1、Chapter 8 Nonferrous Metals and Alloys,Most engineering metallic materials are alloys. Metals are alloyed to enhance their properties, such as strength, hardness or corrosion resistance, and to create new properties, such as shape memory effect. Engineering alloys can be broadly divided into Ferrous

2、 Alloys and Non-ferrous Alloys,Al alloys,Cu alloys,Ti alloys,Mg alloys,Other alloys,Pure Cu Brasses Bronzes Be-copper Nickel silver,Cu Mg Mn Si Zn,a b a+b,Ni-based Pb-based Sn-based Zn-based Zr-based Refractory metals Superalloys Noble alloys,Al Zn,8.1 Al and its Alloys,Low melting point 660.4 Low d

3、ensity (2.7) - 1/3 of that of steel higher strength-to-weight ratio High electrical conductivity - 60% of that of Cu higher conductivity-to-weight ratio High thermal conductivity High oxidation resistance FCC crystal structure: ductile and good formability - easy mechanical processing Easy machining

4、, castable and mostly weldable Nonmagnetic; nontoxic Most recyclable metal - only 5% of production energy required Al alloys are used mostly for four reasons: specific strength, corrosion resistance, electrical conductivity and nontoxity.,Consumption of Al and its Alloys,Containers and packaging (no

5、ntoxity),Electrical conductors (conductivity),Architectural construction (corrosion resistance),Structural applications (strength-to-weight ratio),Aeroplane wing made of Al alloys for their high strength-weight ratio,Proportions of different materials in mobile indurstry,Al is too soft for structura

6、l applications. It is alloyed to improve strength. Al is mainly alloyed with any or combination of five elements: Cu, Mn, Mg, Zn, Si In addition to alloying, Al alloys are also hardened by cold working and by precipitation hardening. Typical mechanical properties: Low elastic modulus: 70 GPa Yield s

7、trength: 100400MPa No ductile-brittle transition at low temperatures,鋁合金分類示意圖,鋁合金型材,鋁鑄件,汽缸頭,Problems of Al Alloys in Application,Low fatigue resistance - virtually no endurance limit Unsuitable for working at elevated temperatures Low elastic modulus Prone to pitting in waters containing heavy ions

8、Attacked readily by strong caustic solutions Anodic to most metals,There are some 200 Al alloys commercially available. The following are commonly used ones: Wrought: 1100 (pure), 3003, 5052, 6061*, 7075* Sand cast: 355.0* Die cast: 380.0 *: can be hardened by heat treatment,Recycling of Al,Al is th

9、e most recyclable metal. The energy (cost) consumed to reproduce one tone of Al from scrap is 5% of that consumed to produce 1 tone premier Al from minerals. This is mainly due to two facts: (1) Al has a low melting temperature (little energy is required for melting) and (2) Al is corrosion resistan

10、t (so little metal is lost). Currently 30% of the world Al consumption comes from recycled products. In developed countries, 41% Al beverage cans are recycled.,8.2 Cu and its Alloys,General properties Yield strength: 20-200 MPa Tensile: 200-400 MPa Youngs modulus: 117 GPa FCC structure: excellent fo

11、rmability Exhibits no sub-zero T embrittlement Castable and weldable Corrosion resistant High thermal conductivity High electrical conductivity,50% copper produced are consumed as electrical conductors,冷凝器管,Cu Alloys Designation (Copper Development Association: CDA),CDAUNS 100C10000 . 799C79900 800C

12、80000 999C99900,Wrought,Cast,Cu and its Alloys,Commercially Pure Coppers Electrical tough pitch (ETP) copper: used for conductors Deoxidised phosphorus copper: heat conductors, piping, tubing, heat exchangers Beryllium Copper (1.5-2.0%Be) (C172000) precipitation hardened high strength comparable to

13、steels: up to 1400 MPa used for springs, bearings, high-strength components Bronzes (up to 13%Sn) Silicon bronze (Cu-Sn-Si, 4%) Aluminium bronze (Cu-Al, 8-12%) excellent castbility good metal-metal wear resistance when lubricated,鈹青銅制品,Cu and its Alloys,Brasses (up to 50%Zn) a-brass: FCC, up to 35%Z

14、n red-brass: 15%Zn yellow-brass: 30%Zn, Naval brass, admiralty brass: yellow brasses + 2% Sn to improve pitting resistance in seawater. b-brass:BCC+FCC, 40-50%Zn: Muntz metal (UNSC28000) Copper-Nickel Alloys (Cupronickel, 90/10 and 70/30) High ductility and formability excellent corrosion resistance

15、 in seawater Strengthened by cold working 85/15 alloy for coinage 70/30 alloy for seawater piping, heat exchangers Copper-Zinc-Nickel Alloys (Nickel Silver) Pale yellow at 10-12%Ni, silver white at 20-30%Ni Decorative applications and silver plated dinnerware,Cu and its Alloys,There are some 800 Cu

16、alloys commercially available. The average designer could solve most application problems with 10 alloys: ETP copper: C11000 (99.9%)(electric tough pitch copper) DHP copper: C12200 (99.9%)(deoxidized high phosphorus copper) Beryllium copper: C17200 Red brass: C23000 (85Cu-15Zn) Yellow brass: C26000

17、(70Cu-30Zn) Free cutting, yellow brass: C36000 (62Cu-35Zn-3Pb) Tin bronze: C90700 (89Cu-11Sn) Lead tine bronze: C94300 (70Cu-5Sn-25Pb),8.3 Ti and its Alloys,Light alloys: Al (2.7), Be (1.85), Mg (1.74), Ti (4.51) The demand for materials of high strength-to-weight ratios from the aerospace and aircr

18、aft industry and more recently from automobile and other transportation industries has promoted the development of these light alloys.,World consumption of titanium and titanium alloy mill products was about 56,000t in 2000, and a further 29,000t was consumed mainly as ferro-titanium in steel and ot

19、her alloys.,Melting temperature: 1678 C Modulus of elasticity: 127 GPa Low density: 4.5 g/cm3 Strengthenable by alloying aero-engines; airframes; commercial and military aerospace industry; space flight Industrial applications: chemical and petrochemical; metal recovery and refining; oil and gas ind

20、ustry; geothermal energy; marine applications; thermal power generation shape memory alloys,鈦合金泵,鈦合金衛(wèi)星框架,鈦管換熱器,8.4 Mg and its Alloys,Over 50% of Mg production are consumed in Al alloys therefore Pb alloys have been developed to improve its physical and mechanical properties. Chemical lead is lead wi

21、th traces of copper and silver left in from the original ore. It is not economical to recover the copper and silver. The copper content is believed to improve the general corrosion resistance and to add stiffness.,Antimonial lead (also called hard lead) is an alloy containing from 2 to 6 wt. % antim

22、ony (Sb) to improve the mechanical properties. It is used in places where greater strength is needed. Hard lead can be used in services up to 93 C. Above this temperature strength and corrosion resistance are reduced. Tellurium lead is a lead alloy containing a fraction of a percent of tellurium (Te

23、). This alloy has better resistance to fatigue failure caused by vibration because of its ability to work harden under strain.,8.5.3 Sn and its Alloys,Sn has two allotropes: a-Sn (grey tin) and b-Sn (white tin). At room temperature, the metallic b-Sn called white tin exhibits a structure having a te

24、tragonal crystal lattice and a high density (7.298 g/cm3), while below the transition temperature of 13.1 C the thermodynamic stable form is the a-Sn, also called grey tin, with a cubic crystal lattice of diamond and exhibiting a much lower density (5.75 g/cm3).,Applications: Solder is now the large

25、st end-use application for Sn, accounting for 36% of total consumption. Tin use in solder has grown very rapidly in recent years with the boom in consumer electrical appliances and electronics. The second important market for tin is in the chemical industries (28%) as a heat stabilizing additive in

26、PVC, catalyst, additive in pigment, and in flame retardants.,巴氏合金軸瓦,焊料,8.5.4 Zn and its Alloys,Pure zinc (Zn) is a hard, dense (7.133 g/cm3), and low-melting-point (419.527 C) metal with a bluish-white luster when freshly cut; it is not tarnished in dry air but becomes slightly tarnished in moist ai

27、r. It exhibits a low electrical resistivity (5.916 .cm) and a good thermal conductivity (113 Wm-1K-1). Zinc crystal structure is hexagonal close-packed (hcp), which explains its hardness at room temperature.,The most important property of zinc metal is its ability to form an alloy with iron so that

28、a thin adherent layer can be applied to the surface of iron workpieces. The zinc coating, obtained either by hot-dip galvanizing or aqueous electrogalvanizing, considerably extends the service life of steel constructions. In addition, Zn alloys can be easily cast into intricate shapes that are used

29、extensively in household goods and automotive equipment, building, and construction utilities.,8.5.5 Zr and its Alloys,Zr and its alloys are ductile and have other mechanical characteristics that are comparable to those of Ti alloys and the austenitic stainless steels. However, the primary asset of

30、these alloys is their resistance to corrosion in a host of corrosive media, including superheated water. Zr is transparent to thermal neutrons, so that its alloys have been used as cladding for uranium fuel in watercooled nuclear reactors.,8.5.6 The refractory metals,Metals that have extremely high

31、melting temperatures are classified as the refractory metals. Included in this group are niobium (Nb), molybdenum (Mo), tungsten (W), and tantalum (Ta). Melting temperatures range between 2468 C for Nb and 3410 C for W, the highest melting temperature of any metal.,The applications of these metals a

32、re varied. Ta and Mo are alloyed with stainless steel to improve its corrosion resistance. Mo-based alloys are utilized for extrusion dies and structural parts in space vehicles; incandescent light filaments, x-ray tubes, and welding electrodes employ tungsten alloys. Ta is immune to chemical attack

33、 by virtually all environments at temperatures below 150 C and is frequently used in applications requiring such a corrosion-resistant material.,鉬制品,鎢棒,由鉭棒加工的熱偶套,Supertalloys are a special class of heat resistant alloys for high temperature applications, such as aircraft, marine and industrial gas t

34、urbines, space vehicles and rocket engines, nuclear reactors, submarines.,Ni-based super-alloy single crystal turbine blades,Jet Turbine engine, many interior components made of Ni-based and co-based superalloys,8.5.7 Superalloys,Superalloys,Iron-Based Superalloys: Fe(65-40%)-Ni(20-40%)-Cr(13-20%) 5

35、0% of its room-temperature strength retained at 750C; suitable for application at 700C. Nickel-Based Superalloy: Ni-Cr(10-30%, Fe, Mo) commercial proprietary alloys: Hastelloy, Inconel, Invar suitable for application at 800C. /pages/home.htm Cobalt-Based Superalloys: Co-Cr(20-30%)-Ni(10-20%) tensile strength at RT: 700-100