What are some of the factors that would promote mass diffusion of a material into another one? $($a$)$ higher temperature, $($b$)$ higher material concentration, $($c$)$ longer process time, $($d$)$ higher pressure, $($e$)$ lower substrate density.

What are the implications of high hot hardness with materials: $($a$)$ The material exhibits higher melting temperature; $($b$)$ the material remains its room temperature strength at elevated temperature levels; $($c$)$ the material retains a good portion of its room temperature strength at elevated temperature levels; $($d$)$ The material will be more suitable as cutting tool materials; $($e$)$ the material will be more difficult to cut at room temperature compared to other materials.

What promote$($s$)$ the viscoelastic behavior of materials: $($a$)$ reduced temperature; $($b$)$ elevated temperature; $($c$)$ Increased material density; $($d$)$ deformation speed; $($e$)$ increased stress level.

For the melting and solidification of materials, which of the following description are true: $($a$)$ when material is undergoing melting $($phase transformation from solid to liquid$),$ the temperature will not change; $($b$)$ for amorphous material, there does not exist a single melting point at which the material transforms into liquid; $($c$)$ the solidification of metal alloys typically exhibits phase segregation; $($d$)$ the alloy materials more viscous as they cool from liquid phase, until completely solidify.

These are multiple choice $/$ single choice questions.

Please answer questions $4-7$

Thanks!