翻譯共8頁 英翻中
INVESTIGATION OF NATURE OF TWO-WAY SHAPEMEMORY EFFECT IN -Mn BASED ALLOYS
The -Mn based alloys with martensitic transformation of such as the binary Mn-Cu and the ones withthe small additions of Cr, Ni, Ge, Si et al. are representatives of the alloys with a pronounced two-wayshape memory effect (1,2). This property is the ability of samples to the alter their shape both withheating and cooling i.e. in the process of the reverse and direct martensitic transformation. Fig. 1illustrates the change of shape of a sample of 80%Mn-19%Cu-1%Ni alloy in the form of anArchimedean spiral manufactured by the twist of a strip at the room temperature with temperature.When the temperature is raised the spiral untwists in the direction opposed to the sign of the preliminaryplastic deformation (curve 1). The process is completed near the temperature of reverse martensiticfinishing point Af. The shape recovery ( rec) is not full: usually it equals 0.2– 0.5 of the pre-deformationvalue depending on degree of the preliminary deformation; the absolute value of recdepends uponstructural characteristics of the martensitic phase (3,4). With subsequent decrease of the temperature thespiral is deformed spontaneously tending to reach the shape which it had at the room temperature (curve2). After completion of the cooling the returned deformation ( rev) is near 0.6 – 0.7 from the shaperecovery value. With continuation of temperature cycling there is a reversible change of the shape(along curve 2) with a very small hysteresis.The purpose of the paper is to report data concerned with the structural mechanism of the reversibleshape memory effect in the martensitic Mn-Cu based alloys. We have investigated the characteristicsof the martensitic transformation, the mechanism of the plastic deformation of the martensite, thedependence of the reversible thermodeformation revon internal microstresses in the -solid solution(after reverse martensitic transformation) and the conditions of formation of oriented internal stressesin the alloys.
Mn-Cu二元合金是具有馬氏體相變的γ-Mn基合金，在其中加入少量Cr、Ni、Ge、Si等元素后，具有明顯的雙向形狀記憶效應(1,2)。此屬性是樣品通過加熱和冷卻，即逆向和直接馬氏體相變過程來改變其形狀的能力。例如：圖1表示將成分為80%Mn-19%Cu-1%Ni的條狀合金，在室溫時卷成阿基米德(Archimedean)螺旋線，當溫度升高時，螺旋線沿著與原來塑性變形相反的方向伸直(曲線1)。這個過程發(fā)生在馬氏體逆相變溫度 Af 點附近。形狀的恢復(ε rec) 是不完全的:依照預變形的程度，一般為預變形值的0.2～0.5左右。ε rec的大小取決于馬氏體相的結構特性(3,4)。接著隨著溫度的降低，螺旋線自發(fā)畸變?yōu)榻咏谑覝貢r的形狀(曲線2)。當完全冷卻時, 根據(jù)形狀恢復值，恢復的形變量(ε rec) 接近0.6～0.7。在隨后的溫度循環(huán)中, 其形狀的變化是可逆的(沿曲線2)，滯后效果很小。
本文研究了馬氏體Mn-Cu基合金的雙向形狀記憶效應的結構機制, 并進一步了解馬氏體轉變的特性、馬氏體的塑性變形機制；以及在馬氏體逆相變后, 熱變形恢復率ε rec與γ固溶體中內(nèi)部顯微應力的關系以及合金中具有擇優(yōu)取向的內(nèi)應力的形成條件。