材料期刊网

利用X射线衍射方法,结合硬度测量及金相观察等实验工作,对镁-6％镓合金时效过程的晶体学进行了研究。结果指出该合金的190℃时效过程可以分为三个阶段: 1.过渡相析出阶段。发现合金在时效初期析出一种属于正交晶系的过渡相β′,其点阵常数以及和基体(M)的位相关系测定如下:aβ′=9.1埃,bβ′=6.2埃,cβ′=24.6埃。aβ′∥[0001]M,bβ′∥[2(2■0)0]M,cβ′∥[01(01■0)0]M。初步测定了薄片状的过渡相在基体中平行于{10■1}M及{11■}M析出。 2.平衡相沉淀阶段。平衡沉淀相β为Mg_5Ga_2,其点阵常数是:aβ=13.72埃,bβ=7.02埃,cβ=6.02埃。测定了β和基体的位相关系为:aβ∥[0001]M,bβ∥[2■0]M,cβ∥[01■0]M。平衡相以魏氏组织析出,有弥散硬化作用,它在基体中的惯析面经测定为(0001)M。 3.过时效阶段。平衡相在基体中的魏氏组织消失,与基体没有一定的位相关系。

A crystallographic investigation of a Mg 6%Ga alloy during aging was performed by X-ray diffraction methods, together with hardness measurements and metallographic observations, The aging process of this alloy at 190℃ may be devided into three staps:1. Precipitation of β′. An orthorhombic transition phase β′ is precipitated at the initial stage of aging. Its lattice constants are: aβ′=9.1(?), bβ′=6.2(?), cβ′=24.6(?), and the orientation relationships with the matrix (M) are aβ′∥[0001]M, bβ′∥[2(?)0]M, cβ′∥[01(?)0]M.A preliminary determination showst hat the thin plates of the transition phase are parallel with {10(?)0} and {11(?)0} planes of the matrix.2. Precipitation of β. The equilibrium phase β precipitated out in a Widmanstatten form in the matrix has a composition of Mg_5Ga_2, with lattice constants aβ=13.72(?), bβ=7.02(?), cβ= 6.02(?). The orientation relationships between β and the matrix are: aβ/[0001]M, bβ∥[2110]M, cβ∥[0110]M. Dispersion hardening always accompanies this precipitation, and the habit plane in the matrix was found to be (0001)M.3. Overaging. The Widmanstatten structure of the equilibrium phase in the matrix disappears, and there is no definit orientation relationship between β and the matrix.