MA법에 의한 Heusler Fe2VAl 합금분말의 제조 및 치밀화
Fabrication and densification of Heusler Fe2VAl alloy powders by mechanical alloying
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본 연구에서는 Heusler Fe2VAl 열전화합물을 제조하기 위하여 순금속 Fe50V25Al25 혼합분말을 기계적 합금화 처리하였다. Fe2VAl 열전화합물을 얻기 위하여 최적 볼밀조건 및 열처리 조건을 X선 회절분석과 시차주사 열량분석을 이용하여 조사하였다. Fe50V25Al25 혼합분말을 60시간까지 볼밀 처리한 경우 bcc 구조의 α-(Fe,V,Al) 고용체가 얻어졌다. 단상의Heusler Fe2VAl 화합물은 Fe50V25Al25 혼합분말을 60시간 동안 MA 처리 후 700oC까지 열처리함으로써 얻을 수 있었다. MA 분말시료의 치밀화를 위하여 인가압력 60 MPa 및 소결온도 900~1000oC에서 흑연다이를 사용하여 SPS 소결을 실시하였다. 1000oC에서 SPS 소결 후 얻어진 벌크체의 Vickers 경도는 870으로 매우 높은 값을 보였다. 또한 SPS 법으로 얻어진 벌크체의 밀도측정 결과, 모든 시료에서 상대밀도 90 % 이상의 금속광택을 나타내는 치밀한 소결체임을 알 수 있었다.
Abstract
We have applied mechanical alloying (MA) to produce Heusler Fe2VAl thermoelectric alloy using a mixture of elemental Fe50V25Al25 powders. An optimal milling and heat treatment conditions to obtain the single phase of Fe2VAl compound with fine microstructure were investigated by X-ray diffraction and differential scanning calorimetry (DSC)measurement. The Fe50V25Al25 MA sample ball-milled for 60 hours exhibits a bcc α-(Fe,V,Al) solid solution. Single phase of Heusler Fe2VAl compound can be obtained by MA of Fe50V25Al25 mixture for 60 hours and subsequently heated up to 700oC. Sintering of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies at 900~1000oC under 60 MPa. The Vickers hardness of bulk sample sintered at 1000oC was high value of Hv 870. All compact bodies have a high relative density above 90 % with metallic glare on the surface.
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