Question

explain why we are doing a solution treatment before aging treatment for alloys. b) describe the microstructure difference between aged alloys with and without solution treatment+quenching.

Answer 1

ANSWER FOR >>a)Solution treatment (also called solution annealing)is a common heat treatment process for many different families of metals ,stainless steels, aluminium alloys ,nickel-based alloys,titanium alloys and some copper based alloys all may require solution annealing.

the purpose of solution annealing is to dissolve any precipitate present in the materials,and transform the material ta the solution annealing temperature into a single phase structure .At the end of the solution annealing process,the alloys are rapidly quenched down to room temperature to avoid any precipitation from occuring during cooling through lower temperature ranges.The single phase solution annealed material will be in a soft state after treatment.

The solution annealing is required prior age hardening /precipitateion hardening.The single phase microstructure created during solution treatment is required to prior to age hardening ,such that only the precipitates formed during aged hardening will be present in the final product .The composition ,size ,and quantities of those precipitate formed during agin will be determine the final products hardness,strength and mechanical properties after aging.It is critical that the structure be properly solution treated prior to aging in order to meet all of these requirements.

ANSWER FOR >>b)Quenching is a process in which a metal(alloy) is cooling at a faster rate .This most often done to produced a martensite transformation.Metallic materials (alloy) consist of a microstructure of small crystals called grains or crystallites.The nature of the grain is one of the most effective factors that can determine the overall mechanical behaviour of the metal- alloy. Heat treatment processes is an efficient way to manipulate properties of the metal -alloy by controlling the rate of diffusion and the rate of cooling within the the microstructure of the metal alloy.

The crystal structure consists of atoms that are grouped in a very weak specific arrangement ,called a lattice .In most case this order will rearrange it self,depending on conditions .When treatment (solution treatment+quenching) is complete then the alloy is supersaturated .The diffusion rate iof alloy atom gets very slow and it becomes very hard.strong.But incase of aged alloys which is not treated with watwr is soft and not strong as before one.