Additive manufacturing by electron beam melting is an affordable process for fabricating near net shaped parts of titanium and its alloys. 3D additive-manufactured parts have various kinds of voids, lack of fusion, etc., and they may affect crack initiation and propagation. Post process is necessary to eliminate or minimize these defects. Hot isostatic pressing (HIP) is the main method, which is expensive. The objective of this paper is to achieve an optimum and simple post heat treatment process without the HIP process. Various post heat treatments are conducted for the 3Dprinted Ti-6Al-4V specimen below and above the beta transus temperature (996oC). The as-fabricated EBM Ti-6Al-4V alloy has an α‘-martensite structure and transforms into the α+β duplex phase during the post heat treatment. The fatigue strength of the as-fabricated specimen is 400 MPa. The post heat treatment at 1000oC/30 min/AC increases the fatigue strength to 420 MPa. By post heat treatment, the interior pore size and the pore volume fraction are reduced and this can increase the fatigue limit.

Abstract
 1. 서 론
 2. 실험 방법
 3. 실험결과 및 고찰
  3.1. 열처리 조건별 미세조직 특성
  3.2. 열처리에 따른 기공의 크기 분포 변화
  3.3. 고주기 피로 특성
 4. 결 론
 References

• 최영신(국립순천대학교 신소재공학과) | Young-Sin Choi (Sunchon National University)
• 장지훈(국립순천대학교 신소재공학과) | Ji-Hoon Jang (Sunchon National University)
• 김건희(한국생산기술연구원 강원지역본부) | Gun-Hee Kim (Gangwon Regional Division, Korea Institute of Industrial Technology (KITECH))
• 이창우(한국생산기술연구원 강원지역본부) | Chang-Woo Lee (Gangwon Regional Division, Korea Institute of Industrial Technology (KITECH))
• 김휘준(한국생산기술연구원 인천지역본부) | Hwi-Jun Kim (Incheon Regional Division, Korea Institute of Industrial technology (KITECH))
• 이동근(국립순천대학교 신소재공학과) | Dong-Geun Lee (Sunchon National University) Corresponding Author