Effect of Grain Size on Transcription Property of Die Shape in Micro Forming of SUS304

Abstract

The microforming of SUS304 stainless steel with fine grain structures is carried out utilizing superplastic phenomenon. The configurations of formed structures are studied, and transcription properties are discussed. In this study, two types of experiments were carried out. One involved tests to form a micro-pyramid on the specimen by Vickers indentation as the die, and the other involved tests to form micro gratings by grinding mark as the die. The processed materials could not make contact to dies at the area around the top of the micro pyramid, which was 4–5 times the diameter of the grain size. It is believed that the flow into the top of the pyramid was blocked by the formation of a bridge of grains. And the lower limit to form micro gratings utilizing superplastic phenomenon was determined to be of the same size as of the grain of processed material.