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Nano-crystal austenitic metal bulk material having high hardness, high strength and toughness, and method for production thereof

a technology of austenitic metal and nanocrystal, which is applied in the field of high hardness, strength and toughness of nanocrystal metal bulk materials, can solve the problems of unable to obtain materials whose grain diameters are reduced down to the nano-size level, and can hardly be reduced down to the nano-order, and achieve the effect of ultra-fine crystal grain structur

Inactive Publication Date: 2006-06-15
NANO TECH INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008] Basically, the present invention makes use of mechanical milling (MM) or mechanical alloying (MA) of a powder mixture of powders of an elementary or semimetal single metal and powders of other metal additives or the like. The resulting nano-crystal fine powders are refined by forming-by-sintering or methods using superplacticity in the forming-by-sintering process down to nano-size levels, thereby providing a bulk material having strength (high strength) and hardness (super hardness) close to the limits achievable with crystal grain diameters reduced down to the nano-size level, and corrosion resistance as well.
[0058] By suitable selection of crystal grain size, composition, or the like, superplasticity is induced in the nano-crystal material, and this phenomenon can be effectively applied to the forming-by-sintering process of MA powders.

Problems solved by technology

However, the crystal grain diameter D of most metal materials produced by melting are usually on the order of a few microns to a few thousand of microns, and D can hardly be reduced down to the nano-order even by post-treatments.
In other words, with such ordinary processes it is impossible to obtain materials whose grain diameters are reduced down to the nano-size level.

Method used

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  • Nano-crystal austenitic metal bulk material having high hardness, high strength and toughness, and method for production thereof
  • Nano-crystal austenitic metal bulk material having high hardness, high strength and toughness, and method for production thereof
  • Nano-crystal austenitic metal bulk material having high hardness, high strength and toughness, and method for production thereof

Examples

Experimental program
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Effect test

example 1

[0070]FIG. 1 is illustrative of changes in the mean crystal grain diameter of each mechanically alloyed element, that is, iron, cobalt and nickel when a 50-hour mechanical alloying (MA) was applied to an elementary powder mixture having an M85A15 (at %) (M is iron, cobalt or nickel), which comprised powders of the elements iron, cobalt and nickel with the addition thereto of 15 at % of carbon (C), niobium (Nb), tantalum (Ta), titanium (Ti) and so on as other elements (A).

[0071] In FIG. 1, DFe, DCo and DNi are the mean crystal grain diameter (nm) of the mechanically alloyed iron, cobalt, and nickel, respectively. From FIG. 1, it has been found that the reduction of crystal grain diameters of each of the elements iron, cobalt and nickel can be more effectively promoted by mechanical alloying with the addition thereto of carbon, niobium, tantalum, titanium and so on, all the three elements being refined down to grain diameters of a few nano-orders.

[0072] It has also been found that t...

example 2

[0079]FIG. 4 is illustrative in graph of the relationships between the mean crystal grain diameter D (nm) of an Fe64-yCr18Ni8TaYN10 (at %) where y=0 to 15, obtained by a 100-hour MA treatment of a powder mixture of elements iron, nickel and tantalum with the addition thereto of iron nitride, and the amount of tantalum added y (at %).

[0080] From FIG. 4, it has been found that the marked grain refinement effect of the additions elements A having the large value of the grain boundary segregation factor β in the binary Fe and A materials is similarly seen in the multicomponent materials based on component Fe as well.

example 3

[0081] A powder sample of Fe99.8C0.2 (% by mass) was obtained by the mechanical alloying (MA) of a powder mixture of elements iron and carbon for 200 hours. Then, the sample was vacuum charged in a stainless steel tube (sheath). Consolidation (i.e., sintering) of the vacuum charged powder sample was performed by sheath rolling (SR) at a temperature of 900° C., obtaining an SR formed product (bulk material) as shown in Table 1.

TABLE 1Mean crystal grain diameter D, Vickers hardness Hv and thevalue of oxygen upon analysis of Fe99.8C0.2 (% by mass) bulkmaterial obtained by 900° C.-sheath rolling (SR) of powdermaterial mechanically alloyed from a power mixture ofelements iron and carbonSampleD (nm)HvOxygen % by massSR formed material*239800.485

The value of D was calculated from Scherrer's equation, and * indicates that the material thickness was about 1.4 mm.

[0082] From Example 3 and Table 1, it has been found that according to the invention, the Vickers hardness Hv of the formed mate...

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Abstract

The invention provides a high hard, strength and tough nano-crystal metal bulk material and a preparation process thereof. The metal bulk material comprises an aggregate of metal nano-crystal grains, wherein an oxide, nitride, carbide, boride or the like of a metal or semimetal exists as a crystal grain growth inhibitor between and / or in the nano-crystal grains. The respective fine powders of nano-metal bulk material-forming components are mechanically alloyed (MA), using a ball mill or the like, thereby preparing nano-metal powders. Then, hot forming-by-sintering treatment such as spark plasma sintering, extrusion and rolling or explosive forming is applied to the powders to obtain a high hard, strength and tough nano-crystal metal bulk material.

Description

ART FIELD [0001] The present invention relates generally to a metal material, and more particularly to a high hard, strength and tough nano-crystal metal bulk material, and its preparation process. BACKGROUND OF THE INVENTION [0002] As the Petch relationship teaches, metal material strength and hardness increase with decreasing crystal grain diameter D, and such relationships hold as far as D is at or near a few tens of nm. Thus, reducing crystal grain diameters down to nano-size levels now becomes one of the most important means ever for the reinforcement of metal materials. [0003] On the other hand, as crystal grain diameters are reduced down to ultra-fine, nano-size levels, most metal materials come to show a unique phenomenon called super-plasticity in a temperature region of higher than 0.5 Tm where Tm is a melting point (K). [0004] Harnessing that phenomenon enables even materials extremely unsusceptible to plastic processing or the like due to high melting points or temperatu...

Claims

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Application Information

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IPC IPC(8): B22F3/10B22F3/00
CPCB22F3/006B22F2003/1032B22F2998/00B22F2998/10C22C9/01C22C14/00C22C21/12C22C38/001C22C38/02C22C38/04C22C38/18C22C38/48C22C2200/04B22F3/08B22F3/20B22F9/005B22F3/14B22F3/105B22F1/0018C22C1/1084
Inventor MIURA, HARUMATSUMIYAO, NOBUAKIOGAWA, HIDENORIODA, KAZUOKATSUMURA, MUNEHIDEMIZUTANI, MASARU
Owner NANO TECH INST
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