Crystalline Structures - Revision history

DT Online at 11:51, 22 March 2017

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	Controlled '''[[Heat Treatment]]''' of metals in general determines their '''[[Crystalline ~~Structures]]~~''', ~~the~~ '''Grain Size''' plus how and when the '''[[Alloy\|Alloying Elements]]''' or impurities precipitate. These changes can have quite dramatic effects upon the mechanical properties of some metals.		Controlled '''[[Heat Treatment]]''' of metals in general determines their '''Crystalline Structure''', or '''Grain Size''', plus how and when the '''[[Alloy\|Alloying Elements]]''' or impurities precipitate. These changes can have quite dramatic effects upon the mechanical properties of some metals.


	[[Category:Materials and Components]]		[[Category:Materials and Components]]

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			=====Heat Treatment and Grain Structure=====

			{{#ev:youtube\|uG35D_euM-0\|200x200\|right\|\|frame\|loop=1&autoplay=0&playlist=uG35D_euM-0}}
	'''[[Heat Treatment\|Tempering]]''' is a process which by controlled reheating enables the internal stress to be relieved and alters the size and distribution of carbides in the [https://en.wikipedia.org/wiki/Martensite '''Martensite'''] to improve '''[[Toughness]]''' at the expense of some '''[[Hardness]]'''.		'''[[Heat Treatment\|Tempering]]''' is a process which by controlled reheating enables the internal stress to be relieved and alters the size and distribution of carbides in the [https://en.wikipedia.org/wiki/Martensite '''Martensite'''] to improve '''[[Toughness]]''' at the expense of some '''[[Hardness]]'''.


			Controlled '''[[Heat Treatment]]''' of metals in general determines their '''[[Crystalline Structures]]''', the '''Grain Size''' plus how and when the '''[[Alloy\|Alloying Elements]]''' or impurities precipitate. These changes can have quite dramatic effects upon the mechanical properties of some metals.


	[[Category:Materials and Components]]		[[Category:Materials and Components]]

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			{{#ev:youtube\|qe6wc-jxOaM\|200x225\|right\|\|frame\|loop=1&autoplay=0&playlist=qe6wc-jxOaM}}
	The aim of [https://en.wikipedia.org/wiki/Steelmaking '''Steelmaking'''] processes such as the [https://en.wikipedia.org/wiki/Bessemer_process#Bessemer_converter '''Bessemer Converter'''] and [https://en.wikipedia.org/wiki/Open_hearth_furnace '''Open Hearth Furnace'''] ''(now superseded by [https://en.wikipedia.org/wiki/Basic_oxygen_steelmaking '''Basic Oxygen Steelmaking'''] and [https://en.wikipedia.org/wiki/Electric_arc_furnace '''Electric Arc Furnaces'''])'' is to reduce these impurities and control the amount of '''Carbon''' which remains.		The aim of [https://en.wikipedia.org/wiki/Steelmaking '''Steelmaking'''] processes such as the [https://en.wikipedia.org/wiki/Bessemer_process#Bessemer_converter '''Bessemer Converter'''] and [https://en.wikipedia.org/wiki/Open_hearth_furnace '''Open Hearth Furnace'''] ''(now superseded by [https://en.wikipedia.org/wiki/Basic_oxygen_steelmaking '''Basic Oxygen Steelmaking'''] and [https://en.wikipedia.org/wiki/Electric_arc_furnace '''Electric Arc Furnaces'''])'' is to reduce these impurities and control the amount of '''Carbon''' which remains.


	~~[[File:Britannica Alloys Plate Figure 11.jpg\|200px\|right\|Britannica Alloys Plate Figure 11\|link=https://en.wikipedia.org/wiki/Pearlite]]~~		All [https://en.wikipedia.org/wiki/Steel '''Steels'''] contain more than the very small amount of '''Carbon''' which will dissolve in '''Iron''' at room temperature. On cooling, excess '''Carbon''' separates out to form an [https://en.wikipedia.org/wiki/Intermetallic '''Intermetallic Compound'''] called [https://en.wikipedia.org/wiki/Cementite '''Cementite'''] or '''Iron Carbide'''. In '''Steel''' which has been '''Annealed''' ''(i.e. heated to above 900<sup>0</sup>C, its [https://en.wikipedia.org/wiki/Critical_point_(thermodynamics) '''Critical Point'''], and allowed to cool slowly)'', the carbide compound can be viewed with a microscope as forming dark coloured areas layered against lighter coloured '''Ferrite''' areas. This mixture is known as [https://en.wikipedia.org/wiki/Pearlite '''Pearlite'''].
	All [https://en.wikipedia.org/wiki/Steel '''Steels'''] contain more than the very small amount of '''Carbon''' which will dissolve in '''Iron''' at room temperature. On cooling, excess '''Carbon''' separates out to form an [https://en.wikipedia.org/wiki/Intermetallic '''Intermetallic Compound'''] called [https://en.wikipedia.org/wiki/Cementite '''Cementite'''] or '''Iron Carbide'''. In '''Steel''' which has been '''Annealed''' ''(i.e. heated to above 900<sup>0</sup>C, its [https://en.wikipedia.org/wiki/Critical_point_(thermodynamics) '''Critical Point'''], and allowed to cool slowly)'', the carbide compound can be viewed with a microscope as forming dark coloured areas layered against lighter coloured '''Ferrite''' areas. This mixture is known as [https://en.wikipedia.org/wiki/Pearlite '''Pearlite'''].

DT Online at 10:51, 21 March 2017

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	It is a commonly experienced that if a piece of wire or thin metal sheet is repeated bent forwards and backwards it will eventually break. The bending or [https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] distorts the '''Crystal Lattice''' and is possible because the resulting '''Dislocations''' are able to move through it until they reach '''Grain Boundaries'''.		It is a commonly experienced that if a piece of wire or thin metal sheet is repeated bent forwards and backwards it will eventually break. The bending or [https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] distorts the '''Crystal Lattice''' and is possible because the resulting '''Dislocations''' are able to move through it until they reach '''Grain Boundaries'''.


	The '''Dislocations''' themselves however, can also inhibit the movement of further '''Dislocations''' by acting like additional '''Grain Boundaries'''. As the number of '''Dislocations''' increases by continued '''Cold Working''', the metal therefore becomes '''[[Strength of Materials\|Strengthened]]''' but eventually sufficiently '''[[Brittleness\|Brittle]]''' to fracture. The lattice can be returned to its initial stress free state, with dislocations removed, by the process of '''[[Heat_Treatment#Annealing\|Annealing]]'''.		The '''Dislocations''' themselves however, can also inhibit the movement of further '''Dislocations''' by acting like additional '''Grain Boundaries'''. As the number of '''Dislocations''' increases by continued '''Cold Working''', the metal therefore becomes '''[[Strength of Materials\|Strengthened]]''' but eventually sufficiently '''[[Brittleness\|Brittle]]''' to fracture. The lattice can be returned to its initial stress free state, with dislocations removed, by the process of '''[[Heat_Treatment#Annealing\|Annealing]]'''.

DT Online at 10:50, 21 March 2017

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	----		----
	<span style="color: green">'''Note:'''		<span style="color: green">'''Note:'''
	[https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] can be beneficial ''(e.g. cold forming bolt heads leaves them strong enough to be useful)'' but also potentially catastrophic. It is for this reason that '''Aluminium''' airframes are given a limited lifespan to ensure that the continuous vibration and flexing they are exposed to, does not embrittle them to the point of fracture.		[https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] can be beneficial ''(e.g. cold forming bolt heads leaves them strong enough to be useful)'' but also potentially catastrophic. It is for this reason that [https://en.wikipedia.org/wiki/Aluminium_alloy '''Aluminium Alloy'''] airframes are given a limited lifespan to ensure that the continuous vibration and flexing they are exposed to, does not embrittle them to the point of fracture.
	</span>		</span>
	----		----

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	=====Work Hardening=====		=====Work Hardening=====

	It is a commonly experienced that if a piece of wire or thin metal sheet is repeated bent forwards and backwards it will eventually break. The bending or [https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] distorts the '''Crystal Lattice''' and is possible because the resulting '''Dislocations''' are able to move through it until they reach '''Grain Boundaries'''. The '''Dislocations''' themselves however, can also inhibit the movement of further '''Dislocations''' by acting like additional '''Grain Boundaries'''. As the number of '''Dislocations''' increases by continued '''Cold Working''', the metal therefore becomes '''[[Strength of Materials\|Strengthened]]''' but eventually sufficiently '''[[Brittleness\|Brittle]]''' to fracture. The lattice can be returned to its initial stress free state, with dislocations removed, by the process of '''[[Heat_Treatment#Annealing\|Annealing]]'''.		It is a commonly experienced that if a piece of wire or thin metal sheet is repeated bent forwards and backwards it will eventually break. The bending or [https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] distorts the '''Crystal Lattice''' and is possible because the resulting '''Dislocations''' are able to move through it until they reach '''Grain Boundaries'''.

			The '''Dislocations''' themselves however, can also inhibit the movement of further '''Dislocations''' by acting like additional '''Grain Boundaries'''. As the number of '''Dislocations''' increases by continued '''Cold Working''', the metal therefore becomes '''[[Strength of Materials\|Strengthened]]''' but eventually sufficiently '''[[Brittleness\|Brittle]]''' to fracture. The lattice can be returned to its initial stress free state, with dislocations removed, by the process of '''[[Heat_Treatment#Annealing\|Annealing]]'''.
			----
			<span style="color: green">'''Note:'''
			[https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] can be beneficial ''(e.g. cold forming bolt heads leaves them strong enough to be useful)'' but also potentially catastrophic. It is for this reason that '''Aluminium''' airframes are given a limited lifespan to ensure that the continuous vibration and flexing they are exposed to, does not embrittle them to the point of fracture.
			</span>
			----

	=====Iron and Steel=====		=====Iron and Steel=====

DT Online at 10:35, 21 March 2017

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	As [https://en.wikipedia.org/wiki/Crystal '''Crystalline Solids'''] form, their atoms pack together as closely as possible - a little like bees creating a [https://en.wikipedia.org/wiki/Honeycomb '''Honeycomb''']. The repeating patterns so formed are known as [https://en.wikipedia.org/wiki/Crystal_structure#Unit_cell '''Unit Cells'''].		As [https://en.wikipedia.org/wiki/Crystal '''Crystalline Solids'''] form, their atoms pack together as closely as possible - a little like bees creating a [https://en.wikipedia.org/wiki/Honeycomb '''Honeycomb''']. The repeating patterns so formed are known as [https://en.wikipedia.org/wiki/Crystal_structure#Unit_cell '''Unit Cells'''].
	~~[[File:Dislocations Image 005.png\|500px\|right\|Dislocations\|link=http://www.spaceflight.esa.int/impress/text/education/Mechanical%20Properties/Dislocations_02.html]]~~


			[[File:Dislocations Image 005.png\|500px\|right\|Dislocations\|link=http://www.spaceflight.esa.int/impress/text/education/Mechanical%20Properties/Dislocations_02.html]]
	__TOC__		__TOC__

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	[[File:Dislocation coin vue en bout et coeur.svg\|300px\|right\|Dislocation coin vue en bout et coeur\|link=https://en.wikipedia.org/wiki/Dislocation]]		[[File:Dislocation coin vue en bout et coeur.svg\|300px\|right\|Dislocation coin vue en bout et coeur\|link=https://en.wikipedia.org/wiki/Dislocation]]
	'''Crystal Lattices''' are distorted when an additional plane of atoms slides in between the regular structure. This allows the metal to be '''[[Plasticity\|Plastically Deformed]]''' because planes of atoms can slide over each other. The line of additional atoms is known as a [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] and they slide through the '''Crystal Lattices''' in a wave motion until a [https://en.wikipedia.org/wiki/Grain_boundary '''Grain Boundary'''] is reached. It follows that if the metal has a large '''Grains''' ''(e.g. they are are allowed to grow by slow cooling or '''[[Heat_Treatment#Annealing\|Annealing]]''')'' then the [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] can move more freely and the metal is '''[[Ductility\|Ductile]]''' and '''[[Malleability\|Malleable]]''' but if small '''Grains''' are generated ''(e.g. by rapid cooling or '''[[Heat Treatment\|Quenching]]''')'' the metal is '''[[Toughness\|Tougher]]''' and can be '''[[Brittleness\|Brittle]]'''.		'''Crystal Lattices''' are distorted when an additional plane of atoms slides in between the regular structure. This allows the metal to be '''[[Plasticity\|Plastically Deformed]]''' because planes of atoms can slide over each other. The line of additional atoms is known as a [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] and they slide through the '''Crystal Lattices''' in a wave motion until a [https://en.wikipedia.org/wiki/Grain_boundary '''Grain Boundary'''] is reached. It follows that if the metal has a large '''Grains''' ''(e.g. they are are allowed to grow by slow cooling or '''[[Heat_Treatment#Annealing\|Annealing]]''')'' then the [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] can move more freely and the metal is '''[[Ductility\|Ductile]]''' and '''[[Malleability\|Malleable]]''' but if small '''Grains''' are generated ''(e.g. by rapid cooling or '''[[Heat Treatment\|Quenching]]''')'' the metal is '''[[Toughness\|Tougher]]''' and can be '''[[Brittleness\|Brittle]]'''.


			=====Work Hardening=====

			It is a commonly experienced that if a piece of wire or thin metal sheet is repeated bent forwards and backwards it will eventually break. The bending or [https://en.wikipedia.org/wiki/Work_hardening '''Working Hardening'''] distorts the '''Crystal Lattice''' and is possible because the resulting '''Dislocations''' are able to move through it until they reach '''Grain Boundaries'''. The '''Dislocations''' themselves however, can also inhibit the movement of further '''Dislocations''' by acting like additional '''Grain Boundaries'''. As the number of '''Dislocations''' increases by continued '''Cold Working''', the metal therefore becomes '''[[Strength of Materials\|Strengthened]]''' but eventually sufficiently '''[[Brittleness\|Brittle]]''' to fracture. The lattice can be returned to its initial stress free state, with dislocations removed, by the process of '''[[Heat_Treatment#Annealing\|Annealing]]'''.

DT Online at 10:01, 21 March 2017

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	[[File:Dislocation coin vue en bout et coeur.svg\|300px\|right\|Dislocation coin vue en bout et coeur\|link=https://en.wikipedia.org/wiki/Dislocation]]		[[File:Dislocation coin vue en bout et coeur.svg\|300px\|right\|Dislocation coin vue en bout et coeur\|link=https://en.wikipedia.org/wiki/Dislocation]]
	'''Crystal Lattices''' are distorted when an additional plane of atoms slides in between the regular structure. This allows the metal to be '''[[Plasticity\|Plastically Deformed]]''' because planes of atoms can slide over each other. The line of additional atoms is known as a [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] and they slide through the '''Crystal Lattices''' in a wave motion until a [https://en.wikipedia.org/wiki/Grain_boundary '''Grain Boundary'''] is reached. It follows that if the metal has a large '''Grains''' ''(e.g. they are are allowed to grow by slow cooling or '''[[Heat_Treatment#Annealing\|Annealing]]''')'' then the [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] can move more freely and the metal is '''[[Ductility\|Ductile]]''' and '''[[Malleability\|Malleable]]''' but if small '''Grains''' are generated ''(e.g. by rapid cooling or '''[[Heat Treatment\|Quenching]]''')'' the metal is '''[[Brittleness\|Brittle]]'''.		'''Crystal Lattices''' are distorted when an additional plane of atoms slides in between the regular structure. This allows the metal to be '''[[Plasticity\|Plastically Deformed]]''' because planes of atoms can slide over each other. The line of additional atoms is known as a [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] and they slide through the '''Crystal Lattices''' in a wave motion until a [https://en.wikipedia.org/wiki/Grain_boundary '''Grain Boundary'''] is reached. It follows that if the metal has a large '''Grains''' ''(e.g. they are are allowed to grow by slow cooling or '''[[Heat_Treatment#Annealing\|Annealing]]''')'' then the [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] can move more freely and the metal is '''[[Ductility\|Ductile]]''' and '''[[Malleability\|Malleable]]''' but if small '''Grains''' are generated ''(e.g. by rapid cooling or '''[[Heat Treatment\|Quenching]]''')'' the metal is '''[[Toughness\|Tougher]]''' and can be '''[[Brittleness\|Brittle]]'''.

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	[[File:CrystalineStructuresInterstitial2.png\|300px\|right\|Interstitial Carbon Structure]]		[[File:CrystalineStructuresInterstitial2.png\|300px\|right\|Interstitial Carbon Structure]]
	* If the contributing atoms are much smaller it is possible they can fit into the spaces between the main metal atoms. This is the case of the alloy '''Steel''' in which '''Carbon''' atoms sit in between '''Iron''' atoms. Such arrangements are known as [https://en.wikipedia.org/wiki/Interstitial_compound '''Interstitial Alloys''']. '''Iron''' will absorb about 0.015% of '''Carbon''' at room temperature to form a Solid Solution known as '''Ferrite''' but all '''Steels''' contain more than this amount of '''Carbon'''.		* If the contributing atoms are much smaller, it is possible they can fit into the spaces between the main metal atoms. This is the case of the alloy '''Steel''' in which '''Carbon''' atoms sit in between '''Iron''' atoms. Such arrangements are known as [https://en.wikipedia.org/wiki/Interstitial_compound '''Interstitial Alloys''']. '''Iron''' will absorb about 0.015% of '''Carbon''' at room temperature to form a '''Solid Solution''' known as '''Ferrite''' but all '''Steels''' contain more than this amount of '''Carbon'''.


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	[[File:CrystalineStructuresDistortedLattice2.png\|300px\|right\|Distorted Lattice]]		[[File:CrystalineStructuresDistortedLattice2.png\|300px\|right\|Distorted Lattice]]
	If the atoms of different '''Alloying''' elements are of the same or similar size, an ordered and layered structure remains and the '''Slip Planes''' remain relatively smooth. But, if of differing sizes the structure may remain generally ordered but perhaps more distorted. It is these distortions in the structure, making the '''Slip Planes''' more irregular and less easy to slide over each other, that can change the physical properties of the resulting '''Alloy'''.		If the atoms of different '''Alloying''' elements are of the same or similar size, an ordered and layered structure remains and the '''Slip Planes''' remain relatively smooth. But, if of differing sizes the structure may remain generally ordered but perhaps more distorted. It is these distortions in the structure, making the '''Slip Planes''' more irregular and less easy to slide over each other, that can change the physical properties of the resulting '''Alloy'''.


			=====Dislocations=====

			[[File:Dislocation coin vue en bout et coeur.svg\|300px\|right\|Dislocation coin vue en bout et coeur\|link=https://en.wikipedia.org/wiki/Dislocation]]
			'''Crystal Lattices''' are distorted when an additional plane of atoms slides in between the regular structure. This allows the metal to be '''[[Plasticity\|Plastically Deformed]]''' because planes of atoms can slide over each other. The line of additional atoms is known as a [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] and they slide through the '''Crystal Lattices''' in a wave motion until a [https://en.wikipedia.org/wiki/Grain_boundary '''Grain Boundary'''] is reached. It follows that if the metal has a large '''Grains''' ''(e.g. they are are allowed to grow by slow cooling or '''[[Heat_Treatment#Annealing\|Annealing]]''')'' then the [https://en.wikipedia.org/wiki/Dislocation '''Dislocation'''] can move more freely and the metal is '''[[Ductility\|Ductile]]''' and '''[[Malleability\|Malleable]]''' but if small '''Grains''' are generated ''(e.g. by rapid cooling or '''[[Heat Treatment\|Quenching]]''')'' the metal is '''[[Brittleness\|Brittle]]'''.