Chapter 13. Nonferrous Alloys

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1 Chapter 13. Nonferrous Alloys
[계보: 무기재료금속재료비철재료] Objectives of Chapter 13 Explore the properties and applications of Cu, Al, and Ti alloys in load-bearing applications. [Nonferrous alloy(비철금속)의 분류] 경량금속과 그 합금: Al, Mg, Be, Ti 내화금속과 그 합금: Nb, Mo, Ta, W 귀 금 속과 그 합금: Au, Ag, Pd, Pt, Rh 기타 비철금속 : Cu, Ni, Co 의 특징과 응용에 대하여 공부함.

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[Al, Cu, Be, Ti, Ni, Co, Au, W,…]

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Chapter Outline ⇒ 비강도 개념 13.1 Aluminum Alloys 13.2 Magnesium and Beryllium Alloys 13.3 Copper Alloys 13.4 Nickel and Cobalt Alloys 13.5 Titanium Alloys 13.6 Refractory and Precious Metals Basic oxygen furnace (전로) 비강도 = 강도/ 밀도 (13-1)

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비철재료의 중요성: 높은 비강도 지각에서 비철재료의 존재량

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(Tm) Density(g/cc) ** 비중과 밀도를 구분해서 설명하세요.

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Section Aluminum Alloys Hall-Heroult process - An electrolytic process by which aluminum is extracted from its ore. Temper designation - A shorthand notation using letters and numbers to describe the processing of an alloy. H tempers refer to cold-worked alloys; T tempers refer to age-hardening treatments. Al (2.7g/cc, Tm = 660℃, FCC) Example 13.1 확인요망

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Hall-Heroult process [가장 경제적인 Al 제조 공정] Al2O3 (alumina) melted to Na3AlF6 (molten cryolite) Al+3 + 3e-1 ⇒ Al (cathode) 2O-2 + C ⇒ CO2 + 4e-1 (anode) Figure Production of aluminum in an electrolytic cell.

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강화효과: 순수한 Al 에 비해서 age-hardened Al alloy는 elongation은 줄어들지만 tensile strength와 yield strength는 약 30배 증가함을 알 수 있음.

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(가공합금) [저융점 재료] ** Al의 표시법: 30계열과 40계열의 차이

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[40계열 Al의 특정: Si ??]

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1xxx, 3xxx wrought alloys consist of single-phase except for small amounts of inclusions or intermetallic compounds. Figure 13.2 (a) FeAl3 inclusions in annealed 1100 aluminum ( 350). (b) Mg2Si precipitates in annealed 5457 aluminum alloy ( 75).

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Solid solution Solubility line Two phases Figure Portion of the aluminum-magnesium phase diagram. (age hardening alloy의 전형적인 상태도)

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As the cooling rate increases Figure (a) Sand-cast 443 aluminum alloy containing coarse silicon and inclusions. (b) Permanent-mold 443 alloy containing fine dendrite cells and fine silicon due to faster cooling. (c) Die-cast 443 alloy with a still finer microstructure ( 350).

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Section Magnesium and Beryllium Alloys Magnesium alloys are used in aerospace applications, high-speed machinery, and transportation and materials handling equipment. Instrument grade beryllium is used in inertial guidance systems where the elastic deformation must be minimal; structural grades are used in aerospace applications; and nuclear applications take advantage of the transparency of beryllium to electromagnetic radiation. Beryllium is expensive, brittle, reactive, and toxic. Mg (1.74g/cc, Tm = 650℃, HCP): 바다물의 마그네슘염화물(Magnesium chloride)로부터 전해에 의해서 추출됨 Be (1.85g/cc, Tm = 1290℃, hex): E = 4.2x106 psi로 steel 보다 큰 E값 가짐  변형이 엄격히 제한되는 곳 사용

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** Lever rule를 정의하세요. Figure The magnesium-aluminum phase diagram. b T a c

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Section 13.3 Copper Alloys Blister copper(조동) - An impure form of copper obtained during the copper refining process. Applications for copper-based alloys include electrical components (such as wire), pumps, valves, and plumbing parts, where these properties are used to advantage. Brass(황동) - A group of copper-based alloys, normally containing zinc (Zn) as the major alloying element. Bronze(청동) - Generally, copper alloys containing tin (Sn), can contain other elements. Cu (8.9g/cc, Tm = 1083℃, FCC): 건식제련(pyrometallurgical process) : Cu ore ⇒ Cu sulphide 변환

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** Annealed Cu와 cold worked Cu 및 age hardened Cu의 비교!

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많은 동합금의 경우 single phase 조직을 유지하면서도 많은 양의 합금원소를 고용한다. (Cu-40%Zn, Cu-10%Sn, Cu-9%Al, Cu-3%Si...) ⇒ Solid-solution-strengthened alloys Figure 13.6 Binary phase diagrams for the (a) Cu-Zn, (b) Cu-Sn, (c) Cu-Al, and (d) Cu-Be systems. ** Cu-Be: 베릴륨 동합금 ⇒Age-hardenable alloys

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Section Nickel and Cobalt Alloys Nickel and cobalt alloys are used for corrosion protection and for high-temperature resistance, taking advantage of their high melting points and high strengths. Superalloys - A group of nickel, iron-nickel, and cobalt-based alloys that have exceptional heat resistance, creep resistance, and corrosion resistance. Ni (8.9g/cc, Tm = 1453℃, FCC): 높은 융점과 높은 강도, 내부식성(STS 재료), 슈퍼알로이 재료  우수한 크립특성 Co (8.8g/cc, Tm = 1495℃, HCP  FCC:고온): 높은 융점과 높은 강도, 마모저항 재료, 보철기구(prosthetic), 슈퍼알로이 재료

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Monel: 60Ni-40Cu 염수와 고온에서 강도와 내식성 우수함. Small amounts of Al and Ti ⇒ Age-hardening by the precipitation of γ’, a coherent Ni3Al or Ni3Ti precipitate. The precipitates resist overaging at temperatures up to 425oC. 인코넬: 니켈을 주체로 하여 15%의 크롬, 6∼7%의 철, 2.5%의 티탄, 1% 이하의 알루미늄·망간·규소를 첨가한 내열합금이다. Figure 13.7 The effect of temperature on the tensile strength of several nickel-based alloys.

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Figure (a) Microstructure of a superalloy, with carbides at the grain boundaries and γ΄ precipitates in the matrix ( 15,000) (b) Microstructure of a superalloy aged at two temperatures, producing both large and small cubical γ΄ precipitates ( 10,000).

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[Turbine blade에서 공냉 원리] Figure 13.9 A turbine blade designed for active cooling by a gas. (b) The high-temperature capability of superalloys has increased with improvements in manufacturing methods (for Example 13.7). ** Single XL, one directional solidified, conventional polycrystalline를 구분해서 설명하세요. [원자배열 측면에서 ]

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Section Titanium Alloys Titanium’s excellent corrosion resistance provides applications in chemical processing equipment, marine components, and biomedical implants such as hip prostheses. (also: heat exchanger) Titanium is an important aerospace material, finding applications as airframe and jet engine components. Titanium alloys are considered biocompatible (i.e., they are not rejected by the body). By developing porous coatings of bone-like ceramic compositions known as hydroxyapatite, it may be possible to make titanium implants bioactive (i.e., the natural bone can grow into the hydroxyapatite coating). Ti (4.5g/cc, Tm = 1668℃) HCP,  882℃  BCC,: 진공상태에서 제조, 높은 비강도, 뛰어난 내식성( <TiO2 피막, 535℃)

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** Ti, Al, Ni, Cu, steel의 kg당 가격은 얼마일까?

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Section Refractory and Precious Metals Refractory metals(내화금속) – These include tungsten, molybdenum, tantalum, and niobium (or columbium), have exceptionally high-melting temperatures (above 1925oC) and, consequently, have the potential for high-temperature service. Applications of Refractory metals include filaments for light bulbs, rocket nozzles, nuclear power generators, tantalum- and niobium-based electronic capacitors, and chemical processing equipment. Precious Metals(귀금속) - These include gold, silver, palladium, platinum, and rhodium. From an engineering viewpoint, these materials resist corrosion and make very good conductors of electricity.

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Nanosized particles of Pt/Rh/Pd loaded onto a ceramic honeycomb are used as catalysts in automobiles. CO ⇒ CO2; NOx ⇒ N2 + O2

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단원 정리를 위한 숙제 1. 경량금속(light metals)을 정의하고, 대표적인 경량금속의 예를 4가지 이상 들라. 2. Al, Mg, Be, Cu, Ti, Ni 금속에 대한 density, melting point, Structure를 쓰라. 3. 내화금속(refractory metals)을 정의하고, 대표적인 금속의 종류를 들어보라. 4. 귀금속(precious metals)을 정의하고, 5. Cu, Al, Ti 금속 및 그 합금의 종류와 사용용도에 대해서 약술하라. ** 본 단원의 모든 예제문제를 이해한 후, 풀이과정을 기술해서 제출하시오