Answer: 
1. High friction
2. High extrusion temperature
Explanation:
 Surface cracking on extruded products are defects or breakage on the surface of the extruded parts. Such cracks are inter granular.
            Surface cracking defects arises from very high work piece temperature that develops cracks on the surface of the work piece. Surface cracking appears when the extrusion speed is very high, that results in high strain rates and generates heat. 
           Other factors include very high friction that contributes to surface cracking an d chilling of the surface of high temperature billets.
 
        
             
        
        
        
Answer:
The diameter increases
Explanation:
The expansion in the metal is uniform in every dimension
 
        
             
        
        
        
Why did you put this on here when you know the answer lol