以平流鑄造法和機械合金法製造Al-Cr-Zr合金

Abstract

本實驗是以平流鑄造單輪法以及機械合金的方法來製造耐高溫強度鋁合金 ，而以Al-Cr-Zr為基本材料。機械合金（Mechanical Alloying ，ＭＡ） 的方法是將預混合粉末 (pre-mixed powder），經由外力不斷的變形、冷 焊和破裂，產生原子間的固態擴散，最後形成固溶相的合金粉末。且研磨 強度的改變，會影響最後ＭＡ粉末的結構，例如在低的研磨強度是可以形 成非晶型的相，而在高的研磨強度可以形成晶型粉末，而且這些相可以經 過改變不同的研磨強度而互相轉變。同樣的在平流鑄造單輪法中，坩堝噴 口與銅輪的間距以及銅輪旋轉的速度，也會影響薄帶的過冷度和厚度，進 而改變Al-Cr-Zr合金的析出情形。本實驗利用平流鑄造單輪法將Al-3Cr-3 Zr、Al-3Cr、Al-3Zr分別在相同坩堝噴口與銅輪的間距以及銅輪旋轉速度 的情況下，製造出急冷薄帶，並在進一步的熱處理下，可以得知θ-AlCr 和Ll-AlZr是Al-3Cr-3Zr主要的析出物，而其析出溫度(precipitation tem-perature) 大致分別為500℃及 400℃。球磨製成的ＭＡ粉末和由Ｒ ＳＰ製造出來的薄帶，此二種不同製程的過飽和固溶體將互相比較，並再 進一步利用熱處理，比較兩者之熱穩定性。利用示差掃描熱量計（ＤＳＣ ）可用以測量薄帶析出物的析出放熱波峰溫度，藉由活化能的計算來判斷 其熱穩定性。同樣的利用ＤＳＣ技術，也可知道ＭＡ粉末在不同的球磨時 間有不同的recovery 再結晶和晶粒成長溫度。本研究有助於爾後擠製參 數之選用。 In this thesis, the fabrication of Al-Cr-Zr alloy by mechanical alloying(MA) method and planar flow casting (PFC) method are reported. Mechanical alloying is a process used for producing powders having a fine microstructural alloy; In the MA process, via the repeated cold-working, deformation and fracturing, a solid-state interdiffusion reaction occurring, and the powders with ultrafine microsturcture was formed finally. The milling intensity strongly affects the phase formation, resulting in amorphous or crystalline material for milling at low and high milling intensity, respectively. Furthermore, the various phases can be In this experiment, the planar flow casting was employed to produce Al-3Cr-3Zr, Al-3Cr and Al-3Zr rapidly solidified ribbons. The phase transformation processes of the ribbons and and MA powders at a continuous heating rate were studies by differential scanning calorimetry. The precipitaion temp. of Al3Cr2 and Al3Zr in the supersaturated solid solution are ca. 500℃ and 400℃, respectively. The DSC studied aoso shed light on recovery, recrystallization and grain growth temp. of MA powder. All these efforts done are helpful for parameter choices in further thermal-mechanical treatments of MA powders and PFC ribbons.