發(fā)布時間：2018-09-06 16:38

【摘要】：高硅鋁合金具有質(zhì)量輕、硬度高、耐磨性好,熱膨脹系數(shù)低等優(yōu)點而被廣泛應(yīng)用于汽車、航空和電子工業(yè)中。傳統(tǒng)鑄造高硅鋁合金中粗大的初晶硅相和富鐵相會割裂鋁基體,嚴(yán)重影響合金的韌塑性及加工性能。噴射沉積連續(xù)擠壓(Spray Conform,簡稱SC)是新近提出的一種材料加工新技術(shù),兼有噴射沉積和連續(xù)擠壓兩種技術(shù)的優(yōu)點,可連續(xù)成形具有快速凝固組織的管棒型線材。該技術(shù)的出現(xiàn)可望為高硅鋁合金的高效低成本制備提供一條新的途徑。本文采用SC法制備了七種高硅鋁合金,研究了合金的微觀組織、力學(xué)性能和磨損性能。為解決噴射沉積區(qū)域較寬,而連續(xù)擠壓機輪槽較窄的技術(shù)問題,研制了雙旋轉(zhuǎn)盤流型控制器以約束霧化射流。研究了霧化氣體壓力和熔液溫度對約束噴射鋁硅合金沉積坯形貌及微觀組織的影響,并結(jié)合人工神經(jīng)網(wǎng)絡(luò)模型,獲得了噴射沉積階段的優(yōu)化參數(shù)。基于X射線分析技術(shù)研究了 Fe含量對SC態(tài)合金中α-A1晶格常數(shù)的影響,發(fā)現(xiàn)Fe含量越高,α-A1晶格畸變越大,晶格常數(shù)越大。探討了 SC態(tài)合金中富鐵相的形成機制,發(fā)現(xiàn)沉積階段霧滴的沖擊和連續(xù)擠壓過程中的劇烈剪切是形成細(xì)小富鐵相的主要原因。研究了擠壓比對SC法制備的Al-20Si合金組織及性能的影響。發(fā)現(xiàn)隨擠壓比的增加,初晶硅相的尺寸不斷減小,且形狀更為規(guī)整。擠壓比較高時,合金具有較高的硬度、強度和耐磨性。當(dāng)擠壓比達(dá)到20時,可獲得初晶硅相細(xì)小(等效直徑約3.3 μ m)均勻且完全致密的合金材料。SC法制備的Al-xSi(x=20,25,30 wt.%)合金中的初晶Si相細(xì)小且圓整,尺寸僅為鑄態(tài)合金的1/20。較高的硅含量形成更大體積分?jǐn)?shù)的細(xì)小硅顆粒,產(chǎn)生更明顯的第二相強化,致使合金強度隨Si含量的增加而不斷升高。相對于同等硅含量的鑄態(tài)合金,SC態(tài)合金的強度、塑性和耐磨性均有明顯提升,且硅含量越高,效果越明顯。SC法制備的Al-20Si-xFe(x=2,3,4,5 wt.%)合金中的第二相主要由細(xì)小的硅顆粒、短棒狀δ相和短針狀p相構(gòu)成。相對于鑄態(tài)合金,Si顆粒等效直徑下降了1個數(shù)量級,富鐵相的尺寸下降1～2個數(shù)量級。SC態(tài)Al-20Si-xFe合金內(nèi)的第二相尺寸細(xì)小且分布均勻,較高的鐵含量會形成更大體積分?jǐn)?shù)的第二相,產(chǎn)生更明顯的強化效果。使得Al-20Si-xFe合金的強度隨Fe含量的增加而不斷升高,當(dāng)Fe含量為5%時,抗拉強度可達(dá)367MPa。相對于同等鐵含量的鑄態(tài)合金,SC態(tài)合金的強度、塑性和耐磨性均有明顯提升,且鐵含量越高,增幅越大。SC態(tài)Al-20Si-xFe合金的高溫(200℃)強度較室溫強度有所下降,而塑性卻有明顯提升。高溫強度隨Fe含量的增加不斷升高,當(dāng)Fe含量為5%時,抗拉強度可達(dá)到192MPa。SC態(tài)Al-20Si-xFe合金具有優(yōu)良的室溫和高溫(200℃)耐磨性能,當(dāng)Fe含量為4%時,高溫磨損率僅為3.8× 10-10g/(N · mm)。
[Abstract]:High silicon aluminum alloy is widely used in automobile, aviation and electronic industry because of its advantages of light weight, high hardness, good wear resistance and low thermal expansion coefficient. The coarse primary silicon phase and iron rich phase in conventional casting high silicon aluminum alloy will split the aluminum matrix, which seriously affects the ductility and processing properties of the alloy. Spray deposition continuous extrusion (Spray Conform,) is a new material processing technology proposed recently. It has the advantages of both spray deposition and continuous extrusion. This technology is expected to provide a new way for the high-efficiency and low-cost preparation of high-silicon aluminum alloy. Seven kinds of high silicon aluminum alloys were prepared by SC method. The microstructure, mechanical properties and wear properties of the alloys were studied. In order to solve the technical problem that the spray deposition area is wider and the wheel slot of the continuous extruder is narrow, a dual rotating disk flow pattern controller is developed to constrain the atomization jet. The effects of atomization gas pressure and melt temperature on the morphology and microstructure of the confined spray Al-Si alloy deposition billet were studied. The optimized parameters of spray deposition stage were obtained by combining the artificial neural network model. The effect of Fe content on the lattice constant of 偽 -A1 in SC alloy was studied based on X-ray analysis. It was found that the higher the content of Fe, the greater the lattice distortion and the larger the lattice constant of 偽 -A1. The formation mechanism of Fe-rich phase in SC alloy was discussed. It was found that the main reasons for the formation of fine Fe-rich phase were the impact of droplets during deposition and the intense shear during continuous extrusion. The effect of extrusion ratio on the microstructure and properties of Al-20Si alloy prepared by SC method was studied. It is found that with the increase of extrusion ratio, the size of primary silicon phase decreases and the shape is more regular. When extrusion is high, the alloy has higher hardness, strength and wear resistance. When the extrusion ratio reaches 20:00, the primary Si phase in the Al-xSi (xF20) 2530 wt.% alloy prepared by SC method with fine primary silicon phase (equivalent diameter about 3.3 渭 m) is obtained. The size of the alloy is only 1 / 20 of that of the as-cast alloy. The higher the silicon content is, the larger the volume fraction of the fine silicon particles is, and the more obvious the second phase strengthening is, and the strength of the alloy increases with the increase of Si content. Compared with the as-cast alloy with the same silicon content, the ductility and wear resistance of the cast SC alloy are obviously improved, and the higher the silicon content is, the more obvious the effect is. The second phase of the Al-20Si-xFe alloy prepared by the SC method is mainly composed of fine silicon particles, the second phase of which is mainly composed of fine silicon particles, and the second phase of the alloy is mainly composed of fine silicon particles, and the second phase of the alloy is mainly composed of fine silicon particles. The short rod 未 phase and the short needle p phase are formed. Compared with the as-cast alloy, the equivalent diameter of Si particles decreases by 1 order of magnitude, and the size of rich iron phase decreases by 1 ~ 2 orders of magnitude. The size of the second phase in Al-20Si-xFe alloy is small and uniform. Higher iron content will form a second phase with a larger volume fraction, resulting in a more obvious strengthening effect. The strength of Al-20Si-xFe alloy increases with the increase of Fe content. When the content of Fe is 5, the tensile strength can reach 367 MPA. Compared with the as-cast alloy with the same iron content, the ductility and wear resistance of the cast alloy SC have been obviously improved, and the higher the iron content, the higher the increase of the strength of the Al-20Si-xFe alloy at high temperature (200 鈩，

本文編號：2226929