High-Diffusivity Path MCQ

Test your knowledge with important High-Diffusivity Path MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more High-Diffusivity Path MCQs at Bissoy

• Grain boundary diffusion makes a significant contribution to the total flux when___(Db and D1 are the diffusivities through the grain boundary and defect free lattice and ȣ, d are the effective thickneβ and grain size).
  ক

  (Db*ȣ/D1*d) > 1

  খ

  (Db*ȣ/D1*d) < 1
• At high temperatures diffusion through the lattice is rapid and g*Dp / D1 is very small so that the dislocation contribution to the total flux of atoms is_______ (Dp, D1 are diffusivity through pipe and defect free lattice and g is the cross-sectional area of ‘pipe’ per unit area of matrix).
  ক

  Extremely high

  খ

  Negligible

  গ

  Low

  ঘ

  High
• Find the frequency factor of the following grain boundary diffusion, if the activation energy is given as 90KJ/mol and the diffusivity at the grain boundary at 1071K is given as 49*10-6m2/sec?
  ক

  1.2mm2/sec

  খ

  1.2m2/sec

  গ

  2.2mm2/sec

  ঘ

  4.2mm2/sec
• The rate at which atoms diffuse along different boundaries is_________
  ক

  Same

  খ

  Different

  গ

  Constant

  ঘ

  Cannot be predicted
• In FCC metals it is generally found that ___
  ক

  Qb >> 0.5Q1

  খ

  Qb << 0.5Q1

  গ

  Qb = Q1

  ঘ

  Qb ̴̴ Q1
• The jump frequency for atoms migrating along the defects is higher than that for diffusion in the lattice.
  ক

  True

  খ

  False
• The relative magnitudes of Db*ȣ and D1*d are most sensitive to_______(Where Db and D1 are the diffusivities through the grain boundary and defect free lattice and ȣ, d are the effective thickness and grain size)
  ক

  Pressure

  খ

  Temperature

  গ

  Volume

  ঘ

  Composition
• In a diffusion couple made by welding together two metals, A and B.A-atoms diffusing along the boundary will be able to penetrate much deeper than atoms which only diffuse through the lattice.
  ক

  True

  খ

  False
• In an average metallic specimen the total grain boundary area is_______
  ক

  Much greater than surface area

  খ

  Same as the surface area

  গ

  Relatively less than surface area

  ঘ

  Much less than surface area
• In general, at any temperature the magnitudes of Db and Ds relative to the diffusivity through defect-free lattice D1 are such that_________ (Db and Ds are grain boundary and surface diffusivity)
  ক

  Db>Ds>D1

  খ

  Db<Ds<D1

  গ

  Db>D1>Ds

  ঘ

  Ds>Db>D1