本文選題：ZL114合金 + Al-Ti-B-Sm��； 參考：《哈爾濱理工大學(xué)》2017年碩士論文

【摘要】：亞共晶Al-Si合金因強(qiáng)度高、密度小等優(yōu)點(diǎn)而備受矚目,但它在凝固過程中會出現(xiàn)粗大、易偏聚的初生α-Al相和片層狀共晶硅組織,嚴(yán)重降低合金力學(xué)性能。細(xì)化變質(zhì)是改善合金組織的重要方法,在工業(yè)生產(chǎn)中得到了廣泛應(yīng)用。本文以ZL114鋁合金為研究對象,首先以1wt.%Al-5Ti-1B和變量稀土Sm對ZL114合金聯(lián)合細(xì)化變質(zhì)為基礎(chǔ),制備最優(yōu)Al-5Ti-1B-XSm細(xì)化變質(zhì)劑,然后采用Al-5Ti-1B-XSm細(xì)化變質(zhì)劑研究細(xì)化變質(zhì)時間和溫度對ZL114合金組織及性能的影響規(guī)律并探討其細(xì)化變質(zhì)機(jī)理。首先,固定Al-5Ti-1B的加入量為1 wt.%,改變Sm的加入量探索最佳的Al-5Ti-1B-XSm細(xì)化變質(zhì)劑。結(jié)果表明,隨著Sm的加入量增加,α-Al相的二次枝晶臂間距和共晶硅的平均長徑比先減小后增加,當(dāng)Sm的加入量為0.07 wt.%時,α-Al相二次枝晶臂間距和共晶硅平均長徑比最小,分別為11.24μm和2.53,抗拉強(qiáng)度和顯微硬度最高,分別為225 MPa和63.2。根據(jù)原子守恒,自制的細(xì)化變質(zhì)劑為Al-5Ti-1B-7Sm。Al-5Ti-1B-7Sm中第二相主要為Ti_2Al_(20)Sm和TiB_2,其中Ti B2分布彌散,無偏聚現(xiàn)象。采用1 wt.%Al-5Ti-1B-7Sm細(xì)化變質(zhì)劑對ZL114合金細(xì)化變質(zhì)的最佳工藝為720℃×60 min,此時α-Al相二次枝晶臂間距和共晶硅長徑比最小,分別為9.28μm和1.84,顯微硬度和抗拉強(qiáng)度最高,分別為70.4和265 MPa。拉伸斷口附近出現(xiàn)韌窩,斷裂面細(xì)化明顯,斷裂方式為韌性斷裂。細(xì)化變質(zhì)機(jī)理分析表明,Ti2Al20Sm與α-Al有8組可能匹配的取向關(guān)系,可作為α-Al異質(zhì)形核質(zhì)點(diǎn),提高α-Al細(xì)化程度。合金經(jīng)1 wt.%Al-5Ti-1B-7Sm細(xì)化變質(zhì)后,初晶形核溫度提高到609.7℃,且初晶凝固時間減少,初晶長大受到抑制;共晶形核溫度為567.5℃、共晶凝固時間2.6 s,均較未變質(zhì)合金有較大程度降低,形核核心減少、凝固時間的縮短是共晶硅轉(zhuǎn)變?yōu)槔w維狀的主要原因。此外,共晶生長速度降低及粗糙型界面特征是共晶硅變質(zhì)為纖維狀的其他因素。
[Abstract]:Hypoeutectic Al-Si alloy has attracted much attention because of its high strength and low density. However, it will produce coarse and easily segregated primary 偽 -Al phase and lamellar eutectic silicon during solidification, which seriously reduces the mechanical properties of the alloy. Refined modification is an important method to improve the microstructure of alloys and has been widely used in industrial production. In this paper, ZL114 aluminum alloy was used as the research object. Firstly, based on the combined refinement and modification of ZL114 alloy by 1wt.%Al-5Ti-1B and variable rare earth Sm, the optimal Al-5Ti-1B-XSm refiner was prepared. Then the effect of modification time and temperature on the microstructure and properties of ZL114 alloy was studied by using Al-5Ti-1B-XSm refiner and the modification mechanism was discussed. Firstly, the amount of fixed Al-5Ti-1B is 1 wt. to change the amount of Sm to find the best Al-5Ti-1B-XSm refiner. The results show that the secondary dendritic arm spacing of 偽 -Al phase and the average aspect ratio of eutectic silicon decrease first and then increase with the increase of Sm content. When Sm is 0.07 wt.%, the distance between the secondary dendritic arms of 偽 -Al phase and the average length / diameter ratio of eutectic silicon is the smallest. The tensile strength and microhardness were the highest, which were #number0# MPa and 63.2 渭 m, respectively, with 11.24 渭 m and 2.53 渭 m, respectively. According to atomic conservation, the second phase in Al-5Ti-1B-7Sm.Al-5Ti-1B-7Sm is mainly Ti_2Al_(20)Sm and TiB-2, in which the distribution of TiB2 is dispersed and the phenomenon of unbiased aggregation is observed. The optimum process for refining and modifying ZL114 alloy with 1 wt.%Al-5Ti-1B-7Sm refining modifier is 720 鈩，

本文編號：1861335