HCPEB辐照AZ91合金表面脉冲电沉积钙磷涂层的组织和性能

发布时间：2018-09-17 18:03

【摘要】：本文在研究强流脉冲电子束(HCPEB)辐照次数对重熔层组织形貌、硬度和耐蚀性能的影响规律的基础上,对HCPEB辐照AZ91进行脉冲电化学沉积钙磷涂层,研究了HCPEB辐照对AZ91表面钙磷涂层形貌的影响规律,并阐明其形成动力学过程。揭示了HCPEB辐照对AZ91表面脉冲电沉积钙磷涂层的耐腐蚀性能的影响规律。实验结果表明,在脉冲电流周期为1 s的条件下,当占空比为0.05、0.10、0.15、0.20时,随着占空比的增加,垂直于AZ91合金表面的针状羟基磷灰石(HAP,Ca_(10)(PO_4)_6(OH)_2)中出现片状二水磷酸氢钙(DCPD,CaHPO_4·2H2_O)。在脉冲电流占空比为0.10的条件下,当周期为0.1 s、1 s和10 s时,随着脉冲周期的增加,垂直于AZ91合金表面的针状HAP钙磷涂层中现片状DCPD。电化学腐蚀与浸泡实验结果表明,AZ91合金脉冲电沉积钙磷涂层之后,耐蚀性能显著提高。其中,脉冲电流周期为1 s,占空比为0.10时,得到的针状纯HAP涂层,致密度最高,孔洞最少,且粒径最细,在SBF溶液中耐蚀性能最好。AZ91合金经能量密度为6 J/cm~2的HCPEB辐照之后,出现大量密集的球状结构、褶皱状结构以及熔坑,粗糙度提高,AZ91合金的硬度由65.6 HV提高至75.0 HV。随着HCPEB辐照次数变多,AZ91合金的重熔层逐渐变厚,粗糙度逐渐下降,α-mg中固溶的al元素逐渐增多,成为过饱和固溶体。hcpeb辐照3次、5次、10次之后,腐蚀电流降低了一个数量级,耐蚀性能得到有效提高。当辐照次数超过10次时,α-mg中固溶的al元素开始减少,析出Mg_(17)Al_(12)相,使电偶腐蚀反应加剧,AZ91合金的耐蚀性能下降。AZ91合金经过辐照之后,表面粗糙度最大,表面积变大,这就使得单位面积通过的电流降低,在其表面电沉积钙磷涂层的形核生长行为发生变化。AZ91合金经过辐照3次之后,粗糙度最大,沉积得到hap和片状dcpd。AZ91合金经过辐照5次、10次之后,表面粗糙度变小,沉积得到的钙磷涂层中只含有针状hap。AZ91合金是否经过hcpeb辐照,对钙磷涂层的沉积生长过程有大影响。沉积时间由1min增加到30min的阶段内,未辐照AZ91合金表面的hap钙磷涂层形貌从条状变为针状;经过5次辐照的AZ91合金表面,hap钙磷涂层形貌从颗粒状变为网状,然后变为片状,最后变为针状。电化学腐蚀与浸泡实验结果表明:与AZ91合金直接脉冲电沉积钙磷涂层相比,AZ91合金经过辐照之后进行脉冲电沉积钙磷涂层,在钙磷涂层和重熔层的双重保护下,耐蚀性能得到有效提高。其中,AZ91合金经过辐照5次之后进行脉冲电沉积钙磷涂层试样在sbf溶液中浸泡14天之后涂层结构保持完整,析氢量是AZ91合金的12.10%,sbf溶液的ph值稳定在7.57左右,耐蚀性能最佳。
[Abstract]:On the basis of studying the effect of high current pulsed electron beam (HCPEB) irradiation times on the microstructure, hardness and corrosion resistance of the remelted layer, HCPEB irradiated AZ91 was deposited by pulse electrochemical deposition of calcium and phosphorus coating. The effect of HCPEB irradiation on the morphology of calcium and phosphorus coating on AZ91 surface was studied and the kinetic process of its formation was elucidated. The effect of HCPEB irradiation on the corrosion resistance of calcium phosphate coating deposited by pulsed electrodeposition on AZ91 surface was revealed. The experimental results show that when the pulse current period is 1 s, when the duty cycle is 0.05 ~ 0.100.100.15g / 0.20, with the increase of duty cycle, the HAP,Ca_ _ (10) (PO_4) _ 6 (OH) _ 2 (HAP,Ca_ _ (10) (PO_4) _ 6 (OH) _ 2) appears in the HAP,Ca_ _ (10) (PO_4) _ 6 (OH) _ 2. When the pulse current duty cycle is 0.10, when the period is 0.1 s ~ (-1) s and 10 s, with the increase of pulse period, the sheet DCPD. is present in the acicular HAP calcium phosphorus coating perpendicular to the surface of AZ91 alloy. The results of electrochemical corrosion and immersion test showed that the corrosion resistance of AZ91 alloy was improved after pulse electrodeposition. When the pulse current period is 1 s and the duty cycle is 0.10, the acicular pure HAP coating has the highest density, the smallest pore size and the finest particle size. The best corrosion resistance of .AZ91 alloy in SBF solution is irradiated by HCPEB with energy density of 6 J/cm~2. There were a large number of dense spherical structures, fold structures and melting pits. The hardness of AZ91 alloy increased from 65. 6 HV to 75. 0 HV. the roughness of AZ91 alloy was increased from 65. 6 HV to 75. 0 HV.. With the increase of HCPEB irradiation times, the remelting layer of AZ91 alloy becomes thicker, the roughness decreases gradually, and the solid solution element al in 伪 -mg increases gradually. The corrosion current decreases by one order of magnitude after being irradiated as a supersaturated solid solution for 3 times and 5 times for 10 times. The corrosion resistance is improved effectively. When irradiation times were more than 10 times, the al element in 伪 -mg solution began to decrease, and Mg_ (17) Al_ (12) phase was precipitated. The corrosion resistance of AZ91 alloy was aggravated by galvanic corrosion reaction. After irradiation, the surface roughness and surface area of AZ91 alloy became the largest and the surface area became larger. As a result, the current passing through the unit area is reduced, and the nucleation and growth behavior of the electrodeposition of calcium and phosphorus coating on the surface of the alloy is changed. After three times of irradiation, the roughness of AZ91 alloy is the largest. The surface roughness of hap and dcpd.AZ91 alloy was reduced after 5 times and 10 times of irradiation. The deposition of calcium and phosphorus coating contained only needle-like hap.AZ91 alloy irradiated by hcpeb, which had a great influence on the deposition and growth process of calcium phosphorus coating. When the deposition time was increased from 1min to 30min, the morphology of hap Ca P coating on unirradiated AZ91 alloy changed from stripe to needle, and after 5 times irradiation, the morphology of hap Ca P coating on AZ91 alloy changed from granular to reticular, then to flake. It turned into a needle. The results of electrochemical corrosion and immersion experiments showed that compared with the direct pulse electrodeposition of calcium and phosphorus coating on AZ91 alloy, the electrodeposition of calcium phosphorus coating was carried out under the double protection of calcium phosphorus coating and remelting layer. The corrosion resistance is improved effectively. After 5 times of irradiation, the coating structure of Ca- AZ91 alloy deposited by pulse electrodeposition in sbf solution for 14 days remained intact, and the hydrogen evolution rate was about 7.57 for the ph value of AZ91 alloy 12.10 / sbf solution, and the corrosion resistance was the best.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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