Microstructure,microhardness and corrosion resistance of laser cladding Ni−WC coating on AlSi5Cu1Mg alloy

The microstructure,microhardness,and corrosion resistance of laser cladding Ni−WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy,X-ray diffraction,microhardness testing,immersion corrosion testing,and electrochemical measurement.The results show that a smooth coating containing NiAl,Ni_(3)Al,M_(7)C_(3),M_(23)C_(6)phases(M=Ni,Al,Cr,W,Fe)and WC particles is prepared by laser cladding.Under a laser scanning speed of 120 mm/min,the microhardness of the cladding coating is 9−11 times that of AlSi5Cu1Mg,due to the synergistic effect of excellent metallurgical bond and newly formed carbides.The Ni−WC coating shows higher corrosion potential(−318.09 mV)and lower corrosion current density(12.33μA/cm^(2))compared with the matrix.The crack-free,dense cladding coating obviously inhibits the penetration of Cl^(−)and H^(+),leading to the remarkedly improved corrosion resistance of cladding coating.

Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium(Yb)addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The experimental results demonstrate that both the Si phase andβ-Al5FeSi phase in the alloy with 0.9 wt%Yb have been remarkably refined,and the Al3Yb intermetallic compound has also been obtained.The Si,β-Al5FeSi,and rare earth phases are further refined in the alloy at 0.9 wt%Yb and hot extrusion.The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density(8.56μA/cm2)of the alloy with 0.9 wt%Yb addition and hot extrusion is 50.6%lower than the untreated alloy(17.33μA/cm2),and the polarization resistance(9252Ω·cm2)was 71.3%higher than the untreated alloy(2654Ω·cm2).The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion,where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.

铝合金表面激光熔覆镍基复合涂层的组织与磨损性能

利用SEM、EDS、磨损试验机及硬度测试仪等设备对铝合金表面激光熔覆层的组织与磨损性能开展了研究。结果表明,当扫描速度为5 mm/s时,熔覆层气孔、裂纹等缺陷相对较少;在熔覆层顶部生成了许多块状及网状的Ni-Al金属间化合物,中部生成了(Ni,Cr,Fe)xCy金属间化合物,底部存在大量具有明显生长方向性的柱状α-Al枝晶。熔覆层顶部及中部保持着高硬度值,中部硬度最高值达8200MPa,是熔覆层底部硬度值的5倍以上。硬度值在熔覆层中部的末端开始显著下降。熔覆层的摩擦系数根据载荷不同其值在0.37~0.43间变化,并随着载荷增加而有所降低。Ni-Al和(Ni,Cr,Fe)xCy金属间化合物等强化相在熔覆层中的生成及其在在熔覆层中上层的均匀分布是改善材料硬度及磨损性能的主要原因。

La对ADC12微观组织及耐腐蚀性能的影响

采用光学显微镜、扫描电镜、能谱仪等研究了ADC12-xLa(x=0,0.3,0.6,0.9)合金的微观组织及腐蚀性能。结果表明,当La含量从0增加到0.6%时,ADC12合金中的初生α-Al、共晶Si和Al_8SiFe_2相会逐渐细化,且耐腐蚀性能逐渐提高。其原因是La含量低于0.6%时,La在变质过程中会吸附在共晶Si相表面,阻碍了腐蚀电子流动,使合金的耐腐蚀性能提高。而La含量达到0.9%时,合金中会生成大量的La-Al-Cu稀土相,该稀土相会与α-Al发生电偶腐蚀,导致ADC12-0.9La合金耐腐蚀性能降低。

超声振动法制备半固态TiAl_3/A356复合材料浆料的微观组织演变（英文）

利用超声振动法制备半固态TiAl_3/A356铝基复合材料浆料,利用扫描电镜和X射线衍射技术研究了超声温度,超声时间和超声功率对半固态TiAl_3/A356铝基复合材料浆料的微观组织的影响。结果显示,初生α-Al颗粒的尺寸随着超声温度和超声功率的降低而减小;随着超声时间的增加,先减小后增大。当超声温度为608℃、超声功率为1000 W、超声时间为60 s时,获得的半固态浆料组织中的初生α-Al颗粒形貌较为理想,平均初生α-Al颗粒尺寸为62μm,形状系数为0.8。微观组织演变的机理是空化效应和声流效应引起的形核率和过冷度的增加。此外,原位生成的TiAl_3颗粒有很强的结合α-Al颗粒的能力。

固溶处理对Al2O3/7075复合材料的组织及力学性能的影响

采用球磨预制块和高能超声等方法制备了Al2O3含量为2.0%的7075复合材料,通过SEM、EDS、拉伸及硬度测试等方法,研究了固溶处理对Al2O3/7075复合材料显微组织和力学性能的影响。结果表明,随着固溶温度和时间的增加,Al2O3/7075复合材料中第二相Mg(Zn,Cu,Al)2逐渐溶入基体中。与Al2O3/7075复合材料相比,经460℃×5h固溶处理的Al2O3/7075复合材料的硬度、抗拉强度和伸长率分别提高了37.2%、19.0%和46.2%。