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采用双脉冲电沉积技术,控制单一变量,在酸性的无氰氯金酸溶液中进行金的电沉积。使用扫描电子显微镜、X射线衍射仪研究了脉冲电流密度和占空比对金铸层表面和横截面形貌,及显微结构的影响。实验结果表明,正向峰值电流密度从2.25 A/dm~2增加到3.75 A/dm~2,铸层晶粒细化,但正向电流密度过大导致表面起伏较大,铸层平整度下降;而反向峰值电流密度从6 A/dm~2增加到12 A/dm~2时,晶粒尺寸逐渐变大,结构也变得疏松。正向占空比由20%提高到60%,会使阴极过电位增大,从而铸层晶粒细化,但是正向占空比过大会造成铸层内部出现孔隙,致密度下降;反向占空比从10%提高到40%,铸层针孔逐渐增多,变薄变脆。通过计算织构系数,可知在较高的阴极过电位下,金铸层的择优取向为沿(111)和(222)晶面;低的阴极过电位下,金铸层的择优取向则沿(200)晶面。
Dual-pulse electrodeposition technology was used to control single variables and gold electrodeposition was carried out in acid cyanide-free chlorauric acid solution. The effects of pulse current density and duty cycle on the surface and cross-section morphology and microstructure of the as-cast alloy were investigated by scanning electron microscopy and X-ray diffractometry. The experimental results show that the forward peak current density increases from 2.25 A / dm ~ 2 to 3.75 A / dm ~ 2, and the grain size of the casting layer is refined. However, the forward current density is too large to cause the surface undulation and the casting flatness to decline While the reverse peak current density increased from 6 A / dm ~ 2 to 12 A / dm ~ 2, the grain size became larger and the structure became loose. Positive duty cycle increased from 20% to 60%, will make the cathode overpotential increases, so that the grain refinement of the cast, but the positive duty cycle is too large will lead to porosity within the casting layer, the density decreased; reverse Duty cycle increased from 10% to 40%, the pinhole gradually increased, thinning and brittle. By calculating the texture coefficient, it can be seen that the preferred orientation of the gold-cast layer is along the (111) and (222) planes at higher cathodic overpotentials and the preferred orientation of the gold- 200) crystal plane.