Gray iron is weak and brittle in tension because the tips of the graphite flakes act as points of stress concentration. 1 1. 14 (a) Cite advantages of forming metals by extrusion as opposed to rolling. Two advantages of extrusion over rolling are; pieces having more complicated cross-sectional geometries may be formed and seamless tubing may be produced.

B). Cite some disadvantages. Some disadvantages of extrusion over rolling are; non uniform deformation over the cross-section and a variation In properties may result over the cross-section of an extruded piece. 11. 23 What Is the purpose of a heat treatment? On what classes of alloys Is It normally used? The purpose of a heat treatment Is to produce a very soft and ductile steel alloy having a .It Is normally used on medium- and high-carbon steels, which, by virtue of carbon content, are relatively hard and strong.

11. 31 what Is the principal difference between natural and artificial aging processes? Natural aging is allowing the precipitation process to occur at the ambient temperature; artificial aging is carried out at an elevated temperature.