層狀結(jié)構(gòu)TiAl基復(fù)合材料合成機(jī)制與性能研究
發(fā)布時(shí)間：2018-12-13 10:50
【摘要】：Ti Al基合金作為綜合性能優(yōu)異的新型結(jié)構(gòu)材料可滿足航空航天超音速飛行器及汽車發(fā)動機(jī)對結(jié)構(gòu)減重和高溫強(qiáng)度的雙重要求。然而Ti Al基合金室溫塑性低,成形能力差,傳統(tǒng)熱軋制方法制備Ti Al基板材相當(dāng)困難。本文通過設(shè)計(jì)層狀結(jié)構(gòu)和引入Ti B晶須增強(qiáng)相提高Ti Al板材綜合力學(xué)性能。本文將純Ti箔和原位自生的Ti Bw/Ti復(fù)合材料箔分別與純Al箔交替堆疊,通過真空熱壓制備出Ti-Al疊層和(Ti Bw/Ti)-Al疊層,并通過反應(yīng)熱處理合成出具有層狀結(jié)構(gòu)的Ti Al板材和Ti Bw-Ti Al復(fù)合材料板材。分析了疊層在熱處理過程中的相組成及相轉(zhuǎn)變規(guī)律,研究了層狀結(jié)構(gòu)形成機(jī)理,對層狀結(jié)構(gòu)Ti Al板材和Ti Bw-Ti Al復(fù)合材料板材進(jìn)行力學(xué)性能測試,揭示了強(qiáng)韌化機(jī)制與斷裂機(jī)理。將真空熱壓獲得的界面結(jié)合良好的Ti-Al疊層進(jìn)行660oC的低溫反應(yīng)退火,Ti原子和Al原子不斷進(jìn)行互擴(kuò)散,生成Ti Al3相,并且Ti Al3相的生長遵循直線生長動力學(xué)模式。低溫反應(yīng)退火2h后,材料中的Al完全消耗,獲得Ti-Ti Al3疊層。由于低溫反應(yīng)退火時(shí)Ti與Al反應(yīng)擴(kuò)散速率不同,組織中存在Kirkendall孔洞,生成相Ti Al3為疏松多孔結(jié)構(gòu)。將疊層繼續(xù)進(jìn)行1200oC/35MPa/2h高溫反應(yīng)退火,材料中孔洞得到彌合,且Ti和Al繼續(xù)擴(kuò)散,反應(yīng)生成Ti Al和Ti3Al,由于材料成分不均勻,存在貧Al區(qū)和富Al區(qū)。隨著熱處理的進(jìn)行,貧Al區(qū)轉(zhuǎn)變?yōu)槿珜悠?α2-Ti3Al/γ-Ti Al)層,富Al區(qū)形成等軸γ-Ti Al層,最終制備出具有雙晶結(jié)構(gòu)的層狀Ti Al板材。由于(Ti Bw/Ti)-Al疊層和純Ti-Al疊層的擴(kuò)散組元一致,且厚度基本沒變,因此對(Ti Bw/Ti)-Al疊層亦采用同種熱處理工藝,制備了具有層狀結(jié)構(gòu)的Ti Bw-Ti Al復(fù)合材料板材,組織由Ti Al層和Ti Bw-rich層交替組成,其中Ti Al層為全層片(α2-Ti3Al/γ-Ti Al)層和等軸γ-Ti Al層交替排列,Ti Bw-rich層為高體積分?jǐn)?shù)的Ti B晶須聚集層。室溫拉伸結(jié)果表明,層狀結(jié)構(gòu)Ti Al板材抗拉強(qiáng)度、室溫延伸率較高,層狀雙晶結(jié)構(gòu)可相互細(xì)化組織。層狀Ti Bw-Ti Al復(fù)合材料板材由于增強(qiáng)相Ti Bw的存在,提高了強(qiáng)度。分析拉伸斷口,全層片(α2-Ti3Al/γ-Ti Al)層斷裂主要為穿片層斷裂和沿片層斷裂,等軸γ-Ti Al層主要為穿晶斷裂和沿晶斷裂。斷裂韌性結(jié)果表明,層狀結(jié)構(gòu)Ti Al板材平行于熱壓方向的斷裂韌性比垂直于熱壓方向的高,且Ti B晶須的引入提高了韌性。層狀結(jié)構(gòu)和Ti B晶須的存在增加了裂紋萌生與擴(kuò)展的阻力,延長了裂紋擴(kuò)展的路徑,起到了增韌的目的。三點(diǎn)彎曲結(jié)果表明,層狀結(jié)構(gòu)Ti Bw-Ti Al復(fù)合材料板材室溫彎曲強(qiáng)度升高,增強(qiáng)相Ti B晶須的引入可提高復(fù)合材料的彎曲強(qiáng)度。
[Abstract]:As a new structural material with excellent comprehensive properties, Ti Al alloy can meet the dual requirements of structural weight loss and high temperature strength of aerospace supersonic aircraft and automobile engines. However, Ti Al alloy has low room temperature plasticity and poor formability, so it is very difficult to prepare Ti Al base sheet by traditional hot rolling method. In this paper, the comprehensive mechanical properties of Ti sheet were improved by designing layered structure and introducing Ti B whisker reinforcement phase. In this paper, the pure Ti foil and the in-situ Ti Bw/Ti composite foil are alternately stacked with the pure Al foil. The Ti-Al laminates and (Ti Bw/Ti) -Al laminates are prepared by vacuum hot pressing. Ti Al sheet and Ti Bw-Ti Al composite sheet with layered structure were synthesized by reactive heat treatment. The phase composition and phase transition of laminated layers during heat treatment were analyzed. The formation mechanism of laminated structure was studied. The mechanical properties of laminated Ti Al and Ti Bw-Ti Al composite sheets were tested. The mechanism of strengthening and toughening and the mechanism of fracture are revealed. The interface obtained by vacuum hot pressing was annealed at low temperature with good Ti-Al laminates, and the Ti atoms and Al atoms were continuously diffused to form Ti Al3 phase, and the growth of Ti Al3 phase followed the linear growth kinetics model. After annealing at low temperature for 2 h, the Al in the material was completely consumed and the Ti-Ti Al3 lamination was obtained. Due to the difference of reaction diffusion rate between Ti and Al during low temperature reaction annealing, there are Kirkendall pores in the microstructure, and the formation phase of Ti Al3 is porous. The stacked layers were further annealed by 1200oC/35MPa/2h reaction at high temperature, the pores in the materials were bridged, and the Ti and Al continued to diffuse. The Ti Al and Ti3Al, formed by the reaction resulted from the poor Al region and the rich Al region due to the uneven composition of the material. With the heat treatment, the poor Al region was transformed into a 2-Ti3Al/ 緯-Ti Al) layer, and the Al rich region formed an equiaxed 緯-Ti Al layer. Finally, the layered Ti Al sheet with double crystal structure was prepared. Because the diffusion components of (Ti Bw/Ti)-Al laminates and pure Ti-Al laminates are the same, and the thickness of (Ti Bw/Ti)-Al laminates is basically unchanged, the (Ti Bw/Ti)-Al laminates are also treated by the same heat treatment process. Ti Bw-Ti Al composite sheet with layered structure was prepared. The microstructure was composed of Ti Al layer and Ti Bw-rich layer alternately, in which the Ti Al layer was arranged alternately with 偽 2-Ti3Al/ 緯 -Ti Al) layer and equiaxed 緯 -Ti Al layer. The Ti Bw-rich layer is a high volume fraction Ti B whisker aggregation layer. The tensile results at room temperature show that the laminated Ti Al sheet has high tensile strength and high elongation at room temperature, and the layered double crystal structure can refine each other's microstructure. The strength of laminated Ti Bw-Ti Al composite plate is improved because of the existence of reinforcing phase Ti Bw. By analyzing tensile fracture, the fracture of 偽 2-Ti3Al/ 緯-Ti Al) layer is mainly translamellar and along lamellar fracture, and the equiaxed 緯-Ti Al layer is mainly transgranular and intergranular fracture. The results of fracture toughness show that the fracture toughness of laminated Ti Al sheet is higher than that of perpendicular to hot pressing direction, and the toughness is improved by introducing Ti B whisker. The existence of layered structure and Ti B whisker increases the resistance of crack initiation and propagation, prolongs the path of crack growth, and plays the purpose of toughening. The results of three-point bending show that the flexural strength of laminated Ti Bw-Ti Al composites increases at room temperature, and the flexural strength of composites can be improved by the introduction of Ti B whiskers.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB333
本文編號：2376417
[Abstract]:As a new structural material with excellent comprehensive properties, Ti Al alloy can meet the dual requirements of structural weight loss and high temperature strength of aerospace supersonic aircraft and automobile engines. However, Ti Al alloy has low room temperature plasticity and poor formability, so it is very difficult to prepare Ti Al base sheet by traditional hot rolling method. In this paper, the comprehensive mechanical properties of Ti sheet were improved by designing layered structure and introducing Ti B whisker reinforcement phase. In this paper, the pure Ti foil and the in-situ Ti Bw/Ti composite foil are alternately stacked with the pure Al foil. The Ti-Al laminates and (Ti Bw/Ti) -Al laminates are prepared by vacuum hot pressing. Ti Al sheet and Ti Bw-Ti Al composite sheet with layered structure were synthesized by reactive heat treatment. The phase composition and phase transition of laminated layers during heat treatment were analyzed. The formation mechanism of laminated structure was studied. The mechanical properties of laminated Ti Al and Ti Bw-Ti Al composite sheets were tested. The mechanism of strengthening and toughening and the mechanism of fracture are revealed. The interface obtained by vacuum hot pressing was annealed at low temperature with good Ti-Al laminates, and the Ti atoms and Al atoms were continuously diffused to form Ti Al3 phase, and the growth of Ti Al3 phase followed the linear growth kinetics model. After annealing at low temperature for 2 h, the Al in the material was completely consumed and the Ti-Ti Al3 lamination was obtained. Due to the difference of reaction diffusion rate between Ti and Al during low temperature reaction annealing, there are Kirkendall pores in the microstructure, and the formation phase of Ti Al3 is porous. The stacked layers were further annealed by 1200oC/35MPa/2h reaction at high temperature, the pores in the materials were bridged, and the Ti and Al continued to diffuse. The Ti Al and Ti3Al, formed by the reaction resulted from the poor Al region and the rich Al region due to the uneven composition of the material. With the heat treatment, the poor Al region was transformed into a 2-Ti3Al/ 緯-Ti Al) layer, and the Al rich region formed an equiaxed 緯-Ti Al layer. Finally, the layered Ti Al sheet with double crystal structure was prepared. Because the diffusion components of (Ti Bw/Ti)-Al laminates and pure Ti-Al laminates are the same, and the thickness of (Ti Bw/Ti)-Al laminates is basically unchanged, the (Ti Bw/Ti)-Al laminates are also treated by the same heat treatment process. Ti Bw-Ti Al composite sheet with layered structure was prepared. The microstructure was composed of Ti Al layer and Ti Bw-rich layer alternately, in which the Ti Al layer was arranged alternately with 偽 2-Ti3Al/ 緯 -Ti Al) layer and equiaxed 緯 -Ti Al layer. The Ti Bw-rich layer is a high volume fraction Ti B whisker aggregation layer. The tensile results at room temperature show that the laminated Ti Al sheet has high tensile strength and high elongation at room temperature, and the layered double crystal structure can refine each other's microstructure. The strength of laminated Ti Bw-Ti Al composite plate is improved because of the existence of reinforcing phase Ti Bw. By analyzing tensile fracture, the fracture of 偽 2-Ti3Al/ 緯-Ti Al) layer is mainly translamellar and along lamellar fracture, and the equiaxed 緯-Ti Al layer is mainly transgranular and intergranular fracture. The results of fracture toughness show that the fracture toughness of laminated Ti Al sheet is higher than that of perpendicular to hot pressing direction, and the toughness is improved by introducing Ti B whisker. The existence of layered structure and Ti B whisker increases the resistance of crack initiation and propagation, prolongs the path of crack growth, and plays the purpose of toughening. The results of three-point bending show that the flexural strength of laminated Ti Bw-Ti Al composites increases at room temperature, and the flexural strength of composites can be improved by the introduction of Ti B whiskers.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB333
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