds of sandwich sheets were obtained. The experimental results show that the forming limit of the AA5052/polyethylene/AA5052 sandwich sheet is higher than that of the monolithic AA5052 sheet, and it increases with increasing the thickness of polyethylene core.

Microstructure and wear resistance of laser clad TiB-TiC/TiNi-Ti_2Ni intermetallic coating on titanium alloy

A wear resistant TiB-TiC reinforced TiNi-Ti2Ni intermetallic matrix composite coating（TiB-TiC/TiNi-Ti2Ni） was prepared on Ti-6.5Al-2Zr-1Mo-1V titanium alloy by the laser cladding process using Ti＋Ni＋B4C powder blends as the precursor materials.Microstructure and worn surface morphologies of the coating were characterized by optical microscopy（OM）,scan electron microscopy（SEM）,X-ray diffraction（XRD）,energy dispersive X-ray analysis（EDS） and atomic force microscopy（AFM）.Wear resistance of the coating was evaluated under dry sliding wear test condition at room temperature.The results indicate that the laser clad coating has a unique microstructure composed of flower-like TiB-TiC eutectic ceramics uniformly distributed in the TiNi-Ti2Ni dual-phase intermetallic matrix.The coating exhibits an excellent wear resistance because of combined action of hard TiB-TiC eutectic ceramic reinforcements and ductile TiNi-Ti2Ni dual-phase intermetallic matrix.

Direct-chill semi-continuous casting process of three-layer composite ingot of 4045/3004/4045 aluminum alloys

Three-layer composite ingot of 4045/3004/4045 aluminum alloys was prepared by direct-chill semi-continuous casting process,the temperature field distribution near the composite interface,macro-morphology,microstructure and composition distribution of the composite interface were investigated.The results show that semi-solid layer with a certain thickness forms near the interface due to the effect of cooling plate,which ensures successful implementation of casting the composite ingot.Two different aluminum alloys are well bonded metallurgically.The mechanical properties of composite interface were measured,the tensile and shearing strengths of composite interface are 105 and 88 MPa,respectively,which proves that the composite interface is a kind of metallurgical bonding.

Interface analysis of 7B52 Al alloy laminated composite fabricated by hot-roll bonding

The bonding interface of 7B52 Al alloy laminated composite （ALC） fabricated by hot rolling was investigated using optical microscopy （OM）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, ultrasonic flaw detection （UFD）, and bonding strength tests. The results show that metallurgical bonding is achieved at the interface after composite rolling. The TEM analysis and tensile tests indicate that the 7B52 ALC plate combines high strength of the hard individual layer and good toughness of the soft individual layer. However, UFD technology and SEM analysis prove that the defects （thick oxide films, acid washed residues, air, oil and coarse particles） existing in the bonding interface are harmful to the bonding strength. To sum up, the composite roiling process is suitable for 7B52 ALC plate, and the content and size of the defects should be controlled strictly. Advanced surface treatment of each individual layer would be beneficial to further improve the bonding quality.

Tribological properties of Ni-base alloy composite coating modified by both graphite and TiC particles

In order to reduce the friction coefficient of Ni-base alloy coating and further improve its wear resistance,Ni-base alloy composite coatings modified by both graphite and TiC particles were prepared by plasma spray technology on the surface of 45 carbon steel.The results show that friction coefficient of the composite coating is 47.45% lower than that of the Ni-base alloy coating,and the wear mass loss is reduced by 59.1%.Slip lines and severe adhesive plastic deformation are observed on the worn surface of the Ni-base alloy coating,indicating that the wear mechanisms of the Ni-base alloy coating are multi-plastic deformation wear and adhesive wear.A soft transferred layer abundant in graphite and ferric oxide is developed on the worn surface of the composite coating,which reduces the friction coefficient and wear loss in a great deal.The main wear mechanism of the composite coating is fatigue delamination of the transferred layer.

Effects of graphite content on microstructure and tribological properties of graphite/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and further improve the anti-wear properties of Ni-base alloy coatings reinforced by TiC particles,graphite/TiC/Ni-base alloy（GTN） coatings were prepared on the surface of 45 carbon steel.The effects of graphite content on the microstructure and tribological properties of the GTN coatings were investigated.The results show that the addition of graphite to the GTN coatings may greatly reduce the friction coefficients and improve their wear resistance.The 6.56GTN and 12.71GTN coatings exhibit excellent integrated properties of anti-friction and wear resistance under low and high loads,respectively.Under a low load,the wear mechanisms of the GTN coatings are mainly multi-plastic deformation with slight abrasive wear and gradually change into mixture of multi-plastic deformation,delamination and micro-cutting wear with the increase of graphite fraction.As the load increases,the main wear mechanisms gradually change from micro-cracks,micro-cutting and adhesive wear to micro-cutting and micro-fracture with the increase of graphite fraction.

基于微弧等离子熔覆—注入技术的耐磨截齿研制

采用微弧等离子熔覆—注入技术在截齿表面制备复合合金层,研制了耐磨无火花截齿。该截齿在采煤过程中不产生火花,可提高煤炭开采的安全性,截齿的耐磨性能也显著提高,其使用寿命延长。

Microstructure and Property of Al‑FeCoNiCrAl High Entropy Alloy Composite Coating on Ti‑6Al‑4V During Annealing Using MA Method

Al-FeCoNiCrAl high entropy alloy(HEA) composite coatings were prepared on Ti-6Al-4V via highenergy mechanical alloying(MA). The microstructures and phase composition of the coatings were studied. A continuous and dense coating could be fabricated at a ratio of 35%(weight fraction)Al-FeCoNiCrAl after 4 h milling.The results showed that the thickness of the composite coatings increased first and then decreased with the increase of milling time. And the hardness of coating increased with the increase of milling time. The phase changed during the annealing process. Part of the initial body-centered cubic(BCC)phase of the composite coatings changed into the L12 phase,(Ni,Co)3Al4 and σ phase after annealing above 550 ℃. Ordered BCC was found in the coatings after annealing above 750 ℃. Only BCC and ordered BCC appeared in coatings after annealing above 1 050 ℃. The hardness of the coatings after annealing at 550 ℃ and 750 ℃ was higher than before because of spinodal decomposition and high hardness σ phase. The hardness of the coatings after annealing at 1 050 ℃ decreased because residual stress released.

Improvement of wear and corrosion resistance of AZ91 magnesium alloy by applying Ni-SiC nanocomposite coating via pulse electrodeposition

To improve the surface properties of AZ91 magnesium alloy, Ni-SiC nanocomposite coatings with various SiC contents were pulse electrodeposited in modified Watts baths containing SiC nano-particles with the concentration of 0-15 g/L. The morphology of the coatings was studied by scanning electron microscope （SEM）. The SiC content of the coatings was measured by energy dispersive spectroscopy （EDS） analyzer. Microhardness measurement of the coatings showed up to 600% enhancement for the sample produced from the bath with 15 g/L SiC. The corrosion behavior of the coated AZ91 alloy was investigated by potentiodynamic polarization method. The results reveal a significant improvement in the corrosion resistance, that is, the corrosion current density decreases from 0.13 mA/cm2 for uncoated specimen to 1.74x10-6 mA/cm2 for the sample coated from the bath containing 15 g/L SiC and the corrosion potential increases from -1.6 V for uncoated specimen to -0.31 V for the sample coated from the bath. The wear resistance of both coated and uncoated samples was evaluated by pin-on-disc tribotester. The results show that the wear volume loss of coated sample is 8 times less than the bare alloy.