铸态AZ31镁合金强流脉冲离子束改性

Modification of casting magnesium alloy AZ31 irradiated by high intensity pulsed ion beams

利用强流脉冲离子束(C+,H+)对变形镁合金AZ31的压铸件靶材分别进行1,5,10,20,30,50和100次辐照实验,分析辐照前后表面形貌和相组成,并检测辐照表面及横截面沿深度方向显微硬度。结果表明:HIPIB辐照次数对靶材形貌影响较大,多次辐照使靶材熔坑呈周期性变化趋势;β-Mg17Al12相弥散分布于α-Mg相中。1～30次辐照,表面显微硬度提高,其主要原因为晶粒细化及微应变导致的晶体缺陷;30～50次辐照,显微硬度显著降低,其原因在于晶体缺陷的演变,如位错移动导致的小角度晶界形成,甚至出现回复再结晶过程;50～100次辐照表面显微硬度略有降低,其原因在于辐照表面组织结构及热力学行为达到稳定态。辐照效应形成冲击应力波导致"长程硬化",20次辐照的横截面显微硬度在距表层30μm和240μm处分别达到极大值1.0GPa和1.3GPa。

High intensity pulsed ion beam （C^＋ , H^＋ ） irradiation of casting magnesium alloy AZ31 target is carried out with shot times of 1, 5, 10, 20, 30, 50 and 100, respectively. The surface morphologies, phase structure, surface and cross-sectional microhardness of irradiated samples are characterized. The results show that the shot times of HIPIB irradiation play a great role on the target morphology, subsequent irradiation on the melting crater has previously generated fuzzy or eliminated the trend; melting craters appear again along with increasing the times of irradiation. The surface microhardness increases straightly after the first to 30th irradiation, lying in grain refinement and micro-strain caused by the crystal defects;the 30th to 50th exposure, there is a significant reduction in microhardness,which lies in the evolution of crystal defects, such as dislocation movement leading to the formation of small angle grain boundaries, or even reply recrystallization;the 50th to 100th irradiation slightly reduced the surface hardness, the reason is that radiation＇s organizational structure and thermodynamic behavior of the surface to reach a steady state. The shock wave effects the formation of ＂long-hardening＂. The cross-sectional microhardness away from the surface 30 and 240 μm of AZ31 ,which is 20th irradiation,reach a great value 1.0 GPa and 1.3 GPa,respeetively.