{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Materials Cribsheet - BEST ONE

# Materials Cribsheet - BEST ONE - M a t e r ia ls Cr ib Sh e...

This preview shows pages 1–2. Sign up to view the full content.

Materials Crib Sheet Mike Bebjak Chapter 3 – Crystal Structures Constants & Conversions giga G 10 9 milli m 10 -3 mega M 10 6 micro µ 10 -6 kilo k 10 3 nano n 10 -9 centi c 10 -2 pico p 10 -12 k = 1.38× 10 -23 J/ atom K = 8.62× 10 -5 eV/ atom K R = 8.314 J/ mol K N A = 6.023× 10 23 atoms/ mol e = 1.602× 10 -19 C m e = 9.11× 10 -31 kg h = 6.63× 10 -34 J s Atomic Structures Atomic packing factor (APF) = atoms in unit cell unit cell / V V CN = number of atoms that each given atom touches in a unit cell FCC – close packed ABCABC sequence 2 2 a R = APF = 0.74 CN = 12 4 atoms/ cell BCC – not close packed 4 3 a R = APF = 0.68 CN = 8 2 atoms/ cell HCP – close packed ABABAB sequence 2 2 a R = APF = 0.74 CN = 12 Braggs’ Law: 2 sin n d λ θ = , Density: i i c A c A n A nA V N V N ρ = = , Planar spacing: 2 2 2 2sin n a d h k l λ θ = = + + . Miller Indices : Steps – lines: 1. Start at any cell corner; 2. Find coordinates of vectors, subtract; 3. Multiply by common factor, planes: 1. Find intercepts in a, b, c; 2. Find reciprocals 1/ a, 1/ b, 1/ c; 3. Multiply to make integer. Notations – lines: [ u v w] , planes: (h k l), families of planes: { 1 1 1} family includes (1 1 1), (1 1 1) , etc. u u = − Chapter 4 - I m perfections Point Defects - Vacancies: Q V RT V N Ne = (N is the total # of atomic sites, Q the energy required to form a vacancy) Thermodynamics: perfect crystal S= 0, add n vacancies to N atoms n S G (G = H - T S). Will create vacancies until G is a minimum. Impurities – Substitutional: replace an atom; Interstitial: lie between atoms; Q sol kT sol X e = . Linear Defects – Dislocations: edge (extra plane of atoms), screw (shear distortion of lattice) dislocations = S thermodynamically unstable. Planar Defects – Grain boundaries: 1 2 n N = (N – avg. # of grains/ sq. inch, n – grain size # ). Solidification Process : 1. Nucleation; 2. Growth; 3. Impingement grain boundaries form. Metals have more vacancies than self-interstitials. Conditions: 3 2 0 J/m 0 J/m V S G G < < G V RT r P e = (probability of getting a critical radius r * ), 1 / t p 3 2 4 4 3 T sol s G r G r π π γ = + , * 2 V r G γ = ' 1 1 1 ' ' 1 1 2 1 1 2 2 m C A C m m C A C A = = + + , ' 1 1 2 1 1 2 2 1 1 2 m m m n C A C n n C A C A = = + + , '' 1 1 1 2 1 2 C C C C ρ ρ = + , ' ' 1 1 2 2 ' ' 1 2 1 1 2 2 1 2 1 2 100 avg C A C A C C C A C A ρ ρ ρ ρ ρ + = = + + , ' ' 1 1 2 2 1 2 1 2 100 100 avg C A C A A C C A A + = = + (C-wt% , C’-at% , C’’-conc.) Chapter 5 - Diffusion Types Interdiffusion : atoms of one metal diffuse into another, Self-diffusion : atoms of metal exchange positions Mechanisms Vacancy Diffusion : substitutional atoms diffuse into vacancies (used by interdiffusion & self-diffusion). Interstitial Diffusion : atoms move into interstitials locations (gases, much faster than vacancy). Steady-state Diffusion – diffusion flux doesn’t change with time: 1 M dM J At A dt = = , Fick’s 1 st Law: dC J D dx = − (D – diffusion coefficient), (q – amount diffusing), q JA = 0 Q RT D D e = Chapter 6 – Mechanical Properties of Metals Types of stresses : Tensile, Compressive, Shear, Biaxial Tension Compression, Hydrostatic Stress: 0 F A σ = , Strain: 0 l l ε = , Shear stress: 0 F

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}