粉末燒結型鈦鐵鉬合金顯微結構及強化機制之探討

Study on the microstructure and strengthening mechanism of the sintered Ti-xFe-6Mo alloy by the powder metallurgy

李尉祥(Wei-Hsiang Li)

指導教授 ： 楊永欽

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2013年)

https://doi.org/10.6841/NTUT.2013.00618

摘要

低花費和良好的性質是鈦合金發展的兩個主要因素，但粉末燒結型鈦合金，常需使用熱壓或熱均壓法來改善其孔隙的缺陷，故成本較高，而添加鐵、鉬不僅能降低材料成本，且兩者與鈦有高的固溶強化效果能使其穩定於bcc β相及降低孔隙率。本實驗針對Ti-xFe-6Mo (x-2, 4和6 wt%)鈦合金，利用不同溫度(1150°C和1200°C)進行真空燒結，再以不同溫度(700°C、800°C和900°C)持溫30分鐘後熱處理，以觀察其顯微結構和機械性質的強化機制之探討。
實驗結果發現，未經熱處理的Ti-xFe-6Mo鈦合金中β相晶界出現穩定之亞共析α相，隨燒結溫度上升晶粒尺寸及相對密度也隨之上升，而1200°C的燒結緻密度較佳，其抗折強度也較1150°C高出許多。鐵含量2 wt%燒結溫度1200°C在β相晶粒中有大量粗大及細小的費德曼組織結構(Widmannstaetten structure)產生，形成散佈強化的效果，其HRA硬度值達68.7以上，而抗彎強度達1197.97 MPa以上，但隨著鐵含量增至4 wt%，其費德曼組織結構細化散佈於β相中，使其抗彎強度下降，但硬度值些微增加，在後續的熱處理會對其顯微組織及強化機制做一系列的探討。

關鍵字

真空燒結 ； 熱處理 ； 鈦合金

並列摘要

The low cost and excellent mechanical properties of titanium alloy are two major reasons of the developments. The powder metallurgy method for titanium alloy could be cost down, but, it often need to use hot pressing or hot isostatic pressure method to reduce the porosity defect. The Addition of iron and molybdenum can reduce down the material costs. The bcc β phase can be stabilized by the solid solution strengthening of titanium and reduce porosity. This study presents the sintered properties of Ti–xFe-6Mo (x = 2, 4, and 6 wt%) sintered at 1150°C and 1200°C under vacuum. The samples were heat treated 30 minutes at three temperatures (700°C, 800°C, 900°C) by a heating rate of 10°C/min and after then quenching in oil.
The results indicated that all alloys made from 1200°C revealed higher tensile strength and relative densities with value of 95.24%. The specimen with 2 wt% iron content and sintering temperature of 1200 °C showed that large number of coarse and fine Widmannstaetten structure in the beta phase and result in the well dispersion strengthening effect. It’s HRA hardness is higher than 68.7 and the bending strength of 1197.97 MPa. But, with the iron content increased to 4 wt%, the Widmannstaetten structure refined and dispersed in the beta phase, so that the bending strength is decreased, but a slight increase in hardness values. The more details will be discussed in the paper.

並列關鍵字

Powder sintering ； Ti alloy ； heat treatment

參考文獻

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