It has been found from the experiments that the joint property (especially tensile related data) of friction stir welded Al matrix composite decreases to 50-60 % to that of base material. The drastic decrease of mechanical property of the weld zone may create problem in terms of force distribution of the structure in real life application. This type of unstable structure may experience sudden failure. Is the high rate of extrusion and forging involve in the friction stir is greatly responsible for the happening or other reason is also there? Can anyone help me in this regard with some references? For Al matrix composite can we use suitable heat treatment for the improvement of mechanical properties?
The cause is due to loss or over-aging of precipitates in the weld zone. This problem occurs in FSW of AA2XXX, AA6XXX and AA7XXX series aluminum alloys. Other aluminum alloys will show improved hardness and tensile strength in the weld zone depending upon the initial condition. It is possible to recover the loss by doing precipitation heat treatment preferably T6. If aluminum composites are welded by FSW in as cast condition, there will not be loss of strength in weld zone but an improvement can be observed.
I totally agreed with what Dr. Isaac said regarding the type of Al alloy used. Usually, the precipitation hardening Al alloys requires heat treatment processes after ending FSW process. As a matter of fact, the amount of heat generated by friction processes greatly affects the microstructure of the welding zone, so that, there is a need to choose the appropriate parameters of the FSW process to avoid the appearance of welding defects and to get sound joints. From my point of view, restoring the material's microstructure to be similar to the original microstructure is one of the most important factors that help to restore the mechanical properties of the material and to compensate for the loss caused due to the effect of heat generated during the welding process.
Dear Uttam,
It is same as explained by Isaac Dinaharan Sir.
@ Isaac Dinaharan thank you for sharing your experience.
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