使用鈦基填料紅外線硬銲鈦合金之研究

Abstract

鈦合金近年來愈來愈受重視，由於其礦產藏量不低，加上近年來的治煉技術進步，且其某些機械性質可比鋼鐵材料更加優異，例如：比強度、常溫及高溫抗蝕性都比常用的鋼鐵材料好，加上鈦合金亦可依不同需求增加合金量來改變其機械性質。實際應用中銲接性質為此材料是能否成為優秀的工程材料的重要指標之一，因此本研究選擇鈦合金的硬銲當成研究主題。 研究中以鈦基填料使用紅外線真空爐硬銲鈦合金，主要研究銲道顯微組織之演化，過去文獻的研究僅偏重在掃描式電子顯微及其全、半定量分析鏡觀察其組織變化，但銲道內合金元素眾多、組織非常的細小，不足以有全面透徹的研究。本研究以描式電子顯微及其全定量分析為輔，搭配穿透式電子顯微鏡為主來分析鈦合金硬銲銲道結構。 首先本研究使用三種鈦基填料Ti-15Cu-15Ni、Ti-25Cu-15Ni、Ti-15Cu-25Ni硬銲SP-700觀察銲道結構，發現在300秒的硬銲，組織差異僅在於銲道中心初晶有所不同，當使用Ti-15Cu-15Ni、Ti-15Cu-25Ni時，初晶為Ti2Ni為主，少量α-Ti及Ti2Cu。而使用Ti-25Cu-15Ni時初晶以Ti2Cu為主。在銲道其他部分三種填料則是α-Ti及Ti2Cu的共析組織和些許殘留在常溫的β-Ti。硬銲1800秒時，三種填料組織皆為過飽合α-Ti及殘留β-Ti。 其次，以Ti-15Cu-15Ni硬銲三種不同結構基材α鈦合金、α-β雙相鈦合金、β鈦合金，發現影響銲道組織最重大的有二種因素，首先為基材的β鈦穩定元素的多寡，其次為Cu、Ni量的分佈情形。

The importance of Ti alloys is increasing due to abundance of Ti mine on earth and improvements of Ti metallurgical technique. Mechanical properties of Ti alloy are better than those of steels, such as strength-to-weight ratio and corrosion resistance …etc. Mechanical properties of Ti alloys can be enhanced based on the demand. Development of joining process is always an important index in application of engineering alloys. Accordingly, the main subject of this study is concentrated on brazing Ti alloys. The study of infrared brazing Ti alloys using the Ti-based fillers are mainly focused in microstructure and phase transformation of the joint. Traditionally, the study of Ti brazing is emphasized on the SEM morphology and EDS chemical analysis results. It is difficult to unveil phase transformation of the brazed joint due inadequate resolution of the facilities. TEM analysis of the joint is required in the experiment. First, Ti-15Cu-15Ni, Ti-25Cu-15Ni, Ti-15Cu-25Ni are applied in brazing SP-700 substrate. There is eutectic in the center of joint for the 300s brazed specimen. Primary Ti2Ni and few α-Ti as well as Ti2Cu are observed in the central region of the joint using Ti-15Cu-15Ni and Ti-15Cu-25Ni fillers, respectively. In contrast, primary Ti2Cu is widely observed from the Ti-25Cu-15Ni brazed joint. Additionally, eutectoid α-Ti and Ti2Cu with retained β-Ti are also found next to the primary Ti2Cu. For the 1800s brazed specimen, the joint mainly consists of over-saturated α-Ti and retained β-Ti. Second, Ti-15Cu-15Ni braze is applied in brazing 3 different substrates, CP-Ti, SP-700 (