265 12.D3 This question asks for us to decide whether or not it would be advisable to hot-work or cold-work several metals and alloys. Tin would almost always be hot-worked. Even deformation at room temperature would be considered hot-working inasmuch as its recrystallization temperature is below room temperature (Table 7.2). Tungsten is hard and strong at room temperature, has a high recrystallization temperature, and experiences oxidation at elevated temperatures. Cold-working is difficult because of its strength, and hot-working is not practical because of oxidation problems. Most tungsten articles are fabricated by powder metallurgy, or by using cold-working followed by annealing cycles. Most aluminum alloys may be cold-worked since they are ductile and have relatively low yield strengths. Magnesium alloys are normally hot-worked inasmuch as they are quite brittle at room temperature. Also, magnesium alloys have relatively low recrystallization temperatures. A
This is the end of the preview.
access the rest of the document.