College - Author 1
College of Engineering
Department - Author 1
Materials Engineering Department
Degree Name - Author 1
BS in Materials Engineering
Date
6-2019
Primary Advisor
Blair London
Abstract/Summary
Two types of tensile bars were observed in this study of golf iron heads for TaylorMade Golf. As-cast and as-cast then machined tensile bars. The tensile bars underwent tensile tests to observe tensile strength, percent elongation, and fracture mechanisms. Furthermore, the hardness of the tensile bars was also taken despite seeing no difference in sample types. However, the as-cast samples did not consistently meet the requirements of percent elongation > 10.00% as there was a sample with 0.00% and another with 1.26%. These samples also showed brittle fracture, instead of the desired cup-and- cone ductile fracture. To investigate further, transverse sections of the tensile bars were sectioned, mounted, ground, polished, etched and micrographs were taken to characterize the differences. The as-cast samples showed regions of segregation along with aligned lath martensite. The as-cast then machined samples were characteristic of basket-weave martensite. The aligned lath martensite was leading to the brittle fracture as the unidirectional nature of the laths formed a pathway for the cracks to propagate quickly. Whereas in the basket-weave martensite, the strain-energy when a load was applied would be dispersed in multiple directions. Slowing down the fracture and leading to ductile fracture instead. In addition, by observing the as-cast then machined samples before they were machined, it became evident that the machining would take off the outer layers of the aligned lath martensite thus making the samples perform better.
URL: https://digitalcommons.calpoly.edu/matesp/209