Digital Twin Science of Metal Powder Bed Fusion Additive Manufacturing: A Selective Review of Simulations for Integrated Computational Materials Engineering and Science

Abstract

A digital twin (DT) is a cyberspace replica of a system, such as manufacturing equipment. A DT consists of statistical models and computer simulations of physical phenomena occurring in the system. The modeling is adjusted to the system based on signals from sensors attached to the system and their temporal changes. In general, a DT is utilized to (i) predict phenomena occurring in the system, (ii) optimize control parameters, and (iii) estimate part replacement schedules. We propose to use a DT to elucidate the unique solidification phenomena occurring in a type of metal 3D printing (i.e., additive manufacturing: AM) process. Thus, we propose that applications of DT that obtain scientific data be referred to as "digital twin science (DTS)." This paper first reviews the fundamental of the AM process, particularly powder bed fusion (PBF) and relevant computer simulations, and then studies on computer simulations conducted to elucidate the relationship between the extreme conditions characteristic of the PBF process and solidification microstructures. The findings achieved by the DTS approach indicate that the combination of experimental and simulation data aid the future development of techniques to obtain required microstructures exhibiting desired properties.

レーザ粉末床溶融結合法のプロセスパラメータの効率的最適化に向けたDeposited Energy Densityへのハッチ間隔の導入

“…成形加工プロセスである [1][2][3][4]．金属 AM は従来であれば複数 のパーツを組み合わせて作られていた金属製品の一体製造も 可能とする [5]．レーザ粉末床溶融結合 (L-PBF) 法は，最も代 表的な金属 AM の 1 つであり，造形プラットフォームへの粉 末の敷設と粉末床へのレーザ走査を繰り返すことで，金属部 材を製造する [2]．また，L-PBF 法では，プロセス中に大き な温度勾配と急速加熱・冷却での凝固が生じる [6]．そうした 特徴的な温度場によって，L-PBF 造形した金属部材は結晶集 合組織 [7,8]，過飽和固溶体 [9][10][11]，準安定相 [12,13]などを 含む特異的な組織を有する．そうした組織に起因して，制御 された弾性率 [14]，高強度 [15]，異方的な熱伝導率 [16]…”

Fusion of Ni Plating on CP-Titanium by Electron Beam Single-Track Scanning: Toward a New Approach for Fabricating TiNi Self-Healing Shape Memory Coating

“…The formation of the Ti 2 Ni phase is also observed in the center of the melt region formed under the P = 200 W condition, as shown in Figure 10a. In the melting and so-lidification process induced by the EB irradiation, the melted liquid solidifies under a rapid cooling rate of 10 5 -10 7 K s −1 , which prevents the system from reaching thermodynamic equilibrium [39]. In particular, the rapid cooling rate can suppress diffusion and segregation relaxation processes, leading to a frozen-in distribution of components [40][41][42].…”

Persistent Homology Analysis of the Microstructure of Laser-Powder-Bed-Fused Al–12Si Alloy

“…Both the complexity of manufacturable parts and the controllable microstructures are characteristics of the L-PBF process. Laser scanning to the powder bed during the L-PBF process rapidly and locally increases the temperature, melts the metal powder, and forms the semi-ellipsoidal melt pools with a high thermal gradient of over 10 7 K/m [6]. Subsequently, the laserscanned regions are rapidly cooled and solidified to form characteristic microstructures including a single crystal-like texture [7,8], metastable phase [9][10][11], and supersaturated solid solutions [12,13].…”