Effect of annealing treatment on the microstructure and properties of cold-sprayed Cu coating

Copper (Cu) coating was deposited by cold spraying, and the electrical resistivity of the coating in both directions parallel and perpendicular to the coating surface was measured to investigate the anisotropy of the coating. Annealing treatment was applied to the coating to examine its effect on the microstructure and properties of the cold-sprayed Cu coating. The examination of coating microstructure evidently revealed that the coating was constituted by the flattened particles, and the interfaces were clearly observed between the deposited particles. The anisotropy in microstructure and electrical resistivity was present in cold-sprayed Cu coating. The electrical resistivity of the as-sprayed coating was higher than that of Cu bulk. Moreover, the electrical resistivity along the direction parallel to the coating surface was lower than that along the perpendicular direction. It was found that annealing treatment led to the enhancement of particle interface bonding and evident recry stallization of the elongated grains and remarkable grain growth as well. The annealed coating presented equiaxed grain structures similar to the annealed Cu bulk with particle interfaces almost disappearing under certain annealing conditions. The coalescence of voids or pores in the coating was clearly observed at high annealing temperatures. Moreover, the annealed coating yielded an electrical resistivity and microhardness comparable to Cu bulk. The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

热处理对机械合金化Ni/Ti冷喷涂层金属间化合物形成的影响

选择了三种球磨时间制备的Ni/Ti机械合金化粉末,通过冷喷涂制备了不同结构的Ni/Ti涂层.涂层组织结构采用扫描电镜(SEM)和X射线衍射(XRD)进行了表征分析.试验发现,随着粉末球磨时间的增加,热处理后的冷喷涂合金转变为金属间化合物的温度下降,涂层的组成相由Ni3Ti,B2-NiTi和Ti2Ni逐渐变成Ni3Ti和Ti2Ni;随着热处理温度的增加,涂层组织中不同成分的金属间化合物的相对量会发生一定改变.结果表明,热处理过程中形成的B2-NiTi金属间化合物在冷却时表现出较高的稳定性.     

等离子喷涂及真空热处理过程中MoSi2涂层的相演变

分别采用MoSi2Mo-66.7%Si和Mo-70%Si(摩尔分数)粉末为原料,在45钢上大气等离子喷涂MoSi2涂层,对喷涂前后相以及真空热处理对涂层相和组织的影响进行了研究.结果表明,以MoSi2为原料喷涂后,涂层主要是由MoSi2和Mo5Si3相组成,MoSi2由亚稳定的MoSi2(h)六方结构和稳定的MoSi2(t)四方晶体结构组成.而Mo-66.7%Si和Mo-70%Si两种粉末喷涂后,涂层均由Mo,Si单质粉组成,喷涂过程没有形成硅化物.Mo-66.7%Si涂层在1 050,1 200℃热处理1 h后,涂层中主相是Mo5Si3,次相为MoSi2.Mo-70%Si涂层在800,1 000 ℃热处理30 min后,生成了少量的MoSi2,Mo5Si3和Mo3Si.在1 050 ℃热处理时,随着时间的延长,MoSi2相含量相对增多,当热处理时间为30,45 min时,由于Mo,Si和Fe之间的反应扩散,还生成了FeMoSi和Fe3Si相.     

Effect of vacuum heat treatment on microstructure and microhardness of cold sprayed Cu-4Cr-2Nb alloy coating

The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.     

Microstructure evolution of semi-solid Mg-14Al-0.5Mn alloys during isothermal heat treatment

A new Mg-14Al-0.5Mn alloy that exhibits a wide solidification range and sufficient fluidity for semi-solid forming was designed.And the microstructure evolution of semi-solid Mg-14Al-0.5Mn alloy during isothermal heat treatment was investigated. The mechanism of the microstructure evolution and the processing conditions for isothermal heat treatment were also discussed.The results show that the microstructures of cast alloys consist ofα-Mg,β-Mg17Al12 and a small amount of Al-Mn compounds.After holding at 520℃ for 3 min,the phases ofβ-Mg17Al12 and eutectic mixtures in the Mg-14Al-0.5Mn alloy melt and the microstructures ofα-Mg change from developed dendrites to irregular solid particles.With increasing the isothermal time,the amount of liquid increases,and the solid particles grow large and become spherical.When the holding time lasts for 20 min or even longer,the solid and liquid phases achieve a state of dynamic equilibrium.     

Microstructure evolution of semi-solid Mg- 14A1-0.5Mn alloys during isothermal heat treatment

A new Mg-14Al-0.5Mn alloy that exhibits a wide solidification range and sufficient fluidity for semi-solid forming was designed. And the rnicrostructure evolution of semi-solid Mg-14Al-0.5Mn alloy during isothermal heat treatment was investigated. The mechanism of the microstructure evolution and the processing conditions for isothermal heat treatment were also discussed. The results show that the microstructures of cast alloys consist of α-Mg,β-Mg17Al12 and a small amount of Al-Mn compounds. After holding at 520 ℃ for 3 min, the phases of β-Mg17Al12 and eutectic mixtures in the Mg-14Al-0.5Mn alloy melt and the microstructures of α-Mg change from developed dendrites to irregular solid particles. With increasing the isothermal time, the amount of liquid increases, and the solid particles grow large and become spherical. When the holding time lasts for 20 min or even longer, the solid and liquid phases achieve a state of dynamic equilibrium.     

热处理过程中SiCp/2024Al基复合材料的微观组织演变

采用真空热压烧结工艺在580℃下制备了35%(体积分数)SiCp/2024铝基复合材料,利用扫描电镜(SEM)、透射电镜(TEM)、能谱(EDS)、高分辨透射电镜(HRTEM)对复合材料热处理过程中微观组织进行了表征,研究了热压烧结后复合材料的析出相的微观结构以及析出相在热处理过程的演变规律。结果表明,热压烧结后复合材料中存在许多粗大析出相颗粒,包括Al4Cu9,Al2Cu,Al18Mg3Mn2,Al5Cu6Mg2和Al7Cu2Fe。随着固溶温度的提高,粗大析出相颗粒逐渐回溶到Al基体中,当固溶温度达到510℃时,粗大析出相颗粒几乎全部回溶到基体中,但还存在少量的难溶相。复合材料经510℃固溶2 h+190℃时效9 h后,除了少量的难溶相,许多圆盘状纳米析出相Al2Cu和棒针状纳米析出相Al2Cu Mg弥散分布于基体中且与基体的界面为错配度较小的半共格界面,圆盘状纳米析出相的直径为50~200 nm,棒针状纳米析出相长度为100~150 nm。     

690合金管冷轧及退火处理过程中的组织演变

利用光学金相显微镜和扫描电子显微镜研究了690合金一次冷轧管在中间退火过程中的组织演变规律,以及不同固溶处理制度对690合金二次冷轧管（成品尺寸管）的晶粒度和碳化物回溶行为的影响,并建立了退火过程中再结晶晶粒长大方程。试验结果表明：一次冷轧管中间退火最优工艺是1100℃/5 min,所建立的晶粒长大模型预测结果与实验值吻合很好,成品管经1100℃/3 min固溶后,平均晶粒尺寸在23.5μm左右,晶粒组织均匀,碳化物完全溶解。     

微量铬强化B10合金形变热处理后的组织及性能

利用真空感应熔炼-铸造工艺制备了微量铬强化的B10合金(即Cu-10Ni-0.3Cr(mass%)合金),并对铸态合金进行固溶、冷变形及退火处理,采用光学显微镜、拉伸测试和四线制测量法等研究了不同处理状态下Cu-10Ni-0.3Cr合金的显微组织、力学性能和电导率。结果表明,铸态Cu-10Ni-0.3Cr合金晶粒为等轴状,晶粒中均匀分布着黑色颗粒状析出相;再结晶退火后合金的组织均匀细小,晶粒内有明显的退火孪晶。铸态合金的导电性最好,电导率为17.15%IACS,900℃固溶2 h后合金的导电性最差,电导率为12.30%IACS。冷轧态(50%变形量)合金的强度、硬度最高,分别为340 MPa、112 HB,延塑性最差,伸长率只有8%;再结晶退火态合金综合力学性能最好;随着退火温度升高,冷轧态合金形变组织逐渐消失,且退火温度愈高,形变组织消失得愈明显,同时晶粒在退火过程中发生长大,最终导致合金强度、硬度降低,塑性增加。     

热处理对冷喷涂Fe涂层组织与性能影响研究

冷喷涂作为一种新型的涂层技术,在制备大部分金属涂层、金属陶瓷复合涂层方面有着巨大的潜力。本文采用冷喷涂在Al基体上制备了Fe涂层,并结合喷涂后热处理研究了涂层组织与性能特点。结果表明,所得Fe涂层的内部组织比较致密;受到喷涂过程中空气的影响,喷涂射流呈现亮流,所制备涂层表面有较大、较深气孔。在较低温度下热处理后Fe涂层的显微组织变化不明显,显微硬度明显降低;Fe涂层与Al基体之间形成约10μm厚度的金属间化合物层。