급속응고된 Al-Zr 합금의 시효현상에 미치는 Si첨가의 영향

Abstract

본 연구에서는 급속응고된 Al-Zr 합금의 과포화 고용도에 미치는 제3첨가 원소 Si의 영향 및 급속응고된 Al-Zr-Si 합금계의 시효특성에 관하여 실험적으로 조사하였다.

Twin-roller 장치에 의하여 급속응고시킨 시편의 응고속도는 10?? K/s 정도였으며, 이때 Al기지내에 Zr은 약 1 wt.% 정도만이 과포화 고용되었다. 그러나 Si의 첨가량이 증가됨에 따라 Zr의 과포화 고용도는 증대되어 Si의 첨가량이 1 wt.% 일때 Zr은 1.7 wt.% 정도 Al기지내에 완전 과포화 고용되었다. 그리고 Si의 첨가량이 증가됨에 따라 Al-Zr 합금의 미소경도는 증대되었다.

Al -1.7wt.%Zr -1.0wt.%Si 합금을 시효처리하면 Si이 우선 미세한 구상석출물을 형성하며 초기 시효경화를 일으킨 후, 잇따라 Zr의 준안정 석출물이 불연속 석출되어 성장하며 최대 시효경화를 나타냄을 알 수 있었다.

An experimental investigation has been made about the effects of the third alloying element silicon on the sold solubility of zirconium in the aluminium, and on the ageing phenomena of Al-Zr-Si alloys.

Rapidly solidified specimens were prepared by a twin-roller quenching apparatus in the form of long, thin ribbon, whose cooling rate was estimated to be about 10?? K/s. Under such a cooling rate, the maximum solubility of zirconium in solid aluminum was extended to about 1.0wt.%. However, it was extended up to 1.7wt.% by addition of 1.0wt.% silicon. With the increase of silicon content, the microhardness of Al-Zr alloys were increased as well.

Ageing of supersaturated Al-1.7wt.% Zr-1.0wt.% Si solid solution appeared to occur in three sequential stages;

Ⅰ. precipitation of silicon as fine spherical particles which harden the alloys, followed by

Ⅱ. discontinuous precipitation of metastable zirconium phases which produce remarkable age hardening of the alloys, and finally

Ⅲ. formation of coarse equilibrium zirconium phases.

An experimental investigation has been made about the effects of the third alloying element silicon on the sold solubility of zirconium in the aluminium, and on the ageing phenomena of Al-Zr-Si alloys.

Rapidly solidified specimens were prepared by a twin-roller quenching apparatus in the form of long, thin ribbon, whose cooling rate was estimated to be about 10?? K/s. Under such a cooling rate, the maximum solubility of zirconium in solid aluminum was extended to about 1.0wt.%. However, it was extended up to 1.7wt.% by addition of 1.0wt.% silicon. With the increase of silicon content, the microhardness of Al-Zr alloys were increased as well.

Ageing of supersaturated Al-1.7wt.% Zr-1.0wt.% Si solid solution appeared to occur in three sequential stages;

Ⅰ. precipitation of silicon as fine spherical particles which harden the alloys, followed by

Ⅱ. discontinuous precipitation of metastable zirconium phases which produce remarkable age hardening of the alloys, and finally

Ⅲ. formation of coarse equilibrium zirconium phases.