• 한국주조공학회지
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• 제33권2호
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• pp.55-62
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• 2013

Effect of Fe and Mn contents on the castability of Al-4wt%Mg-0.9wt%Si system alloy has been studied. According to the analysis of cooling curve for Al-4wt%Mg-0.9wt%Si-0.3wt%Fe-0.3/0.5wt%Mn alloy, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ and ${\beta}-Al_5FeSi$ phases crystallized above eutectic temperature of $Mg_2Si$. Therefore, these phases affected both the fluidity and shrinkage behaviors of the alloy during solidification. As Fe and Mn contents of Al-4wt%Mg-0.9wt%Si system alloy increased from 0.1 wt% to 0.4 wt% and from 0.3 wt% to 0.5 wt% respectively, the fluidity of the alloy decreased by 26% and 33%. When Fe content of the alloy increased from 0.1 wt% to 0.4 wt%, 23% decrease of macro shrinkage and 19% increase of micro shrinkage appeared. Similarly, Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, 11% decrease of macro shrinkage and 14% increase of micro shrinkage appeared. Judging from the castability of the alloy, Al-4wt%Mg-0.9wt%Si alloy with low content of Fe and Mn, 0.1 wt% Fe and 0.3 wt% Mn, is recommendable.

• 열처리공학회지
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• 제4권4호
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• pp.15-23
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• 1991

The damping capacities of the nonthermoelastic bcc type lath martensite and of the nonthermoelastic hcp type thin plate martensite in Fe-Mn alloys were studied. Fe-17%Mn alloy showing the hcp type thin plate martensite was superior to Fe-4%Mn alloy having the bcc type lath martensite in damping capacity. The damping capacity of the Fe-17%Mn alloy became greater with increasing the hcp martensite volume fraction. The damping mechanism of the Fe-4%Mn alloy was well explained by the dislocation model. However, the damping mechanism of the Fe-17%Mn alloy was explained on the basis of austenite/martensite interface moving model. The two alloys showed almost same levels of tensile strength. However, the elongation was greater in the Fe-17%Mn alloy than in the Fe-4%Mn alloy, showing lower yield strength in the former than in the latter. This result was considered to be attributed to formation of stress-induced martensite during tension test.

• 열처리공학회지
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• 제10권3호
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• pp.209-217
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• 1997

Effect of Co content on the microstructure and damping capacity of Fe-23%Mn-X%Co alloy was studied. The volume fraction of ${\varepsilon}$ martensite of the alloy was increased with increasing Co content. The hardness was increased with lowering cooling temperature and increasing Co content in Fe-23%Mn-X%Co alloy, which is ascribed to the increase in ${\varepsilon}$ martensite content. The damping capacity of Fe-23%Mn-X%Co alloy was linearly increased with increasing the strain amplitude, and was constant regardless of Co content at the same volume fractions of ${\varepsilon}$ martensite when the low strain amplitudes ($1{\sim}3{\times}10^{-4}$) were applied, while the damping capacity with large strain amplitudes ($4{\sim}6{\times}10^{-4}$) became higher with increasing Co content at all valume fractions of ${\varepsilon}$.

• 한국분말재료학회지
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• 제23권5호
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• pp.397-401
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• 2016

A lean alloy is defined as a low alloy steel with a minimum amount of the alloying element that maintains the characteristics of the sintered alloy. It is well known that the addition of elements such as Cr, P, Si, or Mn improves the mechanical characteristics of the alloy, but decreases the sinterability. The mother alloy is used to avoid an oxidation reaction with the alloying elements of Cr, P, Si or Mn. The purpose of this study is to determine the change in the mechanical properties of Fe-P-Mo and Fe-P-Mn alloys as a result of the addition of Si. In this article, the Fe-P-Mo and Fe-P-Mn alloys to which Si is added are compacted at $7.0g/cm^3$ and then sintered in $H_2-N_2$ at $1120^{\circ}C$. The P around the macropores and large grains reduces due to the formation of $SiO_2$ as the Si content increases. This is caused by the increase in strength owing to reducing intergranular fracture by suppressing the reaction with oxygen.

• 대한토목학회논문집
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• 제29권4D호
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• pp.483-489
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• 2009

진동 소음을 저감시키는 Fe-Mn 제진 금속을 이용하여 제작된 핑거형 신축이음장치의 피로 내구성을 평가하고자 유한 요소해석과 수직하중 피로시험을 실시하였다. 피로실험은 Fe-Mn 제진금속을 이용한 신축이음장치와 유압가력기(25tonf)를 사용하여 진행되었으며, 그 결과에 따르면 핑거형 신축이음장치에 수직하중을 인가하였을 경우 핑거에서 측정된 최대 응력은 237.6MPa 이며, 이는 제진 금속의 항복강도인 420MPa의 56.6%이였다. 제진 금속을 이용한 신축이음의 피로시험은 도로교 설계기준에 따라 재하위치(KS F 4425)와 재하판($57.7cm{\times}23.1cm$)의 크기가 설정되었고, 그에 따른 200만회 수직하중 피로 시험에 있어서 파괴거동을 나타내지 않았으며 그 내구성과 안전성을 확인하였다.

• 열처리공학회지
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• 제15권6호
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• pp.272-278
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• 2002

The changes in damping capacity with volume fractions of thermal and deformation-induced ${\varepsilon}$ martensites were compared and analyzed in an Fe-23%-Mn alloy. The volume fraction of thermal ${\varepsilon}$ martensite increased with decreasing cooling temperature, whereas that of deformation-induced ${\varepsilon}$ martensite increased steeply up to 10%- of cold rolling and nearly saturated in further cold rolling. In the case of thermal ${\varepsilon}$ martensite, the damping capacity increased linearly with the increase in ${\varepsilon}$ martensite content. For the deformation-induced ${\varepsilon}$ martensite, however, the damping capacity increased continuously up to 70%- of ${\varepsilon}$ martensite, over which it decreased suddenly. TEM microstructures showed that the deterioration of damping capacity above 70%- of deformation-induced ${\varepsilon}$ martensite is ascribed to the introduction of perfect dislocations, which play a important role in inhibiting the movement of damping sources such as stacking fault boundaries inside ${\varepsilon}$ martensite, ${\varepsilon}$ martensite variant boundaries and ${\gamma}/{\varepsilon}$ interfaces.

• 한국주조공학회지
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• 제23권3호
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• pp.153-157
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• 2003

본 논문은 레오캐스팅용 AZ91 합금 슬러리를 제조하는 새로운 방법에 관한 것이다. 그 원리는 AZ91 합금 액상에서 Mn의 용해도차에 의해 생성되는 $Al_8(Mn,Fe)_5$ 정출물을 ${\alpha}-Mg$ 초정 생성을 위한 불균일 핵생성 자리로 사용하고자 하는 것이다. 제조된 슬러리의 미세조직 분석결과 $Al_8(Mn,Fe)_5$ 정출물이 ${\alpha}-Mg$ 내에 위치하고 있어, 이로부터 정출물이 효과적으로 불균일 핵생성 자리로 작용하고 있음을 알 수 있었다. 또한 Mn 함량의 증가는 $Al_8(Mn,Fe)_5$ 정출물 수를 증가시켜 고상분율이 일정할 때 슬러리 내 ${\alpha}-Mg$ 고상의 크기를 감소시키고 구형도를 향상시킨다. 이외에도 냉각속도 및 유지시간이 슬러리 미세조직에 미치는 영향에 대해서도 보고하였다.

• 한국재료학회지
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• 제23권7호
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• pp.385-391
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• 2013

The influence of Cu and Ni on the ductile-brittle transition behavior of metastable austenitic Fe-18Cr-10Mn-N alloys with N contents below 0.5 wt.% was investigated in terms of austenite stability and microstructure. All the metastable austenitic Fe-18Cr-10Mn-N alloys exhibited a ductile-brittle transition behavior by unusual low-temperature brittle fracture, irrespective of Cu and/or Ni addition, and deformation-induced martensitic transformation occasionally occurred during Charpy impact testing at lower temperatures due to reduced austenite stability resulting from insufficient N content. The formation of deformation-induced martensite substantially increased the ductile-brittle transition temperature(DBTT) by deteriorating low-temperature toughness because the martensite was more brittle than the parent austenite phase beyond the energy absorbed during transformation, and its volume fraction was too small. On the other hand, the Cu addition to the metastable austenitic Fe-18Cr-10Mn-N alloy increased DBTT because the presence of ${\delta}$-ferrite had a negative effect on low-temperature toughness. However, the combined addition of Cu and Ni to the metastable austenitic Fe-18Cr-10Mn-N alloy decreased DBTT, compared to the sole addtion of Ni or Cu. This could be explained by the fact that the combined addition of Cu and Ni largely enhanced austenite stability, and suppressed the formation of deformation-induced martensite and ${\delta}$-ferrite in conjunction with the beneficial effect of Cu which may increase stacking fault energy, so that it allows cross-slip to occur and thus reduces the planarity of the deformation mechanism.

• 한국주조공학회지
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• 제35권5호
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• pp.120-127
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• 2015

The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for ${\alpha}$-Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of ${\alpha}$-Al solution for shell mold and steel mold were $72.3{\mu}m$ and $23.5{\mu}m$, respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.

• 열처리공학회지
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• 제14권3호
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• pp.160-166
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• 2001

The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si (X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both ${\varepsilon}$ and ${\alpha}^{\prime}$martensites are formed in ribbon 1 (15.5wt%Mn), while only ${\varepsilon}$ martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of ${\varepsilon}$ martensite is decreased with increasing Mn contents, and those of ${\varepsilon}$ as well ${\alpha}^{\prime}$martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Ms temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. $M_s$ temperatures of the ribbons 1, 2 and 3 annealed at $300^{\circ}C$ for 3 min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and $600^{\circ}C$ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ${\varepsilon}$ and ${\alpha}^{\prime}$martensites decreased because of the presence of ${\alpha}^{\prime}$martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ${\varepsilon}$ martensite increased with increasing annealing temperature.