iECAP态Mg-Nd-Zn-Zr合金的生物腐蚀行为及表面钙磷涂层制备工艺研究
发布时间：2018-11-02 11:54
【摘要】：为了开发高性能生物镁合金及其涂层制备工艺,本文系统研究了一种新型热挤压工艺(iECAP)对Mg-Nd-Zn-Zr合金生物腐蚀行为的影响,以及电化学沉积工艺对钙磷涂层的影响机理。通过调控挤压温度研究了iECAP工艺对Mg-Nd-Zn-Zr合金在模拟体液中腐蚀行为的影响。结果表明,挤压态合金在模拟体液中的耐蚀性优于铸态合金;铸态合金经挤压后,腐蚀方式由局部腐蚀转变为均匀腐蚀;挤压温度从400℃升高到500℃,耐蚀性逐渐提高。经模拟体液浸泡后,形成了主要成分为Mg(OH)_2、HA、(Ca,Mg)_3(PO_4)_2等的腐蚀产物层以及少量结晶状沉淀物。通过调控电化学沉积工艺参数,研究了pH值、温度、电流密度和时间对钙磷涂层的影响及机理。pH值由3升高到5,涂层形貌由针状转变为带状,再转变为球状,不利于FHA形成;pH值决定电解液中OH-数量,随pH值升高,电解液中OH-增多,有利于形核,因此pH值为3到4时针状组织逐渐长大变为带状,当OH-数量过多时,会导致钙磷离子沉淀,不利于形核,因此不利于FHA形成。沉积温度由50℃升高到80℃,涂层形貌由针状转变为带状及球状,FHA结晶度增强;温度决定体系的自由能,温度越高,自由能越大,因此形核速率也大,FHA结晶度增强。电流密度由0.25mA/cm~2增大到1mA/cm~2,涂层由细小的带状和球状组织组成,其中带状组织变得越来越细小;电流密度决定H2和OH-的生成速度,随电流密度增加,两者共同作用,使晶粒变得细小。时间由2h增加到8h,涂层由细小的带状和球状组织组成,且涂层由致密变疏松;时间导致晶体生长差异,部分晶粒优先长大,部分晶粒生长受到抑制,形成了表面疏松的涂层。综上,pH值影响最大,温度次之,电流密度和时间影响较小,涂层的主要成分为FHA。
[Abstract]:In order to develop high performance biological magnesium alloy and its coating preparation process, the effect of a new hot extrusion process, (iECAP), on the biocorrosion behavior of Mg-Nd-Zn-Zr alloy was systematically studied in this paper. And the influence mechanism of electrochemical deposition process on calcium-phosphorus coating. The effect of iECAP process on corrosion behavior of Mg-Nd-Zn-Zr alloy in simulated body fluid was studied by adjusting extrusion temperature. The results show that the corrosion resistance of the extruded alloy is better than that of the as-cast alloy in simulated body fluid, the corrosion mode of the as-cast alloy changes from local corrosion to uniform corrosion after extrusion, and the corrosion resistance of the as-cast alloy increases from 400 鈩，
本文编号：2305938
[Abstract]:In order to develop high performance biological magnesium alloy and its coating preparation process, the effect of a new hot extrusion process, (iECAP), on the biocorrosion behavior of Mg-Nd-Zn-Zr alloy was systematically studied in this paper. And the influence mechanism of electrochemical deposition process on calcium-phosphorus coating. The effect of iECAP process on corrosion behavior of Mg-Nd-Zn-Zr alloy in simulated body fluid was studied by adjusting extrusion temperature. The results show that the corrosion resistance of the extruded alloy is better than that of the as-cast alloy in simulated body fluid, the corrosion mode of the as-cast alloy changes from local corrosion to uniform corrosion after extrusion, and the corrosion resistance of the as-cast alloy increases from 400 鈩，
本文编号：2305938
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