IB DT: Topic 4.2a: Metals and alloys (copy)

credits https://sites.google.com/view/designandinquiry/dp-sl-design/topic-4-final-production/4-2-materials/4-2a-metals-and-metallic-alloys?authuser=0

what is an ore? what is the extraction process like?

rocks that contain metals that can be economically extracted - not evenly distributed around the world, localised in certain areas. sometimes mined in one area and then transported to another where the metals are extracted. extracting metal from ore is complex and energy intensive.

what are metals made up of?

metals are crystalline structures made up of grains

how is grain size determined, and what does it influence?

grain size is influenced by the type of heat treatment a metal receives while it is cooling. rapid cooling forms small grains, slow cooling forms large grains.

• large grains = slow cooling = high tensile strength, toughness, ductility and malleability

• small grains = fast cooling = low tensile strength, toughness and ductility - high brittleness

what is alloying?

mixing one metal with another material (metal or non-metal) - this combination creates a material that has unique properties than if the metal was just used alone. generally, alloying increases hardness and strength and reduces malleability and ductility.

what are the three most common alloys?

• steel: iron and carbon

• bronze: copper and tin

• brass: copper and zinc

what is work hardening?

the process of increasing the hardness of a metal through applying a process when the metal is cold. the most common work hardening method is the application of force to compress the grains through cold rolling.

what is tempering?

the application of heat after work hardening. this reduces some of the hardness and stiffness and increase the toughness and ductility of the metal.

what is a super alloy?

metal alloys that exhibit high degrees of mechanical strength, resistance to corrosion and surface stability.

specifically, a high resistance to creep and high oxidation and corrosion resistance.

what is creep?

the slow expansion or deformation of a material over time. can be exaggerated by high temperatures and prolonged forces.

what is oxidation?

the reaction of a metal with oxygen (e.g. rust). metals may also corrode in the presence of high temperatures and acids or alkalis.

how are metals recovered and disposed of? is this eco-friendly?

metals and metal alloys are easily recyclable. compared to the extraction of raw materials, recycling metals uses less energy, produces less waste and uses materials that have already been extracted.

metals can be infinitely recycled, unlike plastics which can degrade in quality and properties through recycling.

what is design for disassembly? how does it relate to metals and alloys?

• allows for products to be easily and efficiently disassembled without the need for specialised tools, machines or processes.

• since many consumer products such as phones, computers and even cars use large quantities of valuable metals, effective dfd can ensure the environmental impact of the design is reduced.

what are the design contexts of different ferrous metals?

• mild steel: car body parts, general engineering, nuts, bolts, nails, screws

• stainless steel: cutlery, cooking and cleaning surfaces

• cast iron: heavy duty machinery, vices and clamps

what are the design contexts of different non-ferrous metals?

• aluminium: soft drink cans, kitchen foil, engine components

• copper: printed circuits

• silver: jewellery

• tin: solder, tin cans

• zinc: galvanising (protective coatings that protect against corrosion)

what are the different design contexts of alloys?

• brass: castings, marine and plumbing fittings

• high speed steel: used for cutting tools such as drills and saw blades