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Formation Mechanism of Fracture Precursor Induced by Phase Transformation in beta Type Ti-Mo Alloy

β型钛钼合金相变断裂前驱体的形成机制

基本信息

批准号：
07650769
负责人：
HIDA Moritaka
金额：
$ 1.54万
依托单位：
Okayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07650769/
关键词：
titanium molybdenum alloy titanium nickel shape memory alloy omega transformation alpha transformation martensitic transformation {332} <113> twin transition state electron microscopy チタン-モリブデン合金 {332}〈113〉双晶オメガ相変態透過電顕観察逆変態変形

项目摘要

This study has been carried out mainly by electron microscopic observation. The summary is as follows :1. It is well known that hardening and embrittlement of beta type Ti-14Mo alloy are caused by aged (1) -phase formation. According to the study on deformation bands formed during tensile test at the aging temperature, the reverse transformation ((1) *beta) in the band drove preferential plastic deformation (work softening) in the band. This was recognized as an origin of the inacroscopic embrittlement. It was also newly observed that the hardness of over-aged alloy decreased without changing (1) -particle size and brittleness. The transition state, (1) *alpha, prepared by a step-aging made the alloy ductile emitting bundles of needle -like alpha-phase into matrix during tensile deformation. The ductility was better than that of the alloy with large alpha-phase formed by direct aging.2. It is well known that the as-quenched alloys show remarkable ductility with {332} twinning. The twinning mechanism which had not been cleared was determined by a model simulation of atom displacements to {332} twin from bee structure via alpha" martensitic transformation. Cutting and interaction between {332} twins maybe give rise to the local deformation at a kind of fractural precursors which are expected to be planar (1) -phase. The identification with TEM is now in progress.3. In-situ observation on Ti-50.6% Ni shape memory alloy revealed that the deformation in plastic region multiplied the secondary martensitic plates between and/or from the primary ones which were formed during quasi-elastic deformation. Cutting and interaction between the plates led the sample to fracture.4. Several cluster models of a given structure (beta, (1), alpha or alpha") were studied with DX-Xalpha method. The bond orders obtained seems to be effective in comparing the strength of stress induced products which stimulate work softening.

本研究主要通过电子显微镜观察进行。主要内容如下：1.β型Ti-14 Mo合金的硬化和脆化是由时效后（1）相的形成引起的。根据对在时效温度下拉伸试验期间形成的变形带的研究，带中的逆相变（（1）* β）驱动带中的优先塑性变形（加工软化）。这被认为是宏观脆化的根源。新观察到过时效合金的硬度下降，而（1）-颗粒尺寸和脆性没有改变。分级时效形成的α过渡态（1）使合金在拉伸变形过程中向基体中发射成束的针状α相。其塑性优于直接时效形成大α相的合金.众所周知，淬火态合金具有显著的塑性，并伴有{332}孪晶。通过对原子经α”马氏体相变从蜜蜂结构向{332}孪晶位移的模型模拟，确定了尚未明确的孪晶机制。{332}孪晶之间的切割和相互作用可能导致一种断裂前兆的局部变形，这种断裂前兆可能是平面（1）相。TEM鉴定正在进行中。对Ti-50.6% Ni形状记忆合金的原位观察表明，塑性区的变形使准弹性变形过程中形成的二次马氏体片层在一次马氏体片层之间和/或从一次马氏体片层上增殖。切割和板之间的相互作用导致样品被破坏。用DX-Xalpha方法研究了给定结构（β、（1）、α或α”）的几种簇模型。得到的键级似乎是有效的应力诱导产品，刺激工作软化的强度进行比较。