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首頁> 外文學(xué)位 >The physical modeling of grain boundary liquation mechanisms within the heat-affected zone of an aluminum-copper alloy.
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The physical modeling of grain boundary liquation mechanisms within the heat-affected zone of an aluminum-copper alloy.

機譯：鋁銅合金熱影響區(qū)內(nèi)晶界液化機理的物理模型。

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摘要

This dissertation describes the results of a research program which was conducted to physically model, weld heat-affected zone (HAZ) liquation processes observed in Aluminum alloys during welding in the absence of an external strain. Three liquation processes were analyzed using a binary Al-3Cu alloy: (1) intergranular liquid infiltration from the fusion zone; (2) sub-solidus (below the equilibrium solidus temperature) grain boundary liquation due to non-equilibrium segregation during welding; and, (3) sub-solidus liquation (constitutional liquation) of undissolved precipitates in the matrix and along the grain boundary.; Silicon, from an Al-Si filler metal, was observed at the base metal, HAZ grain boundaries, of a solution treated Al-3Cu alloy after gas-tungsten arc welding. With no evidence for crack-backfilling, the mechanism of transport of fusion zone material into the matrix was tentatively identified as liquid metal penetration of grain boundaries governed by liquid diffusion kinetics.; Grain boundary regions in the heat-affected zone (HAZ) of arc welds, in a solution treated Al-3Cu alloy, were examined for liquation susceptibility. The welding experiments showed that certain grain boundaries, adjacent to the fusion line, were depleted in solute (copper), but were not liquated.; Investigation of the third mechanism, involved a comprehensive study of the solid-state, dissolution and liquation-dissolution of matrix and grain boundary precipitates. This represents the first complete study of its type, for any alloy system. The isothermal kinetics of solid-state and liquation-dissolution of &thetas; (Al2Cu) precipitates, were fully quantified during salt bath annealing.; The stability of the grain boundary precipitate dispersion was examined in order to determine the susceptibility of the grain boundary microstructure to liquation. These latter experiments were facilitated by a large, “static” grain structure, and this study may mark the first time that any grain boundary particle dispersion has been fully quantified as a function of time.; Previously derived analytical equations, for approximating the dissolution of metastable precipitates in the matrix, were utilized to: (1) analyze the present, and previous experimental isothermal dissolution kinetics, (2) reproduce isothermal dissolution data; (3) predict solid-state dissolution and liquation-dissolution, during continuous heating processes. (Abstract shortened by UMI.)
機譯：本文描述了一個研究程序的結(jié)果，該程序是對鋁合金在沒有外部應(yīng)變的情況下在焊接過程中觀察到的焊接熱影響區(qū)（HAZ）液化過程進行物理建模的結(jié)果。使用二元Al-3Cu合金分析了三個液化過程：（1）熔融區(qū)的晶間液體滲透; （2）由于焊接過程中非平衡偏析而導(dǎo)致的亞固相線（低于平衡固相線溫度）; （3）基質(zhì)中和沿晶界的未溶解沉淀物的亞固相液化（組成液化）；在鎢極氬弧焊之后，在固溶處理的Al-3Cu合金的賤金屬HAZ晶界處觀察到來自Al-Si填充金屬的硅。在沒有裂紋回填的證據(jù)的情況下，融合區(qū)材料向基體中的傳輸機制初步確定為晶界的液態(tài)金屬滲透，受液體擴散動力學(xué)控制。在固溶處理的Al-3Cu合金中，檢查了電弧焊熱影響區(qū)（HAZ）的晶界區(qū)域的液化敏感性。焊接實驗表明，熔合線附近的某些晶界被溶質(zhì)（銅）所耗盡，但沒有被液化。第三種機理的研究涉及對基質(zhì)和晶界沉淀物的固態(tài)，溶解和液化-溶解的綜合研究。這是對任何合金系統(tǒng)進行的首次此類類型的完整研究。 θ的固態(tài)和液-固溶解的等溫動力學(xué)； （Al 2 Cu）沉淀物在鹽浴退火過程中被完全定量；為了確定晶界微觀結(jié)構(gòu)對液化的敏感性，檢查了晶界沉淀物分散體的穩(wěn)定性。后面的這些實驗是通過一個大的“靜態(tài)”晶粒結(jié)構(gòu)來進行的，這項研究可能標志著第一次晶界顆粒彌散度是隨時間變化的。先前推導(dǎo)的分析方程式，用于近似于基質(zhì)中亞穩(wěn)態(tài)沉淀的溶解，用于：（1）分析當前和先前的實驗等溫溶解動力學(xué)，（2）再現(xiàn)等溫溶解數(shù)據(jù); （3）預(yù)測連續(xù)加熱過程中的固態(tài)溶解度和液化溶解度。 （摘要由UMI縮短。）

著錄項

  • 作者

    Wilson, Andre Lamont.;

  • 作者單位

    The Pennsylvania State University.;

  • 授予單位 The Pennsylvania State University.;
  • 學(xué)科 Engineering Metallurgy.; Engineering Materials Science.
  • 學(xué)位 Ph.D.
  • 年度 2001
  • 頁碼 339 p.
  • 總頁數(shù) 339
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 冶金工業(yè);工程材料學(xué);
  • 關(guān)鍵詞

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