A study of BCC twins in Fe-Mn-Al alloys

• Main Authors: Po-chun Chen, 陳柏邨
• Other Authors: Wei-chun Cheng
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/496ud7

碩士 === 國立臺灣科技大學 === 材料科技研究所 === 94 === Abstract This thesis is to study the BCC twins of a Fe-15.9wt%Mn-4.2wt%Al alloy within the BCC grains. The alloy specimens were treated by hot forging, cold rolling, heat treatment and aging. The alloy is ferrite at temperatures of 1300℃ and 1200℃. There are some stripes observed within the BCC grains after quenching the alloy from 1200℃ or higher temperatures. The stripes were identified as BCC twins in the TEM study. There is no stripe twins in the BCC grains when the alloy was cooled in air after the above heating processes. The twins formed because of the thermal stress during the quenching processes, and the twins belong to mechanical twins. The formation and distribution of the twins are dependent on the cooling rate and specimen thickness, respectively. After being heated at 1150, 1100, and 1050, 800 and 600℃, the alloy consists of BCC and FCC phases. Micro twins also could be observed within the BCC grains, these twins are probably formed during the forging and rolling processes of the alloy. After the alloy was furnace-cooled from 1200℃, the alloy is composed of the BCC and FCC phases. There are some micro twins within BCC grains. The micro twins were formed by the stress between the original BCC grains and the growth of precipitate FCC grains.