新聞資訊
AZ91D鎂合金在激光選區熔化成形中的元素燒損
發布人：上海艾荔艾金屬材料有限公司www.jshcn.cn
更新時間：2015-11-16
利用 OM, SEM, EDS, XRF 和 XRD 等方法研究了 AZ91D 鎂合金在激光選區熔化中的元素燒損機制以及燒損對成形試樣化學成分、顯微組織及力學性能的影響.
AZ91D鎂合金在激光選區熔化成形中的元素燒損ELEMENT LOSS OF AZ91D MAGNESIUM ALLOY DURING SELECTIVE?LASER MELTING PROCESS
利用 OM, SEM, EDS, XRF 和 XRD 等方法研究了 AZ91D 鎂合金在激光選區熔化中的元素燒損機制以及燒損對成形試樣化學成分、顯微組織及力學性能的影響. 研究表明, 成形試樣中 Mg 的相對含量(86.61%~88.68%)低于粉末原料中 Mg 的相對含量(90.63%), 而其 Al 的相對含量(10.4%~12.56%)則高于后者(8.97%). 該結果與基于 Langmuir 模型的計算結果相符, 證明在激光作用下主要是 Mg 發生了燒損. 成形試樣的 Mg 與 Al質量比 η 隨激光體能量密度 EV的增加呈現先上升后下降并最終趨于穩定的演變規律. 采用 55.6 J/mm3的 EV所成形試樣(試樣 No.8)的 η 值最接近粉末原料. 使用回歸分析法建立了 η 與 EV的解析關系, 其擬合度指標 R2系數為 0.858. 成分變化最為顯著之一的成形試樣 No.1(采用 166.7 J/mm3的 EV所成形)與壓鑄態 AZ91D 的組織特征相似, 均為 β-Mg17Al12相呈網狀分布于 α-Mg 基體間的典型凝固組織. 但成形試樣 No.1 的 β-Mg17Al12相含量及其α-Mg 基體中 Al 的固溶量明顯高于壓鑄態 AZ91D. 成分變化導致成形試樣 No.1 的拉伸強度及顯微硬度得到提升, 但使其延伸率有所下降.
Magnesium alloys have attracted more attentions due to their low densities and excellent specific?strengths. However, proper manufacturing methods are still needed to promote further applications of magnesium?alloys due to the shortcomings of conventional processing methods. As one of the most promising additive?manufacturing technologies, selective laser melting (SLM) was utilized to process the most commonly-used?AZ91D magnesium alloy in this work. Element vaporization mechanism during the forming process and the?influence of element vaporization on chemical composition, microstructure, and mechanical properties of the final?products were investigated using OM, SEM, EDS, XRF and XRD. The results show that the relative content of?Mg in the SLM-processed samples (86.61%~88.68%) was lower than that in the original AZ91D powders?(90.63%) , whereas the relative content of Al in the former ones (10.4%~12.56%) was higher than its counterpart?in the latter ones (8.97%). This variation matches well with the calculation by Langmuir model, demonstrating?that element vaporization of AZ91D mainly targets at Mg. With the increase of laser energy density (EV), weight?ratio of Mg to Al (η) in the SLM-processed samples first increased, then decreased and finally tended to be?constant. η of the sample prepared at 55.6 J/mm3?(sample No.8) presented a smallest difference with that of the?original powders. A model illustrating analytic relationship between η and EV was established by mathematical?regression with the fitting index R2?being 0.858. The sample processed at 166.7 J/mm3?(sample No.1) underwent?one of the most remarkable compositional variation and exhibited a typical solidified microstructure similar to the?die-cast AZ91D in which net-like β-Mg17Al12 precipitates were distributed around the α-Mg matrix. However,?β-Mg17Al12 content as well as solid solubility of Al in α-Mg matrix was much higher in sample No.1. The?enhanced tensile strength and micro-hardness as well as the deteriorated elongation of sample No.1 could be?attributed to the composition variation during SLM process.