Response surface and corrosion behavior analysis of nanosecond laser patterned ZK60A magnesium alloy

Abstract

Parallel groove patterns were fabricated on ZK60A magnesium alloy surface using nanosecond laser technology. In order to study the influence of laser processing parameters on the groove size, firstly, the single factor test was used to preliminarily determine the range of laser parameters, and then the mathematical models between processing parameters and groove width (W), depth (D) were established by response surface methodology. The morphologies, elements, hardness and phases of the magnesium alloy with different scanning distances were characterized by lanthanum hexaboride scanning electron microscope (SEM), environmental SEM, microhardness tester and X-ray diffractometer (XRD), respectively. The electrochemical corrosion performances of polished and laser patterned magnesium alloy samples in hanks' balanced salt solution (HBSS) were analyzed and compared using electrochemical experiments. The results show that W first increases and then decreases with the decrease of laser scanning speed (v) or the increase of repetition frequency (f), while D shows an increasing trend; the regression model obtained by the response surface methodology is in good agreement with the experimental values, and it accurately predicts the groove size. The wavy accumulation on the groove surface is caused by the sputtering of liquid materials when the laser acts on the sample surface. Compared with the polished sample, the hardness of samples with scanning distances of 80, 120 and 160 μm is significantly improved, which are 40.30, 30.69 and 29.18% respectively. Ecorr values of polished sample and patterned samples with scanning distances of 80, 120 and 160 μm are −1.4481, −1.6398, −1.5712 and −1.5142 V, respectively; and the corresponding Icorr values are 5.2209 × 10–6, 1.2378 × 10–5, 2.7849 × 10–5 and 6.3782 × 10–6 A•cm−2, respectively. The hydrophilicity of laser patterned magnesium alloy is enhanced, which is conducive to cell adhesion, however, the probability of contact between corrosive medium and samples increases at the same time. In addition, the grain refinement increases crystal defects, thereby reducing the corrosion resistance of laser patterned samples.