Answer:
The hardenability increases with increasing austenite grain size, because the grain boundary area is decreasing. This means that the sites for the nucleation of ferrite and pearlite are being reduced in number, with the result that these transformations are slowed down, and the hardenability is therefore increased.
Answer:
all are zero.
Explanation:
We know that if flow is possible then it will satisfy the below equation

Where u is the velocity of flow in the x-direction ,v is the velocity of flow in the y-direction and w is the velocity of flow in z-direction.
And velocity potential function
given as follows

Rotationality of fluid is given by 



So now putting value in the above equations ,we will find


So
=0
Like this all
all are zero.
That is why velocity potential flow is irroational flow.