【摘要】：Mg作為一種典型的hcp結(jié)構(gòu)金屬,其枝晶形貌和生長取向受到多種因素的影響,目前針對鎂合金中a-Mg枝晶生長模型的描述以及多樣性的起源等問題的研究都比較缺乏,基于此,本文綜述了本課題組在鎂合金凝固微觀組織結(jié)構(gòu)三維表征方面取得的研究成果.借助同步輻射X射線微觀斷層掃描技術(shù)以及相場數(shù)值模型,研究了鎂合金凝固過程中a-Mg(X)枝晶生長選擇多樣性的形成機(jī)理以及固溶合金元素(Al,Ca,Zn和Sn等)、固溶元素含量(溶質(zhì)濃度)等因素對a-Mg枝晶生長選擇和演化的影響.研究結(jié)果表明,固溶元素、固溶元素含量等因素都會對鎂合金中a-Mg三維枝晶形貌和擇優(yōu)取向產(chǎn)生重要影響.在Mg-Ca和Mg-Al(hcp-fcc)合金中,枝晶傾向于以1120或2245為擇優(yōu)方向生長.在Mg-Sn(hcp-bct)合金中,等軸生長的枝晶沿著基面上1120和偏離基面的112X(X≈2)方向形成一種18次分支的結(jié)構(gòu),在Mg-Zn(hcp-hcp)合金中,a-Mg枝晶的擇優(yōu)取向會隨著Zn含量的增加,從1120方向朝偏離基面的1121方向發(fā)生連續(xù)轉(zhuǎn)變,并在轉(zhuǎn)變的過渡區(qū),發(fā)現(xiàn)了超支化的藻狀枝晶結(jié)構(gòu),其原因可能是高各向異性Zn元素的引入帶來的固/液界面自由能各向異性的變化.研究結(jié)果從一定程度上揭示了鎂合金凝固過程中a-Mg枝晶生長形貌和分支結(jié)構(gòu)選擇多樣性的規(guī)律.同時基于快速X射線成像技術(shù)率先開展了鎂合金凝固過程三維微觀結(jié)構(gòu)演化原位表征研究,獲得了鎂合金凝固過程三維枝晶的生長演化過程.
[Abstract]:As a typical hcp structural metal, the dendritic morphology and growth orientation of Mg are affected by many factors. At present, there are few studies on the description of a-Mg dendritic growth model and the origin of diversity in magnesium alloys. Based on this, the research results of three-dimensional characterization of solidification microstructure of magnesium alloys in our research group are reviewed in this paper. The formation mechanism of a-Mg (X) dendrite growth diversity and solid solution alloy elements (Al,Ca,Zn and Sn, etc.) during solidification of magnesium alloys were studied by means of synchroradiation X-ray microscopic tomography and phase field numerical model. The effect of solid solution element content (solute concentration) on the growth selection and evolution of a-Mg dendrite. The results show that the content of solid solution elements has an important effect on the morphology and preferred orientation of a-Mg in magnesium alloys. In Mg-Ca and Mg-Al (hcp-fcc) alloys, dendrites tend to grow in the preferred direction of 1120 or 2245. In Mg-Sn (hcp-bct) alloy, the dendites grown on the same axis form an 18th branch structure along the direction of 1120 on the base plane and 112X (X 鈮，

本文編號：2479745