本文選題：鎂合金 + 納米晶��； 參考：《太原理工大學》2015年碩士論文

【摘要】：鎂及鎂合金憑借自身突出的性能優(yōu)點，，一直被航空航天、汽車工業(yè)和電子通訊等領域視為替代鋁合金、鋼鐵材料的理想選擇。然而，鎂合金強度偏低且塑性變形能力差，使得它在工業(yè)中的應用受到限制。由于鎂合金的機械性能受晶粒尺寸的影響較大，所以可以利用細化晶粒的方式來提高鎂合金的強度和塑性。盡管晶粒細化的方法很多，但都難以真正將鎂合金晶粒細化到納米尺寸。本文中采用了氫化-脫氫法(HDDR)對ZK60鎂合金粉末進行晶粒細化處理，最終獲得鎂合金納米晶粉末材料。 本文首先探究了利用氫化-脫氫法對鑄態(tài)ZK60鎂合金粉末進行晶粒細化處理的氫化、脫氫工藝的參數(shù)路線。然后利用XRD分別測試了氫化、脫氫過程中溫度、氫壓和保溫時間對相組成的影響，利用OM、SEM和TEM觀察了ZK60鎂合金粉末顯微組織的演化規(guī)律，并分析了ZK60鎂合金在氫化、脫氫過程中實現(xiàn)晶粒細化的機理。最后，對比在相同工藝參數(shù)下對純鎂進行氫化-脫氫處理的結果，討論了歧化反應對鎂合金晶粒細化過程的影響。 結果顯示：在氫化過程中，溫度是對反應過程影響最大的因素，溫度越高，反應進程越快，氫化程度越大。延長保溫時間同樣可以起到提到氫化程度的效果。氫壓對氫化過程的影響相對較小，呈現(xiàn)出隨氫壓增大，對氫化程度先抑制后促進的趨勢。脫氫過程中，溫度和保溫時間的影響與氫化過程一致，但脫氫時間不宜選擇過長，避免細化后的晶粒再次長大。綜合考慮，確定了鑄態(tài)ZK60鎂合金晶粒細化的最優(yōu)工藝參數(shù)路線：450℃、2MPa下氫化保溫12h，再在350℃真空下脫氫3h。 采用已確定的最優(yōu)工藝參數(shù)對ZK60鎂合金粉末進行氫化-脫氫處理，由微觀組織的演變過程表明，氫化處理使粉末顆粒發(fā)生應力斷裂而產(chǎn)生許多碎小顆粒，再進行脫氫處理，粉末的顆粒尺寸變化不大，而ZK60鎂合金的晶粒從150~200μm被細化至30nm左右，且大小較為均勻。由純鎂的氫化-脫氫處理結果，證明對于ZK60鎂合金，可以忽略Zn、Zr元素對反應過程的影響，晶粒被細化主要是在脫氫重組過程中實現(xiàn)的，歧化反應對晶粒的細化幫助不大。
[Abstract]:Magnesium and magnesium alloys have been regarded as an ideal alternative to aluminum alloy and steel due to their outstanding performance advantages in the fields of aerospace, automotive industry and electronic communication. However, the low strength and poor plastic deformation ability of magnesium alloy limit its application in industry. Because the mechanical properties of magnesium alloys are greatly affected by grain size, the strength and plasticity of magnesium alloys can be improved by means of grain refinement. Although there are many methods of grain refinement, it is difficult to refine magnesium alloy grain to nanometer size. In this paper, the ZK60 magnesium alloy powder was refined by hydrogenation and dehydrogenation method, and the nanocrystalline magnesium alloy powder material was obtained. In this paper, the hydrogenation and dehydrogenation of as-cast ZK60 magnesium alloy powders by hydrogenation and dehydrogenation were studied. Then the effects of temperature, pressure and holding time on the phase composition during hydrogenation and dehydrogenation were measured by XRD. The microstructure evolution of ZK60 magnesium alloy powder was observed by OMSEM and TEM, and the hydrogenation of ZK60 magnesium alloy was analyzed. Mechanism of grain refinement in dehydrogenation process. Finally, the effect of the disproportionation reaction on the grain refinement process of magnesium alloy was discussed by comparing the results of hydrogenation and dehydrogenation of pure magnesium under the same process parameters. The results show that temperature is the most important factor in the process of hydrogenation. The higher the temperature, the faster the reaction process and the greater the degree of hydrogenation. Prolonging the heat preservation time can also have the effect of mentioning the degree of hydrogenation. The effect of hydrogen pressure on the hydrogenation process is relatively small, showing the trend that with the increase of hydrogen pressure, the hydrogenation degree is inhibited first and then promoted. In the dehydrogenation process, the effects of temperature and holding time are consistent with the hydrogenation process, but the dehydrogenation time should not be chosen for too long to avoid the grain growth after refinement. The optimum process parameters for grain refinement of as-cast ZK60 magnesium alloy were determined, which were hydrogenated for 12 h at 1: 450 鈩

本文編號：1938114