難熔金屬元素對模型Ni-Al-Cr基高溫合金相析出行為影響研究
發(fā)布時間：2019-05-09 05:28
【摘要】：鎳基高溫合金由于其獨特的雙相組織而具備優(yōu)異的高溫機械性能和抗氧化等綜合性能,已成為制造先進航空航天發(fā)動機和燃氣輪機葉片的主要材料�，F(xiàn)代商用鎳基合金大多在Ni-Al-Cr三元系基礎(chǔ)上添加多種合金元素(尤其是難熔金屬元素)制備而成。這些難熔金屬元素同時分布于γ(FCC)和γ'(L12)兩相,主導(dǎo)合金的相析出行為,對合金顯微組織和高溫力學(xué)性能有決定性的影響。因此,開展難熔金屬元素對鎳基合金相析出行為影響的研究,為高性能合金優(yōu)化設(shè)計提供理論指導(dǎo),具有一定的科學(xué)意義及實踐價值。本課題在美國西北大學(xué)原子探針技術(shù)中心開展的鎳基高溫合金及難熔金屬元素添加對合金性能影響研究體系基礎(chǔ)上,采用原子探針層析技術(shù)(Atom probe tomography,APT)和第一性原理等實驗和理論方法,針對不同固溶時效參數(shù)下的多種模型Ni-Al-Cr基合金,研究分析難熔金屬元素R(W、Re、Ru、Ta)對模型合金納米結(jié)構(gòu)、化學(xué)成分及界面特征的影響,主要研究內(nèi)容及結(jié)論如下:(1)探索難熔金屬元素W、Re交互作用對模型Ni-Al-Cr基合金析出相納米結(jié)構(gòu)演化的影響。利用APT實現(xiàn)元素原子的三維重構(gòu),實驗結(jié)果顯示,在淬火狀態(tài)下的合金中,已有球形γ'相顆粒析出。淬火狀態(tài)和時效0.25 h時,部分γ'相顆粒由脖頸連通,說明在早期粗化階段,經(jīng)典Ostwald熟化機制和析出相顆粒合并機制共存。隨著時效時間延長,析出相平均半徑不斷增大,數(shù)量密度則不斷降低。在析出相體積分數(shù)穩(wěn)定時效期間,平均半徑和數(shù)量密度粗化時間指數(shù)和UO模型預(yù)測值接近,說明合金至少處于準(zhǔn)穩(wěn)態(tài)粗化狀態(tài)。(2)分析W、Re對模型Ni-Al-Cr基合金化學(xué)演化的影響,測試分析相析出過程中合金元素在兩相和界面區(qū)域的分布規(guī)律。結(jié)果顯示,在整個時效過程中,Ni的兩相濃度無明顯變化,Al、W元素不斷擴散進入γ'相,Cr、Re元素則傾向流入基體相。W、Re元素擴散性能較差,在兩相中的分配演化速率緩慢,因此,添加W、Re可減緩合金成分平衡進程。合金界面寬度值隨時效時間延長而變小,時效256 h后,標(biāo)準(zhǔn)化界面寬度趨于零,說明長期時效后合金的界面區(qū)域非常狹窄。(3)結(jié)合APT和顯微硬度測試結(jié)果,針對系統(tǒng)添加難熔金屬元素的多種模型Ni-Al-Cr基合金,開展長期時效后合金元素分布規(guī)律研究。研究結(jié)果表明,難熔金屬元素Re、Ru優(yōu)先分配至γ相,W、Ta原子則更多分布在γ'相中,4種元素均優(yōu)先占據(jù)γ'(L12)相的Al位。添加難熔金屬元素后,更多Ni原子停留于γ相中。難熔金屬元素可強化Al、Cr兩相分配行為,提高析出相體積分數(shù),對兩者的強化效果遵循同樣規(guī)律。得益于難熔金屬元素的固溶強化作用與γ'相體積分數(shù)的增長,合金硬度提高。(4)分析模型Ni-Al-Cr基合金長期時效后仍然存在的Ni界面過�，F(xiàn)象,探索添加難熔金屬元素對界面偏聚行為的影響機制。結(jié)合實驗APT徑向分布函數(shù)以及第一性原理計算結(jié)果,對R(W、Re、Ru、Ta)和S(S=Al、Cr)原子結(jié)合能進行計算,并分析R和S原子之間的空間相關(guān)性和結(jié)合能狀態(tài)。分析結(jié)果顯示,難熔金屬元素和溶質(zhì)元素原子之間存在化學(xué)結(jié)合能,R-S結(jié)合能會改變進出γ'相元素的擴散流矢量,增大界面區(qū)域?qū)挾?導(dǎo)致界面處Ni原子局部富集和貧化行為更為顯著。由于難熔金屬元素在基體中擴散速率相對較慢,R-Cr吸引結(jié)合能將減緩溶質(zhì)擴散流,導(dǎo)致Ni擴散性能下降,阻滯Ni原子在界面附近的遷移。
[Abstract]:The nickel-based high-temperature alloy has excellent high-temperature mechanical property and oxidation resistance due to its unique dual-phase structure, and has become the main material for manufacturing advanced aerospace engine and gas turbine blade. Modern commercial nickel-based alloys are mostly prepared by adding various alloying elements (especially refractory metal elements) on the basis of the Ni-Al-Cr ternary system. These refractory metal elements are also distributed in the two phases of the two phases of the metal (FCC) and the sulfur (L12), and the phase precipitation behavior of the main alloy has a decisive influence on the microstructure and the high-temperature mechanical properties of the alloy. Therefore, the research on the influence of the refractory metal elements on the precipitation behavior of the nickel-based alloy is carried out, In order to provide theoretical guidance for high-performance alloy optimization design, it is of scientific significance and practical value. The nickel-based high-temperature alloy and refractory metal element in the technology center of the atomic probe of Northwestern University of the United States have been added to the research system of the effect of the alloy on the properties of the alloy. Based on the experimental and theoretical methods of atomic probe tomography (APT) and the first principle, a variety of Ni-Al-Cr based alloys with different solution aging parameters were studied, and the nano-structure of the model was studied by the study of the refractory metal elements R (W, Re, Ru, Ta). The main research contents and conclusions are as follows: (1) The influence of the interaction of refractory metal elements W and Re on the evolution of the precipitation phase of the model Ni-Al-Cr based alloy is studied. The three-dimensional reconstruction of the element atoms is realized by APT, and the results show that, In the alloy in the quenching state, the spherical graphite 'phase particles are precipitated. In that quench state and the age of 0.25 h, some of the phase-phase particles are in communication with the neck, which indicate that the classical Ostwald ripening mechanism and the precipitation-phase particle combine mechanism coexist in the early coarsening stage, and the average radius of the precipitated phase increases as the aging time is prolonged. (2) analyzing the effect of W and Re on the chemical evolution of the model Ni-Al-Cr based alloy, The distribution of the alloying elements in the two phases and the interface region during the precipitation process of the test and analysis phase is studied. The results show that, during the whole aging process, the two-phase concentration of Ni is not obviously changed, and the Al and W elements continue to diffuse into the matrix phase, and the elements of Cr and Re tend to flow into the matrix phase. W, Re element diffusion performance is poor, the distribution and evolution rate of the two phases is slow, and therefore, adding W and Re can slow down the balance process of the alloy composition. The interface width of the alloy becomes smaller at any time, and after the aging is 256 h, the width of the standardized interface tends to be zero, which indicates that the interface region of the alloy after the long-term aging is very narrow. And (3) combining the results of APT and microhardness test, and carrying out the study on the distribution of the alloy elements after long-term aging for various models of Ni-Al-Cr based alloy with refractory metal elements added to the system. The results show that the refractory metal elements Re and Ru are preferentially distributed to the Al phase, W and Ta atoms are more distributed in the 1 'phase, and the four elements preferentially occupy the Al position of the 1' (L12) phase. After the addition of the refractory metal elements, the more Ni atoms stay in the conductive phase. The refractory metal element can strengthen the two-phase distribution of Al and Cr, improve the volume fraction of the precipitated phase, and observe the same law for the strengthening effect of the two phases. due to the increase of the solid solution strengthening effect of the refractory metal element and the volume fraction of the graphite ', the hardness of the alloy is improved. (4) the Ni-Al-Cr based alloy still has an excess of the Ni interface after the long-term aging of the Ni-Al-Cr based alloy, The binding energy of R (W, Re, Ru, Ta) and S (S = Al, Cr) is calculated by combining the radial distribution function of APT and the calculation result of the first principle. and the spatial correlation and the binding energy state between the R and S atoms are analyzed. The analysis results show that the chemical binding energy exists between the refractory metal element and the solute element atom, the binding energy of the R-S changes the diffusion flow vector of the element of the inlet and outlet ', and the width of the interface area is increased, Resulting in a more significant local enrichment and depletion behavior of the ni atoms at the interface. Because the diffusion rate of the refractory metal elements in the matrix is relatively slow, the binding energy of the R-Cr will slow the diffusion of the solute, resulting in a decrease in the diffusion of the Ni and the blocking of the migration of the Ni atoms in the vicinity of the interface.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG132.3
本文編號：2472512
[Abstract]:The nickel-based high-temperature alloy has excellent high-temperature mechanical property and oxidation resistance due to its unique dual-phase structure, and has become the main material for manufacturing advanced aerospace engine and gas turbine blade. Modern commercial nickel-based alloys are mostly prepared by adding various alloying elements (especially refractory metal elements) on the basis of the Ni-Al-Cr ternary system. These refractory metal elements are also distributed in the two phases of the two phases of the metal (FCC) and the sulfur (L12), and the phase precipitation behavior of the main alloy has a decisive influence on the microstructure and the high-temperature mechanical properties of the alloy. Therefore, the research on the influence of the refractory metal elements on the precipitation behavior of the nickel-based alloy is carried out, In order to provide theoretical guidance for high-performance alloy optimization design, it is of scientific significance and practical value. The nickel-based high-temperature alloy and refractory metal element in the technology center of the atomic probe of Northwestern University of the United States have been added to the research system of the effect of the alloy on the properties of the alloy. Based on the experimental and theoretical methods of atomic probe tomography (APT) and the first principle, a variety of Ni-Al-Cr based alloys with different solution aging parameters were studied, and the nano-structure of the model was studied by the study of the refractory metal elements R (W, Re, Ru, Ta). The main research contents and conclusions are as follows: (1) The influence of the interaction of refractory metal elements W and Re on the evolution of the precipitation phase of the model Ni-Al-Cr based alloy is studied. The three-dimensional reconstruction of the element atoms is realized by APT, and the results show that, In the alloy in the quenching state, the spherical graphite 'phase particles are precipitated. In that quench state and the age of 0.25 h, some of the phase-phase particles are in communication with the neck, which indicate that the classical Ostwald ripening mechanism and the precipitation-phase particle combine mechanism coexist in the early coarsening stage, and the average radius of the precipitated phase increases as the aging time is prolonged. (2) analyzing the effect of W and Re on the chemical evolution of the model Ni-Al-Cr based alloy, The distribution of the alloying elements in the two phases and the interface region during the precipitation process of the test and analysis phase is studied. The results show that, during the whole aging process, the two-phase concentration of Ni is not obviously changed, and the Al and W elements continue to diffuse into the matrix phase, and the elements of Cr and Re tend to flow into the matrix phase. W, Re element diffusion performance is poor, the distribution and evolution rate of the two phases is slow, and therefore, adding W and Re can slow down the balance process of the alloy composition. The interface width of the alloy becomes smaller at any time, and after the aging is 256 h, the width of the standardized interface tends to be zero, which indicates that the interface region of the alloy after the long-term aging is very narrow. And (3) combining the results of APT and microhardness test, and carrying out the study on the distribution of the alloy elements after long-term aging for various models of Ni-Al-Cr based alloy with refractory metal elements added to the system. The results show that the refractory metal elements Re and Ru are preferentially distributed to the Al phase, W and Ta atoms are more distributed in the 1 'phase, and the four elements preferentially occupy the Al position of the 1' (L12) phase. After the addition of the refractory metal elements, the more Ni atoms stay in the conductive phase. The refractory metal element can strengthen the two-phase distribution of Al and Cr, improve the volume fraction of the precipitated phase, and observe the same law for the strengthening effect of the two phases. due to the increase of the solid solution strengthening effect of the refractory metal element and the volume fraction of the graphite ', the hardness of the alloy is improved. (4) the Ni-Al-Cr based alloy still has an excess of the Ni interface after the long-term aging of the Ni-Al-Cr based alloy, The binding energy of R (W, Re, Ru, Ta) and S (S = Al, Cr) is calculated by combining the radial distribution function of APT and the calculation result of the first principle. and the spatial correlation and the binding energy state between the R and S atoms are analyzed. The analysis results show that the chemical binding energy exists between the refractory metal element and the solute element atom, the binding energy of the R-S changes the diffusion flow vector of the element of the inlet and outlet ', and the width of the interface area is increased, Resulting in a more significant local enrichment and depletion behavior of the ni atoms at the interface. Because the diffusion rate of the refractory metal elements in the matrix is relatively slow, the binding energy of the R-Cr will slow the diffusion of the solute, resulting in a decrease in the diffusion of the Ni and the blocking of the migration of the Ni atoms in the vicinity of the interface.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG132.3
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