Aluminum (Al) - based powders have attracted attention as key materials for 3D printing because of their excellent specific mechanical strength, formability, and durability. Although many studies on the fabrication of 3Dprinted Al-based alloys have been reported, the influence of the size of raw powder materials on the bulk samples processed by selective laser melting (SLM) has not been fully investigated. In this study, AlSi10Mg powders of 65 μm in average particle size, prepared by a gas atomizing process, are additively manufactured by using an SLM process. AlSi10Mg powders of 45 μm average size are also fabricated into bulk samples in order to compare their properties. The processing parameters of laser power and scan speed are optimized to achieve densified AlSi10Mg alloys. The Vickers hardness value of the bulk sample prepared from 45 μm-sized powders is somewhat higher than that of the 65 μm-sized powder. Such differences in hardness are analyzed because the reduction in melt pool size stems from the rapid melting and solidification of small powders, compared to those of coarse powders, during the SLM process. These results show that the size of the powder should be considered in order to achieve optimization of the SLM process.

Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.

고추 형질전환체 T1 및 T2세대의 유묘에 역병균을 접종한 결과 유주포자 103개/mL에서 접종 5일후 역병 발병율은 T1-1계통 4.0%, T1-2 10.0%이었으며, 접종 12일후는 T1-1 계통 52.0%, T1-2 계통 64.0%로 대비종인 '금탑'과 '수비초' 100%에 비해 발병율이 떨어져 유주포자 103개/mL에서는 형질전환체의 저항성 계통선발이 가능하였다. 획득된 역병 저항성 형질전환체를 영양고추시험장의 역병 상습포장에서 재배한 결과 생육, 개화소요일수, 과특성 등은 계통간에 다소 차이가 있었으나, 과실모양은 수비초와 매우 유사하였다. 포장에서의 역병의 발생은 계통간에 차이가 많았으며, T2-1-6 계통과 T2-4-9 계통은 시판종인 금탑에 비해 약 30%정도 적었다. 포장에서 선발된 형질전환체는 세대의 진전을 통한 저항성의 고정이 필요한 것으로 판단된다. 이상의 결과로 본 연구에서 확립된 형질전환 시스템으로 고추의 역병저항성 형질전환체의 육성이 가능할 것으로 생각된다.