本文選題：組織 + 性能��； 參考：《沈陽(yáng)工業(yè)大學(xué)》2016年博士論文

【摘要】：鎂合金具有低密度、高比強(qiáng)度、易回收利用等優(yōu)點(diǎn),在電子、汽車(chē)、航空航天等領(lǐng)域得到了廣泛的應(yīng)用。但是一般晶態(tài)Mg合金強(qiáng)度相對(duì)較低,塑性較高,而非晶態(tài)Mg合金強(qiáng)度較高,塑性幾乎為零,因此發(fā)揮晶態(tài)合金的塑性優(yōu)勢(shì)和非晶態(tài)合金的強(qiáng)度優(yōu)勢(shì),成為本文研究Mg基非晶復(fù)合材料的出發(fā)點(diǎn)。長(zhǎng)周期(LPSO)結(jié)構(gòu)不僅可以作為晶態(tài)合金中的增強(qiáng)相,也可作為非晶態(tài)合金的增強(qiáng)相,成為人們關(guān)注的研究熱點(diǎn)。本文采用銅模鑄造法制備了LPSO結(jié)構(gòu)增強(qiáng)的Mg-Ni-Zn-Y系列非晶復(fù)合材料,通過(guò)改變?cè)睾�、樣品尺�?探討成分、冷卻速率對(duì)非晶復(fù)合材料的組織結(jié)構(gòu)和力學(xué)性能的影響,確定非晶復(fù)合材料綜合力學(xué)性能最佳的區(qū)域。通過(guò)改變熱處理溫度,研究LPSO結(jié)構(gòu)演化規(guī)律。主要結(jié)論如下:直徑為2 mm的鑄態(tài)Mg_(77)+xNi_(12)-xZn_5Y_6(x=0,2,4,6,8)系列合金均為非晶復(fù)合材料,在非晶基體中分布著黑色針狀相。當(dāng)Ni8%時(shí),針狀相細(xì)長(zhǎng),主要晶態(tài)相為α-Mg相、Mg_(12)YZn長(zhǎng)周期相;當(dāng)Ni8%時(shí),針狀相粗大,主要晶態(tài)相為α-Mg相、Mg_(12)YZn長(zhǎng)周期相和Mg_2Ni相。當(dāng)Ni=8%時(shí),形成了大小、分布均勻的LPSO相。隨著Ni含量的降低,復(fù)合材料的塑性先增加再減小,Mg_(81)Ni_8Zn_5Y_6的塑性最好,塑性應(yīng)變和總應(yīng)變分別達(dá)到20.23%和22.34%。直徑為2 mm的Mg_(73)+xNi_(12)Zn_5Y_(10-x)(x=0,2,4,6,8)系列復(fù)合材料,當(dāng)Y8%時(shí),非晶基體中分布著片狀α-Mg相和少量針狀Mg)*(12)YZn相;當(dāng)Y8%時(shí),形成粗大針狀相,主要晶態(tài)相為α-Mg相、Mg_(12)YZn長(zhǎng)周期相和Mg_2Ni相。直徑為2 mm的Mg_(77+x)Ni_8Zn_5Y_(10-x)(x=2,4,6,8)系列復(fù)合材料,當(dāng)Y4%時(shí),非晶基體中分布著針狀相,主要晶態(tài)相為α-Mg相和Mg_(12)YZn長(zhǎng)周期相;當(dāng)Y4%時(shí),非晶基體中分布著樹(shù)枝狀α-Mg相、部分Mg_(12)YZn長(zhǎng)周期相和Mg2Ni相。隨著Y含量的降低,兩類(lèi)復(fù)合材料的強(qiáng)度均先降低再升高,Mg_(73)Ni_(12)Zn_5Y_(10)復(fù)合材料的斷裂強(qiáng)度最高,達(dá)到846 MPa。直徑為2 mm的Mg_(77)Ni_(12)Zn_(9-x)Y_(2+x)(x=0,2,4,6)系列復(fù)合材料,當(dāng)Zn/Y0.83時(shí),在非晶基體中分布著針狀相,主要晶態(tài)相為α-Mg相、Mg_(12)YZn長(zhǎng)周期相和Mg_2Ni相。隨著Zn/Y比的增加,針狀相尺寸、含量增加,樣品的強(qiáng)度先減小再增加,塑性均較低。直徑分別為2 mm、3 mm、5 mm的Mg_(75)Ni_(12)Zn_5Y_8和Mg_(77)Ni_(12)Zn_3Y_8系列復(fù)合材料,主要晶態(tài)相為α-Mg相、Mg_(12)YZn相和Mg_2Ni相。隨著樣品直徑的增加,針狀相的尺寸、含量增加,強(qiáng)度下降,塑性先增加再減小。模擬分析了非晶復(fù)合材料中非晶、a-Mg和LPSO等不同相冷卻速率與合金凝固組織的對(duì)應(yīng)關(guān)系,模擬結(jié)果與實(shí)驗(yàn)結(jié)果相符。Mg-Ni-Zn-Y非晶復(fù)合材料的形成機(jī)制為:快速冷卻過(guò)程中,α-Mg相和Mg_(12)YZn相作為領(lǐng)先相先析出,Mg_2Ni相可伴隨Mg_(12)YZn相的析出同時(shí)形核,隨溫度降低晶態(tài)相長(zhǎng)大;當(dāng)溫度降低到Tg以下時(shí),剩余液相形成非晶,最終形成以非晶為基體,晶態(tài)相分布其上的非晶復(fù)合材料。鑄態(tài)、473 K熱處理5 h、773 K熱處理5 h后Mg_(81)Ni_8Zn_5Y_6非晶復(fù)合材料的LPSO相分別為14H、18R、6H結(jié)構(gòu)。LPSO相的穩(wěn)定順序?yàn)?4H18R6H,Ni含量適當(dāng)提高,有利于形成更穩(wěn)定的LPSO結(jié)構(gòu)。Mg-Ni-Zn-Y非晶復(fù)合材料中的針狀LPSO相具有空間網(wǎng)絡(luò)結(jié)構(gòu)。隨著Ni含量的降低,LPSO相數(shù)量增加,尺寸變細(xì)。隨著Y含量的降低,LPSO相數(shù)量減少、尺寸變大。隨著Zn/Y的增加,LPSO相數(shù)量減少,尺寸變大。Mg-Ni-Zn-Y非晶復(fù)合材料的強(qiáng)度和塑性與LPSO相的形態(tài)和體積分?jǐn)?shù)有關(guān),LPSO相尺寸適當(dāng)、分布均勻、體積分?jǐn)?shù)較高時(shí)有利于復(fù)合材料塑性的提高。隨著LPSO相體積分?jǐn)?shù)的增加,復(fù)合材料的塑性明顯增加,強(qiáng)度變化不大。力學(xué)性能最佳的成分范圍為一個(gè)三角形,其三個(gè)頂點(diǎn)的合金成分分別為Mg_(8)3Ni_6Zn_5Y_6、Mg_(79)Ni_8Zn_5Y_8和Mg_(79.68)Ni_8Zn_5Y_(7.32)。獲得了Mg-Ni-Zn-Y非晶復(fù)合材料的斷裂機(jī)制和斷口特征。斷裂機(jī)制表現(xiàn)為非晶剪切帶滑移受到長(zhǎng)周期相阻礙,長(zhǎng)周期相變形誘發(fā)新的剪切帶產(chǎn)生,當(dāng)這個(gè)過(guò)程貫穿整個(gè)樣品滑移面時(shí),樣品便發(fā)生斷裂。Mg-Ni-Zn-Y非晶復(fù)合材料的斷口可分為晶態(tài)相特征區(qū)、撕裂特征區(qū)、脈狀紋特征區(qū),其中晶態(tài)相特征區(qū)可表現(xiàn)為針狀相或光滑的α-Mg相滑移區(qū),撕裂特征區(qū)與鋸齒狀不連續(xù)應(yīng)力-應(yīng)變曲線相對(duì)應(yīng),脈狀紋特征區(qū)是絕熱剪切所造成的非晶基體熔化聚集的結(jié)果,斷口出現(xiàn)裂紋可抑制這一區(qū)域的出現(xiàn)。
[Abstract]:Magnesium alloy has many advantages, such as low density, high specific strength, easy recovery, and so on. It has been widely used in the fields of electronics, automobile, aerospace and other fields. But the strength of the general crystalline Mg alloy is relatively low, the plasticity is higher, and the strength of the amorphous Mg alloy is higher and the plasticity is almost zero, so the plastic advantage of the crystalline alloy and the strength of the amorphous alloy are strong. The degree advantage is the starting point for the study of Mg Based Amorphous Composites. The long period (LPSO) structure not only can be used as an enhanced phase in crystalline alloy, but also as an enhanced phase of amorphous alloy. This paper has prepared a Mg-Ni-Zn-Y series amorphous composite with enhanced LPSO structure by copper mold casting. The influence of the element content, sample size, composition and cooling rate on the structure and mechanical properties of amorphous composites was investigated, and the best comprehensive mechanical properties of amorphous composites were determined. By changing the heat treatment temperature, the evolution law of LPSO structure was studied. The main conclusions are as follows: the cast Mg_ (77) +xNi_ (12) -xZn_5 with diameter of 2 mm Y_6 (x=0,2,4,6,8) alloys are Amorphous Composites with black needle like phase in the amorphous matrix. When Ni8%, the needle like phase is long, the main crystalline phase is alpha -Mg phase, Mg_ (12) YZn long period phase; when Ni8%, the acicular phase is large, the main crystalline phase is alpha -Mg phase, Mg_ (12) YZn long period phase and Mg_2Ni phase. When Ni=8%, the size, distribution are formed. With the decrease of the content of Ni, the plasticity of the composite increases first and then decreases, the plasticity of Mg_ (81) Ni_8Zn_5Y_6 is the best, the plastic strain and the total strain reach 20.23% and the 22.34%. diameter is 2 mm Mg_ (73) +xNi_ (12) Zn_5Y_ (10-x) (x=0,2,4,6,8) series. When Y8%, the amorphous matrix is distributed in the amorphous matrix and a small amount. Needle like Mg) * (12) YZn phase; when Y8%, a large needle like phase is formed, the main crystalline phase is alpha -Mg phase, Mg_ (12) YZn long period phase and Mg_2Ni phase. The diameter of Mg_ (77+x) Ni_8Zn_5Y_ (10-x) series is 2 mm. The matrix is distributed in the dendrimer like alpha -Mg phase, part Mg_ (12) YZn long period phase and Mg2Ni phase. With the decrease of Y content, the strength of the two kinds of composite materials decreases first and then increases. The fracture strength of Mg_ (73) Ni_ (12) Zn_5Y_ (10) composite is the highest, and the 846 MPa. diameter is 2 mm Mg_ (12) series composite material. At n/Y0.83, the needle like phase is distributed in the amorphous matrix, the main crystalline phase is alpha -Mg phase, Mg_ (12) YZn long period phase and Mg_2Ni phase. With the increase of Zn/Y ratio, the size and content of the needle phase increase, the strength of the sample decreases first and then increases, the plasticity is lower. The diameter is 2 mm, 3 mm, 5 mm Mg_ (75) Ni_ (12) Zn_5Y_8 and 77 (12). The main crystalline phase is the alpha -Mg phase, the Mg_ (12) YZn phase and the Mg_2Ni phase. With the increase of the sample diameter, the size, the content, the strength and the plasticity of the acicular phase increase and then decrease. The corresponding relationship between the cooling rate of amorphous, a-Mg and LPSO in Amorphous Composites and the solidification structure of the alloy is simulated and analyzed, and the simulation results and experiments are carried out. The result shows that the formation mechanism of.Mg-Ni-Zn-Y Amorphous Composites is that in the rapid cooling process, the alpha -Mg phase and the Mg_ (12) YZn phase precipitate as the leading phase, and the Mg_2Ni phase can accompany the precipitation of Mg_ (12) YZn phase at the same time, and the crystal phase grows with the temperature. When the temperature is below Tg, the remaining liquid phase forms amorphous, and finally forms the amorphous base. The crystalline phase is distributed on the amorphous composite. As cast, 473 K heat treatment 5 h, 773 K heat treatment 5 h, LPSO phase of Mg_ (81) Ni_8Zn_5Y_6 composite material is 14H, 18R, 6H structure.LPSO phase is 14H18R6H, the content is improved, which is beneficial to the formation of a more stable amorphous composite material in the amorphous composite material SO phase has space network structure. With the decrease of Ni content, the number of LPSO phase increases and the size becomes thinner. With the decrease of Y content, the number of LPSO phase decreases and the size becomes larger. With the increase of Zn/Y, the number of LPSO phase decreases and the size of.Mg-Ni-Zn-Y amorphous composite is related to the morphology and volume fraction of LPSO phase, and the LPSO phase size is suitable. When the distribution is uniform and the volume fraction is higher, the plasticity of the composite is improved. With the increase of the volume fraction of the LPSO phase, the plasticity of the composite increases obviously and the strength changes little. The optimum composition range is a triangle, and the alloy components at its three vertices are Mg_ (8) 3Ni_6Zn_5Y_6, Mg_ (79) Ni_8Zn_5Y_8 and Mg_ (7), respectively. 9.68) Ni_8Zn_5Y_ (7.32). The fracture mechanism and fracture characteristics of Mg-Ni-Zn-Y amorphous composites are obtained. The fracture mechanism shows that the slip of the amorphous shear band is hindered by the long periodic phase and the new shear band is induced by the long period phase deformation. When this process runs through the whole sample slip surface, the sample will break the.Mg-Ni-Zn-Y amorphous composite. The fracture can be divided into crystal phase characteristic area, tearing characteristic area and pulse pattern feature area, in which the crystalline phase characteristic area can be acicular phase or smooth alpha -Mg phase slip zone. The tearing characteristic area is corresponding to the sawtooth discontinuous stress strain curve, and the characteristic area of the pulse pattern is the result of the melting and aggregation of the amorphous matrix caused by the adiabatic shearing. The occurrence of this area can be suppressed by the occurrence of cracks.
【學(xué)位授予單位】：沈陽(yáng)工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG139.8

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